exhaust stuff

[andrewd]

this question goes out to all those that DONT LIKE TO HAVe FUN (courtesy of carroll smith; tune to win) and design exhaust systems here

what sort of collectors do you use? (merge, venturi merge, dump) why would you choose a 4-2-1 over a 4-1, and why dont you all choose the straightest free flowingest pipe design as possible?

cheers all

[DVS`MiRaGe]

i havent designed a exhaust system to answer you collector question but generally 4-2-1 is for an increase in torque with the longer secondary's shifting the max torque up and down the rev range, the 4-1 is for max power

why not to use the most free flowing, there is a requirement for back pressure, the exhaust pressure helps the intake

[Bam Bam]

Q1 Venturi merge - Just cause

Q2 4-2-1 - More tuning possibilities, potential for flatter torque curve

Q3 when your breathing through a 20mm restrictor it takes some talent to make exhaust back pressure a problem.

[imajerk]

4-2-1 can be chosen for a flatter torque curve... that's about it. However, it can create torque which is not reasonable to use, unless you are in the wrong gear (to high). There is no use creating so much torque down low or midrange that you can't use it all (especially in 1st gear).

They are also more complex to design... and can be pigs to use in future cars as chassis design changes etc.

I lean towards very short 4-1 headers as they are simple, and allow the engine to be used from very low RPM to very high RPM because it's not highly ˜tuned'. There is a common misconception that short exhausts are only for high RPM... this is wrong. Just have a look at GM's new V6.

As for collectors, I've used a few different types; Y's, venturi, dumps and drawn. I prefer drawn, as they allow the collectors length to be shorter as it uses the incoming tubes deformations to smooth flow.

Just to blow the lid, I'll give you an idea of what you could be looking at for exhaust and intake.

4-1
(measurements to the valve face)
Intake
Length: 200mm
At approx.: 1300mm2
Incline: 1.5-2deg (large inclines above 3deg can hurt power if you don't know what you are doing, especially on these restricted engines)

Exhaust
Primary
Length: 295mm
Diameter: 34.2mm
Collector: Drawn (this is where you deform the 4 tubes to an ˜X' and have a teardrop outside merging to the tail)
Tail
Length: 600-700mm
Diameter: 47.6mm

4-2-1
Intake
Same

Exhaust
Primary
Length: 400mm
Diameter: 34.2mm
Collector: Drawn (force the 2 tubes to have a flat face between each other)
Secondary
Length: 500mm
Diameter: 42.7mm
Collector: Drawn
Tail
Length: 600-700mm
Diameter: 47.6mm

Now... something that shouldn't be overlooked is the fact the tail has a HUGE impact on the torque curve, so make sure when you dyno you have the muffler on and run into a large chamber (of course, watch out for chamber resonances) so you can make informed decisions about final tail length.

[Jon Prevost]

We use a 4-1 exhaust for focal tuning points. We look at our exhaust as giving us our low end power and the intake is then used to mask over the anti-tuning peak and provide a wide enough power band to be useful. That is with our old single runner intake. Dual runner and crossovers are just like 4-2-1, it's crazy. You will get cylinder favoring at different rpm since pulses will follow one. Think of it as drafting. In the exhaust it isn't as bad as cross-over tubes but it's still there. The only time I would use a 4-2-1 or fancy intake cross-overs is if I had the ability to do individual cylinder trim dependant on rpm. Else go with the classic 4-1 for both intake and exhaust.
Backpressure is always bad and it never helps the intake... ever. If anything, a lower pressure in the exhaust will help cylinder filling. This effect even happens if you have cams with no overlap!
That comment about look at the new GM v6 makes no sense to me. Could you please elaborate. I was under the impression that "short" exhaust headers/manifolds were used for cost and reliability. I wouldn't compare a v6 sedan engine to a race 4 cylinder. It's a completely different beast. We use a pretty short exhaust to help with our high end and then longer (in general) intake for giving use the broader power band. Like I said before. The exhaust gives you one really good point in our usable rpm range. The intake gives you two on a 4 cylinder with these high revs. Tuning the intake to be spread "around" the exhaust peak is usually a good idea. The intake can give you the low end and the "spread" is perfect for tuning right before redline... usually.
Another thing that contradicts with what you've concluded is the impact on the torque from secondary lengths. We have found through testing that the muffler (at least our straight through designs) have had almost nil of an effect on the torque curve. It didn't change anything exhaust rob a lb or 2 on the torque curve. It didn't change the peaks points or the general shape. The collector diameter, primary lengths and diameter make the curve. Everything else is for the rules and/or packaging.

