View Full Version : Ram air v forced air Final conclusions ... looong.
05-31-2003, 01:25 AM
Some of you may have been following 2 of the threads on the RSVR.net forum regarding this. It kind of degenerated into asealed v unsealed argument but at least lots of people including me learned loads about the RSV's engine characteristics.
I managed to get data from dynos, the road, the track, 2 race teams and a shedload of theory. Here are the results of my tests and conclusions.
First, there is no doubting that ram air works on some bikes. I don't think the time, effort and money involved in putting a true ram air system on our RSV will provide any greater benefit over the aftermarket airkits available at the moment. The RSV engine is starved of air, Aprilia must have known this which is why they opted for a forced air system instead. Maybe with a new engine that breathes better they will produce a ram air system - pressurised airbox, air pressure sensor in the airbox and a feed into the ECU (have I missed anything ?)
The debate then turned into a sealed v unsealed debate. tests were carried out in a 240 kph wind tunnel, various dynos and on the road and track.
As the big fan test carried out on this site concluded the RSV produces more power with fans on. I already knew this nearly 2 years ago. I enlisted the help at some stages of Jorge seeing as my own bike which I was testing too had his airkit in. I ran tests using a sealed and unsealed system. The findings were:
a) Both systems provided more power than stock
b) both systems produced more power with a 10mm spacer raising the tank a little - a little Jorge trick - lol.
c) both systems produced even more power with the tank raised a lot - another Jorge trick.
On the road/track this was confirmed. The pull from 3K was trememdous. We used the 98-00 air boot and raised the tank 10mm with spacers. You can all try this yourselves and see for yourself - even more power will get produced.
Arguments were made about the potential loss of power due to hot air getting into the engine and a loss of top end because its not sealed. I put those arguments to bed.
This is an airflow test thread. I did it with the help of Jorge just to see what is actually happening in and around the airkit.
<a href="http://pub189.ezboard.com/frsvrnetfrm3.showMessage?topicID=4837.topic" target="top">Airflow test results</a>
I concluded that not only did we get more power with the system unsealed, only because you are limitting the air that can get into the airbox with a sealed system, we gained mad crazy top end too. I have had the bike 2 days now and the top end rush is akin to an inline 4 !! Re hot air, the next time you get a chance feel what comes out of your breather hose, the same hose which goes into you airbox ! If you don't think that is putting hot air in your engine think again.
Jorge made 2 more secret changes to airflow which I am unable to tell you about, it has nothing to do with engine mods though. I am off to an independant dyno operator this morning once I have fitted a new chain to get some thing on paper. They race RSVs and it is rumored that the guy has the most powerful RSV in britain - with minimal engine work !! I'll say what he says about my bike.
I took a lot of crap over my views here and on the RSVR.net site. I feel vindicated now.
Some food for thought. In England we have the RSV Aprilia challenge, its a one make series where the only mods made to the bike must be Aprilia products. No engine work is allowed. Typically the teams run the SP airbox mod and Akrapovic twin cans or RSC cans. There is also a series called the Supertwins. Any size V-twin bike can race without mod limits I think. There are more RSVs on the grid than anything else. I part sponsor a team in it. The top 3 runners in the series run unsealed systems. Also, where the dates permit, some guys from the RSV Challenge race in the Supertwins series, tell me why the front runners take out their SP airbox/airkit and fit an unsealed system to compete ??
Thank you all for your time, no doubt attempts will be made to defunct my findings, thats fine. I can only lead you to the water - you must drink it. If you think I am lying or joking raise your tank 10mm, this will unseal it. Do a dyno run with fans or go for a ride and see for yourself. As a further test, temporarily remove your filter - its too restrictive compared to the Piper Cross filters we use - you will get more power still.
PS, I would like to thank Jorge for his help in some of my tests and for providing data from his own 3 years of testing the RSV.
05-31-2003, 03:52 AM
Nice work Mr Venjer!;)
05-31-2003, 07:49 PM
Yes indeedy, useful stuff.
Couple of questions Kev:
1. You don't mention which "open" airbox you're using. Is it the Renegade?
2. Where do you route the crankcase breather on the Rene to avoid the hot air?
3. I remember reading some threads around rapid clutch wear. There seemed to be a link to the vacuum initiator in modified airboxes. That is, stronger vacuum leading to greater clutch slipping and faster wear. Can you comment on that?
