dev203d

Fist off I know nothing about tuning so I am sorry if this may sound stupid, but I will be completing my gsr tubro build soon (Stock block with forged internals).....and I want to tune for the best possible MPG with no regard to power so that I can daily the car and take it on long trips without stressing low fuel milage. What is the best possible way I can do this? I was thinking of running 8 injectors (300cc or smaller) and have 4 on for the base map at low boost, and have all 8 come on for the race map. I was also thinking of running the AEM water/meth kit. Let me know what you guys think!

THANKS IN ADVANCE!!!

dev203d

I forgot to include that I am using a turbonetics T4/T4 turbo kit, and the stock Gsr head.

sleepencivic

most tuners tune to 14.5-15.5 afr's while doing 55 mph with no load!

E85B18

Size or amount of injectors wont matter much. About 15.2 afr will give you the best mpg

dev203d

55mpg?!!

dev203d

Thanks that helps!!! Wouldn't that be too lean though and promote detanation?

E85B18

Haha no one is getting 55mpg. Tuning with or without load makes a difference in your target afrs. Go to a tuner with a load bearing dyno and tell him mpg is really important to you.

It won't detonate unless your timing is crazy. With a normal tune, 15.2 is fine (not 15.2 under boost lol). When in closed loop you'll see afrs fluctuate between 14.5-15.2. It's normal. The closer you can keep it to 15.2, the better the mpg you'll get

dev203d

Thanks a lot that helps!!! and does it have to be a load bearing dyno?..also any thoughts on how the AEM water/meth will impact overall?

MR.johnson

i have 2000cc injectors and if i stay out of boost i get around 25mpg. if that helps.

E85B18

No it doesn't have to be. Water meth has nothing to do with mileage, it helps you run more boost/make more power safely. You only use meth when under boost. You don't use any when you're just driving

th3pwn3r

Lighten your car as much as possible and run an LS trans.

Flr Power

E85B18
How did you get that 15.2:1 AFR as the most fuel efficient number?

dev203d

Yes it does!

dev203d

Nicely put. lol

TheFrog

With 1000cc on pump gas I was getting 33mpg. Untill I got into boost lool

E85B18

From what I've read. I've never personally done any specific testing. From another forum that tested:

"MPH: 40 | AFR: 14.7:1, MPG: 28.2 | AFR: 16.0:1, MPG: 26.1 | AFR: 18.0:1, MPG: 30.5"

Results did vary by speed. 18 was best but that is going to hurt your engine... I think 16 is too lean too

darkvader0

I would simply run a wide-band closed loop and set closed loop to lean cruise. That's what I'm doing right now. Experimenting with down to 17.5:1(equiv) on E85.

fcluddington

That seems really lean let us know how that turns out for ya. might want to check plugs after 50miles.

darkvader0

So far so good for the past ~2 months. I started at 15.5:1 and have been leaning it out more and more. I'm not sure if I understand yet how to read plugs on E85. They look much different to me than when running gasoline.

The only thing I can mention is that I had to UP the timing as I lean out in cruise. I was playing around on loaded Mustang dyno and found I lost torque as I leaned out from 14.7:1 to 16:1. I upped timing in that cell and regained. It was doing that consistantly up to 65kpa or so.

No calculations yet for MPG, but I am already getting more per tank, so I know it's working.

inspector01

There is no reason that it can't be tuned for fuel efficency and power, they are completely different loads, so you can do both. And no, you don't need 8 injectors.

Ask your tuner to make sure its as fuel efficent as possible and they should be able to get it to around stock milage if not better, and still making plenty of power. Keep a wideband in the car to monitor all the time. You won't really mess a motor up going too lean at low load, it will break up before doing damage, but you can go pretty lean with E85.

E85B18

pwebb0207

no matter how efficient your engine - MPG will be most effected by your right foot and top speed.

keep your foot light and your speed down.

dev203d

What was your AFR?

Turbo-LS

iTrader: (4)

any compitent tuner will be able to obtain good gas milage, if you stay out of boost it will get 28+ easy. you want to be 14.7-15.5 light throttle cruzing. you shouldnt tune leaner than that it just get things hotter than they need to be and really wont help much for MPG. i get 33 on the highway 24-26 city and about 10 boosting at 400whp lol. overall usually get around 28mpg overall driving some boosting etc..

dev203d

Thanks! Yeah I would be weary of running anything higher than a 15.5 AFR. And who would complain about the 10mpg when ur eating subies with 400WHP! HAHA