, Jon
"Success - it 's what
you do with what you've got." - Woody Hayes
Engine Team

[imajerk]

The new V6 has something similar to what you'd see on an old diesel engine (not surprising from that particular contracted design company). Cost is the biggest issue... but the point I was making is that the engine has a huge RPM band, and doesn't suffer in the lower RPM due to a short exhaust. To say short intake or long exhaust gives a particular effect is premature – it's the whole package that gives a desired effect.

I wasn't commenting on muffler in particular... but the work I've done - tail length does impact dramatically on the torque curve. But, it depends on the whole system as I just mentioned. I simply advised to run with the muffler on to give a true indication of what the engine is doing, and in the event a non straight through muffler is used one would be able to pickup any possible ill-effects so any unwanted holes can be remedied. I've made no contradiction, but if varying tail length makes no difference I'd run as short as possible.

You are right about how to go about tuning an engine... it's a package and tunning the intake and exhaust at different spots gives a nice mix. I call this detuning the enginehttp://fsae.com/groupee_common/emoticons/icon_smile.gif

[PatClarke]

At FSAEA, Ron Tauranac was very critical of the joints in the headers of virtually every car. He holds that the exhaust runners should blend together at a steeper angle so the area across the collector is the same as the header pipes themselves. This to avoid a pressure drop reflecting a wave to confuse the extraction process.
His experience dated back to the Coventry Climax engines in the late '60s, where the headers used on the dyno were far less sexy looking than the ones they built at Brabham, yet they worked better. He has seen nothing in the intervening years to disprove that, and quoted the merge angles used by the 5 into 1 headers used on Formula 1 engines today.
PDR

Rudeness is a weak mans imitation of strength

[andrewd]

hmmm thankyou for you comments ppls http://fsae.com/groupee_common/emoticons/icon_wink.gif very interesting indeed.

so pdr what you are trying to say there about the steep angle collectors is to the affect of:

TUNING OUT UNWANTED PULSES???

thats what i used for our venturi merge collectors (it was a 25 deg angle each pipe) and then the venturi was used to tune out / aid certain frequencies, plus they give an added strength to the pulses too (which might be where we gained power? alot of other factors to consider tho)

i dont agree with imajerk's post about short as' 4-1 headers because most car headers are cast.

i also found that since our exhaust WAS not constructed from a single length of pipe, that the individual bends and additions here and there would also help to broaden and hinder (in parts) scavenging.

i also believe that the original ports on the engine are oversized! http://fsae.com/groupee_common/emoticons/icon_wink.gif

this all coming from a first year uni student and fsae contender so if im wrong: corrections all round http://fsae.com/groupee_common/emoticons/icon_wink.gif

[PatClarke]

I guess if you have a rapid increase in the tube diameter, then the pulses may think they have reached atmosphere and some energy will be reflected back from the junction rather than from the end of the pipe.
PDR

Rudeness is a weak mans imitation of strength

[imajerk]

dboi, just because most cars exhausts are cast doesn't mean the manifold has to be short and simple. I'm around engines of all types every second day and a lot of cast exhausts now are complex - to put it lightly (ie equal length with very interesting twists and turns). Disagree if you want, but the fact something is cast is no excuse to make simple manifolds. Like I've said a few times, it's the whole package – everything affects each other.

Pat, Ferrari's F1's collector over the past few years has really tightened up; it is very short now and has a high incident angle. It's really weird to look at an older engine and look at the ˜03 and see the exhaust much smaller and the collector almost nothing from something that used to be so long. However, there may be aerodynamic advantages from tightening the collector to tighten up the back of the car etc. The drawn type collector I talk about is practical the same but requires the inside walls of the primaries to be pressed together and ˜drawn' out.

Also, the magnitude of the reflected wave is proportional to the change in area...

