exhaust/velocity

Hey, assume that i made a quick disconnect infront of my catalytic converter on my 97 sl. I heard that u could gain around 20hp instantly, and also heard that u risk burning valves because u decrease exhaust velocity, and backflow pressure< which is the good thing? If someone could tell me if this is ok, and the other exhaust options on a naturally aspirated 3000 thatd be great.

those kind of exhaust lengths are for pro drag cars man. yes you would increase some HP, doubtfull it be 20 more though, thats not likely from a 3.0 V6 but youd deffenetly have some consequenses. the car might not even idle correctly without backpreasure, you might burn valves, you'd deffenetly have tons of back-fire, predetonation.
why do you think race cars have thier engines fully re-built after a few runs?

If your turbo you will be fine.

If your NA you should still be fine, but be ready for backfiring everytime you let off the gas.

Race engines are rebuilt every run due to the amount of power they are making. The parts wont hold up for more than a run or 2.

I just hollowed my cat yesterday and i have smoke coming from the exhaust now. Any ideas why? I did notice a big difference in the take off power though.

Could be the remaining little bits of honeycomb burning up, or it could be excess unburnt fuel getting burned in the exhaust.

Your valve seals could be leaking a small amount. Your cat may have been super heating the oil and burning it off before it made it out the tail pipe.

TMD

What whp and qtr mile gains could u expect from 3sx's long na headers and straight cat? on a stock 97 sl.

Also i cant find the stock quarter mile time for the 97 sl i would assume it is aroung 15.2 -manual?

Yeah, mid 15s probably. I know 14.9 has been done on a stock SL. As far as gains with the new long-tube headers, I honestly don't know if anybody has dynod or raced with them yet. I wouldn't expect more than 10-15 tops, but that again is just a guess.