True Twin, Y Pipe, H Pipe, XPipe... What's the difference?

[AndyD]

I've been trying to figure out the difference between H-Pipe, Y-Pipe, X-Pipe, True Twin and Single exhaust systems.
I've had a bit of a look around the interwebs, but all I can seem to find are on American cars with 3000cc+ displacements

Can anyone explain what effect these exhaust types have on the VR4's in terms of:

• Changes to HP/Torque
• Changes to dB
• Scavenging
• Turbo/Exhaust Pulse
• Anything else I can't think of or don't know of

Cheers in advance,

Andy.

[bradc]

For a stock VR-4 you have one oxygen sensor, and as such must have a single pipe unless you have a full replacement ecu with twin O2 inputs or a way of monitoring individual banks.

Simple answer then, don't bother.

[Turbo_Steve]

Going to have to diasgree a little bit, there: an X pipe will work with the single lambda as long as the flange is mounted in the "X".

A well designed X style pipe will actually maintain laminar flow in the pipes whilst allowing the lambda senor to monitor the level of oxygen in the join. Clever stuff.


What I do agree with is that it's usually more effort than it's worth: Unless you're going for bigger turbos, then your spool time doesn't need improving and your not likely to get a significant top-end power benefit out of a specialist pipe.

[AndyD]

Interesting feedback and straight to the point ^_^. Indeed I am not intending to upgrade the turbo's or anything that requires forged internals

I am however quite keen on getting twin rear exits... It just looks prettier How well then would a Y-Pipe setup work?

--Andy

[bradc]

Check out my Gallery, i've got a split at the rear axle going to two tips

[scott.mohekey]

Sorry to revive a bit of an old thread.. but, if I am intending on going the bigger turbo route, forged internals etc etc.. then what sort of exhaust configuration would be best? twin right through? does the exhaust need to be balanced when you're running turbos?

[bradc]

Twin the whole way through would be good yes, or simply going into a single 3.5" pipe.

[scott.mohekey]

So it comes down to whether I want twin exits or not. Cool.

[Turbo_Steve]

Optimal would be two seperate pipes with a balance pipe just before the back boxes. The trouble is, designing that to work properly is quite difficult: ideally you'd need to do some gas-flow modelling.

A pair of 3" pipes with a 2" balancer should be sufficient, though, as long as you can get them the same length and shape.

I would say that would be very dificult on a VR4 (and possibly why Mitsi avoided doing so) and as such I'd go for a 2"-2.5" downpipe from each turbo into a single 3.5" as brad suggests. It's not ideal, but it is much simpler and cheaper. Alternatively, go for two 2"-2.5" into a single 4" or 4.5" pipe to the rear of the car, and then open it up to twin exits.

An ideal system stays roughly the same size across it's entire length. Where this isn't possible, it's best to get larger at each stage to allow for the drop in speed.