Fuel milage tuning

[Gutless]

Ive got a l67 in my 97 firebird. I am using a stock 99 GS tune with the torque management removed. I have no EGR, no cat, cone air filter, 180degree tstat and 3" manifold back exhaust with a good muffler.

I have been getting kinda crappy gas milage. Mixed 75% highway 25% city is like 16MPG. Got 19MPG once on almost pure higway. I am planning on doing a comprehensive tune in a few months but I am going to get wideband as I dont have one yet.

What can be done to bump up the milage? I noticed the commanded AFR at ECT of 195+ is 12.4 but the 180degree commanded AFR is 12.0. Is it safe to change that?

If logs would help I can throw some up.

[GeoJB]

Logs will help!
other wise, just guessing.

You got a PM.

[Rynoman2k3]

This write up helped me the most for getting my mpg's up. It's a little dated as he wasn't using Beta at this time.

http://www.grandprixforums.net/start...ers-43997.html

Basically create a Histogram that compares your LTFT vs your Maf Frequency vs Output Frequency.





Take the info this Histogram gathers.



and Paste Special Multiply by % to your MAF Frequency vs Output Frequency Table ( Engine> Airflow> Maf Calibration> Maf Frequency vs Output Frequency) Then Highlight all and smooth horizontally I believe. Someone correct me if that is wrong.

If this gets your LTFT's within -5 and +5 at cruise you will notice and increase in mpg. I went from 22ish mpg at best to 26.9 just this week. Your maf will still need adjusted when the seasons change to help mpgs.

EDIT: also my commanded afr is like 11.7 for what it's worth.

[Phantom]

Post your tune and a decent scan. What was posted above should be performed on all cars to get the MAF tuned.

[Higgs Boson]

If your car has a properly functioning closed loop system, there is nothing you can do in the tune to increase mileage. Get a tune-up and drive slower.

[Phantom]

There is plenty you can do to help get up MPGs.

First is adjust your driving technique this can turn a grandprix from 19mpg to 25mpg here is where you can make the bigger improvements if you need tips on doing this go to Ecomodder.com

For tuning the following can help:
1. Get your MAF inline (I try for +-3) under 7500hz (above is WOT) this will keep the car from having to adjust the fueling as much being less likely to run slightly rich before it corrects)
2. Scan and slowly increase timing it is more important to do this in the cruse portions of the tune. 1200-2200RPM between .12-.36g/cyl should be the area but it will depend on gearing and other factors. If you see KR back off 1-3degrees you probably do not want to go over 38-42 degrees.
3. Adjust the shift tables so it will shift a little sooner under 20 TPS. This can take a little while to get right because you do not want to shift to low and lug the engine and start getting KR.
4. Bring to TCC lock speed closer to the shift speed for the gear taking the same cautions as in step 3. It is not usually recommended to lower the lock speed for 4th gear.

[Higgs Boson]

There is plenty you can do to help get up MPGs.

First is adjust your driving technique this can turn a grandprix from 19mpg to 25mpg here is where you can make the bigger improvements if you need tips on doing this go to Ecomodder.com

For tuning the following can help:
1. Get your MAF inline (I try for +-3) under 7500hz (above is WOT) this will keep the car from having to adjust the fueling as much being less likely to run slightly rich before it corrects)
2. Scan and slowly increase timing it is more important to do this in the cruse portions of the tune. 1200-2200RPM between .12-.36g/cyl should be the area but it will depend on gearing and other factors. If you see KR back off 1-3degrees you probably do not want to go over 38-42 degrees.
3. Adjust the shift tables so it will shift a little sooner under 20 TPS. This can take a little while to get right because you do not want to shift to low and lug the engine and start getting KR.
4. Bring to TCC lock speed closer to the shift speed for the gear taking the same cautions as in step 3. It is not usually recommended to lower the lock speed for 4th gear.

The MAF and timing should be adjusted properly anyways, regardless of "mileage tuning" or not.

The others are a lot of work for a change in mileage that falls well within driver to driver variance. A waste of time.

Bottom line, go slower.

[matt5112]

Ryan, that tuning method doesn't include the STFT's.

I would suggest this method instead:

http://www.hptuners.com/forum/showpo...64&postcount=1

[Rynoman2k3]

True but most don't want to have to change out the o2 on the front bank to do that procedure.

[Dthreap]

True but most don't want to have to change out the o2 on the front bank to do that procedure.

You don't have to if you have a WB already installed. Just command OL and scan.

[Wingman520]

You don't have to if you have a WB already installed. Just command OL and scan.

x2 on this done it on a few cars and works with no problems