Quest for MPG... lose the SCT/Bama chip?

Hey all I've posted on here before a long time ago regarding my friend's '94 GT. Well long story short the car is basically mine now, my friend moved out of the country and left it here with me I am stuck between buying it from him for cheap (he owes me :lipsrsealed or selling it and getting a portion of the money. In the meantime I've been spending a lot of time driving it and tuning up minor things here and there; plug change, cap & rotor, new O2 sensors, smog pump delete... My main question, my friend bought one of those SCT 4-bank eliminator chips which I helped him install. I've been doing research on them and it seems like the general consensus is they don't do anything besides firm up the shifts (his is auto) and improve throttle response a bit, with a barely noticeable increase in WOT power. He got three 91-octane tunes (street, perf., race) which doesn't really make sense to me in the first place; these stock 5.0's have like 9:1 compression how can you tune it to run "better" on 91 as opposed to regular (85 around here at high altitude)? I have actually experienced pinging when I put 87 (midgrade) in there running on the street tune which surprised me.

So here's the thing, I took the chip out today to see the difference in how it runs and it feels basically the same except the transmission shifts WAYYY earlier (accelerating slowly at part-throttle) and quite a bit slower even when I shift manually with the pedal to the floor (with the chip it hits like a hammer driving this way :headbang. Now I'm thinking, if I instead now bump up the base timing for a little extra oomph and keep the chip out should I get better gas mileage than with the chip? The car has CAI, BBK long tubes, off-road midpipe, 75mm TB (impulse buy courtesy of my friend I know it does nothing at this level) and 3.73 gears. Currently I have been averaging 15-17 MPG with mostly city driving.

On another note what's the best way to correct the speedometer with the shorter gears? Do I get a different speedo gear or is it just done through the computer?

 

Thanks for the quick reply... awesome, I was thinking of getting it re-flashed with an 87 street tune (for max MPG possible) and then leaving the performance and race tunes. Just looked at those speedo gears only $15 guess I'll be grabbing one of those!

Still wondering how a 91-octane tune works on a 9:1 compression engine though...?

 

Took the car for a spin to get gas with the chip still out; filled up with mid-grade (87) then did a Sea Foam decarbon through the intake. It pings just a hair when floored but seemed to lessen up as I did it a few times to blow out the carbon, seems like it worked a little at least. Tomorrow when I get off work I will check the base timing, I've never checked it before and the guy my friend bought it from may have turned it up who knows.

5-oh-MUSTANG if your idle is too high you need to reset your base idle NOT your base timing they are totally different things... turning down your base timing will just make your engine run like crap.

Addermk2 I'm sure you can do a better tune than Bama but this car isn't really a project (that's my 1970 Plymouth Duster ) and I just want to get it running as well as possible without spending money on more performance upgrades. If I did end up keeping this car (read first post) I would use it as a car for my fiance to drive or as a backup daily driver for me so in that case I'm willing to give up 10 HP if it gives me a few more MPG... being able to run regular or at least mid-grade gas would be nice too.

 

OK this must not be the case when the base timing is bumped up, it knocks pretty bad if I floor it completely but running the stock timing seems to do alright. There are a couple maintenance things I want to do at this point, new fuel filter and a new thermostat with a cooling-system flush. I did some searching and limited fuel flow seems to be a problem on these cars, also the fuel filter ought to be replaced every 2 years or so well my buddy bought the car at least 3 years ago and I doubt the filter was ever changed. Also I notice when driving the temp gauge tends to fluctuate between 1/4 and 1/3 the way up it doesn't stay constant.

I'll see if my gas mileage improved at all with the chip out then go from there. I looked up the Moates Quarterhorse I really want to get one of those eventually, also a speedo recalibration tool but budget is real tight right now. Just sucks my buddy wasted $300 on "canned" tunes when he could have spent the same for an actual programming unit so we could tune the car in real-time. If the MPG went up I'll definitely keep the chip out for the time being and look into a shift kit. I swear this AODE shifts so slow and sloppy it feels like it can barely push the car; probably could use a rebuild with 160k miles :undecided:

 

Shoot I did not know that... guess I'll be hitting you up sooner than I thought :thumbsup: Seemed like there were other ways to do it I just assumed, I don't know a whole lot about these cars still

I forgot about the damper slipping looks like I'll have to check that now :blah: Tony Corley I have a '94 with an AODE that J-mod doesn't apply to me unfortunately. Also I need to check the condition of the transmission first, I would be surprised if it's still in good shape at 163k miles.

Going out to clean the grounds off now. I bumped the timing back a bit to 12* we'll see what happens. Also the last sensor I haven't yet replaced/checked is the IAT so that will probably happen today too.