toddk911

"110 octane means I could run 19 psi on stock chips?"

Not with the stock KLR, as it will cut your boost.

OriginalSterm

mbc

toddk911

yes, once you bypass the CV. But he made it sound like a bone stock car and just turn up the boost.

OriginalSterm

I don't believe a stock car should run higher than stock boost, nor should you run less than the factory recommended octane IMO. I'd love to see someone dyno a car on 87 octane with as much boost as they'd like to run. Logging EGTs and knock. Hard numbers (data) would be nice, rather that just a "feeling".

fast951

If they like to run lots of boost on 87 octane, you don't need hard numbers, just count the chuncks of metal arund the dead car.

OriginalSterm

do you have a feel (or proof) of how much boost you can safely and repeatedly run on 87 octane and stock chips?

fast951

No I have no proof, and there is no way I would want to experiment. 93oct is available, why bother with 87oct??

Evan70

Not as much as it used to be. Many of the refineries are upgrading to meet the new standards and are now only offering 91 as the top level. This just happened at one of the the refineries here in Tulsa a few months ago (the others in the area are all already 91 max), so we're out of luck now on anything above 91 unless we want to use race fuel.
This does bring up a question John, what's the max safe boost on 91 octane with your chips? I'd dialed back to 15psi as soon as I had to switch to 91 (had been running at 16.5psi with no problems on 93).

fast951

On pump gas I always advise you run a max of 15psi.. When the knock display is released, you will be able to monitor knock. Till then I'll play it safe.

Evan70

Ok, so I finally got around to hooking up pin 15 to my SBC-iD a couple of weeks ago. Now the big question is, does anybody know what the output voltage is supposed to be? Anyway, running 91 octane set to 15psi, I only see an output on pin 15 occasionally when I shift.

Evan70

Little more follow up on this: It does appear to actually function as I get an occasional voltage spike on it during shifts or on full boost WOT (right around when the turbo hits max boost). The wierd thing is that it appears to not just be a straight on/off voltage, but rather a variable voltage as I see different voltage outputs on it (I'm guessing the higher the voltage the more significant the knock?).

mark944turbo

Awesome info. I wish I had a turbo to experiment with. More people should try this!

Were you able to see it on a multimeter or a scope?

Transaxle

I guess you use a slow ADC to catch the signals? The peaks are very short and it is better to use a digital counter to get them. Here is a view on a 951 with 95 ROZ (German gasoline) with bad knocking (= "KLOPFEN"). The data was taken with a 1000 samples/sec ADC :



Since the AFR was ok, we filled the tank with 100 ROZ gasoline and got this result:



But again - it is better to use a digital port or counter to get the signals from the KLR.

@mark944turbo: I hope your great site will get some more traffic soon...

mark944turbo

Wow!

Transaxle, could you translate the 5 lines in your graph?

I do not understand why a digital input would be better. It would just translate the no volts into 0s and the high volts into 1s correct? To make it easier to count maybe?

Can you post any more info about the way you sampled data? Like engine speed, boost level, etc. Do you mind if I put those graphs up on my site?

I really really look forward to experimenting with a turbo soon. This factory knock detection discovery is HUGE! Now we can tune to mbt much more easily!

Transaxle

LMM = AFM
Vollast = Full throttle signal
DK-Winkel = throttle position
Druck = pressure (signal from KLR)
Klopfen = knocking

The KLR signal is generated by a port command of the CPU. It is very short. If you use a ADC you will just get the signal if it is at the same time when you take a sample. So you may miss some signals between two samples - even at a speed of 1000 samples / sec.

If you use a digital counter, it is triggered by every single signal. The result is than "number of knocks in a time frame".