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JoHNY
Edinburgh,
United Kingdom
Posts: 45
Daytona T595 (97-98)
07 Mar 2008 21:57 |
If i force more air in to box will the ECU sense this and squirt more juice in to the pots?
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mikey
west brom,
United Kingdom
Posts: 104
Premier Member
Daytona T595 (97-98)
07 Mar 2008 22:05 |
no
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bradtx
Pearland, TX,
USA
Posts: 647
Premier Member
Daytona 955i (04->)
07 Mar 2008 23:33 |
Johny, The T595 has a twin snorkle 'ram air' intake. The fuel pressure regulator is plumbed to the air box and in the event there ever is positive pressure in the air box should increase fuel pressure. This is mostly fiction as most T595s run better, or at least sound like they do without the tubes. I just can't see too many situations where positive air box pressure occurs...maybe 100 MPH into a 100 MPH headwind.
Brad
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JoHNY
Edinburgh,
United Kingdom
Posts: 45
Daytona T595 (97-98)
07 Mar 2008 23:42 |
I was just sitting on the loo wondering. If i rammed more cool air in to box would the ECU realise.
I'm doing away with the top fairing, consquently, exposed are the two air intake muzzles exposed like machine guns. I was thinking of ataching large air scoops to the end of these intakes forcing more cool air in to the box. Daft i know, but i wonder if it'd work? Probably wouldn't make a blind bit of difference.
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Frank Jones
NY,
USA
Posts: 1,737
Premier Member
Sprint RS (02-05)
08 Mar 2008 08:15 |
go with scoops like a digger offa jcb tractor
Airflow will increase by 25%........unfortunately, so will drag!!!!!!!!!!
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Ian Stubbs
Leicester,
United Kingdom
Posts: 489
Daytona T595 (97-98)
08 Mar 2008 11:10 |
I also had one of those crazy 'sitting on the loo' ideas some time back, and thought about mounting small 12volt fans at the air intake tubes to blow air in to the air box. I never bothered to try it on the grounds that I think it would make sod all improvement.
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JoHNY
Edinburgh,
United Kingdom
Posts: 45
Daytona T595 (97-98)
08 Mar 2008 11:19 |
Ian, is it just us lot who get these nutty ideas? I suppose if i want to force more air in i should fit a turbo. But then i'll open myself up to all sorts of issues. I used to have an SP1 for a while and it had some kind of valve type air intake system. I can't remember the tech bumph, but apparently a valve used to open/close depending on revs to force more air in to the box. It had it's opening straight through the top fairing and the front of the frame.
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Manny Fagnet
Poland,sorry Reading,
United Kingdom
Posts: 1,455
Premier Member
Daytona T595 (97-98)
08 Mar 2008 11:32 |
Remember-the air box has water drain holes by the snorkel inlets and the snorkels (from memory) also have water drain holes in them.......plus the crank case breather vents into the air box too, so there's a lot of obstacles to overcome before any form of ram will work...
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Phil955i
SouthEast,
United Kingdom
Posts: 1,205
Speed Triple 955i (99-01)
09 Mar 2008 20:17 |
If you look on Ebay under 'Superchargers' there are quite a few listings for electric 'superchargers'. Wether they work or not is another matter...
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
10 Mar 2008 09:25 |
Ram air is a complete crock anyway on a bike - it doesn't work full stop! PB magazine tried a test about 10 years ago now with the ZX9R which had chanbered Ram Air with all sorts of solenoids to open it up at different speeds etc and was considered the last word in Ram Air Technology.
So they ran it up a test strip and timed it when it was fully "ram aired" and then put duct tape over the inlets and did the same run and got EXACTLY the same time.
Sadly ram air and ram air kits (yes you to can spend £50 on some plastic ducting) are in the same league as Phil's electric super chargers
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
14 Mar 2008 23:07 |
Wow, I thought moto GP bikes had holes on the front fairings because it made a difference!!!
Of cores it works!!!! Do you think the aerodynamics technicians would leave air tube holes in the front of the bike if it didn’t!!!!
You crack me up Peter; we did a dyno test on my mates 999r with full carbon tubes and airbox. Set the bike up on the dyno, after a few power runs it was then set rich for high rpm. With my wide band commander in play, flat out on the straight at Philip Island it was spot on!!!
So if you think that your engine would not benefit from the pressure of airflow going into a proper airbox at 280 kph think again.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
15 Mar 2008 09:20 |
Steve
The fact that you put tubes to feed an air box does not make it a ram air system - all air boxes have tubes in but to be ram air it must build an over pressure above atmosphere to force air in to the carbs, (or plenum etc) - on bikes at road speeds this simply does not happen.
If you talk to anyone in the race world (and I can give you the number of several of Corser's and Bayliss' technical crew from Ducati as you mention that brand) and in fact if you bother to read the PB article which was very carefully tested with some of the top engineers in the field you will see it simply does not work.
I designed the intake and exhaust systems on the only team in history to go out and take 1st and 2nd place in their first season nationally and for many WSS and a WSBK teams and have worked with some of the best guys in Moto GP and SBK over the years and have never met anyone who takes the concept seriously. I'm not denying you need a good airflow to the air box and the tubes are needed to duct it from the pressure zones at the front of the bike so it's not trying to suck from the low pressure dead zone where there is less air but that is not Ram Air Steve, it does not build over pressure on the induction to any noticable degree and will not give any extra power.
