I have been told that if you put big exhaust on stock car it will not run. Is this true or not. Spoke to another exhaust shop who said theirs worked fine when tested for zoom article on standard car. Has any one got the CES system?

I have been told that if you put big exhaust on stock car it will not run.  Is this true or not.  Spoke to another exhaust shop who said theirs worked fine when tested for zoom article on standard car.  Has any one got the CES system?

<{POST_SNAPBACK}>

This is true to an extent. The car will still run, just not all that well. Through my tests I found that if the exhaust is too free flowing the computer tends to cut the power. Perfect example is shown in the following dyno sheet ::

Looking at the dyno sheet, specifically the red line (the green line is with cat, the red line is without cat), you will notice that as the power starts to shoot off (ps, notice the difference in power with no cat....shows how restrictive the std one is) the boost begins to spike. Normally your oost should be a nice flat looking line, starting at about 6psi going down to 5, and leveling out at about 4psi. But in this example the exhaust is free flowing enough to allow the turbo to boost up harder. Problem with this is, the std computer has no idea what to do with all this extra boost hence the sudden drop off in power, as shown in the graph.

Regards,

Dean

Edited September 12, 200521 yr by XR6ISM