Well today my friend borrowed a scan tool from his school to see how much knock retard he has in his modded 1999 grand prix gtp. He was going on about how much horsepower loss he is getting so we took his car out and he was getting like 3-4 degrees of knock average up to 7 degrees max under WOT. So then we took my Grand Am out cause I thought i was going to get knock even tho its a N/A engine thats gota fairly low compression. I took the grand am out and I am getting like 5-7 degrees of knock under WOT 1 time 8 degrees so I was wondering is there a safe knock retard that you can get in a car and how much hp can you lose with that kind of knock? Also if I run premium in my Grand Am will I get less knock retard and gain hp actually? Btw everything else looked fine IAT was low no missfires good air/fuel mixture etc.

your buddy needs to get that KR taken care of like yesterday, unless he wants a chunked piston

Ya but what about my Grand Am that has knock is that bad?

Many time KR can be the stock PCM just pulling timing to save wear on the trans and such. Try to run slightly high octane and re run the scan.

The 100% stock 98 Grand Marquis GS I was driving while I was putting the new motor idled like crap with 87 octane. So I started trying 89 & 91 octane and found it idled much better and ran smoother with some midgrade gas. Not a performance car in any sense but it felt like it benifted from better gas.

Ed

Your Grand Am is N/A. Cylinder pressures are MUCH lower so detonation is nowhere near as damaging to the engine as it is with higher cylinder pressures. If you run a higher octane in your Grand Am then yes the KR should be reduced and the car should perform better.

The GTP on the other hand, need to try to kill some of that KR. 7 degrees of KR is not good and he is probably going to end up eventually chunking a piston or something similar.

Check plugs on both cars, hell, replace them with appropriate heat ranges, and gap accordingly..