Alternative Fuels Discussion and Tech on using alternatives such as E85 or Hydrogen or other fuels and/or supplements to Gasoline in Rotary Engines

how many MPGs on e85 are you getting?

Old 11-02-14, 01:44 AM
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how many MPGs on e85 are you getting?

how many MPGs on e85 are you getting? i have been working on my tune and ive gotten about 10-11 mpg but im still rich on lot of cells so im working out the kinks. just wondering on MPGs
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Old 11-02-14, 09:46 AM
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this general question may be one of the most interesting and important...

fuel into the motor related to power output is referred to as Brake Specific Fuel Consumption:


it is not the amount of fuel injected into the motor that determines efficiency, it is the amount of fuel BURNED.

often, fuel mileage and power can track similarly. an efficient engine burns more of the fuel and as such produces more MPG as well as HP.

many factors combine to set this relationship.

last October i drove my car 95 miles from Beyond Redline to my home on E74 (according to my FFS) on exactly 5 gallons. the road was an expressway (74 mph) for 75 of the miles and county roads for the remainder. my AFR was around 13.9. i probably did not get into boost... just cruising at approx 3200 RPM.

i am very close to 20 mpg on E74.

as to power... i had just completed a 45 pull dyno session at around 25/26 PSI w a GT4094r. pretty conservatively tuned around 570/575 SAE... 588 STD. max injector duty cycle was 54% w 4 2000s.

BSFC figures at 56.6 at peak power and 58.6 at peak torque.

i will be back on the dyno within a week generating more data running different injectors.

given your low MPG i suspect you are not burning your fuel efficiently and quite a bit of it is ending up in your exhaust. generally when this happens a significant part of the unburnt fuel also ends up in you intake as well.

exhaust back pressure is a key as well as fuel atomization.

tell us about your setup and let's get tuning.

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Old 11-02-14, 11:58 AM
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13.9 "gasoline AFR" or 13.9 actual?

I'd just like to clarify if you were running rich or lean.

I've found fuel economy benefits (on gasoline) for going richer than you'd expect, under certain conditions.
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Old 11-02-14, 12:49 PM
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"13.9 "gasoline AFR" or 13.9 actual?"

13.9 indicated on my wideband. the actual number would be lower due to the ethanol component.
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