Thought I'd start picking some brains. Just ran through a full tank of gas in my freshly baselined car. By my estimations.....10 MPG. That's with about 98% light just cruising around and breaking it in throttle. Double You Tee Eff.....seriously?

Now.....I say stupid because, it's a very healthy 383 with a decent sized cam (234/244 .610/.610 110* LSA 108 ICL), TFS heads ported by LE, 85# injectors, turbo, FAST XFI, ect. We were having a little low area trouble with the injectors damn near shutting off at idle due to scaling the VE table back to a good AFR causing the Pulse widths to drop WAAAAAAY down, so I'm thinking of making a fuel pressure change to hopefully correct that but still.....10 MPG? I would have expected a little better than that. I'm at 128 miles and below 1/4 tank on the gauge which we all know what that means.

Crazy part is the car is running fantastic. I don't get it.

 

At best I get 13/20 MPG's.

Recently I was getting similar to you and found that the motor was just running fat and a retune took care of that. I also saw that my idle L/R BLM's were badly split mainly due to bad left side plug wires and the aftermarket TB. Once those issues were fixed, the BLMs are now equal +/- a point or two at the most and the MPG's got much better.

 

Smaller injectors with higher PSI would fix your low rpm issues. They atomize way better and are more tolerant to low pulse widths.

Honestly 10MPG doesn't sound too far off for mixed/city driving a thirsty beast like that. My stalled auto H/C setup was getting around 13 city (with a heavy foot and loose stall). Don't underestimate how much driving habits effect fuel economy.

 

All i can say is its a head/cam 383 with a .610 lift cam. I think your expectations are a little off, especially if its a stalled a4 car.

 

needs smaller injectors

 

Needs more boost. Just drive it more, bet it gets better. Plus it wont matter when your making 1000rwhp when you swap the 91mm and start running that Q16 or VP import

 

Lol that will work too

 

**** I call you luck, my buddies car with just a cam only 3.73 geared gets about 12 mpg TOPS with very light throttle. A4 too

 

Sean, our motors are pretty similar (except my cam is a bit smaller) and my injectors are 82#, but I'm probably seeing about 200 miles to a tank (roughly 13 mpg). I'm tuned a bit rich, but not too bad. Just the nature of the beast I suppose.

 

Sean, I say that's about right. You may get more w/ a some fine tuning in there...may. Haven't figured what I get for mpg but I did 8 pulls on a full tank of gas and was damn near empty after the 8th pull...I run 96lb injectors. That outta give ya food for thought.

 

Silas, your numbers on pump?

Neil

 

i'm getting about 7-8 mpg, you ain't doin bad for a beast like that

 

Neil, yep all pump and no meth. 114 tune and a meth tune later next yr.

 

Hey, it's smiles per gallon...... smiles per gallon.

 

I guess my gripe is that I had every intent of driving the **** out of the car, but at 130 miles a tank, I will be stopped from driving it for simple cost reasons.

We're going to do some working on the tune next week, I got an AFPR put on the car yesterday. The injectors vs pressure is causing the VE table to be run so low the injectors are showing a 0.00 pulse width at times, and it's as lean as it can get at 12.xx to low 13's at idle and decel........so we're expecting to pull a bunch of fuel pressure out to lean it out some, and go from there. Could possibly try the old trick of throwing a smaller injector number into the constant in the XFI also........It's being worked out. I'll be happy with 200 miles a tank......but 130 doesn't cut it. It's not a huge cam, not a high compression setup, so light driving I should really see near N/a mileage.

 

The next time I go out, I'll let you know how many miles I get to a tank. My idle afr's are in the high 12's. If I shoot for 13's it doesn't want to act right but it's all because of the 96lb inj's too. The beyotch just likes fuel and she eats more fuel at idle then when I'm on the road. LOL I'm sure I could probably eek out 180 to a tank or maybe more if I drove like granny. She's only a wkend warrior anyways so I don't care about mileage. Don't ya have the fp set at 43psi?


Damn! I didn't know you sold Blue Streak?!

 

Silas, check your PM's. Yeah, I was forced into selling the Vette.......I honestly still get emotional from time to time about it.

How big is your cam??? I know mine isn't helping cause it's got a **** ton of overlap for an FI car.......reversion is a bitch. But........it's not worse than an aggressive N/A cam so I really think I should be doing better. I did have primarily highway miles on teh car this third tank and made it to 100 miles before hitting the 1/2 tank mark.........lol