2"x2 or 3" stainless system

[Forest Pete]

come on techie heads,
would I gain more from 2 2" piped system or just a 3" single pipe system

[Guest]

come on techie heads,
would I gain more from 2 2" piped system or just a 3" single pipe system

.

Not sure on that one, Don't think anyone has fitted a 3" all the way through. I think you may find that it is too large and will cause a lack of back pressure. All exhaust systems need some back pressure to help the engine clear eficiently. With too large an exhaust you can end up with a system that operates like open headers - noisy and inefficient. My car at the moment has a blow on the exhaust manifold, it's amazing how it affects the power delivery. as there is a distinct flat spot between 1500 and 2200 rpm.

Mind you a 3" all the way may work well, I think it's something that someone needs to try to really prove the case.

EDIT.

Just to prove I can't read at this time in the morning, didn't quite get the point to start off with.

Not sure about twin 2" systems either, You would get a larger internal volume from the twin systems however again, the size overall may cause problems. Larger is not always better and there is an optimum sixe for an exhaust where going any larger will reduce either top end or mid range power.


Cheers

[Slugsie]

come on techie heads,
would I gain more from 2 2" piped system or just a 3" single pipe system

I'm no expert on these things, but I do remember reading that with regards to valves, 2 valves will provide a better flow rate than a single valve that has the same total surface area. 2 2" pipes provide 6.28 sq inch and 1 3" pipes provides 7.06 sq inch. So there's probably not much in it.

[truckarms]

Having chatted to a few guys we have come up with the following, alot of the pressure should be used up by the turbo, therefore after the turbo you want to get rid of the gasess as fast as possible, thus based on the maximum flow (i.e largest cross sectional area, the 3 inch wins) and the lowest resitance (i.e. surface area, again the 3 inch wins).
Therefore you want a 3inch system.
very quickly you get 15% more flow through the 3inch pipe and 75% of the friction of the 2*2inch.
Talk to the guys who are going to put it on the car, i am sure the guys who did mine had some software which they hooked up, and worked it all out such that you are getting the optimum exhaust diameter etc at the max torque/rev range (i.e. I get a really sweet note at about 2000rpms on mine) however i dont have a turbo
good luck

[Dog_Book]

I am also no expert, but i used to do supermoto racing and i know this....

Four stroke engines do NOT need back pressure in the exhaust to perform any better. You need to get the gases out as easily as possible, although i do know that the length of the pipe is important as you need the exhaust to be the correct TUNED LENGTH. Forget the last part on Turbo engines...the post after me is right...cheers

ok

[UKWolf]

Having chatted to a few guys we have come up with the following, alot of the pressure should be used up by the turbo, therefore after the turbo you want to get rid of the gasess as fast as possible, thus based on the maximum flow (i.e largest cross sectional area, the 3 inch wins) and the lowest resitance (i.e. surface area, again the 3 inch wins).
Therefore you want a 3inch system.
very quickly you get 15% more flow through the 3inch pipe and 75% of the friction of the 2*2inch.

Spot on - you want the lowest possible back pressure on the exhaust side of the turbo.

This will alow the turbo to spin up faster and run more effeicently, which together with a waste gate controler will increase power very effecively.

A tuned legth exhaust will not mean anything on a turbo as the exhaust pulse will have been flattend out by the turbo.

Ali

[exmee46]

My local garage just sold a 3.0TD with a 3" exhaust system right through (came from the Land of the Rising Sun like that) and it went like a rocket.

No evidence of having been chipped either. Caused a few probs when they tried to fit a towbar tho

Cheers

Kev

[stara]

an overly big exhaust diameter will have too little back pressure, ironically, as a result, the gasses will travel at a lower velocity due an increase in exhaust gas volume being more dense as it fills the larger volume pipe, this will in turn allow the gasses to over-cool and become more dense, slowing the gas even more and compounding the problem. in a perfect world, the exhaust would leave the pipe at the same speed it left the cylinders, but we have to make do with the best we can use, on the surf a 3" pipe to the turbo, and a 2.5" main system is prob as efficient as it can get, although the difference between a 2.5" and a 3" systems would be un-noticeable on the surf, after all, it's not exactly a highly tuned track car. Remember it's not about perceived back pressure, it's about exhaust velocity, the faster the exhaust leaves, the more efficient the burn.

[Forest Pete]

Why aint anything simple,
thanks for all the replies me thinks I will have to lookinto this more
or just make one of each and compare them for performance
Looks like Ive got some welding and bending to do.
will post reaults when done, but it wont be for a while.
Tried a 0-60 today box in standard setting IE not power and over drive on
=7 seconds is this about right

[Greebo]

Why aint anything simple,
thanks for all the replies me thinks I will have to lookinto this more
or just make one of each and compare them for performance
Looks like Ive got some welding and bending to do.
will post reaults when done, but it wont be for a while.
Tried a 0-60 today box in standard setting IE not power and over drive on
=7 seconds is this about right

not unless you pushed it off a cliff!
or is that kph and not mph?

[dirtydog]

thats way out its at least double that

[TOYMOTA]

Why aint anything simple,
thanks for all the replies me thinks I will have to lookinto this more
or just make one of each and compare them for performance
Looks like Ive got some welding and bending to do.
will post reaults when done, but it wont be for a while.
Tried a 0-60 today box in standard setting IE not power and over drive on
=7 seconds is this about right

Yeh that sounds about right cos my 2.4 does it in 7.5sec
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Whilst being towed by michael schumacher in his ferrari.

[Forest Pete]

I will check with a proper stop watch soon but it is not that far off what i said

What should it be then

[dirtydog]

I will check with a proper stop watch soon but it is not that far off what i said

What should it be then

im pretty sure it should be around 15-17secs i think i read it somewhere onece

[Forest Pete]

Its way under 15 sec,and will always spin the inside wheel when pulling away at junctions at 25- 50% acceleration