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max compression on endurance motors with e85, anyone have FIRSTHAND experience?

Old 01-03-2019, 02:39 PM
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Default max compression on endurance motors with e85, anyone have FIRSTHAND experience?

Anyone actually running E85 in run of the mill twin engine v-hull, not some 10 second at wot v-drive or jet boat. Yes, i know it will have less range, yes i know it attracts moisture and yes i'm fully aware that it varies in content between about 68% and 87% depending on time of year. NOT looking for opinions on weather someone should run it or not, looking for real world experience on a good compression number to build the motors with (540 bbc w efi), I'm thinking 12.8 to 13-1 range accounting for fact it often test closer to 75 or 80% so you need some margin of safety. I'm 95% sure I figured out how to input a flex fuel sensor into a typical mefi efi ecu and will be testing my theory on my dyno in near future before going forward with build. Biggest concern I have is to take advantage of the benefits of the alcohol you need a fair amount of compression, to run that kind of compression you need a appropriate cam. A typical cam for even a 12.8-1 motor is usually so big that hp peak will end up well into the 6500 plus range and dry sumps and 30 or 40 hour valve train life are a little more than I'd like to be doing, thanks in advance for any REAL WORLD experience input, Smitty
I DO have some experience running it in supercharged street engines, have dynoed with it before and a twin turbo jet boat and know how to test its content so its not amateur hour.
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Old 01-04-2019, 02:00 PM
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No responses yet Smitty... :-( Following.

Personally, I not sure I see the benefit of it in a NA application. But as far as the build goes, i guess I would sort of look at it like it's going to be an engine made to run on C12 or equivalent since it's about the same octane rating as E85.

As far as the sensor goes. A buddy of mine has successfully run a system where he runs 93 octane and methanol separately and it has two tanks, two fuel rails/injectors etc.

Got any questions give me a buzz!
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Old 01-04-2019, 02:08 PM
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I know Nauti Marine ran alcohol but not sure it was E85. American Ethanol is running E85. Both boosted applications and obviously those mills aren't built for endurance. Otherwise, haven't really seen or heard of any NA applications in pleasure/poker run boats. Hopefully someone chimes in. Otherwise, maybe lean on those doing it for more extreme use and get their thoughts on your intended application?
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Old 01-04-2019, 02:09 PM
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The Factory Billet boat , 51 Outerlimits, twin turbo engines run on E85. They run sensors in the fuel system that monitor water content in the fuel. You can mix fuels, E85, 116 , 93 octane and the computer will adjust. Mike Faucher is the engine builder who would have the answers you are looking for.
https://speedonthewater.com/boat-res...-billet-bullet
https://speedonthewater.com/new-boat...inter-progress
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Old 01-04-2019, 04:09 PM
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The only thing I've seen after running E85 in the boat for 6 years now is some valve seat wear. I don't know why you would need a monster cam if you run decent heads.
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Old 01-04-2019, 04:33 PM
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Originally Posted by GPM View Post
The only thing I've seen after running E85 in the boat for 6 years now is some valve seat wear. I don't know why you would need a monster cam if you run decent heads.
i dont want a monster cam that peaks at a super high rpm but if you bump compression up enough to utilize the octane content you'll need a pretty narly cam or motor will have pretty extreme cylinder pressure, looking for some input, sure somines done it,Smitty
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Old 01-04-2019, 05:08 PM
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Originally Posted by articfriends View Post
i dont want a monster cam that peaks at a super high rpm but if you bump compression up enough to utilize the octane content you'll need a pretty narly cam or motor will have pretty extreme cylinder pressure, looking for some input, sure somines done it,Smitty
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 Im speculating.

You are in somewhat uncharted territory. But that extra 4% of power per point of compression sure is tempting isnt it?

If it were me Id 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
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Old 01-04-2019, 05:21 PM
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I think the guy with the 388 skater by me runs his supercharged motors on it he owns western beef. I am planning running 12.5 on 100ll plans are to run e85 if I get stuck some ware. I think the exhaust seats might suffer over time.
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Old 01-04-2019, 07:30 PM
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Last edited by GPM; 01-04-2019 at 08:25 PM.
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Old 01-05-2019, 08:00 AM
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My experience with Sprint Car Engines on methanol , we tried up to 17:1 but they were a ***** to fuel correctly . Granted this was mechanical Injection , but we settled in between 12.8 - 14.0
depending on circumstances during a refresh. The nascar stuff runs 12.0 mandated by rules, with fuel very similar to E85 , the valve seats are the biggest problem on those engines.
I would think you could use the cam to your advantage , to build cylinder pressure , and not have to rely on static comp for fuel burn efficiency .
Ive been waiting on the E85 revolution in Marine builds , just because we may not have much choice down the road !
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