check out my log...

[1991gs-t]

Hey guys, im trying to figure out why my timing dips so low, even though i have really no knock...heres my log...



RPM KNOCK TIMING O2



4031 0 23 0.8
4903 0 17 0.86 1ST
6156 0 20 0.84
7062 0 16 0.84

4781 0 17 0.88
6156 1 20 0.88 2ND
6781 0 16 0.88

4812 0 20 0.9
5343 0 19 0.9
6062 0 22 0.9 3RD
6468 0 20 0.86


I did a first and second gear for the hell of it, just to compare...
and im a 1990 BTW, so i know that my O2 values dont mean much....

Also when im at WOT, the power band doesnt feel so smooth...some rpm's will feel good, the next will feel a little less powerfull, then good again and so on.....just thought id throw that in too...


im on 91 octaine with a 14b running 1 bar with a stock SMI...

any input will be greatly appreciated

thanks

 

[kpt4321]

Edited because the original formatting made the log hard to read. See below.

 

[1991gs-t]

Originally posted by kpt4321
You've got some pretty solid knock. Now, it may just be because you're running 15 psi on 91 octane on a stock SMIC, I'm not sure.

That's why the car doesn't feel too great though.

??? i only got 1 count of knock...let me redo the numbers...they didnt come out clear.

 

[kpt4321]

Ok. The knock count looks great.

A couple things:

First of all, you're pretty rich. 1990's will read very low on the O2 sensor, so getting down in the low .80's and the high .7's is not abnormal. I don't know if you are tuning with a SAFC, or running stock engine management. However, if you are running stock management, then you should defintely check for boost leaks. A boost leak will make the car run very rich up top, and can also give the symptoms you are talking about. Build yourself a pressure tester!

Second of all, with regard to your timing curve: There are two things going on here. First of all, it is perfectly normal for the timing to drop off HARD at higher engine speeds. For some reason (that I don't agree with or understand), the guys who set up the stock ECU made the timing maps very non-linear. In reality, at each load level, the total timing advance should be fairly constant, and even increase at higher engine speeds. But, since they programmed it that way, you will generally see a peak in timing at 6000 rpm and then a solid drop by 7000. Your numbers match what I would expect to see.

Second of all, you have a 90. 90's have even less agressive timing advance values than 91+'s do, so that's another reason your timing is lower than "normal."

 

[1991gs-t]

As of now, i have a walbro 255HP, AFC, and all the good electronic stuff. My egt's are perfect (~850*C @7000rpm 3rd gear). The thing is, if i move the afc 1 notch leaner in any of the ranges on my high map, i start getting knock, like anywhere from 5 - 10 counts of it. So I left the afc settings as is. Any ideas??

 

[1991gs-t]

bump

 

[kpt4321]

Please don't bump.

Originally posted by 1991gs-t
As of now, i have a walbro 255HP, AFC, and all the good electronic stuff. My egt's are perfect (~850*C @7000rpm 3rd gear). The thing is, if i move the afc 1 notch leaner in any of the ranges on my high map, i start getting knock, like anywhere from 5 - 10 counts of it. So I left the afc settings as is. Any ideas??

Since the car is a 90, I am going to estimate from your O2 voltages that you are running pretty rich. However, as you said, if you lean it out you get knock. That really doesn't leave you with a lot of options. You can lean the car out and just deal with a little knock. You can also try turning the bost down. Another good idea may be to retard the timing 2 degrees or so with the CAS, and then lean it out.