I was reading some older threads on mpg and some of you are getting 20-27mpg crusing light load.

Ever since I went FI, I'm getting horrible gas mileage at crusing approx 250 miles for 16-17 gallons. My a/f is currently around 14-14.7 crusing light load.

I was reading http://autospeed.com.au/cms/title_Tu...5/article.html and it was mentioned somewhere between 15.5-17 can be safe for light load/crusing.

What is a safe a/f ratio for our cars for cruising? I am currently using the haltech.

thanks

 

Your current AF ratio is on point.

 

If your A/F is on point (you sure both banks are 14.7??) and you have stock compression then your timing is way off. No reason to get less than 20mpg on long trips.

 

I avg 26mpg driving back from GA years ago, and that was with 150mph pulls every other mile lol.

 

i've never seen those kinda mpg's. best i ever go was maybe 22 on the stock injectors/stock ecu driving my car to chicago to get tuned. drive home on big injectors and standalone was a good bit less.

whats the stock timing map look like off an OEM ECU between 2000-4000 rpms at whatever MAF voltages aligned with 15 to 5 inches Hg??

 

Let me guess the stock MPG meter said that? LOL

Best I ever got was 29mpg doing 65 a whole tank and zero boosting. I still see >20mpg easy as long as I don't hit boost more than a couple times. Once in boost more than a few times it's game over...

 

Yeah, OP, my wideband says basically the same AF ratio while cruising also.

I believe we have a 20 gallon tank (my fuel meter is not correctly reading). On a 20 gallon tank (91 Cali gas) I can get about 335 miles before my fuel pump starts to make this horrible whining noise and then I know it's time to fill-up.

 

My knockamp reads at exactly 14.6 or 14.7 at constant cruising speed (e.g. maintaining the same speed of 65, 70, or 80). It doesn't really fluctuate at cruising speed.

 

Same here OP im getting about 15-17 miles per gallon on my vortech set-up and seeing 14-14.8 a/f at cruise, going into positives boost once in a while. I'm taking a long trip (500 miles) 1st week of april so I will see what im getting without +boosting!

 

God. This is really the first time I've done the basic calculations to see my gas efficiency. I know the Z isn't the best from the factory but now looking at it with bigger injectors, it's friggin' horrible.

 

Driving back from Dynosty I avg 18MPG all highway

My AF read the same as the OP's under light throttle

 

C'mon man you think I'd trust that POS? Mine was off after the injector swap anyways it was out of the car, I manually calculated it.

Cruising with the 3.3FD when driven sanely its not bad on gas.

 

26mpg while doing several 150mph pulls doesn't seem 'sane' to me LOL. Just one pull like that would throw the MPG's off quite a bit.

 

I was joking earlier I wasn't that bad . I did hit limiter once and was upset because it should have been off lol. But otherwise went easy because everything was new. 711 mile trip I'll never forget it. Don't think I've ever been so happy with my setup. That was 2007.

 

That makes more sense. I can almost watch my gas gauge move downward every time I lay into boost. With a built setup it could only be worse.

 

Boosting its about 9mpg

 

I cruise around 16:1

 

Unfortunately Uprev won't allow target >14.7. Yay for standalones.

 

never seen a real increase in mpg from going from stoich to >stoich lean burn

i think the real gain in mpgs is more based on ign timing and injector firing angles...

 

^+1. stoich afr, maximizing vacuum via timing at cruise, and fast decel fuel cut out gives decent gains in economy. I get 21+ mpg driving within 10 mph of the speed limit on the hwy. 15 mpg daily driving (too many nice back roads to work ). I get single digits on the airstrip days.