08GT4U

i get 23 to 23.5 miles per galon at 65 on cruise control.i have a brenspeed tune with 4.10 gears.with the bama 93 race tune was 18 to 19 with the same set up.my a/f with brenspeed tune is at around 13.0 to 13.5,bama was 11.0 to 11.5 so maybe your tune is really rich thats why your loosing some gas milage.
get it on the dyno before you make any decisions.

sycd

I lost a couple of mpg when I installed the Brenspeed tune originally. I had another problems with a weak bottom-end, and switched to a tune by VMP. Since then I got my bottom-end back, and the couple of mpg back as well.

Gene K

Stock Tune and 87 Octane - 17 mpg City and 27 mpg @ 70 mph.

Bama Mail Order Race Tune and 93 Octane - 19 mpg City and 29 mpg @ 70 mph

Add 4.10 Gears - 20 mpg City and 26 mpg @ 70 mph

Done the old fashioned way with a calculator. No trip computer in my Deluxe.

sweet99

For the few mods you have you are making great numbers. The tune must have helped there and rich tunes make less powerif you are doing any WOT runs in the driving where you I get my tunes from Brenspeed and he has always been good at making changes as I need them. Measure the fuel used. EGR deletes will use MORE fuel if anyone does not know that. Cooler thermostats cost fuel also so maybe the stock T-stat and the EGR should be stock.
Get a wideband to anyone who does not have one. Then you will know if you are rich or lean.
I can't see Brent making part throttle rich as it would not accomplish much as there is little to no knock then. You can always ask him to lean it out once you know what AFR he has you at. Should not be much richer than a 14.0 in a cruise IMHO. DATALOG! know what numbers you have before speaking to Brent or one of the guys who take his calls. I just got a new tune fora fresh build with a 3800rpm stall converter and 4.10's. I expect 20mpg+ on the interstate and will post when I have more than 4 miles on the motor
I also added cams with 230/234* duration at .050" on a 110*LSA and 106* centerline.
Compression is 11.4:1. I do have Edelbrock Victor LT's. A DIY NCAI and UDP's finish the package. Mark

sweet99

Those AFR #'s are at WOT right? What about cruising?

Nuke

I may have dropped 1 MPG after my tune. But the driving got more spirited...

KeneticEnergy

thats what i experienced as well.

i may be switching to a tillman tune just for fun; my tips are blackened as well. i hear too much about bama tuned cars having problems and support being slow

no thanks. my brenspeed runs pig rich but it aint gonna blow up

sweet99

How many ofyouguys have either a colder T-stat or an EGR delete? Just curious as I have a 180 T-stat. Mark

sweet99

Man, I reread this and with a cold air system and an exhaust you got 283whp. That is a lot! A CAI is worth 10whp at BEST and the exhaust is worth maybe 10whp at BEST on a stock motor. Stock these are 225 on the dyno so the tune gave you 38whp? If you had not mentioned the mileage I would have to call BS on the tune with those mods. That HP gain is SC gain. You needa laptop and to datalog as whn in cruise you should not run much richer than stock, maybe even leaner. You must be leaner at WOT as a lean AFR without knock makes more power as you probably knew. This is of ointerest to me as my car goes on the road monday and I have used Brenspeed tunes for 3 years and last year he got me .2 better than a so called auto/converter expert tuner and Brent was just getting into auto tuning but I did lose mileage. However I went from stock(25+mpg) and added SHM #2730 cams and the SVO intake. Lost .4 to start and gotit back plus .2 with the Brenspeed tune.
Again, an EGR delete or colder T-stat will cost mileage. I have the EGR but a 180* and will do the mileage with a stock T-stat to bget the diference in engine temps.Mark

sweet99

Stock any car runs off the O2 sensors and that is 14.7 or stoich. Now at WOT, out of closed loop that would be different. Brent will not send a tune that would melt a piston. With a power adder or even a radical NA build a DYNO tune is needed. Brent cannot make the car run richer at closed loop. That is controlled by the O2 sensors.
Deleting the EGR or adding a colder thermostat will cost mileage. I have an automatic with 4.10's, 3800rpm stall, Comp 230*/234* cams on a 110*LSA yielding 12* of overlap at .050" lift with a 106* centerline and with less than 500 miles it got 19.5 on an interstate loop I run for mileage testing. Adding a good cai such as a JLT may require more fuel due to the extra air entering the motor. I'll be changing back to a stock T-stat and trying a colder plug and will report mileage changes.