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
16 Mar 2008 21:26 |
Wow it all happens at your place then, you should put some of those skills into practice on Triumph's
You can have an air intake turned backwards under the tank like on the 2002 Daytona’s or you can have a purpose built set of tubes that gets clean air into the airbox.
Which one is better? If the motor is mapped properly it will make use of the extra clean air that gets at high speed from the air tubes!!!
If that wasn’t the case why do they bother to make them in the first place?
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Phil955i
SouthEast,
United Kingdom
Posts: 1,205
Speed Triple 955i (99-01)
16 Mar 2008 22:54 |
http://www.sportrider.com....._ram/index.html
A tad more scientific than PB magazine's 'test' I would say.
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
16 Mar 2008 23:38 |
Looks like it's on!!!
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JoHNY
Edinburgh,
United Kingdom
Posts: 45
Daytona T595 (97-98)
17 Mar 2008 00:05 |
Well i'll give it a go, what have i got to lose after all. All i have to do is manufature suitable scoops and atach them to the snorkels. Might look a bit unconventional but that doesn't bother me as i'm a bit of a freak anyway. I'll let you all know if it works.
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
17 Mar 2008 04:49 |
simply put, anything that even slightly helps put more combustible mixture in the chamber, makes more power.
period.
the caveat of this being, some years (like my old 02 955i and up) have "atmospheric pressure sensors" (actually airbox pressure sensors, which is better anyway for our purposes) and some do not.
If your year does have the sensor and/or a properly functioning fuel pressure regulator plumbed to compensate for air box pressure, then yes, the bike will recognize the greater amount of air being introduced and will add more fuel to maintain the target fuel/air ratio, and make more power.
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
17 Mar 2008 05:59 |
I totally agree and that is what I have been saying all along.
Thing is Cerberus, the MC1000 only samples air pressure ever 8 or 10 seconds from memory, so I hope it's a long bit of road that we travel. If the ECU was to sample fast it would be awesome, you could use it to MAP boost with a Turbo or Supercharger, no need for a piggyback brain for boost fueling…
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
17 Mar 2008 06:02 |
ah.. this i did not know..
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 08:25 |
Phil - I would actually say the Sportrider test was less scientific - they try to mimic 150mph wind speeds all through the rev range and then duct it in to the air inlets. Let's see - how may bikes do you know that do 150 mph at 3000 rpm or 7000 or even 12000 - for most that is almost peak revs flat out so of course if you force air from a compressor in to the air box and have fuel set up to match you will see more power - but that isn't what happens on a road bike. You don't see any sort of over pressure at road speeds and almost none at race speeds - plus you have a whole host of issues with low and high pressure zones which move depending on speed. Very interesting article though and worth looking in to some more, thank you.
Steve, I'm not even going to bother discussing something with you if you're going to be personally rude.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 08:46 |
For those with a real interst in the subject this article puts it quite well without being too mathematical
Of all of the applied sciences, fluid mechanics is among the most difficult for many people to comprehend. It is a relatively youthful applied science as well, meaning that it has not had two or three centuries of work to mature into an applied science on par, with say, chemical combustion. To make matters worse, it is mathematically defined almost entirely by experimentally-determined mathematics.
This last point is the true differentiator between those who only understand concepts, and those who can quantify what they are discussing. Truly, quantification is the real skill of the engineer. It is one thing to speak about qualitative issues (the “what” of the physical sciences); it is entirely another to quantify them (the “how much” and “to what extent” of the same). In grade school, students are first taught about “closed form mathematics” and then that these mathematics are typical of scientific expression. A good example of this is Newton’s famed “law of action and reaction”, the mathematical expression of which is a succinct F=MA. So straightforward. So simple. Three variables in perfectly-defined harmony. Given any two of them, the third is easy to nail down.
Unfortunately, a vast, vast majority of the mathematics used in engineering are NOT closed form. Instead, they are multi-variable correlations valid only for a narrow set of circumstances. Deviate from those narrow circumstances, and a new expression must be experimentally derived. Fluid mechanics is almost entirely defined by these experimentally-determined expressions, further muddying an applied science not well understood.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 08:46 |
And if there ever were an applied science for which common sense is wholly inappropriate, it is fluid mechanics. Virtually nothing obeys the “common sense” rules of observation, explaining why those who believe in ram air have extreme difficulty in believing that is simply does not exist.
The Deeper Explanation begins with a basic explanation of engine principles. Air and fuel must be combusted at a specific ratio, namely, 14.7 parts air to 1 part fuel (this is a chemical ratio). Stuffing more fuel into the cylinders without increasing the amount of air they also swallow will get no gain whatsoever. So the hot rodder’s adage “more air = more power” is proven correct. Figure out a way to stuff more air into the cylinder at any given RPM and throttle setting, and you can burn more fuel. Since burning fuel is what makes power, more air truly does create more power.
The amount of air which is inducted into a cylinder is a function of the air’s density. As the air flows through the intake tract, it loses pressure, and as the pressure decreases, so does the air’s density. (Denisty is mass divided by volume. Since cylinders are a fixed volume, increasing the density will also increase the mass of the air in the cylinder.) There are two ways to increase the pressure and density of the air inducted into the cylinders:
- Decrease the pressure drop from the throttle plate to the cylinders
- Increase the starting pressure at the throttle plate.
Ram air is an attempt to do the second. Under normal circumstances, the air at the throttle plate is at atmospheric pressure, and this pressure drops until the air reaches the cylinders. Ram air would start the process at some pressure higher than atmospheric, and even though the drop is the same, the cylinder pressure is higher because of the increase at the start.
