Ok i got my wideband installed and after some tunning i got my wot afr to 12.7-12.9 at wot. problem is the car detonates with stock timing....Im confused idk what could be causing this? I can audibly hear the detonation right at around 5k rpms until i shift.

I have my shift points set at 5600 rpms and 80mph so that it shifts according to rpm not mph.

So i pulled 2 degrees from 5000 on up and 85kpa-100kpa and it is still making a detonation noise at wot.

I know that with more efficient combustion chamber you dont need to run as much timing but is it normal to have to pull some timing from stock on a head/cam lt1 at wot?

The heads are hand ported factory stockers plugs are fresh tr6's gapped at 35 thousands and the cam is comparable to the lt4 hotcam. car has a walboro 255 and 32lb injectors. at part throttle my afr is always between 14.1-15.0 any idea guys? Should i just keep pulling 1 degree at a time until it goes away?

 

Do some logging to see how much timing it is pulling and where, for a better understanding. You may be pulling it out in the wrong area.

 

+1 with above .. Another factor is the PCM magically adds timing at higher RPM's. When you look at the failing condition your actual timing may be higher than the tables, just prior to the knock pulling timing. Also a PCM remembers conditions that cause knock and will then pull timing at those conditions even w/o the knock occurring. However you are hearing pre-detonation so it's obviously really happening.

 

Thank's guys heres a small update to this.

So i continued to pull timing until i hit 29 degrees and it was still detonating. At this point i was perplexed so i decided to add some fuel went into my maf tables and gave the appropriate area's +2 and reprogramed and what do you know no detonation....But when it shifts from 2nd into 3rd at around 4500 im getting some audible detonation still.

Now my wideband was reading about 12.9-13.1 so maybe my engine just needs more fuel?? But when i get some more time im going to find out how much air im taking in around the 4500rpm area and give it some fuel there as well.

 

I would adjust the wot tables before the maf tables. From talking to others and my car included LT1 like a litte more fuel. Mine runs best at around 12.5-12.8. Every car is different though.

 

Try colder plugs.

 

My bud in cal sez you can only get 91 octane fuel. Not good for control of cyl knock/ detonation. I sent him a flash file and it knocked all over since I trimmed the knock table back and advanced the timing. an great, but, he said knocked @ WOT.

I don't like to dial back timing on my ride. It takes power down, alot. So, I went to Evans cooling NPG. Much of the knock is due to hot spots in the cylinder. Evans cooling can stop this.

Although I don't live in cal, I run 15 psi with 34* timing @ WOT. I refuse to dial back since I know this is a power killer. (97ss 383-D1 MM6)

Find it @ evanscooling.com.
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