exhaust size?

[kmchow]

What's the exhaust (exit "tip" size) size on racing cars these days--Nascar, F1, CART, IRL, WRC, Nascar, Supertouring, FIA GT, LMP, etc..

thanks ahead.

[Sparky]

Is this just a general enquiry, kmchow, or are you gonna do something fiendish with this info!?

NASCAR tailpipes actually exit from below the left hand sill. Because of the proximity to the ground, the twin pipes are flattened into extended ovals of about 6 x 2 inches (150 x 50mm)I would hazard a guess that the total area of these pipes would be equivalent to a 3.5 - 4 inch (85 - 100mm) diameter.
I am not sure if the diameter varies significantly with track speed/length.
I expect there would be a difference between restricted and unrestricted cars.

Formula 1 exhaust pipes are going through a transition period at the moment. The trend now is to have the pipe exit vertically through the engine cover, to optimise the pipe length. There are twin exits, one per bank of the V10 engine, and each exit is approx. 4 inches (100mm)in diameter. This varies team to team, as the way the pipe exits the bodywork is different in each car.

SuperTouring and WRC exhausts are not that exciting I'm afraid. Most I've seen are singles, approx 3 inches (75mm) in diameter. They (mostly) terminate under the rear bumper.

CART and IRL pipes are similar to F1. The Turbo application of CART doesn't seem to require any increase in diameter. These exit under the rear of the gearbox.

The rest, I'm unsure. There doesn't seem to be any benefit to using an exit diameter of more than 4.5 - 5 inches. (115 - 130mm)
Likewise, no self-respecting engine tuner would use much less than 3 inches diameter on even the smallest ouput engine.

Tuned length appears to be far more important than diameter of section. If the pipe length is calculated correctly, 'pulse extraction' will actually aid exhaust flow, by creating a vacuum in the pipe at the correct time (in relation to the firing stroke.)

I stand to be corrected on any of the above, and I hope it's of some use!

[Sparky]

I've found a pic of Ferrari's upper exhaust vents:



I hope this is the sort of thing you were looking for...

[Crash Test]

Sparky ol chum, i hope Mr Sutton asked for permission to take that photo....it's not the sort of thing Mr Ferrari would go around showing to the public.....

[Peter Mallett]

There's another problem which dictates the size. NOISE. I could run a much more efficient single system and exot it under the sill if I didn't need to put two stonking great big boxes into the system. Ergo, my system exits under the back bumper. Super Touring in the UK suffers the same problem. that may be why the opel Vectras in the German TC performed better than the BTCC Vauxhalls last year.

[kmchow]

I asked the question for several reasons.

1)B/c I wonder if they (real racing ones) look any like the sewer sized (huge) exhaust tips run by most kids today on their street cars.

2) Since I am a big ST fan--I don't recall seeing too many dual exhaust tips on ST car. Are they allowed? I've only seen them once on a Italian ST Audi. Interestingly, no other Audis in other countries.

3) Theoretically(??), doesn't having 2 instead of 1 exhaust tip allow for more exhaust to be expelled from car? OTOH, 2 exhaust tips are heavier than one? Ask specifically about ST, but other racing series comments are welcomed.

4) Ditto for location? Left, centre, right side of rear bumper? Could centre be best?
Ask specifically about ST, but other racing series comments are welcomed.

Many thanks for those responding!!

[Sparky]

1. I dont know of any race car that uses exhaust pipes that size. I think that they're trying to make up what they're missin elsewhere. (Dimensionally speaking of course!)

2. and 3. Dual exhaust tips. ermmm... no. Engines with manifolds that produce a single downpipe will not gain any power by re-emerging as a dual-tipped tailpipe. This is cosmetic only.
A proper dual exhaust, as fitted to a V engine will greatly enhance the power output, especially if a balance pipe is used. This is a section of pipe between the two halves of the dual exhaust system, and it allows each cylinder too 'see' two possible exit routes. What this doess in practice is increase torque at low to middle revs by as much as 20%. Very useful mod for (virtually) no expense. Peter, have you tried/are you permitted to try a balance pipe? It makes an amazing difference to part throttle pick-up and drivability!

4. Location is more often than not a packaging issue. On a street car, the exhaust will usually exit to the kerb. (Or the opposite side to the driver.) Obviously, with a competition car there is not usually any need preserve the original location of the fuel tank, as there will be a fuel cell within the vehicle. This ideally allows a straighter run for the exhaust. Another consideration on a super-tourer is the vehicle ride height. These tend to run from anything between the standard height to less than an inch of clearance. The exhaust position and diameter will have to take second priority to that of the handling and aero - raising the car because the exhaust hangs too low is unacceptable. Some classes allow exhaust tunnels let into the floor, but I don't believe this is true of International ST.

I hope this answers your questions, Mr Chow! And everyone else, please feel free to correct / add!

