Hello. I have autotap and my car is getting knock. It is not the same everytime making think it could be false knock. I was going to run race gas and see if it goes away. The only race gas I can get here is Sunoco 260GT Plus. It is 104 octane. Is that to much to run in my car? It is an off road fuel but I will be running it at the track.

 

if its unleaded then your fine to try it if its leaded or low lead then i wouldn't run it for long otherwise you better kiss your o2 sensors goodbye before too long

 

I wouldn't waste my money on race fuel......its either in the tune or false knock......just tune it out

 

If you can change the tune yourself, try lowering the WOT timing just a bit. IF it does nothing to cure the knock..then put in the 104 unleaded and see if it goes away...if it doesn't, then its false and you could safely set the retard degrees to 0 in the several different knock tables...thats is if you can't find the source of the false knock....

 

I don't have the ability to tune my car. I just have the data logging portion. I bought the car used and the previous owner had it dyno tuned using LT-1 edit. Timing is advanced 3 degrees on motor. When I ran nitrous I had the digital six pulling 5 degrees of timing. Sometimes I get 2 degrees of knock just stalling the car to 1200 rpm.

 

In that case, try the race gas, then at least you'll know if its real knock or not...otherwise you'll never know. Get the highest unleaded and you'll be ok..its usually 104 or 101 depending on brand or what your local speed shop has. You only need to have an empty tank, then just put in 5 gallons and then take a spin to WOT.

 

Thanks for the info.

 

Do you have a LT4 KM?? Also some 76 gas stations sale VP 100 octane

 

You can mix about half 104 half 93 (or 91 depending on where you live), that will save you some dough. I don't know how loud your exhaust is, but things like headers, roller rockers, cat-backs, etc can defiantly increase false knock. You could always invest in LT4 knock module, it should help (as the LT4 came stock with roller rockers), since it is a bit less sensitive.

If theres still knock and you're fine on higher octance gas, you can pretty much say for sure its false, and just get someone to tune it for you.

 

I do not have the LT-4 knock module. Will look into that. Do not have headers or roller rockers just borla catback. No 76 stations here that have the stuff that I am aware of. I live in Grand Rapids, MI. I found a VP distributor about thirty minutes from me. Calling them tomarrow.

 

LT4 KM will run you about $40, unless they've gone up in the past year and a half. But you can probably bypass that if you just do the race gas thing.

 

Some have success with the LT4 KM, but I never did and I've heard alot of times it introduces even more knock unless the knock is truely caused by the roller rockers. I program my own PCMs so detuning how much retard can occur is easy for me, and I have several LT4 modules sitting on the self.
I've heard of headers causing false knock, but I think that idea is false as the sensor listens to noise within the engine. Take a stethoscope or other listening device and hold it up to your engine while its running and you will not even hear the exhaust, even if you hold the device on the header themselves you don't hear the exhaust, you can hear the rotating assembly turning and thats what the knock sensor should be hearing as well.
I took an old stethoscope of my wife's and pulled the flat end off and attached about a 1 ft. peice of steel fuel line to it and use that, just stick the fuel line down on the part to listen too while the other end is connected to the remaining part of the stethoscope..works great to find those pesky little noises.

 

If I find out it is false knock can I send my pcm somewhere to get tuned or do they have to be able to see the knock while car is running to tune it out.

 

A data log of the knock would be perfect, then the tuner will know exactly at what rpm and TPS to detune. You want to leave as much sensitivity at the "other" rpms and TPS in case real knock ever occurs. You can either tune all knock out, or reduce the max amount of retard at those loactions, leaving some ability to reduce timing if knock is heard...so if you were experiencing say the max at 8 degrees, it could be changed to only pull 1.5 degrees at that rpm.
You may want a degree or two removed form the timing table. I've seen way too many tuners add too much timing to get you bigger hp #s and remove / reduce the ability to reduce timing from real knock altogether....you think all tuners care how long your motor lasts after you leave the tuning shop??

 

Went to the track and ran a mix of VP 103 and 93 octane and the knock is still there. One run it was reading knock retard of 12, the next run was none, and the last run was 7. My A/F ratio on the bottle was btween 11 and 11.5.