348 torque loss after going from cats/dual can to single can/test pipes. Help Please!

If you lost some torque it's probably your cam set up. Since you lost some back pressure that may have lead to the loss. If the cams were running any sort of valve over lap, then the loss of back pressure will have affected the previous scavenging affect of the over lap. So ............. if that is what the problem is then engine will have to be yanked and the cams retimed to compensate for the better exhaust flow. Either that or, try putting the cats back in and see what that does. The cats will slow up the exhaust flow a little bit.

But just for kicks. Try disconnecting/reconnecting the battery and then letting the car relearn the warm up parameters. Do this after the car has sat all night. Let it warm up for about 15 minutes, then go take it for a nice long drive. See if that helps.

 

can you explain the test pipe difference to the straight pipes?? Are you speaking of hollowed out cats??

 

Perhaps your exhaust flows more freely now, thus letting your intake breathe easier, which in turn causes you to run leaner than before. Would a leaner mixture lose some torque?

If so, then you can enrich your fuel/air mixture by turning the screws on your MAFs just a bit (lower resistance between pins 1 and 6 equal richer mixture).

 

Test pipes = politically correct way of saying straight pipes. In CA (and other socialist states) it is illegal to replace your cats with straight pipes, however you can temporailiy use test pipes for off-road purposes.

BTW, our SS cars (and Spiders) have the single can and we have the same factory torque specs with cats, but higher Hp, as the older cars.

 

I put the same "test pipes" on my '94 with stock single can muffler and I did not notice any loss of power. Even low end torque.

 

Same MAFs on all 348's, so they all have the same MAF mixture screws.

The O2 sensors are *ignored* at full throttle. O2's are also ignored when the motor is cold.

At other times, yes, the O2's will compensate mixture.

 

I know you didn't change the timing. I was talking about the original timing having some valve over lap dialed in. The only way you would know would be to retime it. Not really worth it unless you are racing. The 348 isn't really a torquey car any way.

 

The 355 is !!!

 

I call BS! 228.6 lb.ft. for the lowly 348; 268 lb.ft. for the vaulted 355. Pfft. Hardly a torque monster! It's the gearing that really gets you going goth-ster...