I am a big noob so take it easy on me haha. If i have some aftermarket headers and a test pipe, how will the performance be if i'm still running with the stock exahust. is this bad? would you suggest buying a new catback or something similar? Any help would be great! thank you! BTW i have a 4cyl. 2000 accord if that matters.

 

Well it will be a restriction. However, on a N/A 4 cyl I am sure the difference will be noticeable....but Barely.

 

I'm unsure why you would get a test pipe then restrict it with stock piping?

The point of a testpipe is to remove the restriction of the catalytic converter and allow more freely flowing exhaust.

 

i think it's fair to assume the stock manifold is a major restriction and it's upstream from everything else so a good header isn't a bad idea.

but after that, where's the bottle neck? what's more restrictive, the cat or the piping? unless flow across the cat is more restrictive than the pipe afterwards then the test pipe is worthless. just playing devil's advocate..

 

If you're upgrading the stock manifold and removing the cat, which yes are probably the two most restrictive bits on the car. You'll have most likely a 2.25" or 2.5" collector on the end of the header (the most common I've seen are these),then go into a testpipe (we'll assume of same size) and then into stock diameter piping which is right under 2".

What becomes the bottle neck at that point? I guess that was more of my point. If you're going to go through the trouble of freeing it up in the front of the car why would you slow it back down right below your feet?

 

right, that's a good point about the common header collector sizing.

 

It's all good, I mean I guess you *could* have an aftermarket header that was the same size as OEM but that kinda defeats the purpose You could just chrome your OEM one haha.

 

haha, bling!

 

Got a question am I able to use a test pipe on stock headers ? On a d15 or do I have to use aftermarket