Just how would this increase in pressure at the throttle plate occur? The oft-wrong “common sense” says, “If a scoop is placed in the airstream flowing around the vehicle, the velocity of the air ‘rams’ the air into the scoop, thus increasing the pressure.”
Why is this incorrect? There are two types of pressure: static and dynamic. Placing of one’s hand in front of a fan, or out of a moving car’s window, clearly exerts a force on the hand as the air diverts its path to flow around it. Most people would say “See? This is a clear indication that ram air works. Clearly there is pressure from the velocity of the air.” Well, this is correct, but only to a point. This is an example of dynamic pressure, or the force any moving fluid exerts upon obstacles in its path as the gas is diverted around the obstacle.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 08:46 |
What an engine needs is static pressure. This is the pressure the same fluid exerts on any vessel containing it at rest. For those who were physics/chemistry geeks, it is the pressure caused by the force of the molecules bouncing off of the walls of the container. The key to understanding the difference between static and dynamic pressure lies in the velocity of the gas. Dynamic pressure is only a momentum effect due to the bulk motion of the fluid around an obstacle. Static pressure is an intrinsic property of a gas or fluid just because the molecules of the fluid are moving around. Any fluid which is moving can have BOTH dynamic and static pressure, but a fluid at rest only has static pressure.
The point of ram air would be to increase the static pressure, which would correspond to an increase in the in-cylinder air density, and of course, more air. Superchargers and turbochargers do what the mythical ram air purports to do. A supercharger trades the power of the belt and uses it to compress the air in the intake tract. This energy trade-off results in an increase in intake air pressure, more air in the cylinders, more fuel burned, and more power. A turbocharger trades the power of the hot gases and uses it to compress the air in the intake. The overall effect is the same – an increase in intake static pressure.
For ram air to work, it would have to trade the energy of the air’s velocity (as the vehicle moves through the air) for an increase in static pressure (since static pressure is a part of a gas’s internal energy, we see this is TRULY a trade in kinetic energy for an increase in internal energy). Now for the true reasons why ram air is a myth:
- The way for air velocity to be traded for an increase in static pressure is to actually SLOW IT DOWN in a nozzle of some sort. This is easily the MOST counterintuitive part of fluid mechanics for most people. The “common sense” mind says “In order to increase the pressure of the intake, the velocity of the air needs to be increased, just as increasing the speed of a fan exerts more force upon the hand.” Not only does this confuse dynamic with static pressure, but is also misses the point, which is to trade the kinetic energy of the gas for an increase in internal energy. How can this trade occur if the kinetic energy of the gas is increased? It cannot, and in fact, the only way to trade it is to use the velocity of the gas to compress itself – by slowing it down.
-
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 08:47 |
Below about Mach 0.5 (or about half the speed of sound), air is considered “incompressible”. That is, even if the correct nozzle is selected, and the air is slowed down (the official term is “stagnated”) there will be zero trade. No kinetic energy will be traded in as work capable of compressing the air. The reasons for this are not discussed here; the reader may consult any reputable fluid mechanics textbook for confirmation of this fact. In plain English, a car is just too slow for ram air to work.
Still not enough evidence? Here is a little test. For ram air to work, the nozzle must be of a specific shape. The “Holley Scoop” for the Fiero is the wrong shape, by the way. The fact that it has no net shape at all immediately means it cannot effect any kind of energy trade off, so it cannot possibly create ram air. This is also true for the hood scoops on the Pontiac Firebird WS6 package as well, by the way.
What shape must it be? There are two kinds of nozzles. Pick one:
- Converging. This nozzle gets smaller as the air flows through it. It has a smaller exit than entrance. If the nozzle were a cone, the fat end is where the air would enter, and the narrow end is where it would exit.
- Diverging. This nozzle is opposite the other; it gets bigger as the air flows through it. With a larger exit than entrance, the narrow end of the cone is where the air would enter, and the fat end is where it would exit.
So, which is it?
Without hesitation, most of the “common sense” crowd will answer “Converging.” BZZZZT! Thank you for playing anyway! We have some lovely parting gifts for you! Bill, tell ‘em what they’ve won….
The answer is “divergent”. Yes, the nozzle would have to shaped so that the skinny end is pointed into the air stream, and the fat end connects to the throttle plate. How can this be right? Remember, to increase the static pressure of the intake air (which is the true “ram air” effect), the kinetic energy of the air must be traded to compress the air. This is done by slowing the air down, or stagnating it, and the only way to do this is with a diverging nozzle. Ah, but since air is incompressible at automobile speeds, it doesn’t matter any way.
Conclusion
Ram air is a myth because it does not exist, for the following reasons:
- Air is incompressible at any automobile speed., meaning that the kinetic energy of the air cannot be used to compress the air and raise the static pressure.
- The “ram air” nozzles commonly employed on automobiles tend to be the wrong shape. A divergent nozzle is required for ram air. Straight-profile scoops cannot provide a ram air effect.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 08:52 |
[edited]:
For those who are good at maths the formula
dP / P = (v2) / (2RT)
is what you need to work out the possible increases in static pressure
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Boycie
Brrrrrrrritain,
United Kingdom
Posts: 8,492
Premier Member
Speed Triple (05->)
17 Mar 2008 09:14 |
Back to Nitrous then JoHNY
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Boycie
Brrrrrrrritain,
United Kingdom
Posts: 8,492
Premier Member
Speed Triple (05->)
17 Mar 2008 09:15 |
Good article btw Pete
Saves a lot of blah blah pub talk
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
17 Mar 2008 12:34 |
Did you get (A Gragham Bell) on cd and just copy and paste!!!
