Thread: Went 3" Exhaust, Lost hp...

Well I went from a 60mm (2.36") exhaust to a 3" exhaust and lost power.

60mm exhaust: 173hp, 137tq

3" exhaust: 162, 146tq.

Well in the process I modified the stock ve secondaries cause they were dented up. Made them 2" in diameter and 19" long. Otherwise I used the stock ve manifold primaries.

Before:







After:








Could it be the secondaries were too long and fat? (I'm a waiting a modded SSAC)

Could it mean that I need to reduce timing? running 15* base.

Mods:

20ve, 16ve cams
Calum basic
ve MAF
ACT HD pp with stock disc
JWT pop charger

vvl points - 5100rpm.


Will post graphs as soon as I can.


Peace

that's interesting...

interesting that you gained torque, but lost hp, obviously quicker in the midrange.
I found no gain up top going to 3" either, the myth that 3" is always better is under fire it seems.

hmm interesting stuff, was looking at getting 3" system myself over the next week or so...
could be that the real benefits from the 3" are gained if ya get n1 or similar cams..

what are the original secondary size and length?

Need SAE corrected dyno graphs to compare.

The title may be a bit misleading. I dont think it's really the 3" that caused the loss of power but more the mod to the secondaries. Too long, too big.

@ Speedyd, the stock ones were definitely shorter, if you look at the pics. Will measure when I get a chance.


Not gonna take off the 3" (even tho I have the 60mm). Will get the ssac as mentioned b4.

Peace

About 4" longer secondaries, and larger. Peak torque is going to be lower in the rpm range as you know. I'm curious to see how far down it dropped. Interesting the 3" didn't seem to make up for the difference.

Nizmo, just watcht Thor and see where he goes.

You are truely over thinging things but I guess thats what you have to do to see the light.

The Formula is simple and easy but you have to be willing to follow.

X2 but +9wtq is good