Running on methanol
- Thread starter Mike13
- Start date
G'day Mike,
You will need something in the vicinity of 12 to 13:1 compression ratio to make good use of methanol. Although ratios far in excess of 15:1 have been used. Because of the large main jets that have to be used you will need large bore fuel taps and fuel lines and fittings. Because you have a lot of fuel going out of the tank, don't forget to have a large breather to get replacement air in. All dependent on engine condition, you are going to need main jets around the 1200 mark. Amal GPs' are made for Methanol, others will have to be modified by generally opening out the float needle and seat.
You will need something in the vicinity of 12 to 13:1 compression ratio to make good use of methanol. Although ratios far in excess of 15:1 have been used. Because of the large main jets that have to be used you will need large bore fuel taps and fuel lines and fittings. Because you have a lot of fuel going out of the tank, don't forget to have a large breather to get replacement air in. All dependent on engine condition, you are going to need main jets around the 1200 mark. Amal GPs' are made for Methanol, others will have to be modified by generally opening out the float needle and seat.
To offer an alternative perspective. Although methanol motors can tolerate very high compression ratios without detonation occurring you don't need to raise the compression to get some of the benefits burning alcohol offers. For example - I've raced an 8 valve Indian with 5:1 compression running on alcohol which went very well. Additionally, don't get caught up in the hype of going over rich as alcohol needs an increase of 2.4 times in flow rate - any more and you're simply going to wash the bore and fill the oil tank with fuel by being over rich. The 1200 main jet size quoted is used for carburettors which have the jet block remote from the main airflow stream (such as Amal GP) so the jet experiences less pressure differential (vacuum). When using carbs with the needle set in the middle of the slide go for an increase of 2.4 times. Ogrilp400 is right though in that you want the jets to meter the flow - not the fuel supply system. I believe there is some good advice give in the book "The First 40 Years". Good luck - David.
We tried a 600 Methanol motor in BHRC a few years ago big lines and 13:1+ we never found a lot of advantages a bit faster but a harsher motor and always that worry about going lean ,or a blockage ruining the motor. Finally what a hassel draining the damm thing and running up on petrol after every meeting paint burning off wearing gloves still got a few gallons in a big drum Vincents don't run very hot anyway and in short races the advantage is negligible.
You have to enjoy your racing and somehow it took the edge off it
You have to enjoy your racing and somehow it took the edge off it
I think MIke forgot to say that he races his Comet (quite successfully) so he's not looking for the occasional quick boost.
H
ps on the other hand, I might try NOS and if it works I might put it on the bike as well.
H
ps on the other hand, I might try NOS and if it works I might put it on the bike as well.