so I had an autotap obd2 data logger thingy hooked up to my car for a few test runs and I did see above 5500 rpm that im getting a maximum of 8 degrees of knock retard, what is causing this and how do i get rid of it
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Detonation is the cause. Higher octane fuel, retarding ignition timing or adding an intercooler are the possible fixes.
- 93 mph in the 1/8 mile
Member of J-Body Of Michigan.
I'm already running 93 octane so thats not something i can fix, being that its winter and the intake pipes are cold i doubt intake temp is the problem, shouldnt need to retard timing
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
You are boosted and non-intercooled, you should be pulling timing.
- 93 mph in the 1/8 mile
Member of J-Body Of Michigan.
nah, something's funky.... Rich's car doesn't get any timing pull and its making more power than Rodimus'... check your plugs first, how many heat ranges colder than stock are you now? May want to try another range down... Also, what are you're a/f's now Matt? Especially when you're seeing the retard? EGT's?
Is it 8 degrees constant while you're over 5500, or is it just at one or two rpm points? Also, have you done multiple runs to verify how consistently it does it?
8 degrees isn't considered toooooooooo bad on the vw motronic ecus, we normally shoot for 2-3 degrees, with a max of 6. But I'm not sure how good/bad it is with the eco.
Timing advance is computed by several things.... The advance that the computer attempts to run is set by IAT, ECT, RPM, and TPS, and possibly a few other inputs that I'm forgetting... Timing PULL is very dependent on the ECT, IAT, and knock sensor voltage...
You Penn. guys have to pump your own gas right? I guess that eliminates what I was about to say about if you watched the attendant to make sure he put in the right stuff... I always do, after a Jersey J got diesel in his tank when he wasn't paying attention...
Arrival Blue 04 LS Sport
Eco
Turbo
Megasquirt
'Nuff said
The suggestions above should help, if you still have problems try water wetter in the coolant, got rid of my knock retard, I'm not boosted though. Works by getting heat our of the head eliminating hot spots that can cause detonation by making the coolant more effective at absorbing heat, and it's cheap. Anything you can do to keep heat out of the engine bay will help as well.
15.3 @ 89.97mph, 14's on the way?
did you actually check the timming ?
while you were looking at the timing retard
showing activity on the knock retard shows the computer is recognizing something is there , if the timing is still in the high 10's to 20's , everything is fuctioning correctly
alky injection will also help out , as the water in the alky mix will cool the combustion temps and help prevent knock in the cylinder
some cars will pick up knock readings from having motor mounts , also phantom knock does happen from other things in the motor
so just because the knock retard shows activity doesnt mean the timing is getting pulled out , its just telling you the computer knows something is there
on my cav ive seen knock retard readings up to 5 , and still had actual timing in the low 20's
you only have part of the needed info to make a decision on what to do
you can try using 100 octane gas , and see what your knock readins are , if its still there then it shouldnt be spark knock unless your extremly lean
ive tried 3 different sets of plugs with no difference, I have water wetter in it already, yea i always use 93, Gas stations dont sell 100 so thats really not an option, my alky injection seems to make no difference at all, the autotap only measures knock retard im not sure that theres an option for regular timing
1989 Turbo Trans Am #82, 2007 Cobalt SS G85
Knock retard IS retarded timing. A knock sensor voltage reading would indicate there is something there, but if it's registering knock retard, that's because it's retarding your timing isn't it? In my datalogging I would show 22 degrees timing advance at WOT in 3rd with 4-5 degrees of knock retard. Once I got my knock under control (1-2 degrees under the same conditions) I would show 27-29 degrees timing advance. I could be wrong, but that has been my experience.
15.3 @ 89.97mph, 14's on the way?
the atuo tap is a laptop program right ? then it should read all forms of data from the pcm
if its the right program im thinking of
just because the knock retard shows 4-5 degrees doesnt mean its always pulling that much out
the computer will keep that much shown , then retard or advance the timing as needed
but keeps 4-5 showing tell its not recieving a signal any more , it will go up or down depending on the signal creating the noise the sensor is seeing
if you have any place that sells 100 or higher unleaded race fuel , it worth a shot to see if that makes any difference , keep in mind the more 93 you have in the tank the more dulited the 100 will be , i usually try to add the 101 in my tank when im close to empty
if none of this is helping the knock retard , then its possible yours is picking up a noise that isnt spark knock
keep in mind you want to see some movement on the knock retard to know the computer is doing what it can to keep the motor alive
you can de-senseitize the knock sensor , by lowering the tq setting it was tightened at , but keep in mind the above statement
I use obd-2.com's carcode software, and the knock retard is in real time, even when the knock retard #'s drop off the timing advance takes a while to raise up to the level it would be at had there been no knock retard. With the software that I'm using, knock retard is what it's reading NOW, not a peak reading. The effects I've seen have been that if knock retard peaks at 5 degrees for only a moment, the car's timing advance drops a similar amount, and slowly climbs back up trying to get to the high 20's as long as it doesn't see knock again, and you can feel the difference between a run with 5-6 degrees knock retard, and a run with 1-2 degrees of knock retard. Not sure what the software you use is like, but that's been my experience.
15.3 @ 89.97mph, 14's on the way?
5 degrees of knock retard means your timing is retarded by 5 degrees. Simple as that.
Ta, Paul.
