Exhaust flow talk

[novocaine]

I just re-read this thread and its really helpful. Thanks for all the input.

I just bought a second hand aftermarket exhaust, and I need to have it fitted.
Right now I have a stock blacktop header that runs into 50mm secondaries anda 57mm collector.
After the first silencer its mandrel bent 63mm pipe till the end.

Because the secondaries on my stcok header asre too narrow, there is something like an immediate 8mm increase in diameter to 50mm.

The new header is a 4-2, the exit pipe diameter is 48mm.
My question is, is it ok to go with 50mm secondaries straight from the header?
This would mean the header into 2 50mm pipes joining into a 57mm collector and into 63mm after the silencer.

OR

would it be best to go with 2 48mm pipes into the 57mm collector. The difference seems miniscule to me... And im sure 50mm would be better.

Any thoughts? I have vvt for the low down torque.

[HybriD07]

isn't 63mm and even 57mm way to big for a 16v?

I have a 4 to 1 header with 1 pipe of 50mm outside diam. to the back.
At the end it's split up in 2x 50mm and even now it feels like i lost a little but off power in high rpm.

My guess would be that 57mm is too big for a standard 4age or even a tuned one.

Does this make any sense or do i have no idea what im talking about, this only comes from experience.
My brother has a swift sport (same spec as 4age, 1600 16v 125bhp stock) and we used a 60mm pipe on that and he lost a lot of hp, so we instantly swapped for 50mm pipe and it runs very well.

[novocaine]

4A GE 20V. There was a noticeable increase in response ad a much smoother ride after fitting the 63mm...

[F0Bman]

Contact Hytech in Irvine,CA USA. He makes exhausts for F1, FA, and Nascar he might be able to help you.