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Thread: Ethanol Fuel

  1. #1
    gie187's Avatar
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    Ethanol Fuel

    Does ethanol fuel actually hurt engine performance for seadoo 4tec


  2. #2

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    I think the current line has been designed to handle ethanol in the fuel, it is the rubber components that are the issue. As far as performance, I think it is all the same. If you ran straight gas then you may squeak a tiny bit more power out. This is from a general understanding of ethanol combustion vs. gasoline combustion.

  3. #3
    WBoulton's Avatar
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    ethanol will make more power, but it's bad for the ski really.

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    Quote Originally Posted by govenatorx View Post
    .... it is the rubber components that are the issue. As far as performance, I think it is all the same. If you ran straight gas then you may squeak a tiny bit more power out. This is from a general understanding of ethanol combustion vs. gasoline combustion.
    +1

    Ethanol has about half the energy content of gasoline on a volume basis.

  5. #5
    WBoulton's Avatar
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    Ethanol burns much cooler and allows more timing. on a stock boosted engine it will make a little more power due to the drop in combustion temps.

  6. #6
    I've run E85 exclusively in my turbo daily driver for the past 3 years. Making just about double stock whp and still on original stock block. I do my own tuning and road logging. Dyno and track proven for years now, so I feel pretty good about it. For tuned forced-induction cars, whp gains are ~10% and tq gains 15-20%. There are small gains, primarily in torque, to be had with just running E85 without a tune but most of the gains come from being able to run greater timing, more boost, and leaner AFR's. E85 is extremely resistant to knock. Engines love it. I've beat the hell out of my car at the track and dragstrip and the stock block keeps humming along happily. I also put a few gallons in my Jeep occasionally.

    I doubt late model Sea Doo's would have any issue with rubber components, but it is hard to know for sure. Obviously the engineers had to choose modern hoses, etc., that are capable of handling the 10% ethanol added to gas in many parts of the country, so we know the Sea Doo handles "E10" just fine. My hunch is that either it will handle ethanol or not. And we know that it does. E85 I don't know but E10 no problem.

    I don't see any way that 10% ethanol could be bad for a 4tec. But I don't know these engines all that well and I really don't know anything about tuning them. If anything, there should be a little more power and a little more knock resistance, and possibly lower EGT's. All in all though, I don't think 10% ethanol blend vs. pure gas is really going to make any difference at all. If staring at a pump with 2 buttons with equivalent octane ratings, I'd probably pick the 10% blend for the boat.

  7. #7
    I'll add a little more info for anyone that is curious. E85 conversions are quite popular here in Colorado especially in forced-induction applications. I know that nobody is talking about converting a boat for E85 but maybe this will clear up some possible misconceptions. From the moderator of e85forums.net (a conversion, racing, and tuning site):
    Full source here.

    Why is E85 a better fuel ?

    Ethanol and is a very turbo friendly fuel for many reasons.
    1. It has a much higher evaporative cooling power than gasoline so the intake air charge in the cylinder is significantly cooler that it is with a comparable mixture of gasoline --- that means higher VE.

    2. Its octane as blended in E85 is rated at 105 but it acts like 112-118 octane gasoline in boosted applications, its blending octane when added to gasoline is rated at 118, so it is a very cost effective octane booster.

    3. Ethanol burns faster than gasoline, but has a slightly longer ignition delay during the slow burn phase of combustion so the engine does not do as much negative work fighting rising cylinder pressures due to large ignition advances. The total ignition advance for E85 is almost identical to the ideal advance for gasoline so it does not cause the ECU problems when you mix them.

    4. At proper mixture you actually are releasing more energy in the cylinder due to the higher quantity of fuel you can burn. ( Ethanol can burn efficiently at much richer mixtures than gasoline can) That means about a 5% increase in energy release all by itself.

    5. Peak combustion pressures are actually lower for ethanol than for gasoline but the cylinder pressures stay higher longer, so you have more (longer) crank angle that is usable by the engine. This lower peak cylinder pressure also helps with detonation control.

    6. It will, at proper mixtures lower EGT's by around 200 deg F, but due to the higher quantity of exhaust gas products it produces you do not lose any spool up (in fact I would wager spool up is better).

    7. It is much cheaper ( if you go to a station that is not trying to price gouge).

  8. #8
    k-dub's Avatar
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    Those are some great points and I won't argue that more power can be made on alcohol, race car guys wouldn't go through the hassle if it wasn't worth it.

    But I think the reason we are in a little bit of disagreement as far as what E10 will do to performance is a matter of tuning.

    These boats run open loop fueling so unless you are altering the fuel map or adding larger injectors or a RRFPR the mixture will remain the same between E0 (straight gas) and E10 (10% ethanol).

    Stoich for ethanol is 9:1 where gas is 14.7:1, what this means is you need alot more alcohol for good combustion than you do gas. That is why if you look at the fuel system on an engine that runs on alcohol everything looks so massive, the fuel economy is horrendous because you need to use a whole lot of it.

    As far as the higher latent heat of vaporization of alcohol helping to cool the intake charge I have trouble believing that will help at only 10% and most of all it is injected right behind the intake valve so it won't have much time at all to absorb any heat from the incoming air.

    The one aspect of E10 that is beneficial as well as a big problem is that it is an oxygenator which is great as far as power is concerned but it also makes it hygroscopic (absorbs water) which is a real problem with boats.
    Last edited by k-dub; 07-05-2011 at 09:14 AM.

  9. #9
    ^^ Great points. Thanks. You have a better understanding about the ecus and engines on these boats than I do. I didn't know that they run exclusively in open loop. Therefore no fuel trims since no AFR feedback to the ecu, eh? If that is the case that makes the 4tec's pretty sensitive to fuel changes. Makes me wonder if there is any knock control on these boats, or whether they monitor Patm (I'm at 6000' ASL). Sorry, getting off-topic.. I'll need to find some tuning threads sometime. Thanks to your info, I'm now neutral on using E10 or straight gas if given the option. Don't think the 10% is enough a difference to benefit or to harm.

  10. #10
    k-dub's Avatar
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    Quote Originally Posted by Guy on the water View Post
    ..... I'm now neutral on using E10 or straight gas if given the option. Don't think the 10% is enough a difference to benefit or to harm.
    Agreed. I think the storage of the ethanol laden fuel is the biggest concern.

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