samluke

I have been chasing a boost bleed down problem on my stock Turbo S for some time, without success. The behaviour seems to be associated with knock so I have wired up a counter to see if I can see what's happening.

I run regular pump gas 91 octane. My car records 10-20 knock counts, or even more, per hard throttle application. Its rapidly counts as boost comes on and then stops increasing after a couple of seconds, probably as the ignition is being retarded. I have a buddy with a 2.8, big Turbo and various other mods and he barely gets any counts on his car.

I have ordered a Lindsey knock harness and new knock sensor in the hope that it will clean things up. I now have a baseline for reference.

Intersted to know if anyone else has looked at knock count and what is typical?

tedesco

what electronics did you use and how did you wire it into the harness? I think the flash codes don´t do knock counts. I tired something similar myself but could not count even a single event. I am runing 1.4bar on 92 oct without any issues since 1/2 year on my daily driver.

samluke

I used a counter from Curtis, it was less than $20. It requires a 12Vpower plus ground and reads the 5v signal from the KLR. It seems to work pretty well, for seeing whats happening.
http://www.skycraftsurplus.com/index...OD&ProdID=1001 Do a search for counters. The one I chose was the digital event counter which is currently $12.95

Hooks into the KLR harness on Pin 15. It seems to work great. The neat thing is that its the KLR reporting what it has decided is knock, which is what really matters, not the raw signal from the knock sensor. Its harder to read than say a light, but the count number is far more informative about what the KLR thinks is going on.

I can't take credit for finding the counter, it was my friend with the 2.8. The count on my car is completely different that his car. The consistently high count would certainly explain my issues, just don't know why yet. I am hoping that my problem is bad shielding/noise or shorting in the knock harness. Hopefully the new harness will fix it, if not, I am not sure where to look next.

Rogue_Ant

Hmm, this thing is very interesting... I thought pin 15 put out more info then just knock counts?
The most info I've found about pin 15 is here:

https://rennlist.com/forums/showpost...4&postcount=43


How have you verified that your counter is actually capturing knock counts?


Rogue

ross255

As pin 15 is supposed to be a yes/no output, it should be a 0 or 5v reading.
That is what I have found so far. The only problem I have with it, is that I dont think my smt6 has a fast enough sample rate to catch all the signal.
You do get a little bit of 'noise' that registers around 0.5v, but when it do get a knock then it will give you a 5v spike.

Rogue_Ant

Interesting... I might have to configure my system to see if I can catch this.


Rogue

tedesco

Thanks for the info. I used a basically identical counter for my tests but got some doubt about its speed because I could not get even a single count. Manually triggered it worked well. Maybe I will try again...

Zero10

So how are you guys tapping into pin 15?
Is there already a wire there? (I haven't looked yet, but want to make some kind of warning system)

amschnellsten

are you just splicing in to pin 15. and does this work?

ross255

Yep, just splice into pin 15, I am not sure where it goes, but a guess would be the plug under the bonnet that you use to flash the codes.

samluke

Yes I just spliced into 15, and ran the counter off a spare 12v and ground.

I did some more testing tonight.

I forgot to state before that the DME and KLR box in my car for the last test were fitted with Autothority chips and restricted banjo bolt. On that test with 91 octane I was getting anywhere from 10-20 counts/throttle. For testing tonight I put the stock boxes back in and stock banjo bolt. The count really settles down, but I am still getting a couple per throttle application. One great thing about the counter is that you can verify if you need higher octane fuel or not. Clearly with the autothority chips and banjo, I am getting straight into knock each time. So to make use of them I will have to run race gas.

I can't run my car much right now, as the cambox gasket has decided to leak oil on the exhaust.

I am still going to go ahead with the new harnesses and fix the cambox gasket plus a few other winter chores and then see where we get.

samluke

PS you don't have to go inside the plug just splice onto the wire. Mines an 89 and on my car it was blue with a white stripe I think.

Pin 15 is the output from the KLR to the DME that knock is occuring its either high or low. The duration would also be important as that tells you how long its occuring. But for less than $20 I think its good information as my experimentation with the Autothority proved. The goal is obviously to be able to run consistently hard and get barely any counts

Zero10

Why not use a the output to trigger a transistor, then use that to trigger both the count and a LED. This way you could get a visual indication as well as a count.
As for the duration, I would assume that the output signal is of very very short duration, since a knock event itself is very short as well.

Rogue_Ant

The signal is short, in the link I posted earlier, Transaxle said that he was using 1000 samples/sec ADC.


Rogue

samluke

I guess it depends what your trying to use the counter for. In my case its simply as a troubleshooting aid, with the added benefit that I can see if higher octane fuel is really helping me.

Yes you could easily hook up a light, but as the duration is very short you would have rig up a circuit to keep it lit for long enough to see it. The counter does all that and more.

Even if you had a light, there's not much you can do about it during normal driving, unless you have some kind of adjustable timing control on the fly.

I see a counter as a cheap, aid to tuning and diagnostics, similar to an AFM. The goal is to run consistently without counts. So if you have the capability to adjust timing, and Air/fuel and have access to high octane fuel you can play around to get both air fuel right and no knocks.

In my case I am Estock clubracing so I am only using it for is troubleshhoting. I think its a great tool and am kicking myself for not installing one sooner. I have often wondered if running race gas in a stock car was worth the money, now I can know for sure.