Gains from E85 (ethanol) on an N/A bolt on 370Z

POS VETT · 09-22-2015, 07:20 AM

In the case of my GM truck, the drop in fuel consumption is way less than 30%. The drop in energy content is also less than 30%. The number 30% or 33% is used to size up injectors and fuel pump to give them cushion so that they work in a smaller duty cycle.

E85 has a much higher knock resistance and it burns at a lower temperature, these two traits allow the engine to run at near stoichiometric (i.e. leaner) and at very advanced ignition timing for a more complete burn producing a better use of the fuel. When a PCM senses a knock with E10, it backs off timing and injects more fuel to combat its destructive effects, meaning power output is lower and fuel consumption is higher, then the driver uses more throttle to compensate which makes the fuel consumption of E10 is now much closer to that of E85, or possibly, even less.

Push370zzz · 09-22-2015, 10:19 AM

Quote:

Originally Posted by Chuck33079

Right, doesn't e85 usually result in a pretty substantial drop in mileage? It's about 30% less energy by volume than pump gas and that's why you need more volume than pump, right?

Yes. E85 has about 72% as much energy as an equivalent gallon of gasoline. E10 should have about 96%.

Quote:

Originally Posted by POS VETT

In the case of my GM truck, the drop in fuel consumption is way less than 30%. The drop in energy content is also less than 30%. The number 30% or 33% is used to size up injectors and fuel pump to give them cushion so that they work in a smaller duty cycle.

E85 has a much higher knock resistance and it burns at a lower temperature, these two traits allow the engine to run at near stoichiometric (i.e. leaner) and at very advanced ignition timing for a more complete burn producing a better use of the fuel. When a PCM senses a knock with E10, it backs off timing and injects more fuel to combat its destructive effects, meaning power output is lower and fuel consumption is higher, then the driver uses more throttle to compensate which makes the fuel consumption of E10 is now much closer to that of E85, or possibly, even less.

The drop in energy content is very close to 30%. E85 is absolutely better for power, particularly in boosted applications, due to what you pointed out. That said you are just not going to get better or even close to the gas mileage you'll get on regular gasoline or E10.

http://www.edmunds.com/fuel-economy/...ison-test.html

https://en.wikipedia.org/wiki/Gasoli...lon_equivalent

Chuck33079 · 09-22-2015, 10:48 AM

Quote:

Originally Posted by Push370zzz

Yes. E85 has about 72% as much energy as an equivalent gallon of gasoline. E10 should have about 96%.

The drop in energy content is very close to 30%. E85 is absolutely better for power, particularly in boosted applications, due to what you pointed out. That said you are just not going to get better or even close to the gas mileage you'll get on regular gasoline or E10.

E85 vs. Gasoline Comparison Test

https://en.wikipedia.org/wiki/Gasoli...lon_equivalent

Right. So if someone is claiming the same, if not 1-2 miles per gallon improvement, they are in error since it would not be possible to get the same mileage on a fuel that has less energy by volume. Maybe he's looking at the mpg gauge which is now wrong due to different injectors?

I'm also unclear how someone can claim a power improvement from going to E85 without any timing adjustments. Can someone explain how that works? I'm at a loss.

njobe89 · 09-22-2015, 11:30 AM

Quote:

Originally Posted by Chuck33079

Right. So if someone is claiming the same, if not 1-2 miles per gallon improvement, they are in error since it would not be possible to get the same mileage on a fuel that has less energy by volume. Maybe he's looking at the mpg gauge which is now wrong due to different injectors?

I'm also unclear how someone can claim a power improvement from going to E85 without any timing adjustments. Can someone explain how that works? I'm at a loss.

if you just switch to e85 without a tune, you won't make any power. with the correct tune you are supposed to make power... not sure how other than it's higher octane rating than 93.

Chuck33079 · 09-22-2015, 11:53 AM

Quote:

Originally Posted by njobe89

if you just switch to e85 without a tune, you won't make any power. with the correct tune you are supposed to make power... not sure how other than it's higher octane rating than 93.

That's what I thought as well, but someone in here is claiming that he saw a power increase with zero timing changes. I was under the impression that the additional power from an E85 tune came from the additional timing you could run.

njobe89 · 09-22-2015, 11:57 AM

Quote:

Originally Posted by Chuck33079

That's what I thought as well, but someone in here is claiming that he saw a power increase with zero timing changes. I was under the impression that the additional power from an E85 tune came from the additional timing you could run.

i'm in the process of getting gtr injectors and then setting up a tune and i'll see what i gain. right now im at 324, but i've heard that the dyno at z1 reads high and i'm going to a different place this time.

synolimit · 09-22-2015, 02:10 PM

Quote:

Originally Posted by njobe89

i'm in the process of getting gtr injectors and then setting up a tune and i'll see what i gain. right now im at 324, but i've heard that the dyno at z1 reads high and i'm going to a different place this time.

The OP has OEM injectors so the gauge should read right as it goes off of injector duty cycling. I'd personally stick with Z1, good to be on the same dyno! I'm betting now Jon does have tuning secrets but remember they read "high" because they use 5th and STD. Ask him to do a run in 4th and SAE. I'm betting you come down to about 309 as that's what others use. The last 370z I tested with my ported parts made 324 in 5th SAE. He had ported TB, upper and lower, FI lth and CBE and gen 3 CAI. in 4th he only put down 316. I'm guessing since you don't have ported stuff the dynojets read about the same and not reading high, it's just what you run and correct for is all.

Push370zzz · 09-22-2015, 04:47 PM

Quote:

Originally Posted by Chuck33079

Right. So if someone is claiming the same, if not 1-2 miles per gallon improvement, they are in error since it would not be possible to get the same mileage on a fuel that has less energy by volume. Maybe he's looking at the mpg gauge which is now wrong due to different injectors?

I'm also unclear how someone can claim a power improvement from going to E85 without any timing adjustments. Can someone explain how that works? I'm at a loss.

They are mistaken if they believe that under similar conditions they are seeing similar fuel economy (much less an increase) with E85 over E10 or regular petrol.

E85 allows you to change the timing to a range not possible to run on standard gasoline due to knock. Without a tune to take advantage of it, you should not see any difference in power. It's like putting 94 octane in a Prius.

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09-22-2015, 07:20 AM	#1 (permalink)
POS VETT Track Member Join Date: Apr 2015 Location: Columbus OH Posts: 612 Drives: Z34\|C4LT4\|C6Z06\|V25 Rep Power: 3367	In the case of my GM truck, the drop in fuel consumption is way less than 30%. The drop in energy content is also less than 30%. The number 30% or 33% is used to size up injectors and fuel pump to give them cushion so that they work in a smaller duty cycle. E85 has a much higher knock resistance and it burns at a lower temperature, these two traits allow the engine to run at near stoichiometric (i.e. leaner) and at very advanced ignition timing for a more complete burn producing a better use of the fuel. When a PCM senses a knock with E10, it backs off timing and injects more fuel to combat its destructive effects, meaning power output is lower and fuel consumption is higher, then the driver uses more throttle to compensate which makes the fuel consumption of E10 is now much closer to that of E85, or possibly, even less.