After fighting knock retard since I've owned the car, I may have finally figured out something worth sharing. After running a gallon of race fuel here, a gallon there, I threw in about 6 gallons on an empty tank to diagnose the problem and remove any doubts. Turns out it was, in fact, true knock.

I have been pulling quite a bit of timing out of the car lately since the cam install. After pulling up to 5* in the 4k-up table I seemed to really wake the car up. Best of all: ZERO knock retard.

I have never considered the stock timing to be the culprit, but it seems like the only logical explanation of my knock problem.

Anyone else decrease the stock timing and get rid of knock retard? Seems like GM would have gone on the conservative side, but if that was the case they might not have used a knock sensor .

Ryan

 

what table did you pull the timing from? "timing vs ?" and at what rpm is all your timing in that table? and what is your total timing in that table?
Sorry for the multiple q's. I'm just trying to grasp this as I will be working on my pcm soon.

 

Timing vs kpa table. I don't have the file here at work, but I will email you the a file when I get home if you like. It is a 306/stock heads tune.

Ryan

 

Certainly.
Cars respond to timing very differently. Some like more timing, some with the same mods like less. Probably the best way to check your adjustments is having the car on the dyno, but since you're saying it isn't getting any KR anymore, you're on the right path.

 

I do agree that the stock timing map is very aggressive.

 

I am fighting the same problem too, however, I have gotten rid of almost all my knock except for when I shift it pulls timing. How much total timing are you running as shown by datamaster or other scanning program?

 

I would shoot for 36-38*.
Then when you get it to the track or dyno try 32, 34, 36, 38....etc until you get the best hp or mph starts to fall off at the track.

 

Dan: easy question - What is total timing?

Is that the highest value in the timing table or something?

Ryan

 

Total timing is something I'm used to talking about with a carbed car...it would be the maximum advance you'd get.
On our cars you have complete control over timing at all rpm and all load (map).
I guess you could say total timing is the amount of spark advance you'd see on your datalogger...not what you see in the spark tables.
Does that answer your question?

Also, as madwolf was hinting at...set your car up to have the maximum amount of timing you can get without retard. But I wouldn't go over 38 on shown on a datalog.
Then when you take the car to the track or put it on a dyno you can see what different amounts of timing can do and see what your car likes.

 

Ok, that makes sense. Thanks Dan.

Ryan

 

I think people have found that cams with a good amount of overlap (such as the cc306) require more advance in the lower RPMs and less in the upper, to run the best.