[andrewd]

interesting, but we are all talking about pulse tuning here right, not neccesarily talking about flow charateristics (which still should be considered- a straighter pipe is still better than a bent one)

[imajerk]

I did a design paper early this year, and anyway, the idea about primaries going into a secondary and a then a tailpipe (or whatever the arraignment), is to create low-pressure regions just over the valve as it opens (to pull the exhaust out; opposite for intake). So, you can set-up a multitude of reflected waves, which at different RPMS hit the valve with low pressure. So, in fact you way want a reflection at a collector, and than another reflection latter on... also, you can get wave reflections from bends. Like I've said, the change in area dictates the strength of the reflected wave, so the less the change in area in the primaries collector, the more reliant the engine is on the tail length etc.

Giving a high incident angle can either be good or bad – it depends on internal geometry – not just the incident angle. For example, a Y collector with high incident CAN create a larger reflected wave than a dump collector.

In conclusion...

[Daves]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>what sort of collectors do you use? (merge, venturi merge, dump) why would you choose a 4-2-1 over a 4-1, and why dont you all choose the straightest free flowingest pipe design as possible?<HR></BLOCKQUOTE>
First, I chose the 4-2-1 because it is lighter weight than 4-1. With 4-2-1, the primary tubes only have to be half as long as compared with 4-1. This is due to the "interference action" mentioned in Philip H. Smith's book The Scientific Design of Exhaust and Intake Systems.

Secondly, I chose the 4-2-1 for its improved silencing due to the high pressure waves entering the interference branch instead of the main primary tubing.

Thirdly, the 4-2-1 was chosen for its improved midrange power over the 4-1, but I am not certain that this is true with our engine yet.

Finally, I chose the 4-2-1 for its smaller packaging. Since the tubes only need to be half as long, they can collect sooner. This means fewer bends in the tubing.

All "merge" collectors are of the Venturi design. Ones that are not are simply named for how many tubes they combine, such as 4-into-1 collectors.

Lastly, I did choose "the straightest free flowingest pipe design as possible." Please see the prototype model picture.

http://what3542.5u.com/dave/fsae/2004_exhaust.jpg

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[Brent Howard]

That looks quite large. Where does your driver sit? In our car that exhaust system would not package at all, however the driver would have a great seat warmer.

Brent

www.ucalgary.ca/fsae (http://www.ucalgary.ca/fsae)

[andrewd]

dude that is choice work there mate http://fsae.com/groupee_common/emoticons/icon_wink.gif

i found tho that the 4-2-1 was actually the same length as the 4-1, its just the collecting stage was somewhere before the last / 4-1 collector would be placed

ive also noticed that some ppl dont run with a tailpipe (tube from last collector to the muff)

why is this??

[James Waltman]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by dave_s:
First, I chose the 4-2-1 because it is lighter weight than 4-1. With 4-2-1, the primary tubes only have to be half as long as compared with 4-1. This is due to the "interference action" mentioned in Philip H. Smith's book _The Scientific Design of Exhaust and Intake Systems_.

Finally, I chose the 4-2-1 for its smaller packaging. Since the tubes only need to be half as long, they can collect sooner. This means fewer bends in the tubing.
<HR></BLOCKQUOTE>

Dave,
Can you clarify why 4-2-1 is lighter weight than 4-1? It doesn't make any sense to me. If weight was a consideration in your design why is the system so long? What tubing are you using and what do you expect the final weight to be. I suspect your system will be very heavy.

Smaller packaging can't really be a concern of yours either, can it? That thing is huge. Can you post a pic of your chassis? We can't figure out where the driver sits.

What is you target RPM range for resonance?
Do you have provisions for the tubes to change size as they heat up?
Are your primary runners the same length? It is tough to tell in the picture.

I'm not trying to be hard on you Dave; I just see some flaws with your reasoning. Sweet model.
To open myself up for equal criticism I have posted pics of our two headers.

First is our naturally aspirated set. 4-2-1 with slip fits at each joint. The next two are our turbo set. 4-1
http://dot.etec.wwu.edu/fsae/v35/images/Headers%202_JPG.jpg

http://dot.etec.wwu.edu/fsae/SharedPictures/Turbo%20Headers/DSC04523.JPG
http://dot.etec.wwu.edu/fsae/SharedPictures/Turbo%20Headers/DSC04546.JPG

James Waltman
http://dot.etec.wwu.edu/fsae/
Vehicle Research Institute at
Western Washington University

[Daves]

The header will make a nice seat warmer for our driver, but it did last year, too. I may have to shorten the primaries or angle them to our 45 degree seat angle, but they can stand to be shortened since this is an extremely high-rpm engine compared to a street car.