I think you need one of my hats on your head!!!
Inline Image
Peter, you started getting personal with me when you did not reply to my emails regarding one of your cans that a customer of mine had on his bike. It's OK I fixed it for you!!!
I’m still curious why you reduce the bore size of the secondary pipe other than it was the only size you had at that time!!!
Inline Image
Your secondary pipe.
Inline Image
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 12:53 |
[edited]:
Steve, if I had received an email from you I would have replied. I don't really understand your hat comment but I take it you now understand Ram Air a bit better and realise you were wrong? With regard to bore sizes I will happily explain exhaust design to you sometime as well if you drop me an email with your questions... If you use peter@trident-exhausts.com it will definately get to me.
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
17 Mar 2008 15:01 |
Peter- that is a great read but i have to make a couple comments.. it wouldn't be me if i didn't 
And this will sound like a cop-out but i am essentially unschooled in physics except by way of what i have read along the way, so I may be ill equipped to make the argument at the moment.. But just because someone knows how to write a decent dissertation on a subject does not mean they are necessarily correct.
The writer greatly overly-simplifies the dynamic forces at work in any engine and makes some presumptions which are wholly inaccurate by using analogies to other systems which are not really equitable at all..
making more power is more about VOLUME of air/fuel getting into the chambers, and many engine builders say it is even more about velocity. Greater pressure in the airbox only serves to move more volume into the chamber..
null:
The amount of air which is inducted into a cylinder is a function of the air’s density |
true, but not the whole story by far.
.. i need a cup of coffee and a walk around the block to wake my brain up before i go any further.. my brain has gotten flabby of late..
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
Premier Member
Enthusiast
17 Mar 2008 15:55 |
I suspect that any of us without at least a degree in fluid dynamics has little to say on this subject. Of course if you can get more air in (and conversley have the ability to get rid of the products thereof) and then feed that air with fuel then you wil make more power. I found the sports rider article less than useful on a number of levels. The other one went far above what I know. I do know this though, feeding cold air in greater quantities with more fuel works but am still sat on the fence wrt ram air systems.
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Phil955i
SouthEast,
United Kingdom
Posts: 1,205
Speed Triple 955i (99-01)
17 Mar 2008 16:59 |
Peter, you're doing the wrong job, you should have been a polititian mate  . If you read the Sports Rider article again it says that they placed the forced air supply at some distance from the air intakes on the smaller bikes & OK, that air pressure isn't available normally at lower revs/lower speeds but they're still making more power at the top end (when you would be getting a degree of positive pressure, not much I agree, probably only a few millibars) than without the ram air. Sounds pretty conclusive to me.
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
17 Mar 2008 17:13 |
i'd like to see wind tunnel dyno results to settle the question, once and for all.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
17 Mar 2008 17:20 |
Sadly I think the test had more to do with cold air that ram air in a hot dyno room but never the less the physics prove that it does not work and what I said above about the race teams I've spoken to and worked with is true - not one takes it seriously and they are all a lot smarter and better funded than me to make that judgement... If we ignore the physics and some rather dodgy dyno results I would say that racing is conclusive enough - they spend multi millions on GP and SBK bikes and try to wring every last bit of power they can and are at high speed much of the time when ram air would be at it's best and yet... they all think its a joke!
However, that's what this place is for, a bit of healthy debate and exchange of ideas so I look forward to seeing what else people find to argue one way or another.
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Phil955i
SouthEast,
United Kingdom
Posts: 1,205
Speed Triple 955i (99-01)
17 Mar 2008 17:37 |
It does make me wonder why they've persevered with ram air for the last 20 years, it hasn't been a passing fad like 16" front wheels & fork anti-dive. The Japanese don't usually persevere with an idea unless it's of positive benefit.
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
Premier Member
Enthusiast
17 Mar 2008 17:48 |
Marketing mate marketing.....
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
17 Mar 2008 19:41 |
[edited]:
With regard to bore sizes I will happily explain exhaust design to you sometime as well if you drop me an email with your questions... If you use peter@trident-exhausts.com it will definately get to me.
BTDT, no reply!!!
If you don’t mind, you can keep your reverse bore technology to yourself thanks. If I needed advice from you Peter them I’m in deep shit, I don’t recall dropping the ball!!!!
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
20 Mar 2008 19:44 |
i am drafting a proper analysis and rebuttal of the above article as we speak. i'll be giving a quiz afterwards ;P
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Boycie
Brrrrrrrritain,
United Kingdom
Posts: 8,492
Premier Member
Speed Triple (05->)
20 Mar 2008 20:30 |
Is it an "open book" quiz or do I have to write the answers on the inside of my shirt cuffs ?
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
20 Mar 2008 21:59 |
open book for sure 
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
20 Mar 2008 22:05 |
ok, i enjoy a debate like nobody knows.. but i can't be bothered to spend hours debunking falsehoods.. but here's what i came up with:
Quote:
a vast, vast majority of the mathematics used in engineering are NOT closed form. Instead, they are multi-variable correlations valid only for a narrow set of circumstances. Deviate from those narrow circumstances, and a new expression must be experimentally derived. Fluid mechanics is almost entirely defined by these experimentally-determined expressions, further muddying an applied science not well understood. |
By the authors own admission, these multi-variable mathematical correlations are only valid for a narrow set of circumstances. This is very relevant here, as I will show that the narrow set of circumstances presented are being (intentionally or unintentionally) misrepresented and are therefore invalid.