4. Where do you stand on the 5,000rpm flat spot issue? ;)
05-31-2003, 08:44 PM
The vacuum port for the slipper clutch is below the throttle butterflies so airbox changes should have no affect.
05-31-2003, 08:49 PM
And if you really enjoy backin her in "Rossi" style disconnect it and plug the port,,, hhoooo hooo thats fun but kinda dangerous, I'll leave that stuff for my xr100.
05-31-2003, 08:50 PM
Maybe I missed it but could you please explain the difference between ram air and forced air.
05-31-2003, 08:56 PM
Ram'er. I hardly even know her.
06-01-2003, 04:24 PM
Unsealing an airbox kills the resonance effect- you are bound to see some loss of power in the low or midrange. I would love to watch a similar test using an eddy current dyno that can accurately measure part-throttle response and roll-ons. That's at least as important as peak power numbers.
06-02-2003, 09:08 AM
Thanks for the responses. To answer a few questions:
DeTuono, I run the Renegade airkit. The crankcase breather is rerouted to the chain so any excess oil will lubricate the chain. There is a new thread on RSVR.net regarding this very thing with pics too. See<a href="http://pub189.ezboard.com/frsvrnetfrm3.showMessage?topicID=4873.topic" target="top">Rerouting breather</a>
I am not aware of any greater clutch wear on modified airboxes, does anyone have any info on this ?
The 5k and 8k flat spot, hmmm, this was discussed a little while ago. My understanding was that no one mod - exhaust, chip or airkit managed to get rid of the dip. People with various combinations of aftermarket products still had the dips. I don't but I have the rene chip, airkit and slip on exhaust, I have a smooth curve with no dips whatsoever. This weekend an airkit was fitted to a 00 R and although it smoothed the curve the 2 dips were still clearly visible. He had a MHP race can and standard eprom.
Some chips also create a larger than normal dip and then "play catch up". This gives the illusion that the bike is much faster under acceleration but in reality it is merely catching up.
The difference between Ram air and forced air is one utilises a pressurised airbox, sealed and has a air pressure sensor in it that connects to the ECU. Forced air is simply forcing air into the engine. The Ram air effect needs higher speeds to operate where forced air operates at any speed. A ram air system will provide greater benefits at over 120mph but this is not always the case - it may provide a benefit of some kind but to use a blanket argument that it is better than a forced air system - as our RSVs employ - is grossly incorrect.
RickyJ, don't put too much emphasis on the affect of loss of resonance. I was talking to one of the engineers from our race team who brought this up, he mentioned the rule/law regarding this and pulses every 2K or so. He said according to the tests they have run any possible loss of power is negligible and did not need worrying about. All the tests they did were on Valencia's GP circuit using a 240 kph fan and eddy current dynos !
06-02-2003, 11:26 AM
So...why do top factory teams all use sealed systems? Does your friend know something that all the factories don't? It's not meant as a dig, just a sincere query. I've also heard that Jorge doesn't recommend the shorter SP-style stacks that apparently work well with the Evo airkit. Again, why? Regardless of what anybody says, I'd like to see an eddy current shootout between these airbox mods. Seeing is believing, hearing about it's less so...
06-02-2003, 11:45 AM
I'm having trouble with this part...
1) if you raise the tank with the stock airbox you are not "unsealing" it so there should be no difference...so I'll assume you were not talking about doing this on a stock airbox setup.
2) if you raise the tank on the evo "race" style kit then you are allowing air to bypass the filter media which will produce more power and also rob engine life. That is not an argument that the engine is starved for air but that the air filter induces some power loss... which should be a given as it is needed if you want your engine to last. Simply changing to a K&N type or evo filter helps gains some of this power back w/o sacrificing the filtering capability.
I'm not saying the Rene kit doesn't work for you, you sound sold on it. I just don't get the 10 mm test thing for any other design.
You could also remove the tank and get huge power gains but then the bike starts to look funny :D
06-02-2003, 07:12 PM
Ram Air / Forced air??? A question of definition... I agree with the ones given but isn't the real defining factor the pressure sensor?
If, for instance you could achieve a 3 or 4 bar increase in pressure, and tuned for the higher end, the bike would be way rich at high rpm/slow speed. Conversely, if you tuned for the ambient pressure and got up to pressure you would be running very lean. Muzzy used to build the airbox to include the carbs and eliminate the pressure sensing circuits.
