3" turbo back exhaust

[motty225]

going to be going for a stage 2 map on my LCR soon, just need to sort out my exhaust, i was planning on going for the piper 3inch downpipe with decat, and getting a custom made 3"system to mount upto that with no silencers just a backbox, will there be a problem with this? i.e to free flowing? or is this a decent setup for a stage 2? i dont want to make things worse

 

[Braindeadhmster]

I'd love to know this too. As far as i've searched it will be ideal for me cause desiels dont need back pressure.

 

[JamJay]

You want as little back pressure as possible after the turbocharger to help increase BHP & torque, they don't work like NA cars where too little back pressure results in a loss of BHP & torque. A free flowing exhaust helps with exhaust gas temperatures and can increase the life of your turbo. At Stage 2, you'd see no benefit from fitting a 3" system when compared to a 2.5" system really, it'll just be a bit noisier. It's when you start creeping over the 300bhp mark that you want to think about a larger cat-back system but if that's your plan, you're future proofing yourself if you do it now.

 

[leon cupra r]

You want as little back pressure as possible after the turbocharger to help increase BHP & torque, they don't work like NA cars where too little back pressure results in a loss of BHP & torque. A free flowing exhaust helps with exhaust gas temperatures and can increase the life of your turbo. At Stage 2, you'd see no benefit from fitting a 3" system when compared to a 2.5" system really, it'll just be a bit noisier. It's when you start creeping over the 300bhp mark that you want to think about a larger cat-back system but if that's your plan, you're future proofing yourself if you do it now.

Just out of interest and sorry if this is considered a hijack, why do NA cars need backpressure? I would have thought that the less pressure the better as the gasses would flow out of the cylinders more easily? Sorry if this is me being thick!

Ben

 

[JamJay]

From what I understand, a turbocharged car creates sufficient back pressure from the turbo so a free flowing exhaust is not an issue but as NA cars do not have this, a vacuum needs to be created in the exhaust tubing to help pull the gasses out. This is all down to the diameter of the pipe and it's crutial to get it right to optomise the performance given from an exhaust system, too small and you lose power as the gasses can't escape easily enough, too big and you lose your vacuum.

 

[leon cupra r]

Ahh right i always thought that by back pressure it meant pressure pushing back towards the engine (as in it would slow down the gasses trying to be pushed out of the cylinders) which is why I always wondered how this would benefit! But yeah see what you mean now thanks for clearing that up for us!

So the bottom line is with a turbo, bigger really is better for exhausts!

 

[turbin]

from what i understand, a turbocharged car creates sufficient back pressure from the turbo so a free flowing exhaust is not an issue but as na cars do not have this, a vacuum needs to be created in the exhaust tubing to help pull the gasses out. This is all down to the diameter of the pipe and it's crutial to get it right to optomise the performance given from an exhaust system, too small and you lose power as the gasses can't escape easily enough, too big and you lose your vacuum.

+ 1

 

[jamiebennett81]

At Stage 2, you'd see no benefit from fitting a 3" system when compared to a 2.5" system really, it'll just be a bit noisier

really? no difference at all?

will help peak power, with it being larger and more free flowing, its less strangled, so even on a stg2 it is going to help, maybe not by much, but possible up to another 10 ponies (depending on the dyno.....)

 

[leon cupra r]

at stage 1 is there any restiction from the standard manifold + exhaust then, is it worth looking at upgrading in the future?

 

[jamiebennett81]

at stage 1 is there any restiction from the standard manifold + exhaust then, is it worth looking at upgrading in the future?

Depends what power you want really

There will always be a restriction, how big that restriction is, depends on how much power you want

stg1 is typically just a remap and filter, so there will be little benefits from fitting a TB exhaust and manifold

stg2 there are definite benefits to be had from the exhaust, but again fitting an uprated manifold is not required at this point as the power of the turbo is still well within limits of the K04 stock manifold

stg3 will typically be TB exhaust, manifold and turbo

you only need to start upgrading the exhaust if you are looking at stg2+, and as for the manifold, you only need to upgrade this if you are going for a Hybrid K04 (or bigger setup) to get the optimum power from it. You could run on the standard manifold on a hybrid k04 but I wouldnt recommend it, purely for longevity of the turbo as already said with keeping EGT's as low as possible

 

[JamJay]

really? no difference at all?

will help peak power, with it being larger and more free flowing, its less strangled, so even on a stg2 it is going to help, maybe not by much, but possible up to another 10 ponies (depending on the dyno.....)

I posted up a while ago about it and the general opinion was that it would be marginal, as you say. It's worth trying though and see what figures it makes and compare to a 2.5" or 2.75" (same dyno if poss) as it might work quite well. A 2.75" system is well within limits of Stage 2 though so personally I can't see it making alot but i'd love to be proved wrong