E85 vs 91 for street

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dstemmerman

dstemmerman

1972 Dart Swinger Denver
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Planning a 408 build. Trying to decide on E85 vs 91 and respective compression ratio. I have one station down the street that sells E85. I already have steel fuel lines and plan on installing an electric fuel pump regardless. I typically keep my drives approx 20 miles or less. Would be 80% street and 20% track. Just trying to figure out if I go with 12+:1 using E85 only or go with 10.8:1 which allows me to use 91 if needed. I understand it is all about educating myself on the nuances of E85 and making a personal decision, just curious if there was a consensus one way or another.

If relevant:

Elevation: 6,000 (Denver)
Heads: Trick Flow 190 60cc when released in Sept
Cam: TBD FT solid
Horsepower goal: 450-500 would be nice.
 
I don’t understand how it doesn’t cover you. If it is the difference with the compression ratio, think of it this way, if E85 isn’t available but only close, what will you do if there is a desperate need of it when your elsewhere?

The gain in ratio would be a small gain. If you went from 10.5-1 to 15 -1, it would be an interesting gain. But your not going up a lot in power. You can achieve your power goals with 91 octane on a 10-1 ratio. Going to 12-1 and using a less efficient fuel seems pointless to me.
 
Having a newer Durango that is E85 capable, I figured I'd give it a go and compare economy vs price per gallon and see which was more cost effective. My average on 87oct was 20mpg at roughly $3.20gal. My average on E85 went down to 12mpg at $2.80gal. the local high octane available is 93oct and is around $3.80 a gallon. So even with the more expensive gasoline, it would still be more cost effective than E85.

So my price per mile actually went up noticeably with the cheaper E85. Ive tried this test back to back a couple times with nearly identical results regarding driving style.

Anyways,I know it's not exactly what your asking, but if there isn't going to be a noticeable power gain, might wanna do the math and compare local high octane price vs E85 and see which would be more economic.
 
Interesting results. Your getting a lot less miles per tank but at a economic advantage.

My engine builder asked me if I wanted to do an e-85 build last time around. I turned it down. It was just more than I was ready to fuss with and the build was targeted to be a bit more mellow than he thought I was going for.

It’s still a good idea in many cases. You just have to be aware of the lower btu return on the e-85 as well as the higher consumption rate of the fuel. It is really nice that you can run a really high ratio with it.

For myself, it is all the extras that needed to be done on top of the basic build of the engine. I wasn’t willing to “go there” just yet.
 
We been using it for years now in our bracket racing cars...I use it cause at 2.50 a gallon vs 8 bucks a gallon race gas. Using the same braided line and the same 140 gph pumps...changed out fuel filters as required.
Only thing other thing I changed fuel cells from 5 gallons to 8 gallons as just to make it easier.

On weekend race we burn a good 30 gallons of fuel...do the math and you see why I use it. I buy it from the same station and it always checks at 85% ...there is no winter blend in nevada...as it looks like there is no winter in vegas this year..LOL
 
What I want to know is, you talk as if you build the low compression engine that you can just swap back and forth between E85 and pump gas. I don't think you can do that with the same carburetor, can you? With the minimum power gains you'd see from going 12 compared to 10, I would go 10 and use pump gas.
 
Rob I s correct! You can not use the same carb back and forth on the regular gas and the e-85.

The carb needs to be modified for more volume of fuel to move through it.

Once you modify the carb for e-85, you will not be able to jet down for regular gas.

You would need two separate and distinct carbs.
 
Tony, would you or do you run e-85 in your cars everyday and around town or are your cars mostly/only strip?

What are some of the in’s and out’s not mentioned so far?
 
RustyRatRod said:
What I want to know is, you talk as if you build the low compression engine that you can just swap back and forth between E85 and pump gas. I don't think you can do that with the same carburetor, can you? With the minimum power gains you'd see from going 12 compared to 10, I would go 10 and use pump gas.
Click to expand...
The plan was to make a decision on fuel choice and purchase the correct carb. I know there are many factors involved when using E85 due to the corrosive properties as well.
 
I drive my junk on the street a lot so for me e85 was out of the question. I end up in a lot of small rural towns that just don’t have it yet and I do not want to be stranded over something like that.
 
dstemmerman said:
The plan was to make a decision on fuel choice and purchase the correct carb. I know there are many factors involved when using E85 due to the corrosive properties as well.
Click to expand...

Well I don't know a lot about E85, which is why I posed part of my response as a question. I know that methanol carburetors differ greatly from gasoline carburetors, but my E85 knowledge is nil.
 
rumblefish360 said:
Rob I s correct! You can not use the same carb back and forth on the regular gas and the e-85.

The carb needs to be modified for more volume of fuel to move through it.

Once you modify the carb for e-85, you will not be able to jet down for regular gas.

You would need two separate and distinct carbs.
Click to expand...

That's what I thought, but I wasn't sure. I wonder if EFI would make that more possible?
 
Today’s cars are felxable/smart enough to handle both fuels. I don’t know jack about the aftermarket stuff though I would guess a simple set of phone calls would answer that.
 
rumblefish360 said:
Today’s cars are felxable/smart enough to handle both fuels. I don’t know jack about the aftermarket stuff though I would guess a simple set of phone calls would answer that.
Click to expand...

