Re: reducing lag via exhaust efficiency

["Graydon D. Stuckey" <graydon@apollo.kettering.edu>]

On Mon, 23 Mar 1998, Sargent Schutt wrote:

> On your sub-4k boost lag issue: I am considering upgrading to a hybrid turbo
> and RS2 manifold. First I'm (still) waiting on my Stebro exhaust. It will use
> dual hi-flo cats to 2.5" dual pipes with free-flow (no baffles) mufflers
> (center and rear). That should reduce back pressure a little. Then the RS2
> manifold and hybrid turbo, along with (perhaps this won't be necessary) a
> better down pipe (Graydon - would your unit work here? Anyone else got any
> suggestions for improvement). I will go with Ned for the chip.  

My downpipe is designed for the stock turbo on a stock 1-pc manifold.   
The 20V cars have their turbos in a different spot, so my 'pipe won't work.

> Question: if you replace the manifold and the rest of the exhaust with a more
> efficient, free-flowing system, I would exect less lag from cruise/idle,
> though a little faster boost loss with shifts would occur. What is the
> collective wisdom on reducing lag vis a vis the exhaust on hybrid turbos?
> QSHIPQ? Scott Mo.? Graydon? Anyone else? I know there are other IC and intake

The exh turbine is basically a heat pump, which takes heat out of the exh 
to drive the compressor.   As such, it will work best when the pressure 
drop across it is greatest, so you want the biggest, lowest restriction 
exhaust possible on it to get the fastest spoolup.

> path modifications which will help throttle response and therefore lag, but
> what of exhaust mods? Significant lag reduction there, or is it a waste of
> money (save the ear candy)?

Some others here can go into great detail on the technology of a turbo.   
I just know that when I put the big 3" exh system on my car I saw the 
boost come on almost 1000rpm lower in the rev band. 

Later,--------------------------- -   -   -   -
Graydon D. Stuckey		 / \ / \ / \ / \
graydon@apollo.kettering.edu	|Mr. Muffler... |
810 733 0255			 \ / \ / \ / \ /
--------------------------------- -   -   -   -