Is a 2.5 inch bore too small for bpu?

Hi i have a uk spec TT which is fully decatted but i dont have a boost controller at the moment. The cat back exhaust is a custom made job which was on the car when i bought it but the bore is only about 2.5 inch.

What i want to know is the bore too small, will i loose any power from it?

The car pulls very well alot quicker that my last standard TT but im just wondering if it would benefit from a bigger bore. Also it makes one hell of a mad noise, it sounds like a really powerfull single with a baffle in the exhaust. Will this be because of the bore?

Thanks:)

2.5" will be just the job for a bpu. Most decats are 2.5".

2.5" is fine as Class One says. I think smaller bore exhausts sound good

I had a 2.5" Straight through and i didn't peak more than 1.0Bar, as soon as i slapped a 3", i could get it up to 1.3Bar

I'm running a 2.5" decat with a single;)

cheers lads but i mean the whole exhaust not just the decats, does it make a difference

?

The stock system branches to a twin 2.25(?) inch section to the back box. However it does have 3 very restrictive silencers so combined with an open system 2.5 through the whole lot might be okay. I've not seen a cat back for sale thats smaller than 2.75 inch though.

I had a 2.5" Straight through and i didn't peak more than 1.0Bar, as soon as i slapped a 3", i could get it up to 1.3Bar

What cat back did you have? Some exhausts can be restrictive at the resonater box, I wouldnt risk it, 3inch minimum with a 2.5inch restrictor ring, if anything your egt's would be lower

The stock system branches to a twin 2.25(?) inch section to the back box. However it does have 3 very restrictive silencers so combined with an open system 2.5 through the whole lot might be okay. I've not seen a cat back for sale thats smaller than 2.75 inch though.

My old stock system only had one box and that was the rear one...it did branch like you say...but no boxes there..is this normal:search:

My old stock system only had one box and that was the rear one...it did branch like you say...but no boxes there..is this normal:search:

Nope, that would have been aftermarket. All supra's AFAIK had a twin box system in the 1st part of the cat back.

Nope, that would have been aftermarket. All supra's AFAIK had a twin box system in the 1st part of the cat back.

oooo might have to put that up for sale then:D...cheers

My old stock system only had one box and that was the rear one...it did branch like you say...but no boxes there..is this normal:search:

Nope, that would have been aftermarket. All supra's AFAIK had a twin box system in the 1st part of the cat back.

Homer is wrong, the stock twin turbo exhaust branched into 2 sections but met at the back box. It is the NA stock exhaust system which had 2 extra boxes on the pipework.

Homer is wrong, the stock twin turbo exhaust branched into 2 sections but met at the back box. It is the NA stock exhaust system which had 2 extra boxes on the pipework.

Mine didn't. It was a single pipe from the cat back. It now resides on Mr Angry's car and was a Toyota option.