Sealed air box??? No air getting in??? I don't think so. Regulating the method of flowing the air maybe but not sealed. The only time you need to worry about sonic pulses is when there is a line of molacules bumping into each other. In an exhaust or "sealed" airbox this can be a problem.
Whaddy Current Dynos??? Why would you want to know how much power you can make at partial throttle openings??? Can I put out a fire peeing on it instead of using an extiguisher??? Can I cook a microwave dinner at half power for twice as long??? Can your wife have an orgasm without batteries??? What is the point???
The reason for the SP stacks not working is velocity. (get it) The air for the longer stroke of the standard engine requires that "tuned pulse" thingy and proper air velocity going into the combustion chamber.
Not that I really know any of this stuff, but it sounds good And so does my open air box.
06-03-2003, 12:36 AM
I've got the SBK replica Akropovic ehaust and the SBK Eprom that comes with it, and the system provides a signifigant boost in power and smoothness, especially in the mid-range. The stock setup's dip in power in the 5500rpm range is gone, but every other mod I've tried (with the exception of the shorter Evoluzione "SP style" velocity stacks) brought the dip right back, regardless of gians elsewhere in the rpm range.
The Evoluzione shorter velocity stacks gave me just over 1 hp from 9Krpm and up, and kept every bit of the lower rpm's pull.
The Evoluzione airbox kit, brought the dip right back, whether with the lid on ("street",with the spacer), or off ("race") (with the flap to seal to the bottom of the tank), and gained less than 2 hp either way, while losing 3-5 hp in the 5,000 to 6,500 rpm range.
The Factory Pro Eprom (on either map) couldn't touch the smoothness of the SBK Eprom (wavy dyno lines), and showed no overall gain on the dyno, but I'll admit it felt "snappier" getting on the throttle, which was fun on the street, but I took it right back out the first wet trackday, where the smoothness and predictability of the SBK chip felt much safer and predictable (read:faster), wet or dry.
About the ram air:
Evoluzione says the race kit isnít guaranteed to seal properly, hence their "dusty conditions" disclaimer. With the barely detectable difference in the lid-on (sealed) vs lid-off (potentially unsealed) airbox dyno curves, running the lid on gives peace of mind (engine longevity?), and versus a not-necessarily-airtight race-box seal (or just the Rene airkit), you know you at least have the potential for some ram air to work.
06-03-2003, 04:50 AM
Some good points raised. Let me answer your questions.
1) RickyJ, top factory teams use sealed systems. However, have you seen the internals of those bikes ? They have nothing in common with the bikes we ride, thats a major difference. Take the RSV SP. You need to spend £15-20K on the bike, then to release the power and get to the 150hp quoted by Aprilia you have to spend a further £15-20K on the superbike upgrade/kit. By that time the bike is totally different. Privateers in BSB and WSB are spending £50K - £100K + on their setups - our bikes cost £8K
2) 02Prilia, yeah, I meant if you have a non stock airbox. Don't misunderstand, the point of raising the tank is to prove you get more air flow and more power. By restricting airflow - sealed airkits, restrictive filters, you are denying air that the RSV needs. Some people ride their bikes with 10mm spacers on permanently, I am only suggesting it as a test. The filter placement plays a big part. By having the filter over the trumpets you maximise airflow but still protect the engine. My butterflies were clean as a whistle when I checked them. Remove your filter for 5 mins and feel the extra power. Tie a stocking over your trumpets to have some protection at least. You must try it to see - the power surge will suprise you. I already did it with an Evo style airkit.
3) HagaSteve - THERE IS NO RAM AIR. Its forced. Any airkit will benefit from forced air on the RSV. You would have to go some and spend loads of cash to get RAM AIR. Lid on/Lid off and engine longevity, don't forget, the unsealed airkit I have has its filter on the trumpets, I am not compromising my engine's safety.
4) Re dyno curves. Simply having a dyno run with small or no fans after an airkit mod seems useless to me. You are not going to see proper gains. With proper dyno fans - a la Fuchs dynos, you will see proper gains. I think the difference between sealed and unsealed may be larger than you might expect. I also want to get our engineer to email me his findings and explanations regarding these pulses. He did tell me but it went WHOOSH - straight over my head LOL.
