3" DP, 2,75" exhaust and 450BHP?

[Nero]

Now that my suspension is as good as new, it's time to go further with the power on the S2. If don't upgrade quickly, I'm afraid that I'm going to buy a M5 with an instant 400bhp. :mischeif:

I own this S2 for a year and I have a RS2 ic installed, Dahlback intake and have a Wagner cast EM, 044pump and 7A cams laying somewhere. A RS2 turbo will soon be installed, but I know that Bram soon will force me to upgrade further. He might even throw me a vicous proposition for his old CT turbo that I can't refuse to convince me, that's how bad that guy is.

There is an EPS ss exhaust placed, with decat pipes, but unfortunatly the former owner had it made in 2.5". Nice exhaust, nice material, nice welds and very good for 300bhp... But not really an upgrade. Having the bill also, 800 Euro...

I want a 3071 in the future, so I need a new exhaust also, that's clear.

I know that 3 inch is the way to go, but my garage is laying quite high, nice with rain, but a pain to come in with the S2. I already have adjusted the garage so that I don't have clearance problems driving it in the garage.

Can I get away with a 3" downpipe, and a true 2.75" further on till the end? This all in combination with a 3071 on a Wagner cast EM? Doesn't need to be maxxed out, I have a Vems unit in the S2 with EGT so it's gonna be mapped within the right limits.

[Jamo]

Yes you can others have done it like Rusty.

As long as the downpipe is 3" the rest of the system can be more forgiving in size especially if you will be running no CAT I'd say go 2.75 over the rear axle

[Rusty]

Aye, although mine's only 2.5", it's only the last metre and there's very little restriction before that

It also helps to dull the noise down a little as there's a change in diameter.

Theory is that the exhaust gases have cooled a little by the time they reach the narrower pipe and thus it has less of an effect and may even help as it will speed the gas up a little, helping the subsequent exhaust 'pulse'.

[GazzaG60]

i have 3 inch striaght through on the coupe.

i bet you can hear it from there on a good day. i love it though.
no point trying to be discreet with nearly 500hp.


clearance is only an issue with low cars. mines fine.

[Nero]

Theory is that the exhaust gases have cooled a little by the time they reach the narrower pipe and thus it has less of an effect and may even help as it will speed the gas up a little, helping the subsequent exhaust 'pulse'.

Already thought so, but didn't want to be shot.

I need clearance at the exact middle of the car, to drive it in my garage. If it scrapes, it's mostly around the decat flanges. So probably at the middle, I want to go 2.75".

I want to install a racecat, something like Bram.

[GazzaG60]

a race cat is often about 5 inch for a 3 inch system.

mine bolts up nicely in the middle. if anything the issue is the flanges from the downpipe to the centre section. clearance around the rear shaft is pretty close though.

[Jamo]

Already thought so, but didn't want to be shot.

I need clearance at the exact middle of the car, to drive it in my garage. If it scrapes, it's mostly around the decat flanges. So probably at the middle, I want to go 2.75".

I want to install a racecat, something like Bram.

You could go 3" into twin 2.5 inch straight through pipes rejoining into a larger bore over the axle if space is the issue.

My system was like this when I bought the car, straight through it's o.k but with cats would strangle the system.

Depends how focused you are on top performance

[Rusty]

I have 100CPI sports cat and it passes the MOT... eventually

[Bram]

I would go with a 3" DP and 2.75 over the rear axle. In case the EGT's go too high with that GT3071R you can always install a screamer to release some exhaust gasses. I would also try to place the 200 cell race cat close to the downpipe, so it does not come close to the ground when you drive into the garage. So do not place the cat in the middle of the exhaust pipe length

[Rusty]

Could run the WG pipe alongside the exhaust to the rear / side of the car too

[Nero]

That's a nice option!

[A80Avant]

your EGTs will only go high on the 3071 if you buy the 0.63AR. Your exhaust wont make an unsafe issue with going 3inch down to 2.75.

i had that setup and 0.63AR 3071 with twin 200cpi cats and 2 boxes and was still able to have 1.8bar of boost to the red line and decent power (around 420hp)

Now, i have the same 3inch downpipe and 2.75 cat back, same 200cpi cats and 0.82AR GT3076 and my EGTs have gone down, and im able to have 500hp without problems, holding 2bar till 7000rpm. and 0.79 lamda.

[Nero]

your EGTs will only go high on the 3071 if you buy the 0.63AR. Your exhaust wont make an unsafe issue with going 3inch down to 2.75.

i had that setup and 0.63AR 3071 with twin 200cpi cats and 2 boxes and was still able to have 1.8bar of boost to the red line and decent power (around 420hp)

Now, i have the same 3inch downpipe and 2.75 cat back, same 200cpi cats and 0.82AR GT3076 and my EGTs have gone down, and im able to have 500hp without problems, holding 2bar till 7000rpm. and 0.79 lamda.

That's all you need to say! Thanks.

Bram and I already had decided that it has to be a 3071 .82 or a 3076.

[A80Avant]

that would be interesting, as i must say it would bring the boost slightly later, but presumably not much later than the 3076.The 2 turbos have different turbine wheels so there must be a difference between them, but if mine comes at about 3800-3900rpm on 4th gear, it should bring the 3071(0.82ar) at least 200rpm sooner. 3d gear as well.

[Rusty]

That's a nice option!

Seen a motorcycle silencer used on that too