So I've been looking at my tune (trying to figure out why I have KR) that came on the car when I bought it and calculated the AFR from the tables. It starts at 12.1 at 2000RPM and decreases to 11.2 at 5600 then to and 11.35 at 6000. That seems ridiculously rich to me....
Any input?

 

I take it this is only WOT A/F ?
If not it is RIDICULOUSLY RICH.
At WOT the A/F ideally for best power is ~12-12.2:1; most calibrators will error on the rich side as it is a safety margin to prevent "leaning out" the engine. ANYTHING over about 11.7-11.5:1 seems pretty rich to me. You definitely would not have knock retard due to the A/F ratio here....look at something else for that; when rich one is LESS likely to have spark knock.

 

Yea, this is only for WOT. I was comparing it to the stock tune and other tunes with cams and every tuned car seems to be in the 12.2-13.2 range.

Just did a bunch of searching on the subject and decided to raise it. Anyone know of the power loss caused by such a low AFR?

On a side note, the knock (12 degrees ) seems to jump right out at me at around 3000 RPM so if anyone was any ideas, let me know

 

On most N/A cars we target around a 13.0 AFR (give or take a few .1's). All cars are different. Sometimes we find that cars like the fuel more for whatever reason, so we give it!

For S/C and Turbo cars the AFR kinda varies... i'd say sometung around a low 12 or high 11 would usually be good, but for cars running more boost definately in the mid 11's would be best. If you have alcohol injection that helps too

It just all depends on what the car wants. Dyno it, richen it up a touch and see what it does, if it makes HP then cool. If that doesn't work lean it out a little and see what happens, they say "lean is mean" but just be watching everything and making sure you aren't detonating. Once you have a good AFR then trying messing with the timing (1 or 2 degrees at a time usually), again listen for detonation.

 

Listen for detonation? Get a scan tool, if you can hear it, you have waaayyy too much knock. 4-5 degrees will destroy bearing over time and can't be heard. A scan tool is a must to tune any car on the dyno or not.

Timing will also effect AFR so as you adjust timing, you may have to go back and adjust fueling. If you have too much timing to begin with, there nothing that adjusting the fuel will do. Make sure your knock is not false by draining the tank and fputting in a few gallons of 101 unleaded and see if the knock is gone or reduced. Knock can also be caused by excessive carbon build up so even the stock timing may be too much until it is cleaned out.

 

Thanks for the replys. I actually just put 2 gallons of 100 octane in when I only had about 2 gallons of 93 left in the tank. I took a datamaster log before the 100 octane, put 100 in, let it idle for about 5 minutes, then took the same route and another datamaster log.
Do you think that 100 octane would make a difference? It didn't seem to affect the knock.
If anyone has the time to look at the logs and hopefully tell me its false knock , that would be greatly appreciated.

 

figure out your knock issue before you start messing with the air fuel ratio... 12 degrees will make a decent difference.

 

You can't really tell from the log that its false. I first thought you could send it to me and I can compare it to some of mine from my '95 when it was having 8-10 degrees of knock with a virtually stock tune, but your setup is far from stock so it would do no good to compare.. I ended up removing 4-6 degrees at various places at WOT to cure it. I wrote it off a todays poor 93 gas and some carbon build up ona 85k miles motor. Runs alot better now that the knock is gone.

Your mixture of 2 gal 93 and 2 gals 100 would end up being 96.5 octane...it may have not halped much. I used straight 103 unleaded in mine and it went from 8-10 degrss to about 7-8 degrees of knock. Only way to find out for sure is to remove lots of timing and see how it reacts, then start putting some timing back in till you reach the limit. 1-2 degrees too much timing can cause a lot more knockk than 1-2 degrees.

 

Lol, I just removed a lot of timing in the problem area. It happens almost instantly around 2900 RPMS and even when its only around 35% throttle. I brought it down to 28 degrees and it still had 13 degrees of retard, running on my mix. That makes me believe it has false knock. I might just try bringing it down to like 15-20 degrees and see if that does anything.

I cant hear or feel anything out of the ordinary when it happens, I cant even feel a loss of performance going from 0 to 13 degrees instantly. I also tuned the knock right out and took it for a test run and no bad sounds or anything happens. So, Im assuming its false but I want to correct in case I ever do get real knock.

 

If you have light audible ping during a dyno pull you aren't going to hurt anything.... I'm talking about adjusting the timing 1 or 2 degrees at a time and always making sure there is enough fuel there.

As far as a scan tool almost all cars that get tuned are hooked up to EFILive during the pull, but sometimes it doesn't tell you everything you need to know, experience does come in handy every once in a while.

In case you didn't already know this 94lt1, don't tune using a mix of fuels or a higher octane that what you will normally run... I am assuming that you already knew this. If you are always going to run the same fuel/mix then have at it... most of the cars we tune are just on 93. On alot of boosted applications its 93 and alcohol injection (its becoming more and more popular).

 

I'm not really tuning for performance here, I'm adjusting the spark tables and octane to see if the knock is false. If it is false, I'm either going to tune it out or desensitize the knock sensor.

So far, on my 96.5 octane mix, I retarded my spark 15* from 2400-4000 rpms. Ran datamaster and STILL picked up 9* of retard at 3000 rpms (at 40% throttle), bringing my total advance down to 9* So would I then assume 9* of the knock is false and knock 9* off the max allowable knock tables?

 

I thought 12.8-13.1 was optimal for A/F at WOT, but I think it's already been stated.

Dan