will you lose horsepower if you go with the 2.5 and not a 3 inch downpipe with a high flow cat and 3 inch exhaust?

 

The answer to your question is based on how much whp you plan to make. Plan to make a **** load of hp = yes. If you plan to just do a chip, boost controller, bov, turbo back exhaust, and intake -- then NO.

If you keep the stock, 2.5" cat, which is very high flowing for a stock cat, then you will be fine with a 2.5" HKS dowpipe. But if you plan to upgrade your downpipe to a 3", then you will have a longer upgrade path -- you would want to run either a 3" test pipe or 3" high flow cat in your set-up (there's no point in running a 3" dp if you plan to keep the stock, 2.5" cat -- you would then have dreadful pipe diameter fluctuations .... big/smaller/big and that kills flow).

Basically, if you plan to make huge power down the road (say, 320-350+hp at wheel), then a 3" downpipe is best but you will also need to upgrade the o2 housing (outlet that dp connects to) to 3," to maximize the benefits of a 3" turbo back. Basically, a 2.5" will do the same as a 3" until you start making big power, and follow the same/similar upgrade path that I just presented. People that want to just slap on a dp and go w/o all the otha bs usually go with a 2.5" downpipe. Of course this is somewhat subjective...

......... and a 3" cat-back is fine regadless of the size dp/cat you pick.

Hope this helps. PeAceOut!

EVO1 in da house!

 

thnax, i am planning on going 3 inch exhaust and 3 inch high flow cat with either a 3 or 2.5 inch downpipe but probabaly a 2.5 because i do not plan on making huge horsepower. my car is already having problems stock. i cant imagine if i were to mod the hell out of it.

 

NP Mr. Kazoo!

Either set-up you described above will work out just fine ... but keep in mind that may not even notice big gains with a bigger hi-flow cat, although it will help ... I can't say that the gains will be worth the added expense. I've tested my set-up (below) with the stock cat vs. a 3" RMR test pipe, and the test pipe won but not by as much as I thought it would. Sorry to hear that you are experiencing problems with your Tarmac evo ... anything major?

 

well my engine was doing something funny, like letting off all boost at 4,500-5,200 RPM's and then it quit doing it. Now i have to have my tranny placed which i found out today becasue my tranny fluid leaked out and it ate up my clutch. Oh well, its under warranty so i'm not as upset

 

That still sucks, warranty or no warranty.

 

yea, now i have to break in my tranny right? how many miles till i can go to the track? o yea do u have an RMR filter or an exaust"?
cant decide between RMR or AMs

 

I'll have a catback this week (RMR) and I have a downpipe and control arm available and can get cat delete pipe any time !

 

doesnt the cat delete pipe come with the downpipe or does it cost extra?

 

extra. downpipe goes to the cat

 

i know i was just thinking if you buy the downpipe, you get a free cat, but nevermind. hey can you get ralliart wheels too? black preferably?

 

yes, I can Import Ralliart wheels. Don't have much info on them yet but I can get them.

 

price on wheels?

 

What about the deletion pipe that Ultimate racing sells that says no check engine lights? And it doesn't come with an O2 harness either.

 

Now I am very confused about what to get.
I wish HKS was making 3 inch

What is the best DP you can get after HKS?