Me either! I guess I am just old and set in my carbureted gasoline ways. But "I just bet" that there's somebody out there in aftermarket land that has something that can make it happen.
 
I’d say so. I just don’t know. I also seem to just simply like those confounded crazy mixing devices myself.
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BA90A95D-E1F6-41F9-9227-5015D0579A99.jpeg
 
I had an idea once
to run a 6bbl with E85 on the outboards and gas on a small center carb, aluminum heads and lotsa cylinder pressure.
Another idea was a Dual-Port with a small spreadbore and same split fuel idea.
I've been waiting for a Dual-Port so show up here cheap, but that waiting thing's been going on now for several years. I kindof lost interest when my 367 made way more power than I expected, on 87E10.
 
dstemmerman said:
Planning a 408 build. Trying to decide on E85 vs 91 and respective compression ratio. I have one station down the street that sells E85. I already have steel fuel lines and plan on installing an electric fuel pump regardless. I typically keep my drives approx 20 miles or less. Would be 80% street and 20% track. Just trying to figure out if I go with 12+:1 using E85 only or go with 10.8:1 which allows me to use 91 if needed. I understand it is all about educating myself on the nuances of E85 and making a personal decision, just curious if there was a consensus one way or another.

If relevant:

Elevation: 6,000 (Denver)
Heads: Trick Flow 190 60cc when released in Sept
Cam: TBD FT solid
Horsepower goal: 450-500 would be nice.
Click to expand...

I think you're gonna have trouble getting air up there as is, and you will have to run extra cylinder pressure. With aluminum heads, and a typical big street cam with a 68* ICA , you'll want to run an Scr well over 12 or 12.5 anyway.Oxygenated is kindof a natural for you
At 10.8 I don't think you'll find a cam with a small enough ICA, to not be somewhat soft on the bottom, with iron heads.
Have you run your combos thru the Dcr calculator yet?
I think the difference from sealevel to 6000 is like 30 psi in cylinder pressure. Yeah that's what I keep seeing.
Suppose you want to run at least a 230* cam to find some air up there. And a solid FT, so that could be a 268/276/110.. Installed at 108, I get an ICA of 62*..When you put that into the Wallace at 10.8/6000ft,I get; 151psi and a VP of 148. Because it's a stroker that might not be too bad.And you can run iron on that.But generally, 148 VP is about what a warmed up 367 like mine makes, and I'm not unhappy. But it's a 360. If I had a stroker, I'd expect more.
So, at 151 psi, there's quite a bit of room for improvement. At 11.3, the pressure jumps to 163, and VP to160. That's an increase in VP of 8%.And that's about the limit for 91 gas and iron heads.A VP of 160 is quite good.

But for aluminum heads and E10/15 gas you can hit 185/195 psi, and that would get you 12.4 Scr/184psi@181VP , a killer bottom end.And normal for aluminum heads. Normal meaning won't detonate on pumpgas.
I can't speak to running 12.4 at WOT at 6000ft; you'll need to talk to the builders. I can only speak to the numbers in this case. The highest I have run was 11.3. and currently at 10.9
And all this with a 268* solid Ft cam, with an ICA of 62*. If you want to run more cam, it's back to the calculator. But 12.4 is an easy build I think; flat-tops at zero deck with 5cc eyebrows,60 cc heads, and the rest in the gasket .039/8.9.
____________________________________________________
I run a cam pretty close to that, at 900ft, in my 367 at 10.9 Scr and 175 psi.....on 87E10. I have run over 185psi on 87E10. Some guys on FABO have reported over 200psi on pumpgas; I'm assuming 91.
 
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rumblefish360 said:
Tony, would you or do you run e-85 in your cars everyday and around town or are your cars mostly/only strip?

What are some of the in’s and out’s not mentioned so far?
Click to expand...

probably not....First I would not build a engine that requires racing gas as a street engine....

the same carb can not be used for e85 and gasoline as said internally the e85 must flow 25 to 30% 'more fuel that includes main and idle circuits....
 
vntned said:
Having a newer Durango that is E85 capable, I figured I'd give it a go and compare economy vs price per gallon and see which was more cost effective. My average on 87oct was 20mpg at roughly $3.20gal. My average on E85 went down to 12mpg at $2.80gal. the local high octane available is 93oct and is around $3.80 a gallon. So even with the more expensive gasoline, it would still be more cost effective than E85.

So my price per mile actually went up noticeably with the cheaper E85. Ive tried this test back to back a couple times with nearly identical results regarding driving style.

Anyways,I know it's not exactly what your asking, but if there isn't going to be a noticeable power gain, might wanna do the math and compare local high octane price vs E85 and see which would be more economic.
Click to expand...

There's something not figured in here, either. E85 is heavily subsidized so (we) are paying even more for it
 
True, but the bottom line is what your paying at the pump no matter what fuel is used and how often your pumping the fuel your using.

Score we get political about this, the thread topic should be stuck to. Not the political side of it.
 
just wondering, with today’s vehicles that are Flex Fuel capable, I have read more than once that the fuel mileage really goes down when running E85 compared to regular gas.
Wonder how much of that mileage loss is because the Flex Fuel motor is not compensating for the higher compression that E85 is capable of running when compared to regular gas?
 
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