Dboi, Wollongong used a tailpipe before and after their muffler last year. However, I do not think a tailpipe is advantageous for high-rpm power. Every length of tailpipe adds to the primary length. When doing primary length calculations, the tailpipe length is included in the length that appears to just be for primaries. Also, a tailpipe adds an additional 2 or 3 pounds, which is not really desired in the exhaust system.

Why do you think a tailpipe might be necessary? I myself am not very clear on this topic.

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[Daves]

James,

I am basing the lighter weight theory on the following from Philip H. Smith:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>A four-cylinder system designed to make use of interference (4-2-1) phenomena would require its cylinder branches to be half the length, or less, of the equivalent branches when these are arranged to operate independently. (4-into-1)<HR></BLOCKQUOTE>

I interpret his book to say that longer primary tubes are necessary for independence of the cylinders, so the exhaust gas from one cylinder does not enter the adjacent cylinder as on most cast iron factory car manifolds.

Then he says for a given engine and rpm, there is a critical length of primary tubing needed for proper scavenging. Above this critical length, the pressure wave will not become any larger or smaller. This critical length changes with rpm, though. At 10,500 rpm (where we want peak bhp), the critical length is probably under 1 foot.

Finally, he goes on to give formulas for primary length. Using his first formula based on maximum torque at 8200 rpm, I get a primary length of 33 inches. Using his second formula (based on valve throat diameter, bore, stroke, valve overlap), I get a primary length of 21.5 inches.

For how high rpm these engines are, I'd say 21.5 inches is sufficient. Based on the theory given by the author in the quote above, if a 4-2-1 design is used, the tubes only need to be half the length to the first junction when compared to a 4-1 design. Therefore, for the length after the first junction, only 2 tubes must be used instead of 4.

To simplify:
4-1 design: 21.5" primaries
4-2-1 design: (21.5"/2)=10.75" primaries

However, the author does not give a formula for calculating secondary lengths. In this case, both 10.75" primaries and secondaries would probably be sufficient.

So 4-2-1 is lighter than 4-1 (for the same design constraints) because it uses less tubing.

Now about the model I presented earlier. I know the angle probably runs into the seat and the tubes are altogether longer than necessary for this F4i engine. I do not have access to our entire car model as I am at home right now. I can tell you that I got those dimensions from the same book I got the other dimensions. Here is another quote:
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>In the case of a four-cylinder having four ports, the paired Y-branches from the outer and inner cylinders should merge at a distance of not more than 18 in. from the flange (on the head).<HR></BLOCKQUOTE>
There is also a picture showing 18" primaries and 24" secondaries. That is why I am showing 18" primaries and 24" secondaries. I will change this model to fit our chassis, so the primaries may be about 11" with 11" secondaries.

Please see the picture for the next-to-most-recent header I modeled at school. I was basing that header on some SAE papers by Lawrence.T.U. The only purpose of showing this header is to tell you that it fits our chassis, so there is plenty of room for a header that long. Our fuel tank placement may be controversial, though.
http://what3542.5u.com/dave/fsae/old_exhaust_design.jpg

Now back to my most recent model:
The tubing we are using is 1.375" 18-gauge (.049" thick) mild steel for primaries. Then 1.625" 18-gague for secondaries. Then 2" for the final outlet. With a density of .283 lbs/in.^3, Solidworks says the header alone is 8.25 pounds, so I expect the final weight (if that one is built) to be 10 pounds.

After shortening, it may go down to 7 or 8 pounds, and it may be stainless steel at .290 lbs/in^3.

Our target rpm for peak torque is 8200 rpm and for horsepower is 10,500 rpm.

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Do you have provisions for the tubes to change size as they heat up?<HR></BLOCKQUOTE>
What do you mean? How is this reliably possible?

Yes, the primaries are equal-length (in all pictures), even though they may appear to not be.

One area I'd like help with is secondary lengths and tailpipe lengths.

Now for the criticism about your headers:
Your primaries look to be awfully large diameter. Are they 1.5"? We have used 1.5" the past two years, and they seem to work well. The greatest part is that all local muffler shops have 1.5" tubing. However, theoretically, it seems too large unless not collecting. How did you get such short secondary lengths? And how did you get such long primaries (look about 24")?