06-03-2003, 09:33 AM
Would you repeat this test on your eddy current dyno? That's the tool for measuring the overall effect not just top end. Even top racers don't stay WFO for very long, and part-throttle operation is critical- moreso on a streetbike! How's that saying go in Italian? "Fatti...non pugnette".
ed apriliaforum com
06-03-2003, 10:10 AM
we did do it on our eddy-current Factory Pro dyno (built by Mustang).....with plenty of fan power drawing in fresh air from outside (not recycled air)
I love the debate.....more hits than the "big boob" thread......and I'll say this........
all Milles that we work on, and that we want to have max power will have fully sealed ducts.....even smoothed out on the inside.....
why take away what the factory did?? simply improve on it.....the amount of air coming in through the airboot during our tests was convincing enough......your motor will love the fresh cool air coming in at 130mph when your going 130mph.
06-03-2003, 10:14 AM
I will agree that anytime you increase airflow or decrease air resistance then it will result in more power.
By removing the air filter, altering the air filter, or simply bypassing the air filter by raising the tank you will see more power.
This in no way proves the engine is starved for air. I'm not saying the engine would not benefit from easier breathing but that this particular test is giving a false impression.
2 (more) problems I have with what you are saying (and I appreciate the civil debate).
1) Look beyond your butterflys for the dirt build up. I had the "open" type filter over my stacks and when I removed it my butterfly's were clean... but it was just below them where I could see the dirt film accumulating. Now I'm not sure if this same film of dirt would be present with the stock set up but only because the base of the filter seemed to allow leaks at the ends where it was not secured by the side screws. Also the opening for the sensor under the filter area provided an area where unfiltered air could enter the engine so I felt more "safe" with the stock setup.
2) While the more air theory may be valid though not proved by bypassing the filter media, there is one major problem with the filter over stack design (IMHO). The largest volume of air immediately over the stacks produces the best throttle response. Once that air is "used" up then the restrictions of the filter comes into play.
I noticed with the filter over stacks that when I twisted the throttle there was a definite lag before the engine responded. I will admit I felt a stronger pull once past this lag and I thought I could get used to it. Further testing showed I did get used to it but lost power on the top (due to ram/forced air? doesn't matter).
Switching back to the stock setup brought back a noticably better throttle response, a little less initial grunt but stronger top end. Not to mention that I got rid of the oily smell from the breather as well and the extra noise (which some may like). I read somewhere that WSBK Ducati's run air filters in the intake tubes to maximize the airspace "under" the throttle bodies...
If you are racing for money and rebuilding your engine often then the reduced filtering should not be a problem. The extra midrange should help more at the track.
I guess my point is not to say one design is better than another but that by raising the tank or adding fans in an of itself does not prove the engine is starved for air. If you bypass the filter media then what is the point unless you're going to run the bike without filters? If you point 150 mph air down the tubes and gain hp what is the point unless you drive in a hurricane and even then the aerodynamics will aid you more than hp gains.
Thanks for the ear.
btw.. testing was done moded bike vs a standard bike to compare the changes. Variables in temp, wind, etc would affect both bikes the same as they started out side by side in each test.
06-16-2003, 05:29 PM
02Prilia / HagaSteve,
You guys are running the stock box with Evo filter only (02Prilia) and stock box with stock filter (?) with SP stacks (HagaSteve)???
...just lookin' for a little clarity :cool:
06-17-2003, 10:45 AM
Me, stock box evo filter.
06-19-2003, 09:57 PM
after reading this topic, I put on 800 miles since Tuesday afternoon and am now VERY aware of that 5-6.5k flat spot. I'm going to try the stock box again.
Damon Slowpoke Baumann
06-19-2003, 10:52 PM
Just a quick question. You reroute the oil breather to the chain and any mist actually lubricates the chain..Correct?..However isnt the whole idea of running that line to the airbox to create a vacum and seal the piston rings better..Maybe my minds going way out there with what I do to my race cars but I figured the theory was the same..Anyone have input on that??
06-20-2003, 01:05 AM
The breather only vents into the airbox so any fumes go back into the engine where they are burnt - its a emission regs thing.
Mind you I like your theory, how is that supposed to work?
06-20-2003, 09:44 AM
In some applications I believe it is helpful for the pistons to have the least amount of pressure below them. On my Kawasaki the breather tube had a one way valve that allowed air out but not in thus creating a vacuum or at best a low pressure area below the pistons which would help "suck" them down (in reality it would prohibit pressure building up and slowing the piston on the down stroke).
This is all my theory and I don't know if or how it applies to the rotax but the airbox could aid in "sucking" out the air below the pistons as much as rerouting unburnt stuff for emissions.
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