bmmonte gave me great advice and got me going in the right direction on chip tuning. And I want to go further. I am sure alot can be done to improve my gas mileage. Right now I barely get 12 mpg on an 85 GMC fullsize, 305 (bone stock converted to TBI ; 7747, all sensors working), 2 wheel drive, 5 speed manual transmission with a lightweight driveshaft, 3:08 gears, 27 inch tires. I read on another thread that someone had a similar setup and was getting 18-20!! I'd be happy to get 15-16 but don't know really where to start. I have done some logging and really don't think I am getting in to PE (if it is mainly based on 60% TPS). Any advice on tuning or hardware would be greatly appreciated.

 

Advice on hardware?

U realy need to hit the stickies up top and start reading. Volumes of it is right there :-)

As far as mileage on TBI apps, seach for posts by Grumpy and Prevost concerning the matter, I know there are at least two of them

later
Jeremy

 

hey man thanks! Just so I aint missing anything, stickies are the threads located at the very top of the DIY Prom tech board, right?

 

You are probably refering to the LE9 305 4x4 suburban that I tuned. Or my G20 perhaps.

Make sure you have good, even compression, the base timing is correctly set with the timing connector unplugged, make sure your factory cat is not plugged. Make sure that you have 305 injectors, 305 Prom chip, and 305 knock sensor. Also make sure the .Bin you have is for a standard transmission.

The % TPS for PE varies depending on RPM. 60% TPS in the lower cruise RPMs is definately into PE mode.

Other than that it is time to look into tuning.