Putting on X51 headers and Fabspeed Hi-flow cats tonight. I've read conflicting reports on this site (searched alot) and it still seems debatable whether on not I need to unplug the battery for four hours after I modifiy the exhaust. Has there been any definitive answer from porsche technical or dyno, etc or should I just try it anyways. Thanks,

 

yes, unplug it. car may (will) feel very sluggish if ECU was not reset as computer imho is not programmed to expect sudden increase of the air flow in exhaust.
but not for 4 hours - 10 minutes is more than enough to reset ECU.

 

Just disconnect the negative terminal of the battery for a few hours, that's all.
CATTMAN

 

Yes. Just disconnect the negative terminal while you do the install (make sure you don't close your hood). That's what I did, and it worked great.

 

Oh, and be sure to open your windows an inch or two. This is so that when the doors open and close, you won't stress the glass on the seal, since without battery power the little adjustment the glass makes won't be operable.
CATTMAN

 

I don't think it makes a difference, as the ECU is designed to adjust air/fuel on the fly. However it won't hurt it either, and like your home computer, sometimes a restart works wonders.

 

i does make a difference in how fast ecu adjusts to new settings. it will adjust one way or another but without reset it takes much longer. when i did put my 200 cell cats on a first drive it was an immediate feel that half of torque was suddenly gone. reset returned it all back.

 

I didn't reset mine, and everything felt great from the day I installed it.

Like I said it won't hurt anything, and like you suggested that it will come around eventually if you don't....I guess the debate continues

 

Me too Ed, I didn't reset and the car felt good right from the get go. Just make sure you get a couple of good WOT runs and that should adjust the A/F ratio just fine.

Dave

 

WOT is the only way to drive these cars