More on Poor Gas Mileage

[bolokid]

I thought I had solved the problem but to find out it is only partially solved.

I have a 91 Festie with a recently rebuilt B3, auto, a/c and p/s. I was getting 30 mpg while the CEL was flashing. I changed the O2 sensor and the light cleared but still mileage was poor. I advanced the timing and the mileage went to 41 mpg. I thought that problem was solved.

Yesterday I drove 400 miles on the interstate at 70-80 mph and once again mpg ranged 27-30 mpg.

Today I drove another 150 miles but at 55-60 mph and the mpg was 43. I notice that at 55-60 I am only pushing down on the throttle very little. At 70-80 I am really mashing the pedal, probably 80-90% of full throttle.

I am beginning to wonder about the catalytic converter? Partially plugged muffler?

Anybody else experience the same or have similar experience?

Thanks

[bhearts]

A vacuum gauge on my aspire shows roughly 10 inches of mercury to maintain 65. And it only goes down from there as I speed up. Vacuum is directly related to fuel consumption, as why a head wind gives lower vacuum numbers, and tailwind gives higher vacuum cruising numbers

[bhearts]

I'd highly recommend a gauge, so you know the immediacy reading of your throttle position

[Eaglefreek]

Autos aren't known for spectacular mpg.

[TominMO]

70-80 mph = 27-30 mpg
55-60 mph = 43 mpg

Problem solved.

Bear in mind that the autos are only 3-speed trannies, and really wind out at hwy speeds. Add to the the basic non-aerodynamic properties of Festies, and it sounds to me like your car is running fine. Gotta go 5-speed for good mileage in a Festy or Aspire.

[bhazard]

41-43 mpg is awesome for an auto. Your car is fine.

[jason_]

Hold your hand out the window at 55 and 75.

Now imagine that whole car bucking the air.

Drive slower. You're wasting fuel trying to drive faster through air density.

My diesel does 46-48mpg in 6th @ 55. 80mph it does like 35mpg.

Different cars, engines, design, gearboxes.... Same variables are air density and speed....







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[bolokid]

Hold your hand out the window at 55 and 75.

Now imagine that whole car bucking the air.

Drive slower. You're wasting fuel trying to drive faster through air density.

My diesel does 46-48mpg in 6th @ 55. 80mph it does like 35mpg.

Different cars, engines, design, gearboxes.... Same variables are air density and speed....







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This is the first 4 cylinder I have ever owned. Speed does not effect the mpg in the E class but does a little (maybe 10%) on the Ford V-8's.

I thought 25% drop was a bit excessive but I guess it is not. My next Festiva build will have a 5 speed.

Now I am wondering if a 1.6 (like Ian has) would handle the speed a little better. Anyone have thoughts on that?

Thanks for the input.

[jason_]

You're burning more fuel to push air the faster you go. You answered your own question with your own statement when you posted your speeds and fuel consumption. And then needing more throttle to go faster. The air drag exponentially gets worse the faster you go.

Diesel, gas, v4, v6, v8, v10,, 12, v16, i4, i6, w block, rotary, flathead, all have the same issues..... Air.

You'll need to floor that v8 Ford you claim that has minimal losses if you try and buck air @ 110mph.


My 2.0 turbo diesel did 54mpg in 6th on flat ground puting the scenic route in upper Michigan. Basically 1000rpm idling doing 35mph.

I did 85mph back home , and averaged 34mpg.

Upping your engine size will take less throttle, yes, but you'll cut your own throat on it needing to increase injector pulse width to satisfy 14.7:1....

I guess enjoy chasing your own tail.





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[bolokid]

So the bottom line is.......enjoy the scenery or pay.

Thanks.

[bhearts]

You could mil your head....

[jason_]

You could mil your head....

Haaa, brings back memories drinking and milling my head.....

058" and 3cc aluminum is a fuzz too much for pump gas without a 160* stat, and even then I made the hole a fuzz bigger to encourage extra bypass.





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[bhearts]

Haaa, brings back memories drinking and milling my head.....

058" and 3cc aluminum is a fuzz too much for pump gas without a 160* stat, and even then I made the hole a fuzz bigger to encourage extra bypass.





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And that brings back memories about why you never sprayed water into your intake air.

[TorqueEffect]

Last couple fill ups have been terrible on my B6. Getting very low 30s.

[Chobobulous]

Last couple fill ups have been terrible on my B6. Getting very low 30s.

You only have 4 so far are you running the b6 ecu?