hawk 7

iTrader: (2)

Is there a noticeable power difference between these two diameters of downpipe?

FC Drifter

i wouuld think so. maybe not a huge difference on a stock turbo but im sure youd be able to notice on an aftermarket turbo. i got a 2.5 inch on my T2 and it works well for me.

hawk 7

iTrader: (2)

I am not going to go crazy on my turbo upgrade probably just a BNR stage 1. I am going to have a cat with my exhaust this time and it seems that most of the aftermarket hi flow cats are 2.5". So I wanted to know if there was a big power difference if not I'll probably go with either a mindtrain set up or the Bonez.

FC Drifter

id say a 2.5 would work fine for you then

RexSe7en

yea I would agree with FC Drifter. Really no need need for the 3"

E6KT2

What are the benefits of using a smaller pipe on a turbocharged car? None. Use the 3".

Ryde _Or_Die

E6KT2 got the idea. Why go with a 2.5"? 3" is less restrictive, so the real question is "why go with a 2.5"?

hawk 7

iTrader: (2)

The reason I was considering the 2.5" downpipe is that I want to use a cat with my system. And the two systems that I was looking at both have 2.5" downpipes. The Bonez and the Mindtrain systems. I am considering the racing beat system but I would like for the car to be emissions legal. I thought about putting a cat in where the presilencer is in the racing beat system. Can this be done? And I would go with the 2.5" if the 3" is overkill.

poor college student

newb question. are dp's more suited for use just in turbo's as opposed to n/a's? yes? no? and why?

Ryde _Or_Die

They don't usually call them downpipes for NAs but some people do. For all-out power in an NA headers are recommended. But a "downpipe" will give you just about the same gains and alot less noise.

poor college student

what are headers, and why isn't it called a downpipe in an n/a? what is it called? is there something like the dp? wow, i'm lost...

amemiya

GO BIG OR GO HOME! what does your guys ***** hurt? the turbo is all the back pressure you need so the bigger the better so get the 3" and get a universal high flow 3" cat, and make some "noise" or go home sell your car by a honda and let a man drive your car. "no guts no glory"

Pinfield357

but who makes a 3" high flow cat???

Drakk0r

A 3" open exhaust on a stock turbo will cause some boost problems. You'll see max boost (almost 1 bar) at around 5500 rpms, which will then start falling to 0.6 bar by redline. A 2.5" exhaust is better suited to a car with the stock turbo (and wastegate).

amemiya

who said anything about open exhaust??? I had a full 3" on the stock turbo and boost went up to 10 psi. yes you need a fcd. but bigger is better on a turbo car.

Drakk0r

Your post made no sense. And BTW, 1 bar = 14.7 psi. And bigger is only better if you have a wastegate to keep up with things. The stock wastegate (Series 4 cars anyway) is too small to bleed off enough exhaust when using a full 3" exhaust system. Which is what causes the boost problems.

FC Drifter

and if you read some of his previous posts, he wants a cat in his exhaust. i know of no catalytic converter that has a 3" inlet and outlet. if he got a 3" dp he would have to have it cut down to go into his cat. why bother with all of that when he can just get a 2.5 dp. sometimes its not about the power, but about meeting the requirements he wants.

NZConvertible

Really? There’re uncommon here because no one uses them (not required), but in Australia there available everywhere, quite cheap too. I’d be surprised in they’re hard to get in the US. There’s nothing hard about coning down to 2.5”. Even if the rest of the system is 2.5”, a 3” DP will still increase power and response over a 2.5” one. The first section after the turbo is the most important because it’s where the gases are hottest.

E6KT2

Hey guys, GOOD CALL on the fuel cut issue. I am just to used to the Haltech I suppose. There is a disclaimer usually with all TII exhaust queries which is "A high flow exhaust will raise the boost. Tuning is necessary." If you can't tune for the DP, then by neither. If you can, get the 3".

AlixxxilA

be men and get the 80mm downpipe from tannabe. 3 1/2 inch muahaha

NZConvertible

3 1/8" actually; 3.5" is ~90mm.

purefunrx7

I don't know a whole lot about turbo's, but my friend's with them said that 2.5" would be the largest to go on a non-turbo rx-7, and that the choice size for turbo would be 3". just my 2 cents.

Ryde _Or_Die

Ok....well...go to www.racingbeat.com. They have pics of their products. Look at exhaust components and look at a header and then a downpipe. RB does call the straight pipe off the exhaust manifold a downpipe for an NA. A downpipe is just a straight pipe, a header has pipes coming from each exhaust port and then can be collected into one pipe or just go back into 2 pipes (true-dual exhaust on a rotary).

MrFuzzy

iTrader: (1)

Dont you lose torque with a 3" system?