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Thread: Stock convert to alcohol, mehanol / nitromethane

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    Team Member Dvdracing's Avatar
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    Default Stock convert to alcohol, mehanol / nitromethane

    Dearest All,


    What steps to consider if converting stock motor to pro = alcohol / methanol / nitromethane ?

    Regards,
    Dvd

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    As a rule of thumb, the fuel volume is 2.1 times more than gas. So with the same size carb, the main nozzle and main jet must be increased. A typical gas engine is about 6:1 effective compression ratio. For methanol you can run 8.5:1 ECR Spark advance can be advanced as alcohol burns slower.
    When you get into Nitro that is hole different game. Less ECR, less timing. More fuel and you must flush the engine after running as it is very corrosive. To be best you would even run a different pipe.
    What type of engine are you working with?
    Hope this helps.

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    Team Member Dvdracing's Avatar
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    Hi Mike,

    I am working on research converting Yamaha 30hp x 2 cylinders, also plan converting a 56 omc in future

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    Mike covered the main points above perfectly.

    Also keep in kind the following..

    All non metal components in the fuel system must be compatible with methanol.

    The fuel pump and fuel lines need to be of sufficient capacity to flow more than twice the current volume of fuel.

    Needle/seat normally has to be increased as well.

    Be prepared for the added maintenance. Purging the fuel system after running alcohol is recommended. One of my drag racing buddies hooks up a handheld fuel tank with gasoline and runs the engine until it fully purges the alcohol.

    Rob

    Sent from my SAMSUNG-SM-G900A using Tapatalk

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    Team Member Dvdracing's Avatar
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    What power gain to be expect ?

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    This is a quote from Larry Meaux, the man I would argue has dyno'ed and collected more data on automotive racing engines than anyone I know of.

    This is from a forum post over on speedtalk.com concerning the requirement of having to increase port cross sectional area to get the most from alcohol as a fuel.

    "...you'll loose an immediate 8-12+ % PerCent Loss in Ve% just switching over to Methanol -vs- Gasoline,
    ..but you'll usually also pickup that same 8-10 % PerCent gain in Torque
    with Methanol, even with the Ve loss

    there's more HP/TQ waiting for you if you could recover more of that 8-12 Ve% Loss

    further optimizing the Intake Port Runner cross-sectional area, port velocity, port shape for Methanol will get you even more TQ/HP gains, especially mid-range to top-end MPH/ET ."


    That quote is driven by the fact that the increased volume of fuel occupies a portion of port cross section that would normally be used by the air traveling through the ports.

    One of the most attractive aspects of running alcohol is that is has a much wider tuning window. There is a perfect fuel/air ratio for alcohol, but it will run and make decent power when the jetting is out of whack. The same error with race gas will net either burned pistons or fouled plugs.

    Rob

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    This is a quote from Larry Meaux, the man I would argue has dyno'ed and collected more data on automotive racing engines than anyone I know of.

    This is from a forum post over on speedtalk.com concerning the requirement of having to increase port cross sectional area to get the most from alcohol as a fuel.

    "...you'll loose an immediate 8-12+ % PerCent Loss in Ve% just switching over to Methanol -vs- Gasoline,
    ..but you'll usually also pickup that same 8-10 % PerCent gain in Torque
    with Methanol, even with the Ve loss

    there's more HP/TQ waiting for you if you could recover more of that 8-12 Ve% Loss

    further optimizing the Intake Port Runner cross-sectional area, port velocity, port shape for Methanol will get you even more TQ/HP gains, especially mid-range to top-end MPH/ET ."


    That quote is driven by the fact that the increased volume of fuel occupies a portion of port cross section that would normally be used by the air traveling through the ports.

    One of the most attractive aspects of running alcohol is that is has a much wider tuning window. There is a perfect fuel/air ratio for alcohol, but it will run and make decent power when the jetting is out of whack. The same error with race gas will net either burned pistons or fouled plugs.

    Rob

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    Quote Originally Posted by PPRINT View Post
    Mike covered the main points above perfectly.

    Also keep in kind the following..

    All non metal components in the fuel system must be compatible with methanol.

    The fuel pump and fuel lines need to be of sufficient capacity to flow more than twice the current volume of fuel.

    Needle/seat normally has to be increased as well.

    Be prepared for the added maintenance. Purging the fuel system after running alcohol is recommended. One of my drag racing buddies hooks up a handheld fuel tank with gasoline and runs the engine until it fully purges the alcohol.

    Rob

    Sent from my SAMSUNG-SM-G900A using Tapatalk

    All very important points here.
    To convert a modern carb to alcohol is a task. Flushing engine with gas as Rob mentioned is a must. Most fuel pumps won't work for this. That is why Pro engines use a pressure system. An electric pump may be required. Inlet needle seats may need to be custom made. No rubber tipped needles. Main nozzle would need to be custom made.

    Thinking about 70 OMC, I don't think you could get enough fuel into the carb with the small hose fittings they use.
    I found some great fuel line from McMasterCarr for alcohol. I put it on my small gas tank for flushing the engine and it melted. Floats in new style carbs I would not trust with alcohol Tygon yellow hose is very good for both but it is so soft you must be careful it does not kink.

    It might be wiser and cheaper in the long run to modify the engine correctly and run a medium race gas.
    Porting head work and good reeds can gain you like fuel. All that with fuel is even better but not a do it your self program.

    Just converting to Alcohol could add 10-15%. Not really a lot compared to properly modifying an engine at 35% gain of good gas.
    So much depends on the details of you application.

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    You won't get anything like the full benefit of methanol unless you raise the compression a fair amount. But if you go on to use some percentage of nitro, you don't want all or maybe any of that added compression. In either case, read up on the hazards of methanol (poison, don't get any in your eyes, burns with an invisible flame) and nitro (explosive, can auto-ignite and leave the engine running even with the ignition system switched off). Mike's alternative ideas sound wise. Alky and nitro are wonderful racing fuels, but expensive and a pain to deal with in a playboat.

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    Team Member Master Oil Racing Team's Avatar
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    I had to laugh Smitty after reading what you said about auto-ignite and continue to run even with the ignition system switched off. In 1969 my Dad thought we should experiment with nitro to see what it was all about. I ground a few more CC's out of the head of our FA Konig (pre sliding pipes), and Floyd Hopkins came down from Covington Louisiana with props for us to test. We did not change the timing because we did not know what we were doing....only that the head needed to be opened up some. My Dad cranked the motor while the boat was on the stands down by the water. I was standing up by the throttle and the motor fired instantly. I never even touched the throttle, but that motor immediately revved to who knows how many RPM's. I pushed the kill switch, but the motor was still screaming. I reached back toward the battery and jerked the wires hard enough to pull them loose from the connections. Still screaming. All this took place in only a matter of seconds. Then Jack Chance, on the right side of the transom, put his hands over both carbs and that stopped it. There was a willow tree next to the pier about twenty feet away and Floyd Hopkins was hiding behind it. We all thought that motor was going to explode and release shrapnel everywhere.


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