max compression on endurance motors with e85, anyone have FIRSTHAND experience?
#11
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From: frankenmuth michigan
You are correct. Most guys running it are drag racers with huge cams to bleed off cylinder pressure, and carburetors which will run cooler. Chris Uratchko claims to have run it as high as 16/1. But with a boat cam, and durability in mind I think you are on the right track that it needs to be much lower.
I suspect that many people run E85 way too lean but it tolerates it. Those might be the guys claiming you can only run 12.5-13 on it, but I’m speculating.
You are in somewhat uncharted territory. But that extra 4% of power per point of compression sure is tempting isn’t it?
If it were me I’d run it on 100LL from an airport with a lead additive. That should get you similar octane, be cost competitive and a 40% better fuel economy. You could also pull all of the timing out of it in a pinch and run on pump piss with out changing your tune.
Are you going to run MEFI?
good luck, keep us posted
Yes, Im going to use mefi, Im also going to wire a flex fuel sensor in and test it BEFORE building the motors. IF I can make the flex fuel sensor work work properly I'm also going to dyno the 12.8 motor on e85, keep adding 93 to it until I see KR to know how much gas you could actually mix in if you had to. Im thinking high 12's is going to be a safeCR, maybe Ill do the calcs for 13.3 or so w a .040 head gasket and build it that way and if im seeing kr on long hard pull start raising heads to lower cr,
#12
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Joined: Nov 2005
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From: Fredericksburg, Va
Smitty, as you know we have been racing on E85 for over 6 years now, love the stuff, we only use in boosted apps. Its great on boosted apps with its cooling effect, we run 25lbs with on innercooler, without boost would need about 12-1 to make worthwhile. You will burn about 40% more fuel and need to be able to move that much more, so fuel system needs to be capable...call me if you want to go over anything..Rob
#14
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From: frankenmuth michigan
So as far as using mefi, going to test THAT in near future on mule motor. IAT on 500 efi is filled w zeros there is pw modifyers from top to bottom based on 0 to 5 volt analog reference. Ive also filled them in on builds based off what innovation does on their 500 efi, made pretty much ZERO difference as iat is pretty constant on a boat. So flex fuel convertor puts out a 50 to 150 mhz signal, you can buy a convertor box that changes it to a 5 volt analog output. This can be inputed into iat table and pw modifyer adjusted accordingly. I also bought a IAT extension with both ends on it so i dont have to whack the factory end off to make a connection. So my idea is to install a gm continental sensor on return line as they are only avaliable w a 3/8 oem style tube and its too small to be on supply side. So my plan is to find where straight e-10 analog voltage falls on table at and where e85 signal falls at and scale everything in between . Can do this just cycling fuel pump w motor off. Then pull mule motor w various mixtures and make sure afrs follow. If this works and im pretty sure it will then bump compression on mule motor w piston change and see what happens. Of course fuel pump, lines and injectors will be appropriately sized. Fun stuff!. As far as fuel temp, go, wont be able to compensate for that at all BUT thats really for oem applications where you would be running it in real cold weather!
#15
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My 10 year old engine with 8-10,000 miles did not have any valve seat wear. I do run alcohol lube in every tank of fuel. Alcohol has no/very low lubrication properties. Most don't run lube because there is some gasoline in the mix. For the price of the alcohol lube I think it is a no brainer.
I also run a flex fuel sensor and have my after market ECU adjust the boost, fuel and timing depending on alcohol content.
The flex fuel sensor has a linear output- 0 volts at 0% alcohol and 5 volts and 100% alcohol.
I can tell you its not as simple as just adding say 40% fuel at 85% alcohol, it is not linear. My engine needs less fuel at lower rpms/loads than at higher loads-boost. I would have to check my table but it could be +25-30% at lower loads and 40% at higher loads.
e85 has a much wider "safer" a/f window. My alternator failed about 6 years ago and I didn't realize the voltage was about 10v. I did a pull on the street with 15psi and the a/f was 14:1. I was on it for a bit before I realized what was going on. Engine never skipped a beat or got hurt. I was a true believer of e85 than. If that was on gas I could have hurt a piston or blown the head gasket without a doubt.
#16
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Joined: Mar 2004
Posts: 2,696
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From: Pa
I can't speak for a marine engine but having been using e85 in my street car for about 8-9 years, love it. Turboed small block Ford running 15psi-900hp.
My 10 year old engine with 8-10,000 miles did not have any valve seat wear. I do run alcohol lube in every tank of fuel. Alcohol has no/very low lubrication properties. Most don't run lube because there is some gasoline in the mix. For the price of the alcohol lube I think it is a no brainer.
I also run a flex fuel sensor and have my after market ECU adjust the boost, fuel and timing depending on alcohol content.
The flex fuel sensor has a linear output- 0 volts at 0% alcohol and 5 volts and 100% alcohol.
I can tell you its not as simple as just adding say 40% fuel at 85% alcohol, it is not linear. My engine needs less fuel at lower rpms/loads than at higher loads-boost. I would have to check my table but it could be +25-30% at lower loads and 40% at higher loads.
e85 has a much wider "safer" a/f window. My alternator failed about 6 years ago and I didn't realize the voltage was about 10v. I did a pull on the street with 15psi and the a/f was 14:1. I was on it for a bit before I realized what was going on. Engine never skipped a beat or got hurt. I was a true believer of e85 than. If that was on gas I could have hurt a piston or blown the head gasket without a doubt.
My 10 year old engine with 8-10,000 miles did not have any valve seat wear. I do run alcohol lube in every tank of fuel. Alcohol has no/very low lubrication properties. Most don't run lube because there is some gasoline in the mix. For the price of the alcohol lube I think it is a no brainer.
I also run a flex fuel sensor and have my after market ECU adjust the boost, fuel and timing depending on alcohol content.
The flex fuel sensor has a linear output- 0 volts at 0% alcohol and 5 volts and 100% alcohol.
I can tell you its not as simple as just adding say 40% fuel at 85% alcohol, it is not linear. My engine needs less fuel at lower rpms/loads than at higher loads-boost. I would have to check my table but it could be +25-30% at lower loads and 40% at higher loads.
e85 has a much wider "safer" a/f window. My alternator failed about 6 years ago and I didn't realize the voltage was about 10v. I did a pull on the street with 15psi and the a/f was 14:1. I was on it for a bit before I realized what was going on. Engine never skipped a beat or got hurt. I was a true believer of e85 than. If that was on gas I could have hurt a piston or blown the head gasket without a doubt.
#17
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Joined: Jan 2006
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From: St. Pete Beach, FL
Nice. Is it possible to measure octane?
#19
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Joined: Apr 2013
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From: Lake Winnebago
Wonderful fuel......I have a lot of experience with it.
Unfortunately, my experience falls in the turbo/jet boat/drag/street category.
Ive strongly considered it for my large boat....but availability on the water and range reduction deterred me.
The closest thing Ive used it for endurance is I set up a turbo 460 ford tow vehicle (crew cab F350, ZF 5 speed) for a buddy.....twin tanks staged injection....flips over to E85 at about 3 lbs of boost.....normally runs 87 oct on small primary injectors
Unfortunately, my experience falls in the turbo/jet boat/drag/street category.
Ive strongly considered it for my large boat....but availability on the water and range reduction deterred me.
The closest thing Ive used it for endurance is I set up a turbo 460 ford tow vehicle (crew cab F350, ZF 5 speed) for a buddy.....twin tanks staged injection....flips over to E85 at about 3 lbs of boost.....normally runs 87 oct on small primary injectors



