Fine tuning
Hey, great site. Looks to be a lot of knowledge here.
My car actually runs great. I would like to do a little fine tuning though with increased fuel mileage in mind. I'm running a stock 5.0, aod trans and 3.00:1 rear gear in a 3000 or so pound car. Currently I'm getting 16-18 mpg. I'd think that with this setup that I'd see 20+ mpg, but so far no.
I wonder if someone could look at my log files and suggest some tuning ideas to get the mpg up to snuff. The first file is a 30 second log at idle and the second is a quick acceleration to 60 mph and holding there for a couple of minutes. If a log of anything else is needed, just let me know.
Thanks for your time!
https://www.dropbox.com/s/uj8xx1nt7jylhwq/DashBoard20.csv?dl=0
https://www.dropbox.com/s/wrlidmm4k0srznx/DashBoard21.csv?dl=0
Well, looking at it, I guess the second file contains both the 0-60 run and the 30 seconds at idle. Not sure what the first log file is.
Log looks good. Tuning for mpg is tricky to advise on. First the liability. Second, every combination is different.
I would adjust the idle AFR. This is nearly the same process as setting idle mixture screws on a carb. Lean out for best idle and vacuum. Check plugs to fine tune. Then I would use that AFR as a baseline for the rest of my AFR matrix. Leave full throttle a little richer, to prevent detonation, and lean cruise out a little more. You will know when it is too lean. It will begin to surge ever so slightly.
Hey Austin, thanks for the response. I made a few adjustments today and I'll attach another log file. This log is 30 seconds at idle and a brief run at 60 mph. I set idle AFR to 14.6, which seems to be about the max before idle quality degrades, I set the 1100 45kPa to 14.7 and the 3000 45kPa to 15.2
Do I continue to increase the 3000 AFR target until I notice misfire at cruise and then decrease?
I set the initial timing back to 8 degrees BTDC, I had it at 10 but I noticed some slight detonation under hard acceleration. Despite that, the plugs look pretty normal.
https://www.dropbox.com/s/zx0stwmbm5gecg4/DashBoard23.csv?dl=0
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I think you are heading in the right direction. Keep working on it. Reminder, this is at your own risk.
I would check your total timing before backing off the initial. May have other issues.
Switched the advance from ported to manifold vacuum, initial timing set at 14 degrees btdc, total 38 degrees at 3500 rpm. Went from 17 mpg to 23-25 mpg. Will play with afr some more, currently 14.1 at idle and cruise and 12.6 @ wot. Pretty happy with it so far.
One question though, is it normal for the handheld to show rpms all over the place? I set the idle @ 750 rpm and according to the handheld it varies from about 680 to 825 rpm at idle. The engine doesn't sound like its hunting for idle rpm, in fact it sounds rock steady. I'm curious as to what causes this.
Quote from new2me on August 2, 2019, 9:15 pmSwitched the advance from ported to manifold vacuum, initial timing set at 14 degrees btdc, total 38 degrees at 3500 rpm. Went from 17 mpg to 23-25 mpg. Will play with afr some more, currently 14.1 at idle and cruise and 12.6 @ wot. Pretty happy with it so far.
One question though, is it normal for the handheld to show rpms all over the place? I set the idle @ 750 rpm and according to the handheld it varies from about 680 to 825 rpm at idle. The engine doesn't sound like its hunting for idle rpm, in fact it sounds rock steady. I'm curious as to what causes this.
Yes, it will vary a bit. Normal
So assume tuning idle AFR as you would with a carb, does that mean Fitech can be tuned with the engine running?
And can I also assume that the ultimate goal is to have the learn figure as low as possible? If so, what is a reasonable number?
Quote from 65sohc on October 9, 2019, 8:13 pmAnd can I also assume that the ultimate goal is to have the learn figure as low as possible? If so, what is a reasonable number?
Yes you can tune AFR while running.
Tuning the cam tables is where you can tighten up the tune. I like to see learn values within +/- 10%.