964 Exhaust Question

[JoeP]

     I am an incorrigable tinkerer and want to build my own cat-free exhaust for my 964.  (Raspier sound is probably 80% of my reasoning, and weight is only 20%.)

     Will a free-flow exhaust affect the ECU's fuel/air calculations enough to damage the engine?  I plan to eventually install a high-flow airbox cover and a chip.  I just do not want to spend all of that money at once if I can help it.  I've already spent a politically incorrect sum this season.

     Thanks.....

[Larry Herman]

No it won't, not if you are just driving it on the street.  If you are tracking it, I still don't think that you would have a problem, but you could always spend the $150 it takes to get it dyno'd and check the Air/Fuel mixture just to be sure.

[Mike Andrews]

Joe,

 

It's a sickness isn't it

 

With the number of people that have already done something similar I would also think you'd be ok.  As Larry suggested, to get the most (power) out of this you could have the car put on a dyno and have them do a custom chip if the A/F ratio needs attention.

FWIW, you could just pick up a European pre-muffler to put in it's (the cat) place.  That will still look like a cat (to the untrained eye) and the car should still pass emissions. If you still wanted it a little louder, you could replace the rear muffler with a by-pass pipe.  The muffler that goes under the right side behind the tire is pretty efficient.  That’s the way my RS America was setup and it sounded pretty nice.  Not too loud but you could tell it was different.. 

 

As to the airbox cover.... if you can find an extra stock one, you can cut it or drill holes in it.  Or you could just cut up the one on your car, but most people like to save those parts just in case they want to go back to stock.