ok i dont know if this is the right place to be askin but anyway my budy has a dataloger and we went to the track this weekend we both have lt1s his 94 with false knock moduel and mine a 95 no knock moduel he is showing about 4degrees nock on all the shifts and i only saw it on the shift from 2nd to 3rd any ideas what could be the cause of this?? is that much knock normal??? any info would help
Thanks Evan

 

I know this is not the answer you are looking for, but as a card carrying smart A$$, I hereby tender my opinoin----perhaps we would be considerably better off if we didn't have data loggers, scanners, etc. I realize that it is nice and perhaps prudent to monitor our engines for possible problems or for getting maximum performance, however, if an engine is running fine and the A/F is optimized and the pcm tuned for the combination, why go out of your way to find and analyze, what are in all probability minor things.

I know I will get flack from my response, and I deserve it.JMHO

 

if you are running headers, especially longtube headers, there is a gooooood chance the damn sensor is sending a "false knock", otherwise i agree with bubba, if its running fine and you dont hear, feel or see any mechanical problems, run it as it is with the proper tune and setup

 

When you get knock retard between shifts, it is typically from the sudden decrease in MAP pressure. This makes your PCM think the timing is too advanced and suddenly adds knock retard. It's fairly common I believe.

I think Injuneer explains it in his PCM scanning turorial.

From Injuneers website:
http://members.aol.com/InjuneerZZ/ScanMast.htm
"Using the "record" feature of the ScanMaster at WOT, many people have seen 4 to 8 degrees of retard. This is where the record features come in handy. If you hold down the recall button, you see minimum O2 level on the left and maximum retard on the right. Now hold down both the recall and mode buttons, and you will get the MPH at which the min O2 and max retard occurred, again, O2 on the left and retard on the right. Think about when this occurred. Invariably, you will find that this was at one of your shift points.

My theory (being an M6 type) is that on lifting throttle shifts, the sudden drop in MAP (remember the timing map above) on closing throttle causes the PCM to put in a few degrees more timing, and just as it has added this timing, you whack the throttle open as soon as you've got the next gear, and bang…. too much timing, here comes the retard. One way to explain it, and it tells you your motor isn't having any unhealthy problems, and not experiencing dangerous continuous knock, but still not good. Remember, it pulled all the timing back out real fast, probably overshot, and is putting it back in real slow. You are not at the better, more advanced timing."


Dan

 

Hey sorry to bring this back but I was looking at the searchs and found this. This was the exact answer I was looking for. What stereomandan posted there does exactly what my datamaster shows with the MAP. Now if the map if creating the knock how do we fix that. The most i get is 4.3 retard degrees.

Thanks

 

The MAP is not creating the knock directly. The knock is due to the PCM putting timing advance in when the throttle closes briefly (low MAP/high vacuum), then throttle opens suddenly (high MAP/low vacuum) and there's too much advance for a brief period, and there's enough knock for the PCM to start to pull timing using the knock retard system. MAP is used as a measure of engine load, and is one axis of the spark advance tables. You could probably eliminate the effects by reducing the knock retard attack rate and increasing the decay rate.

 

okay you say the throttle breifly closes and opens is casuing the map to change. But I have a auto how does the throttle close?

 

Go read the quote.... my analysis was based on:

I didn't say that my theory applied to an A4.

 

yah I knew you werent referring to a a4 but I was thinking since you are talking about a manual, and automatics dont need to open the throttle blades I was just trying to think or find out what is causing the drop in map if the throttle blades are not closing?