[This message has been edited by Sparky (edited 24 May 2000).]

[Peter Mallett]

<BLOCKQUOTE><font size="1" face="Trebuchet MS, Verdana, Arial">quote:</font><HR>Originally posted by Sparky:
Peter, have you tried/are you permitted to try a balance pipe? It makes an amazing difference to part throttle pick-up and drivability!<HR></BLOCKQUOTE>

My exhaust was designed and built by the man who built them for Spice so I expect thats what I've got. Given that though I may need a different cam to get the best out of it.

[Sparky]

I have a collection of US 'Musclecar' books, and my fave one is on the Dodge/Chrysler/Plymouth cars of the '60's.

The Dodge 6-pack Hemi equipped Fury's and Coronet's, with cross-over pipe, was good for another 5% horsepower, and 21% torque.

A short balance/cross-over pipe fitted below the trans bellhousing will increase the efficiency of the system by 75%!

Check it tomorrow Pete! Perhaps the Old Spice man forgot!

[yelwoci]

The balance pipe works particularly well on V8s. I have yet to see one working on a Ford V6 like Peter's on which most exhaust designs have 3:1 headers just under 1m length with the Y pipe merge point 0.5m further on.

On my road going Rover SD1 V8 (215cu, 3535L) I modified the engine myself, 'gas flowing' and blancing the chambers with electric drill, flexidrive and my corner store burr!
With the standard exhaust it went up from 155bhp to 185bhp. A mild/rally/tow cam (Kent180) and a drainpipe system toook it to 210bhp. Then I played around with the balance pipe and I was amaised at the differences. The peak power never changed 'cos it was limited by air flow (modified 2x 1 3/4" SUs, was going to 2" but couldn't find them....the car had to look standard you know!).
The closer to the engine, I think the power band shrunk and rose, further back and the band widened and lowered in the rev range.
The actual location was reasonably sensitive and the distance between full short and full long was only about 75cm.

I managed to avoid much housework, etc, with this very necessary investigation which was too technical to spend valuanble time explaining to the foaming spitting firebrand that I 'shared' my life with at that time!

:-)
ianC

[Sparky]

Ian,

I believe Peter's system is a true dual, it exits under the rear valance as on the original three litre Capri's, With one 2in pipe each side. Pete says he probably does have a balance pipe, but I'd still be happier if He would crawl under there and physically touch it! I wonder what the difference would be if there isn't one!

Mmmm...Free horsepower....Doh!

[yelwoci]

Without wanting to give any of Pete's secrets away(!) it has been found that using a classic 3:1 into Y with single 3" system to tail produces the most power in Group1 engine tune.
Each header joins together at about the start of the bellhousing, with a single pipe to the Y-point just after the gearbox flange, often just to one side, then 3" to rear.
This is what I believe Pete to have.

The quickest Capri in the championship (Skid Scarborough) had a very short system pipe/muffler and feeds ahead of the rear wheels. Again a single outlet.

Many have tried the dual pipe method, both as road and race cars on the Ford V6.
I belive in our series Colin Potter ran his with dual pipes but has reverted to a single.

It is claimed to worth 15-20bhp!

As I said it (balance pipe) works on V8s....(does it work on V10 and V12s?)

IanC

[Peter Mallett]

Yelwoci has it about right. For info, the man who tunes it reckons mine to be one of the most pwerful V6s he's seen on his rolers. That being so, I must be a really **** racer!!!

BTW. The other V6 which comes close to mine is Steve Higgs'. His problem is the cam which comes in at a punch around 5.5K and climbs to 7K. Mine is softer and it is noticeable at places like Donington where (due to some appalling brakes) I was running with Steve. He would catch up at the end of the back straight but I would accelerate out of Gerards(?) onto the pit straight and leave him behind.

Memo. Must get a Group 1 cam.

[Dino IV]

Great stuff, guys!
With the chance to be slightly ST off-topic, mr. Chow, I have a question. The actual length of the exhaust from exhaust-port to pipe-tail is extremely important because of the forced extraction aid - the great techno 'uomo universalis' Sparky already mentioned it.

A variable length system - similarly to variable inlet systems, even entering hillclimb efforts these days - would greatly enhance overall performance. I know for sure it's forbidden in F1 but I am very curious if it's in use in any other series or vehicle, or at least allowed.

Regards,

Dino IV.

[kmchow]

Dino IV wrote:

&gt;A variable length system - similarly to &gt;variable inlet systems...would greatly
&gt;enhance overall performance...I am very &gt;curious if it's in use in any other series?
&gt;or vehicle, or at least allowed.
&gt;
DO you mean variable length INDUCTION or EXHAUST system? 'Cause the Ford Windstar minivans and Ford Escort/Focus cars in NA use such a method to get more hp.

[Dino IV]

Yes, that's what I meant. Cool. I didn't know that. There must be more veheciles equipped with it then ...
What about racing cars?