stineal

at what bhp does a 2.5" bore exhaust become restrictive?

Skooby53

iTrader: (1)

I would say 340-350 is probably as far as I would go with 2.5". Always worth fitting a 3" if planning more power in the end.

harvey

iTrader: (48)

Probably somewhere past 400 bhp if it is a reasonable design.
I always fit "3" inch so it never becomes an issue, certainly not on a 2 litre up to around 600 bhp.
Go for a design with proven results. I prefer something that is fairly straight like the Scoobymania system although the Revolution which is not as straight still gives similar results, both are 3" however.
CATS even a Sport Cat will cost some power.

Power Junkie

iTrader: (1)

Im getting 400 on one at the moment (H&S turbo back), I am changing to a 3" system next month so I will know what difference it makes.

harvey

iTrader: (48)

It will be good to hear your first hand feed back.

Henrik

iTrader: (5)

I'd be interested to know this also.

PowerJunkie, are you having the car remapped afterwards, and what other changes have you made?

Power Junkie

iTrader: (1)

I will be getting the car re mapped once its on. all the other mods have been done, I just wanted to see if the 2.5" would get the power, The 321h is hitting 1.7bar so i would like to get that down with the 3" and hopefully get the same power or maybe more. I will keep you posted.