Postby Weatherhound » Wed Nov 04, 2009 11:32 am
Pro Nova,
The are big differences between conventional thinking with gasoline and methanol. Pretty much everything on the intake system needs to be much larger to get the most out of methanol. You will use about 1.8 times the amount of methanol than you will from gasoline. That means the intake charge density is much higher. Since liquids are not compressible, more room needs to be made to get enough air in the cylinders.
You need minimum 1.8 times more (AFR around 6.0:1), so carburetor applications begin finding handicaps when the HP levels approach 900. This is because there is so much wet flow required, fuel distribution and atomization begin to really hurt, and the parasitic drag of the large droplets basically shut down the flow potential. Dart has some flow comparisons for both wet and dry flow. Even with gasoline, flow tapers down on the flow bench.
On a relatively large displacement engine, an 850 CFM alky carb is too small. 1150 or more CFM, with float bowl extensions could be sufficient. The Enderle pump is most likely an 80A good for 6.9 gallons per minute at 8000 crankshaft RPM.
Typically methanol engines that pop out the exhaust on the top end are too rich (with injected applications). I would assume the same for carbs as well. It takes a lot to lean out a methanol engine to the point it pops out the exhaust. You would see a massive power loss and the engine would labor to climb in RPM. It would be safe to say that the carb is so small you are going to run too rich in the high end.
16Marty,
As far as injected applications, make sure you have the clearances set if you are not satisfied with your current HP levels. I have a bird catcher. The blade clearance is 0.006". The barrel valve leak down is around 15% using 100 psig air pressure. The high speed return in cooler weather is 0.100" and in the hot season 0.120". I have a 0.065" high speed dump poppet that kicks in around 6800 RPM. I am running an 80A belt drive pump with a Victor2 tunnel ram.
If you converted back to gasoline, I would make sure the heads have not been designed for only methanol applications. My 540 is using the BMF head from CFE with the 410cc intakes. That would be way too big for gasoline service unless I turned the engine to 10,000 RPM. If the engine was designed to run solely on methanol, you could lose a significant amount of HP and torque. It would be a good "all the time" nitrous engine.
Regards,
Brian