moving on swiftly from suspension and brake mods the next logical step is the engine.
Under no curcumstances do I want to lose the burble of the exhaust.
I am at first thinking of "free" mods to do with airflow to and from the engine, bell mouth the turbo inlet /outlet, bellmouth the throttle body and knife edge the butterfly, Just making the flow of air as smooth as possible.
What I am concerned about is when it comes to the headers / up pipe etc. I must keep the boxer burble, what headers do I use. I am thinking of blue printing first and see what power gains can be achieved before I spent more wonga on new headers,things like cutting the cats out the standard ones and smoothing the flow at the flanges and bends ( I assume there is one in the cross pipe?).

 

I also notice at the end of my downpipe (catless)it reduces from approx 3" down to fit PPP centre section, is it worth continuing this 3" size all the way to the back box (PPP) and then reducing it to fit at that point. (would like to keep PPP back box, as it is easier to make a pipe with a few bends, than it is to make a box )

 

Changing to a stainless unequal length manifold changed the exhaust note considerably - no longer sounds like a Scoob.

But it goes much faster, so not much of a compromise

Richard

 

Manifold-wise, the HKS one makes suprisingly little difference to the general sound of the car. Just no more drone and some nice person seems to have removed the treacle that must used to have been in the engine

 

'John'

Do you know which Turbo is on the Sti Ra Ltd Vs2's ?

Ta

 

http://www.iwoc.co.uk/impspec2.html doesn't list the turbo for your model.

 

Maybe its a TD05?

 

Air cools as it gets further back so the reduction is not so bad.

Changing the PPP centre and backbox to something freer flowing will help. Changing the turbo to something bigger will arguably be the most dramatic single thing you can do - less back pressure, denser charge, more airflow, less retardation. Sadly you also end up with more lag and a higher boost threshold, but if you choose carefully you will have a tremendous powerband from 3500 to the red line unlike the TD04L loses the plot way too early no matter what you do with the breathing. Having said all of that I am presuming your car has a TD04L in the first place - depends on model of course.

The off beat boxer note is related to unequal length manifold as well as the resonant properties of cast iron.

I have a SS manifold, and the boxer sound is attenuated, and the whole thing takes on more of a motorbike sound when revving which really grows on you. But the turbo was FAR more effective.

[Edited by john banks - 8/10/2002 11:01:50 PM]