Dearest All,
What steps to consider if converting stock motor to pro = alcohol / methanol / nitromethane ?
Regards,
Dvd
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Dearest All,
What steps to consider if converting stock motor to pro = alcohol / methanol / nitromethane ?
Regards,
Dvd
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.
Hi Mike,
I am working on research converting Yamaha 30hp x 2 cylinders, also plan converting a 56 omc in future
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
What power gain to be expect ?
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
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
Quote:
Originally Posted by PPRINT
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.
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.
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.
Lordy, Wayne, that sounds semi-exciting, at least!! I never heard one rev like that. on the occasions I saw this happen, when an engine started running away the throttle-man whacks it closed and the full-butterflies at least limit the rpm. But with the engine still running, somebody generally grabs an oar or some other hard object and shoves it against the side of the flywheel while somebody else thinks to clamp his hands over the carbs. But if the engine was screaming, anybody would be tempted to back off from it like a grenade that was starting to swell.
I still have my little old A Konig, as parts in a box, very mildly ported exhausts with the "lawn-dart" pipes and tiny carbs (25mm bored to 26mm). When running right, which usually wasn't for all that long, I could see about 75 on a Keller speedometer on a heavy Marchetti. If I'd known then what I've learned since, I think I could have done a lot better, but as it was, the only record I set was for being an exceptionally dumb young guy.
dvd, are you getting the messages? What are ya gonna do when a fully-cowled playmotor on nitro starts running away on the boat ramp with a lot of clueless non-racers and kids all around you wondering what the heck . . . ?? It's great that you aspire to do some hands-on outboard hot-rodding, but you'll have more fun, learn more, and make friends with a bunch of liked-minded fellas if you do this in a racing context. If you are anywhere near where the U.S. Title Series runs one of their all-PRO races, go spend a day and see if you don't come away all charged up to be an alky racer.
Auto-ignite.....been there, done that, wouldn't do it again. In the late '90's in a prior life as a snowmobile drag racer, I rode a 1/4 mile asphalt sled for a guy....not fast by today's standards, but fast for the day....low 9's @ mid 140's. One day he decides to run it in a big $$ bracket race on 20% nitro. I got it through several rounds ok....then someone forgot to shake the can before filling the sled (nitro falls outta' suspension pretty quick). Tanks full of close to 100%. Burn it out, run the rpm up to 'stage' it and it keeps on going.....and going. Uh-oh. Kill switch no workee. Grab a BIG handful of brakes, get against the guard rail, get ready to let it go on it's own, and mercifully.....it seizes. I don't remember....but I probably ruined a good pair of skivvies. All I could think about was "What if it had happened after the launch and I go into the 'sand trap' at 140+".
That was the last time I ever drove anything on a drag strip that you sat on top of....and the last time I ever raced anything that someone else prepped.
I can laugh about it now. Nitro smelled great, though....even better than castor.
Jim
My first trip to Depue in 1972, I was checking out Ron Anderson's AOH rig in the pits. One of the things I noticed was he had real low boat stands. The only reason I noticed this was because my mentor ( Dick Fickett) had real high boat stands. Dick said it was much easier on his back working on the motors. Ron went to warm up his Konig and it was the first motor I ever heard auto ignite. Ron walked back and put his right foot up on the rope plate to stop the motor. No sense of panic, just went on working like it never happened. I am sure that this was not the first time it had happened to him. The guys out West sure liked their nitro.
Ron had about 10 MPH on me.