Your 4-1 turbo header looks kind of short, but you can get away with that because of blow-through and the higher velocities. Why did you not use a merged collector for this application, though? The collector does not appear to taper at all. Also, I hope your header is not supporting the turbocharger. Why do you have two outlets from the turbocharger? Are you attaching two mufflers?

[This message was edited by dave_s on January 04, 2004 at 08:32 PM.]

[Matt Gignac]

The two outlets are for the main turbine outlet and for the blow-off valve outlet.

I'm assuming you'd need some kind of collector or two mufflers, or do you even need a muffler if you are able to keep the noise under 110db?

We run a turbo, and a tiny little 8" long muffler that was enough to keep us under 110db, and at 2000 rpm above the engine speed we were supposed to test at. I'd be interested to know if the muffler is absolutely required if we can get the noise level under 110 db without it?

Matt Gignac
McGill Racing Team

[Charlie]

When you are trying to decide what RPM range you want your exhaust to boost, try to be open minded. Instead of just assuming you want help around your theoretical peak tq or bhp number, think about the deficient areas of the power curve. I think you'll find you can boost other areas of your power curve using your exhaust while losing little or nothing vs. focusing on your peak tq.

Your intake will still determine the bulk of your power curve's shape. Use your exhaust (which is much easier to modify and can package a nearly infinite amount of ways) to make your curve better and your car more driveable.

Not-so-great pic of our header & collector (http://www.eng.auburn.edu/organizations/SAE/AUFSAE/03scales.jpg)

-Charlie Ping

I just need enough to tide me over until I need more.

[James Waltman]

I think that you were asking how to allow for expansion and movement. We used a slip joint on the NA headers. There are several other ways to do it though. Some production cars use flexible exhaust tube or ball joint flanges. It might not even be necessary that's why I was asking.
http://dot.etec.wwu.edu/fsae/SharedPictures/DSC02169.JPG

All our primary tube is 1 3/8"�. I wasn't the one that did the calculations for the lengths but we were trying to go longer to bring the power down in the RPM range. Also, packaging was a major motivator in primary length on the NA set. We don't have room to make them join behind the driver.

Yes, the turbo header is short - about as short as we can get it. We would have made it shorter if we could have. The taper for the collector is dictated by the size of the four tubes going in and the turbo inlet size. What sort of taper do you think it should have? Is a merged collector what you have in your drawings? Why should we have used a merged collector? That pic of the turbo header was taken right as they were completed. The support for it had not been completed yet.

We are going to get the sound equipment on it soon to see if it will work. We have done two turbo cars here before and neither has used a muffler. The tail pipes on those cars are a little more substantial than what I showed here. Both previous cars had the wastegate outlet collector integrated with the main turbine outlet collector. We are hoping that we can get away with it. It looks mean doesn't it?
http://dot.etec.wwu.edu/fsae/SharedPictures/Turbo%20Headers/DSC04552.JPG



James Waltman
http://dot.etec.wwu.edu/fsae/
Vehicle Research Institute at
Western Washington University

[This message was edited by James Waltman on January 04, 2004 at 09:38 PM.]

[andrewd]

the idea of the tailpipe is to increase the power range, and we found this critical in the design of the headers...

we also found that while keeping the over length of the exhaust the same, that changing collector position by reducing or increasing
primary and secondary lengths that we could broaden the rpm range further...

it was also noted that while this is a restricted engine, smaller header pipe diameters actually increased power, rather than deteriorated it...

lastly (for now) is the choice of header arrangement, i dont mean 4-2-1 or 4-1 rubbish, but rather its physical ARRANGEMENT or packaging, a free flowing exhaust (straightest possible tubing) on an engine can still produce a wack curve, while the same length piping and different arrangement can produce a smoother curve!, why do you ask?

my guess is this; if you have cylinders running differently, by means of lean and richness, then each primary WONT produce the same strengthed pulse. so to accommidate this, you need to choose a different arrangement by slightly longer or short headers on one group (4-2) and or constriction through bends...

ciao

[Daves]

Regarding expansion and movement, I know Wollongong and Michigan State used spring clips to hold their exhaust together last year. I thought this was for quick disassembly. Michigan State pulled their exhaust apart in front of our eyes, but they kind of had to in order to reach anything. In our case, I don't trust slip joints or springs. We will be welding as much of it as we can. We will also ceramic coat the inside and out to reduce heat transfer. We may also use stainless steel to reduce heat transfer, but that's the only reason I can see for using stainless steel.