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
20 Mar 2008 22:06 |
Quote:
The amount of air which is inducted into a cylinder is a function of the air’s density. As the air flows through the intake tract, it loses pressure, and as the pressure decreases, so does the air’s density. (Denisty is mass divided by volume. Since cylinders are a fixed volume, increasing the density will also increase the mass of the air in the cylinder.) There are two ways to increase the pressure and density of the air inducted into the cylinders:
- Decrease the pressure drop from the throttle plate to the cylinders
- Increase the starting pressure at the throttle plate. Ram air is an attempt to do the second. Under normal circumstances, the air at the throttle plate is at atmospheric pressure, and this pressure drops until the air reaches the cylinders. Ram air would start the process at some pressure higher than atmospheric, and even though the drop is the same, the cylinder pressure is higher because of the increase at the start.
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Here is where the author's understanding of the dynamic forces in an induction tract falls apart. Air flow through the intake tract is not a simple or constant flow, but rather is constantly varying based on the low pressure intake pulses of each cylinder's intake stroke. The only way that the pressure inside an airbox (or at the throttle plate) is ever at atmospheric, is if the engine is not running, so thats one basic premise of the presented dynamics already out the window. (also the author's intended meaning when he says “at the throttle plate” MUST be above the throttle plate, but though that detail is quite important, it goes unclarified) To the contrary, the pressure at the throttle plate is a constantly changing value due to induced flow of air into the throttle bodies and the combustion chambers, causing low pressure waves and subsequent reversion (higher pressure) pulses. Even if we averaged all the negatives and positives for a net clean air pressure (clean side of the air filter) it would be some amount below atmospheric due to the restriction that the filter itself creates to the flow of air. That's another hole shot in the premises used for the author's explanation.
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
20 Mar 2008 22:12 |
Quote:
What an engine needs is static pressure. This is the pressure the same fluid exerts on any vessel containing it at rest. For those who were physics/chemistry geeks, it is the pressure caused by the force of the molecules bouncing off of the walls of the container. The key to understanding the difference between static and dynamic pressure lies in the velocity of the gas. Dynamic pressure is only a momentum effect... |
Certainly, a true forced induction system would be preferable, but the combined static and dynamic effect of ram-air systems is still very real, and the clue is in the author's own words
“Dynamic pressure is only a momentum effect” Very true, but the air flow into an engine is a dynamic environment. Engines are often seen as being air pumps so let's say hypothetically, a 1 liter engine is running at 6000RPM @ WOT (wide open throttle), it would be pumping 3000liters of air per minute. According to NASA's site, air has a mass of 1.229 Kg/cubic meter, so about 8.1 pounds of air per minute. Therefore as that mass of air is moving through the engine at some velocity, it has a very real amount of momentum. The ram-air system utilizes the forward motion of the vehicle to take air which is already accelerated in the direction of induction (relative the air tract), thus minimizing the induction lag that would be caused by stagnant air being accelerated into the induction system.
Quote:
The point of ram air would be to increase the static pressure, which would correspond to an increase in the in-cylinder air density, and of course, more air. |
I'm quite sure that it does exactly that, even if only slightly.. even if it is just bringing airbox pressure UP TO atmospheric pressure on the clean side of the air filter(after averaging all the pulses), since it would normally be in some negative state by virtue of the inertia of the air being drawn into the airbox at high speed versus being offered at the entrance to the airbox with some dynamic pressure and already accelerated to a greater speed than zero (non ram-air induction).
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
20 Mar 2008 22:15 |
peter:
all air boxes have tubes in but to be ram air it must build an over pressure above atmosphere to force air in to the carbs, (or plenum etc) - |
WRONG! all a ram air system has to do is create a greater pressure in the airbox than would have been there without it, and it is effectively capable of creating an increase in performance.. and airbox pressure is never at atmospheric unless the engine isn't running!
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
21 Mar 2008 09:02 |
Have to disagree here Cerberus, but having spent enough time on this already I think rather than trawl through the net and my books on fluid dynamics I will see if I can address the question to others and then post their responses one way or another. I am thinking of one or two of the race bike designers (I know the guys who design and build Ducati's SBK and GP bikes) and perhaps also the head of Automotive Engineering at one of the UK's major universities (whom I don't know well but had contacted me last year about placements for his students)
As you know my belief and that of everyone who I've met in the race and tuning world over 20 years is that it is a myth but as you make a good argument (though if you use the math above you will get aroudn a 2% increase in air pressure at 150 mph which would give virtually nothing in terms of increased power) I will spread the net wider to get some more expert opinions. If you know any friendly physicists, designers etc then perhaps you would do the same...
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JoHNY
Edinburgh,
United Kingdom
Posts: 45
Daytona T595 (97-98)
21 Mar 2008 09:18 |
Whilst the folk here spat this is what i've done so far. Bought myself to 180mm black funnels, cut the ends off whilst removing the snorkels of the bike.
Now i have fit the funnels in to the air intake tubes either side of the rad. One thing's for sure the roar of the intake air is sure to increase. Whether it'll increase power even in the slightest i'l wait and see.
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
21 Mar 2008 10:40 |
and they now say (an increasingly large majority) that the link between CO2 and global warning is a falicy (which most sensible people have known forever anyway) and that the levels of CO2 present today are neccesary for living and are not contributing to the falicy of Global Warming.
