Black 91 Z28

I know that the more spark you run the more fuel you have to add. The Spark Table on the S_AUJP has a lot more timing than the original one. How much is will this impact my mpg? How are the folks doing mileage wise who are running proms based off of S_AUJP.

Yes, I know if I want good great mileage go drive a honda. But my current 12mpg in the city is hurting me. I get around 25 on the highway though...

JPrevost

Actually the more timing you run the less fuel you should need. Unless of course you're wanting to run the engine on the verge of destruction, which by all means pump in a bunch of fuel to soften the blow and increase your dynamic compression .
Seriously though, with a leaner AFR you can burn less fuel without detonation. This is because leaner AFRs burn slower (flame front has to "find" fuel in the mix as compared to a denser fuel mixture).
I'd just run the bin as is and make changes, decrease the timing if you don't trust it and sneak back up watching your knock counts with a datalogger.
You're getting pretty good milage on the highway but what gears do you have out back? I've got 3.73's and I'm scooting along with 23mpg. If you've got lower gears I'd be shooting for a mpg or 2 more than you currently are. Anything over 22mpg highway isn't aweful but getting more than 12mpg city seems to be everybody's concern. I'd look at a tight stock TC if that's a major concern of yours. I get between 10 and 15 in the city with my loose 2800 stall , at least it's lock-up.

JP86SS

iTrader: (1)

Mine runs about the same although I'm a little rich right now cause the TV cable is slipping at times when I poud it to the floor
I get about 12 when city driving and am also looking to clean it up for a little more (maybe fix my EGR) but with my converter not really doing much below 2K I don't think theres much I'm gonna gain there.
I've also got 3:73's with 700R4 and the highway is about 19-23 MPG depending on how fast I go. (faster actually gets better but can't run 85 everywhere)
I do have the converter locking early and not unlocking in DFCO.
I have some more work to do on hyway mode and think I can get a little more there with some changes too.

Black 91 Z28

Hmm I've still got the 3.23s out back. I'm running the stock converter with the setting from the S_AUJP. I'm just scratching my head trying to figure out what it is in city. I'm sure some of it comes from my 5 mile 10 minute hop to and from work each day. My car is in good tune and runs well. As for knocks I'm knock free except for WOT around 4K but I'm working on that.

JPrevost

Lots of cold engine short trips is what kills milage, especially in the city.
Stock setups run really rich on startup to get that cat up to temp as fast as possible. Just having a cold engine is another reason for needing a richer AFR.
If you don't have cats you can lean it out some and try removing some timing. I've found my best milage on the highway is when I remove timing! It's odd because highway mode has a SA advance, I don't know what it is but I think there's something to be said about efficient combustion chamber designs.

JP86SS

iTrader: (1)

I'm running a 185 F Tstat to keep the temp up. I never really liked having a 350 run at 165, seems too cold to me. Maybe bump your up to get it up to temp quicker if your not having any cooling problems.

Black 91 Z28

If anything it seems to be cooling too well which I think may have some baring on my mileage. It bearly gets to 160-170*F on my trip which bothers me cause its 50-60*F right now and I think it should be running warmer. I guess I'll check/change the thermostat this weekend.