cmn

So, I'm getting my car retuned with AEM EMS, 68mm TB, Megan racing header and possibly Skunk2 cams, valve springs and retainers. I have a Berk TP at the moment, which I believe is 63mm. Would I se any gains or advantage in getting a 70mm testpipe for an NA tune? Or will that not make a noticeable difference?

whiteflash

You bought cams, TB, springs, retainers, and a header before you bought an intake or exhaust? Interesting.

Either way, if you're keeping your exhaust stock then don't go with a larger testpipe. The test pipe / HFC rule of thumb is that it should in terms of diameter, greater than or equal to your header collector, and equal to or less than the piping diameter of your exhaust. Otherwise you'll create a bubble in the flow and create a lot of pressure.

Opc

yea, don't even worry about the test pipe.. why a 68mm tb? run a 72 and reweld the pinch and port match, always makes great gains.

are you running a stock exhaust... kinda a waste if you have engine flow work

JmanS2k

if you're running a stock exhaust then just keep what you have. if down the road you switch to a 70mm catback then you might as well get a 70mm tp or hfc and then retune it.

Dingodogspeed

Wait, I have a question,,, your test pipe should be bigger then your header collector but smaller then you exhaust pipeing?

cmn

I have an Injen "CAI" and HKS exhaust as well, but I'm not sure if I will use the intake or not. So the conclusion here is that it should be somewhere between the collector size and exhaust size if they are different...

H22toF20

Just make it the same size as the exhaust.

Kermdaddy

Usually they should be the same but sometimes that is hard to do. You never want to go up and down in sizes. This would cause friction losses and rob power.

Seems that 3" is the rave right now.

H22toF20

It's been the rave for along time now in the Honda community and it should be. The s2k crowd is just a little behind.

whiteflash

In theory, eitherway works..... usually it's easier just to match to the size of your exhaust though. But the testpipe or hfc should never be larger than your exhaust diameter.