However I expect someone to take a different view.....
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
21 Mar 2008 23:50 |
Verbal flatulence is a big problem here, more so than CO2!!!
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
22 Mar 2008 10:58 |
[edited]:
Steve - sometimes people with intellegence like most here like to use words to describe ideas and opinions they have - sometimes that takes a lot of words if it's a complex idea - then there's those who just likes to insult anyone they disagree with because intelligent debate and opinion is beyond them...
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
22 Mar 2008 11:39 |
X-man - more than that Global Warming is a fallacy - there is good temperature data for around 160 years across Europe Africa and the USA (ie pre and post industrialisation) and worldwide temperatures have climbed an average of 0.2 degrees in that entire time!
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
22 Mar 2008 12:21 |
Peter, thats exactley what I was saying. Its a load of crap pushed by a government that sees an easy buck earner in the 'green' issue. Take our road tax hike for instance...
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
22 Mar 2008 13:00 |
Peter you are on thin ice with me don't push your luck!!!
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
22 Mar 2008 13:33 |
And I think you prove my point for me Steve! If you have any constructive opinions or facts to press your view point on ram air then please make them - otherwise leave those who do to discuss it
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Gary
Southampton,
United Kingdom
Posts: 192
Speed Triple 955i (99-01)
22 Mar 2008 21:15 |
Please ladies!!
What an interesting thread. I for one am interested to learn whether ram air works or not. Mr Sorrell thinks it doesn't and is prepared to argue his case. Cerberus thinks it does and will argue his case as well. Mr Phillips who's bikes and custom parts I have always greatly admired also thinks it does but seems to be adopting an, "It works because I say it does" atitude and will insult anyone who disagrees. Come on Steve you can do better than that dont just give us anecdotal evidence about your mates Ducati explain the science of why it works and dont kill the thread with you insults and threats. As for your dont push your luck comment, what are you going to do! your on the other side of the world!!
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
22 Mar 2008 21:32 |
Well I have emailed my contacts at Ducati Corse and at Loughborough University so hopefully will get some independent and learned opinions back in the next couple of weeks. I'll post whatever I hear in support or against...
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
22 Mar 2008 23:30 |
Sorry guy’s, I got a bit off track with Sorrell, I do him a favour saved him a load of grief by fixing a problem that one of my customers had with a slip-on can purchased from him.
I don’t get so much as a thank you!!!! I’ll start another post related to that problem later.
Anyway, I’m not going to let that spoil the fun………
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
23 Mar 2008 09:03 |
[edited]:
And still proving my point...
Any constructive comment on how or why you think ram air works?
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PegLeg
dorset,
United Kingdom
Posts: 424
Premier Member
Speed Triple T509 (97-98)
23 Mar 2008 19:01 |
Peter on a totally different subject do you have an E-mail address? ( sorry for hijack )
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
23 Mar 2008 19:37 |
there you go from further up the thread.
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Cerberus
Connecticut,
USA
Posts: 5,163
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Enthusiast
23 Mar 2008 20:16 |
for the record, i have passed this question upstream to solicit the input of student engineers and their professors at a semi-local college.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
23 Mar 2008 21:58 |
Thanks cerberus - be interesting to hear some more opinions
Thanks Xman
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Garry Peterson
Sth National Park,
Australia
Posts: 82
Daytona 955i (99-01)
25 Mar 2008 18:34 |
[edited]:
All I know is that the air box on my LSR Busa does have postive pressure...but its got to be doing more than 160mph and increases with speed.......how do I know ?
also the Denso ECU has compensation tables for fuel trims based on Throttle position , rpm and surprsingly gear position
also if any of you have been more than 200mph on a N/A motor ram air is your HP friend....free if designed well
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
26 Mar 2008 11:56 |
I’m not sure you will get away with just that comment Garry; you need to back it up with complicated mathematical equations.
Seat of your pants is not good enough for some people on here.
A 2bar MAP sensor can work it out though, it sits in the airbox and with an ECU that samples MAP fast, any increase or decrease in pressure can be logged.
I’ve seen race bikes burst apart with positive pressure, I have also felt the force of the wind trying to drag me off my bike at high speed, not 200 just a wee bit under. That is positive pressure in my book!!!!
Below is the Wikipedia’s low down on the subject.
Ram-air intake
From Wikipedia, the free encyclopedia
ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion to increase the static air pressure inside of the intake manifold on an engine, thus allowing a greater massflow through the engine and hence increasing engine power.
The ram air intake works by reducing the intake air velocity by increasing the cross sectional area of the intake ducting. When gas velocity goes down the dynamic pressure is reduced while the static pressure is increased. The increased static pressure in the plenum chamber has a positive effect on engine power, both because of the pressure itself and the increased air density this higher pressure gives.
Ram-air systems are used on high performance vehicles, most often on motorcycles and race cars. Ram-air has been a feature on some cars since the late sixties, but fell out of favor in the seventies, and has only recently made a comeback. Modern parachutes use a ram-air system to pressurise a series of cells to provide the aerofoil shape.
At low speeds (subsonic speeds) increases in static pressure are however limited to a few percent. Given that the air velocity is reduced to zero without losses the pressure increase can be calculated according to:
dP / P = (v2) / (2RT)
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
26 Mar 2008 12:09 |
Looks like these guys are doomed then.
http://www.ramairbox.com/
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
26 Mar 2008 12:20 |
because I'm a sceptic (and we've done a few very unscientific tests on our dyno) I still tend to think its because the engine is being fed clean cool air via the 'ram air' system rather than the effect of any 'positive' pressure influence gained. Evryone harps on about 'static' pressure but to feed a high revving litre bike with air takes an awful lot of air never mind trying to keep that air at above atmospheric pressure within the confines of a motorcycle airbox.
