kyle97

iTrader: (10)

Im headed to a dynojet dyno this weekend for my first shot at dyno tuning. Im runnin a speed-density, closed loop tune and I've already dialed in the VEs using EFILive and an LC1. Im currently running a relatively flat AFR curve at 12.96:1 and about 30* WOT advance.

I have a 2-3 degrees of knock retard during WOT, but i think it is false knock becuase it doesnt go away when i remove timing. If this becomes a problem during the session, im just going to disable the knock retard completely (its already desensitized)

My plan is as follows ( i only have 1 hour to work with)
1. Set the PE afr by doing a baseline run, a run with a 5% (across the board)increase in fuel and a run with a 5% decrease in fuel. Pick the direction out of the three that gives the most power. Then repeat using only a 2% change in either direction.

2. Set WOT timing by doing a baseline run, a run with a 10% (across the board) increase in timing, and a run with a 10% decrease in timing. Pick the run that generates the most power, repeat with a 5% change.

3. Repeat step 1 if time allows

What do y'all think? I feel like this will get me pretty close to optimum fuel/timing in the time i have. I am choosing to maintain the same curve shape for the fuel/advance by multiplying across the board. If i had more time, i might try to optimize for a given rpm range (say optimize for every 1000 rpm).

oange ss

iTrader: (50)

changes in timing can affect AFR, AFR changes affect knock tendency....KR you're gettin now may not be false, could be lean or rich misfire, depends on how close your LC1 is to actual AFR....things tend to get out of hand when your under a time crunch...keep that in mind and good luck

Redline-Motorsports

iTrader: (3)

I agree 100%! You are better off paying a bit more for dyno time to get it right that stabbing at the tune. Throwing a percentage at timing is not a good idea. The timing table needs to be massaged as needed to optimum timing. I would get AF close, error to the rich side, and then start bumping up the timing. If the motor likes the timing it will use more fuel and lean up the mixture. As ss stated a rich or lean mixture can still cause KR. We don't really know your setup but if you throw 15 degrees across the WOT part of the timing table and you still get KR, it's most likely false.

You also should let the car cool a bit between pulls and one hour might not alllow.

Alvin

iTrader: (2)

It sounds like you have the right idea.

Power output as a function of spark and fuel would look something like a moutain on a 3-d landscape. Say timing is East/west and fuel is north/south. What I mean by that is you may short yourself by dialing in one and then going after the other. Of course at that point you might be splitting hairs on something that changes a bit on the road anyway.

I would say focus more of your time on not what timing fits in the car but what makes the best power at each interval of the power band. Fueling is easy to get on the road but its hard to feel that extra 5 hp in different spots an optimized timing curve might get you.

kyle97

iTrader: (10)

Thanks for the suggestions. It sounds like i should shell out the $$ for an extra hour of time to keep things less rushed. Also, I should spend more effort with timing and pay attention to how my timing changes affect AFR.


I am wondering one more thing -- which has a more pronounced effect on power: timing advance or afr changes?

If i bump the timing +/-1* how much hp difference are we talking? +/-1-5hp?

What about AFR? how much change in hp should i expect from a 0.1 change to AFR? Im sure it is slighly different for any engine, but with changes this small, will i even be able to detect a difference in the dyno graphs?

gametech

iTrader: (1)

Also, tuning for max power spark advance on a dynojet could lead to real knock on the street under load. I would run some 104 unleaded just to verify that the KR you are getting is false before making what could be a costly assumption.

Doc

iTrader: (9)

Don't rush things. Nail down that false KR first. I know it might seem mundane and all but if you are spending the jack on the dyno time, I would make sure that all the bugs are worked out. Without further details about your setup, I know you know this already but I will just throw out the biggest cause of false knock...exhaust setup banging! Good luck man, take the high road.