4" Dump Pipe

[Max Power]

Ive got a 3.5" dump pipe and am looking at getting a 4" to remove any restriction.

Ive read somewhere else that there isnt much point in having a larger dump pipe if the turbo is the same. Ive also read that a 4" dump pipe takes away some bottom end torque.

Im currently at 325rwkw and dont want to increase power too much more but rather remove some boost as its currently at 18psi.

Since the 325/18 tune where the IC was found to be the restriction, Ive gone to a larger IC and want to sort out the exhaust before it goes back for a retune.

So can the experts add their 2c worth?

Ive also got a 3.5" cat and 3.5" pipe that splits into 2 3" pipes at the diff and out the back on opposite sides.

I was told that the cat can be hi-flowed to fit the 4" pipe which will replace the 3.5".

Is this the right way to go?

[Max Power]

Bump.

[MiKa]

I've read a thread on this but cant find it atm but if I remember correctly..... The member who had his 4" fitted noticed that his car when hitting boost was more 'calm' before, it was all over the shop.... so yeah I think u do loose abit down low.. He is running 300+rwkw. I reckon the larger IC will do a great deal with lowering the psi needed to make the same sort of power u have.. The 4" will help but it comes at a price... I'll be quiet now and let some ppl more in the knoe talk... Just my 2c

Mike

[blueboost]

3.5 inch one is fine, I still have the stock one,

I have tuned with both, and still are not sure which one I like the most, they both out flow mine,

I still think the cat will be your bigest restriction, even with a 5inch. imo

DaVID

[F6_Charlie]

I fitted a 4" dump pipe not to long ago mate, I think mika is talking about my post I done a couple of weeks ago now.

In my case.

I lost alittle down low torque but like I said its only alittle bit, but from about 3000 - 3500rmp upwards it just pulls like a train

Before it use to hit boost and be sideways all over the place now it hits boost and still kicks out but alot more tame, then next thing you know your getting pushed back into your seat as its hit the 3000 - 3500rmp mark and its just pulling.

Iv'e actually been thinking of going down to a 3 1/2" dump pipe though only due to the fact that the 4" is good for high top end power oh and the whislte it makes when spoolin.

All the above is what I have found thur my car so dont hold me to it, but hope it helps you out mate.

If your still keen on a 4" mayb we could work out a swap or something.

cheers charlie

[Max Power]

Thanks guys. Youre swaying me away from the 4" dump. Any more feedback will be appreciated.

How about what I said about the rest of the exhaust? Will changing the intermediate pipe to 4" from 3.5" and hi-flowing the 3.5" cat to suit the way to go?

[Adam]

I would stick with the 3.5".

[Max Power]

Wow Adam. Wasnt expecting that. Thought bigger was better.

So shouldnt I touch a thing or just upgrade the cat and if so with what?

[F6_Charlie]

To be honest mate I wouldnt change anything your exhaust sounds fine to me.

dont waste money on things you dont need to, mayb just look into a bigger cooler if that

Edited 07/04/07 12:52 AM by awsmxr

[Adam]

  Max Power said:

Wow Adam. Wasnt expecting that. Thought bigger was better.

So shouldnt I touch a thing or just upgrade the cat and if so with what?

I say that because I have a 4" dump pipe and it's to big IMO. There's just not enough clearance around it.

Secondly, I'd doubt that there would be much advantage in going just 0.5" bigger in a pipe, cat maybe but not a free flowing pipe.

325rwkw's and your looking at more, I'd be looking at engine internals very seriously.