Given that wikepedia:
At low speeds (subsonic speeds) increases in static pressure are however limited to a few percent. Given that the air velocity is reduced to zero without losses the pressure increase can be calculated according to: dP / P = (v2) / (2RT) |
what does the dp/p=(v2)/(2RT) actually stand for? I would guess dp/p is the pressure int he airbox divided by atmospheric? v would be velocity? divided by ???
can some one throw a light on this?
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Cerberus
Connecticut,
USA
Posts: 5,163
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Enthusiast
26 Mar 2008 12:24 |
a few % increase in static pressure should have a real measurable effect on performance.
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
26 Mar 2008 12:34 |
but we are talking less than ~700mph...I should imagine the losses are great the slower you go.
What size a Triumph airbox? 3 litres? How much air does the engine need per revolution...1/3 litre? so at 10,000 rpm it needs around 3000 litres a minute or 50 litres a second? from a 3 litre airbox; so that needs to be filled 17 times a second to maintain static atmospheric pressure....thats a lot of air.
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Garry Peterson
Sth National Park,
Australia
Posts: 82
Daytona 955i (99-01)
26 Mar 2008 19:07 |
Steve, I could go into the fluid dynamics and you know my background..but really its lost on 98% of people as its boring to an extent...although the theory closely follows the practical data that has been logged ..mostly on Hayabusa's as these tend to dominate Land Speed events
Alot depends on the position of the "ram air" intakes and if they are in a high or low pressure area in front of the bike..the clean , cool and undisturbed attribute of the ducts is prob more important for most road bikes.
R stands for the Universal Gas constant..PV=........
You'll never supply enough air to obtain positive pressure on a dyno with a Hayabusa on it...Xman you are on the right track..they consume enormous volumes of air...and if its cold air even better..density
The other thing is,,, to "gain" any benefit from ram air dynamics at speed is that you need a completely sealed airbox and the ducts leading to it from the front fairing??? anyone looked at the triumph setups???...pretty poor from my observations
Xman you are correct in the calc at 100% VE's , however the air demand is often less than this BUT often greater than 100% VE with N/A motors and resonate tuning plays a vital role ..as Steve P said air boxes can blow apart from this or vibrate in and out..maybe 1/2 to 1psi over an area of X..do the maths
Well designed ram air can yield up to 6 or 7 % increase in power at 200mph..
Now back to earth where we all ride at legal speed limits.....ram air aint worth a pinch of salt.
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
26 Mar 2008 21:10 |
Thanks Garry, I thought you were going to get all technical and fill the post with your excellent knowledge of making an engine go very fast for a long time.
So bottom line is we are all of the opinion that a well a designed airbox with good ducting to collect clean cool air from the front of the bike is advantageous.
The pissy little revers intake on the top of a 2002 Daytona airbox with a little hole would greatly be improved by a redesigned the airbox and using ducted tubes!!!
Ram air dose work if it’s designed correctly and you are going over 160 mph, but it’s not very effective at 30 mph around town or a blast up the strip because you would only see results at the very end of the strip just as you are about to shut off.
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
26 Mar 2008 22:13 |
phew, glad I'm a sceptic and I know shit about fluid dymanics but my gut feeling was along the right lines..we have done a bit of work on the zxr400 wrt to ram air and its benefits.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
26 Mar 2008 22:37 |
My maths gives just under 2% pressure increase at 200 mph which would show almost no increase in power at all... But it's late so someone tell me if I got the equations wrong
Garry - interesting input, thanks for coming in on this
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Manny Fagnet
Poland,sorry Reading,
United Kingdom
Posts: 1,455
Premier Member
Daytona T595 (97-98)
29 Mar 2008 10:28 |
[edited]:
Wow! 71 posts on a phenomenon that arguably doesn't exist!
Seriously though-i enjoyed the above!
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exdane
Santa Rosa,
USA
Posts: 49
Daytona 955i (99-01)
10 Apr 2008 05:50 |
It would seem a 4-stroke liter engine needs 500cc of air per rev. regardless of number of cylinders, not 1/3 l. as x-man speculated.
This in turn means the air-box has to be filled 25 times/second, - even more of a task.
Could it be that rather than focusing on achieving positive pressure in the air-box, simply approaching atmospheric pressure is a measurable advantage?
I'm with Steve on this one. Common, or maybe not so common, sense would appear to dictate that air-fill is better with the ram-air than with the little 'pissy revers' intakes of the '02
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Android
Dereham, Norfolk,
United Kingdom
Posts: 574
Premier Member
Daytona T595 (97-98)
15 Apr 2008 23:30 |
Mmmm....nufink like a bit ov science eh!
It surprises me that 'O' level physics wasn't used to prove that speeding up air reduces its pressure.
I would've used the theory of flight as the easiest explanation because everyone accepts/understands that aircraft fly.
An aircraft wing has a cross-sectional shape which is flat on the bottom surface and curved on the upper surface. As the wing moves forwards its leading edge splits the air, this air has to run over and under the wing and join back up at the trailing edge.
In order for this to happen the air running over the top surface has further to travel and therefore travels faster to get to the trailing edge than the air moving in a straight line under the wing.
