Aloha all, I currently have a 93 eg8 (152xxx miles, motor has about 130xxx)5 speed with a y7/y8 mini me running a P28... I am getting pretty bad gas mileage.. like 20mpg, and have since the motor was swapped.... Everything runs great, no CEL, just get bad gas mileage. I mostly do city driving (about 40mph max) for the most part... I wouldnt say i drive like a grandma, but I also dont burnout, race, or drive like an idiot. I hit VTEC in 2nd every now and then...O2 sensor was recently changed, so i dont think that is the problem
My thoughts: I have read that a P28 was designed to run a Z6, and that because the Y8 is a little different that it doesnt run to its full potential on the p28(different fuel and timing curve) could this be why my MPG's are so bad? Would my only solution be to get a chipped ecu, and get the car tuned? Is this over kill on a stock motor with basic bolt ons?
Also if I do get a chipped ecu I was thinking about lowering my VTEC crossover point.. Currently it is at the stock crossover (about 5500)...
My reason for wanting to do this is that I still have the LX transmission, so sometimes getting up to 5500rpm can be hard... Im thinking if I can hit VTEC at about 4500-4800, it might help me get through the gears faster, and maybe compensate for the super long gears...
any useful info would be appreciated

 

I would say that after any engine swap especially when ecu's are being swapped/altered you would want to have it tuned @ your local speed shop. Edit : or anyplace that someone can tune them, not necessarily a speed shop.