Fuel Economy Woes - 8.5mpg

[Corbic]

So I'm currently averaging about 130-140 miles per tank. The math (miles driven / gallons added) is coming out around 8-10mpg.

This involves a few lights, some 45mph cruising and some 60mph cruising.

No pulls, no sprinted driving and lots of short shifting.

AFR (AEM) is reading all clear with an idle around 14 and bouncing 11-16 with on/off throttling etc.

Car made 605whp, 2.2 KB, EGR delete, Catted X, Borla back on 315 M/T Streets and a 3.31 SRA.

I'm well aware a modded Cobra is going to get poor MPG, but this is beyond abysmal. This is so bad my brain is saying "you can sell the powertrain for $10k and drop in an LS3 for 7k"

 

[jrichber]

Something seems off. I am around low teens when doing town cruising as it gets in boost here and there. But on the highway I am in the 20's.

 

[01yellercobra]

That's pretty bad. I got better with 80lb injectors. But I imagine the gears and short shifting isn't helping things. Wind it out a little.

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[Steve Cea]

I'm pulling 650 hp on my 03 and if I drive it normal I average 14-16 mpg ? So yeah I would agree, something is off ??? Check that tune !!!

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[Zemedici]

I get 6-8mpg, 619whp 2.3l whipple car with 60# injectors. About 150 miles out of a tank.

My 04 got about 11mpg, just seems to be the nature of the beast.

 

[R3dfireCobra]

What fuel are you running? Seems like E85 mileage numbers.

 

[c6zhombre]

What fuel are you running? Seems like E85 mileage numbers.

Exactly. That's right in range with what I get on E85. I could easily surpass those mpg figures, but I'm not short shifting, highway cruising, or taking it easy on my tank. That's lots of blasts lol

 

[Corbic]

What fuel are you running? Seems like E85 mileage numbers.

93 Octane

 

[GNBRETT]

geez thats worse then E85 at full boost smashing it all night. somthn is way off in ur tune.

 

[01yellercobra]

I get 6-8mpg, 619whp 2.3l whipple car with 60# injectors. About 150 miles out of a tank.

My 04 got about 11mpg, just seems to be the nature of the beast.

Isn't your commute something like 3 miles?

 

[gimmie11s]

im getting about 14mpg or so per tank with drag radials. not great at all, but not 8mpg either lol.

 

[Zemedici]

Isn't your commute something like 3 miles?

used to be - moved away and now its longer.

Its 5 miles. hahahahahaha literally 3 exits

 

[cj428mach]

"Checking" your tune would be a waste of money.

You basically said that your mileage sucks even when you're not in boost, your O2 sensors are always looking for stoich unless you're in open loop which only takes place during cold start up and WOT. If you log your STFT and the ecm is making corrections you're in closed loop. That means your problem is something mechanical like an exhaust leak, bad O2 or a miss causing a false lean condition.

The only thing a bad tune could do is command full time open loop with a crazy commanded lambda or crazy commanded lambda at WOT.

 

[PaxtonShelby]

Maybe you're looking at the tach and not your speedo.

 

[mustanginky]

Do you smell gas around the outside of the car? Or fresh gas? I suspect a tank gasket or iirc the filler neck gasket could be leaking.

 

[Corbic]

Do you smell gas around the outside of the car? Or fresh gas? I suspect a tank gasket or iirc the filler neck gasket could be leaking.

Nope

 

[Corbic]

"Checking" your tune would be a waste of money.

.

I'm actually going to do a compression test before I do anything else.

 

[TP03]

Maybe your heavy from too much cargo... couldn't resist.

 

[Corbic]

Maybe your heavy from too much cargo... couldn't resist.

Huh?

 

[TP03]

Looks, cargo capacity, value.

Just messing with you