When the air travels faster relative to the slower air its pressure drops relatively. This means air pressure under the wing is higher and it is this which pushes the wing up creating lift to acheive flight.
If you sit on an aircraft wing when its flying you will feel the force of the air pushing you backwards off the wing and the same applies to underneath. So this shows there is a dynamic pressure that comes from moving forward through air but it is the relative change in static pressure above the wing that creates the lift.
That is my understanding, or lack of it. Which brings me down firmly on Peter Sorrell's side of the arguement.
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
Premier Member
Enthusiast
16 Apr 2008 11:03 |
[edited]:
exadane, I don't think anyone is saying that filing the airbox with cold clean air as much as you can is anything but the right ting to do. Indeed I reckon that if you can keep the the airbox around atmospheric then that will give a measurable gain; the discussion hinges around whether you can get the airbox to a positive pressure that is significant wrt atmospheric....of course any increase will transfer directly to power.
On a different subject can you explain the machining to the speedo drive to me for fitting k5/6 legs to a Triumph?
Oh Android, can you come back to this when you are off the drugs m8.....
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Android
Dereham, Norfolk,
United Kingdom
Posts: 574
Premier Member
Daytona T595 (97-98)
16 Apr 2008 13:41 |
X-Man I'm still 'flying' mate
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
Premier Member
Enthusiast
16 Apr 2008 18:05 |
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
18 Apr 2008 00:12 |
Still gets me, how when a bike is dynoed and is set with an AFR of 12:1 at high rpm and on the track flat strap at high speed it’s reading 12.5:1 with the same wideband commander 02 sniffer that was used on the dyno. The engine was not hot; it was at running temp on the dyno.
So what as changed? I can only think that it’s the airflow. Lots of air being forced into the airbox at high speed as changed the AFR. This test has been done at different days with both good and bad weather. Both Dyno and track are at sea levels.
This is what I have found in the real world, no maths and charts, there are lots of constant changing factors that are at play in the test bed that will not always show itself on paper.
Here we go again……………
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Cerberus
Connecticut,
USA
Posts: 5,163
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Enthusiast
18 Apr 2008 04:02 |
another factor to add to that Steve, is the vacuum scavenging of the exhaust(from the negative pressure pocket behind the exhaust outlet at speed), helping to create greater flow.
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
18 Apr 2008 08:32 |
Are you positive it’s negative?
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X-Man
Chesterfield/Derbys,
United Kingdom
Posts: 8,379
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Enthusiast
18 Apr 2008 11:03 |
carbs or injection? cos if injection then there are too many variables....
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Cerberus
Connecticut,
USA
Posts: 5,163
Premier Member
Enthusiast
18 Apr 2008 11:46 |
steve.. i guess its not really negative pressure per se
maybe a more proper term is a relatively low pressure pocket.
i'm not positive its negative..
but i'm positive its not positive
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Paddy3101
Hampshire,
United Kingdom
Posts: 88
Premier Member
Daytona T595 (97-98)
18 Apr 2008 13:02 |
In terms of preasure, everything is relative. You can't really have "negative" preasure.
The difference in preasure can be negative. But that just depends on which direction you are measureing it in.
Same with velocity, are you accelarating the air up to the speed of the bike as it enters the air-box, or are you slowing the air down to zero in the air-box.
Doesn't really matter which way round you look for the formulas, just need to use the right reference point...
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Steve Phillips RaceComp
Adelaide,
Australia
Posts: 535
Premier Member
Speed Triple (05->)
03 May 2008 09:36 |
Well I have emailed my contacts at Ducati Corse and at Loughborough University so hopefully will get some independent and learned opinions back in the next couple of weeks. I'll post whatever I hear in support or against...
Any news from the boffins then PS?
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
04 May 2008 22:52 |
Steve - still waiting on my guy at Loughborough but Ducati came back with - "it's permissable (in racing) and if it worked we would use it - we don't" - which whilst a useful indication is hardly scientific so still waiting....
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tim seyffert
llandrindod wells,
United Kingdom
Posts: 679
Premier Member
Daytona T595 (97-98)
05 May 2008 11:18 |
my only take on this above is that when i ran a ford rs turbo s1 in the depths of winter on a cold and frosty morning the car youd to go like stink, stick it on a really hot summers day and the difference was highly noticable, something to do with density of the air methinks, no science or maths reqd just seat of the pants testing.
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Peter Sorrell
South East,
United Kingdom
Posts: 819
Premier Member
Daytona 955i (04->)
05 May 2008 11:23 |
Tim
Cool air is much denser and on a turbo car particularly you will see a marked difference - especially if they have poor intercooling like the fords. This is however, not in dispute at all - cool air is always better and a good supply of cool air is essential but what we all seem unsure of is whether Ram air works - that is effectively using the speed of the bike moving through the air to force air under above atmospheric pressure into the engine - like a free turbo in effect. Most of us seem to think it's rubbish but a few think not - and the science so far shows both sides hence the confussion!!
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StumpyDave
Lincolnshire,
United Kingdom
Posts: 1,206
Premier Member
Daytona 955i (04->)
08 May 2008 12:51 |
If maintaining a neutral pressure were sufficient, would engines perform better with open bellmouths.
Sitting the air intake in open atmosphere should get you pretty close to a neutral intake pressure. It is possible that this would then be too variable with movement and wind to allow the injection system to accurately meter the pressure available.
My fluid mechanics knowledge is limited. Laminar flow at a more macro scale for CivEng doesn't scale well to this type of issue.
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