3" dump pipe into 2.5 system is it OK?

[JustCallMeOrlando]

Umm, how about no. My car is my daily driver so a) I can't have it droney, and b) it spends a lot of time on the road being a "target". I also spent a lot of money making sure I had the bits of paper making it 100% legal, last thing I want to get done for is a gutted cat.

[brett_celicacoupe]

i wouldnt say its droney at all, more whistley than droney. you could always fit one of those electric valves to quieten your engine at the flick of a switch.

did i say gut? i meant super-hi-flow


but i still say its worth trying at least for 1 drag or dyno run

[Ghetto-AW11]

On my car with a 2.5 inch full system it was a HUGE limiting factor, and this is a 4agte. Running a full 3 inch system has given huge improments in turbo spooling and power, changing from a standard highflow 3 inch cat to a metal substrate bodied cat also had huge gains, ie 20rwkw. This is @ 20psi.

[JustCallMeOrlando]

Running a full 3 inch system has given huge improments in turbo spooling and power

Can you quantify this or did it just feel better because you'd just paid for it?

[Ghetto-AW11]

Yes i pay for things and feel better? What a stupid comment...

Dyno proven, and before you ask me to post the graphs, i dont have them

[twentyEight]

On my car with a 2.5 inch full system it was a HUGE limiting factor, and this is a 4agte. Running a full 3 inch system has given huge improments in turbo spooling and power, changing from a standard highflow 3 inch cat to a metal substrate bodied cat also had huge gains, ie 20rwkw. This is @ 20psi.

Could this be beacuse the top end of the system is now 3"?

So really your power increase has been because you have better flow where the air is more dense, rather than because the whole system is larger...

[30psi 4agte]

I noticed alot better response when i fitted a 3" dump on my old 2.5 inch exhast. The turbo definatley boosted quicker and stronger.

As for outright power the 2.5 inch system shouldnt be resticting the power by that much !!!

Sure there is no blockage / stuffed cat or anything like that ??

[JustCallMeOrlando]

Yes i pay for things and feel better? What a stupid comment...

It's not a stupid comment at all. Initially I drove my car after tuning and thought it felt better, part of that was because I wanted it to feel better because i'd just parted with my cold hard cash. After a while, and after comparing figures though, it quickly became apparent that it hadn't.

[JustCallMeOrlando]

Sure there is no blockage / stuffed cat or anything like that ??

Unless the cat suddenly collapsed nah. I'd be a bit disappointed, it's only 25000km old.

[Ghetto-AW11]

you guys have got to remember my car is an aw11 mr2, the whole exhaust wouldnt be more then well, 3 metres? and it has a fair few bends, so ofcourse in my application the increase of size is going to make a much greater difference than with a normal front engined cars exhaust.

[twentyEight]

you guys have got to remember my car is an aw11 mr2, the whole exhaust wouldnt be more then well, 3 metres? and it has a fair few bends, so ofcourse in my application the increase of size is going to make a much greater difference than with a normal front engined cars exhaust.

I do understand what you mean, but your exhaust would be more 1.5m surely... The exhaust on my RA28 is 3m!

[Ghetto-AW11]

It loops around! if it went straight out it would be 1.5metres.

[JustCallMeOrlando]

Your point still stands though that it will have much more bends than a conventional system.

[cycleofabuse]

Now I would have thought it depends on what setup you're running. If you're running a 3sgte at 10psi I wouldn't think a 2.5" section would matter much as its not really all the much flow through the exhaust. But if you have a 2jz-gte running 18psi it's going to have ahell of a lot more flowing through the exhaust.
But I'm no expert.

[twentyEight]

It loops around! if it went straight out it would be 1.5metres.

I understand now...