To allow for movement, I will use rubber mounts to mount the muffler to the chassis. If short enough, the header will only need to mount to the engine head.

I did not show merged collectors in either of my drawings because they are usually not helpful for 2 into 1 collectors (which we will use 3 of). However, Car Craft wrote an article about merge collectors located at http://www.carcraft.com/techarticles/0304_merg/. This picture shows the difference between a regular 4-into-1 collector and merged one.(top to bottom)http://www.carcraft.com/carcraft/techarticles/116_0304_merg_1_s.jpg

I think the theory behind a 4-1 merged collector is that it smooths out the flow (reduces turbulence) after collecting. However, it is not better in all applications. It would be interesting to try it, though. In fact, Burns Stainless (http://burnsstainless.com/) sells all their collectors as "merge collectors." These are way overpriced (way cheaper elsewhere), but I'm just illustrating that they are at such an advantage that they are the only kind Burns sell.

I hope the turbo alone works well at silencing. If it does, it may mean many more teams will be turbocharging soon. I did notice yesterday that the photos of one of the Vikings (the white one) did not have a separate muffler

About designing for lower rpm horsepower, the effect may be the following (from our 2002 car):
http://what3542.5u.com/dave/fsae/2002_dyno_sheet.gif This system (intake only - the exhaust dimensions and geometry were copied from the Honda header) was designed for maximum torque at 8500 rpm. [edited] It achieves maximum torque there, but I don't like how it affects the horsepower curve. It is kind of annoying when driving this car to get shot forward twice. Last year I believe our team designed for peak torque at 10,000 rpm.

2 things I am concerned about for our car are the following:
1. Will our aluminum muffler hold up during dyno testing?
2. Is there much to be gained by using dual exhaust with the F4i?

[This message was edited by dave_s on January 05, 2004 at 08:12 AM.]

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>This system was designed for maximum torque at 8500 rpm. A jump is noticed at 8500, but it certainly isn't the peak.

That's something I've noticed about the restricted F4i engines -- the peak horsepower and torque are at the same rpm, unlike the unrestricted engine.<HR></BLOCKQUOTE>

If your torque peak is not at 8500, then where is it? You are saying your peak HP and peak TQ are at the same RPM? Am I reading your graph wrong or something?

Why would dual exhaust be beneficial in any 4 cylinder?

As for the torque curve, that is pretty good. So why not use your exhaust to fill that hole?

-Charlie Ping

I just need enough to tide me over until I need more.

[Daves]

I made a mistake, but I corrected it.

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[andrewd]

sorry wrong post above

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by dave_s:
Regarding expansion and movement, I know Wollongong and Michigan State used spring clips to hold their exhaust together last year.
[This message was edited by dave_s on January 05, 2004 at 08:12 AM.]<HR></BLOCKQUOTE>

thats cause i designed the gongs exhaust,

everything was slip on, cause it was easiest to manufacture (questionable), and could be easily dissasembled and reassembled

regarding leakages, these puppies are negligable, and after a short time are stopped because of the carbon deposits

[Daves]

Is this a photo of the exhaust you designed, Dboi? What was your overall header length? What were your primary lengths and secondary lengths? How was your engine horsepower curve? What did you use to do those fancy bends?
http://what3542.5u.com/dave/fsae/Dec_May_08.jpg

Neglecting the discontinuities, what do you think of this? 26" total length (until secondary collector)= 11" primary length + 17" secondary length. Maximum torque hopefully at 10,500 rpm.
http://what3542.5u.com/dave/fsae/26_inch_exhaust.jpg

[This message was edited by dave_s on January 06, 2004 at 12:42 AM.]

[andrewd]

no sorry that exhaust was for stumpy

did you see this years exhaust on serge?

we made an extra 1 kw abroad and 5Nm EVERYWHERE

whether that can be put down to exhaust alone is not my decision, we engine boys did shit loads of testing (in the order of and mostly greater than 100 dyno testings of different setups), and credit goes out to all the boys, when had improved intake, sump, cooling (yes thats right) and exhaust this year...

all those sexy curves were constructed from simple elbow bends of different radii and angles and cut and shut to fit...
http://fsae.com/groupee_common/emoticons/icon_wink.gif

hope that helps

[Daves]

No, I have not seen serge's exhaust.

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