kasturbo

You said that you switched boxes, any chance that you just have a bad klr? What happens if you put the ape chip in the klr box that wasn't getting the knock?

samluke

I had pretty much ruled out DME's and KLR's. I have tried a number of them and each time I get the same behaviour, the boost peaks as it should and then falls back after 2-3 seconds, as if its sensing knock and pulling it back and advancing timing. I can change the peak with banjo bolts, chips etc but not the bahaviour. I have replaced all the control elements a number of times, including a new Lindsey Clubgate wastegate wih no appreciable difference in behaviour.

It all began a couple of years ago during a clubrace. If I get on the alligator strips too hard it causes an ABS fault. In those days I had to key off and then on again to re-set. Since then I have added a re-set switch. After one high speed re-set the car came back with virtually no boost, I hit it again and it came back, but its never been the same since.

Harnesses are on their way. I am going to change out the wiring and then do some more troubleshooting. I would like to know what other experiences are for knock count. Now I am back to stock I am still getting a couple per throttle application which I still think is too much. The only other refernce point is my buddys 2.8 and he barely gets any events. I would try higher octane fuel if I had access to some, just to see if that made a difference. I guess I could go the other way and put 87 in, I would then expect to see much more activity.

Rogue_Ant

Cut your fuel with Xylene. Will be safer to go up in octain rather then down.


Rogue

amschnellsten

counter just arrived going to give it a try.i am using autothority chips and I am getting maxhp chips hopefully today or tomorrow in the mail.

Rogue_Ant

Any results?


Rogue

amschnellsten

actually have not had time to install. I am going to do it tomorrow night. One quick question. Did you hook up the fourth terminal for a reset. Or does the counter just reset after counts?

samluke

Ijust hooked up the power and ground and pin 15. So it keeps adding to the count. You have to remember the last count but for what I am using it for its acceptable.

I ended up replacing my entire engine harness plus the knock sensor over the weekend. I figured if I just did the knock and crank sensor wires and I was still having problems I would wonder if it was something else in the harness. I changed belts at the same time. I just have to finish it up and start testing again to see if anything has changed.

Amschnellsten, Please post what results you get when you do full throttle runs to see how it compares with my results. I find that simply mashing the throttle in almost any gear gets a count or two. No need to change gear, just get the turbo to spool up.

amschnellsten

i will. I have not got my car out again yet. having a little running maf, chip problem.

Rogue_Ant

I plan to hook up a counter as soon as I get my car back together (currently installing new turbo)...
Will let you know my results.


Rogue

samluke

I changed my engine harness (what a pain!!!), and installed a new knock sensor. The car runs great. However with stock everything, I get a consistent knock count of 5-6 in 5th gear each time I use full throttle and get into the boost. I wasn't expecting such a high count with a stock setup, and max 12psi boost. Without feedback from other cars, its hard for me to know if this is normal or not. I can only think that with only 91 octane available its enough to get into knock. Next time I am at the track I'll use some higher octane gas and see if it affects the results. I have never bothered to run race gas thinking that I was just throwing a lot of money away, but maybe I do need it, to realise the full potential of the car.

Rogue_Ant

Possibly what might be more important is how many counts a truly stock car gives. Then we will have something of a baseline of acceptability.


Rogue

Trucho-951

I always run 100 Octane Unleaded race gas at the track, it's cheap insurance agaist blowing the engine. I think I spend about $120 per day (20 gal/day), but it feels great to know that it's saving me thousands $$ in potential engine repair. I've talked to other 951 track guys and they are also doing the same. So don't think of it as throwing $$ away, think of it as saving $$.

hp18racer

As I understand it, the optimum operating point is the lowest octane that doesn't knock. Higher octane means lower burn rate, higher EGT, lower power.

I used the knock hit counter samluke described to find what I believe to be a nearly optimum octane for a given boost level. I'd pick the boost I wanted to run and start with a nearly empty gas tank of all 100 octane. I'd run a few laps and add mixtures of progressively more 91 until the knock hit rate per lap would go up. I was looking for something less than 50 counts per lap. 50 is an educated guess. Motronic 944's knock page (I'd put the link in but I am not allowed to) shows what the signal looks like under heavy knock. From samluke's observations, 10 per second may be the magic frequency the computer considers unsafe. Playing with boost and octane I can definitely see a direct relationships between boost level, octane and number of knock hit counts.

If I understand all this correctly, the counter provides a way to not only run safe but also make optimum power.

I'd also really like to know what somebody sees on a totally stock car. I'd LOVE to know what someone sees with more sophisticated computer/test equipment (John @ Vitesse, can you tell us?) to correlate the knock count rate to the KLR pulling timing and dumping boost

Rogue_Ant

Give me a week or so for the weather to clear up here, and I will post a log in Hz of my results... but I'm not going to have any ignition timing correlation.


Rogue

Trucho-951

Wow, this is great stuff, but once you found the optimum octane for your desired boost, did you return for a full set of laps to see if your gas mixture held up once the coolant and oil temps, and piston temps went up due to heat soak?