The age-old argument methanol vs. gasoline.

About those BTUs.
Gasoline: 116,090 btu/Gallon
Methanol: 57,250 btu/gallon

methanol vs. gas fuel mix is 6.4:1 vs 14.7:1.

Doing some math: methanol has 2.3 times more (14.7/6.4 = 2.3) fuel per given volume vs. the gasoline (assuming stochiometric ratios).

Multiply the Methanol BTU value by the 2.3 and you have an equivalent BTU value for stochiometric combustion in the same combustion chamber volume.

More math: 2.3 x 57,250 = 131,675 BTU/2.3 Gallons of methanol.

Let's not forget the cooling effect due to latent heat of vaporization of methanol vs. that of gasoline. Methanol's latent heat of vaporization makes it get really cold (sub zero temps) when it vaporizes, the more fuel that gets vaporized the more cooling you get. This is why top alcohol motors have ice on top of the superchargers at the end of a run. Cooler air is denser air and denser air occupies less volume IE more mixture can fit inside the combustion chamber.

There's more bang for the buck with methanol vs. gasoline for a given volume of each mixture in the combustion chamber. The cooling effect is just an added benefit.

Getting the mix to be perfect to me seems to be a function of the compression raito and the camshaft. I've seen the methanol injected 20 degree motor be very finicky and touchy on the dyno only liking 1 or 2 number moves on the main pill. Going from 110 to 130 picked the motor up from 988 to 1122. Same thing with timing, 2 degrees up or down from 30 killed 80 HP.

My theory is that all of these big cubic inch non-conventional headed motors have very high static compression ratios (15:1 or higher) and they don't seem to be methanol friendly in that the tuning window is extremely narrow. I haven't proved this theory, but my thoughts are it's about flame front speed vs. cylinder pressure. Camshaft design could help drop some of that, but that's over my head at the moment so don't have any idea what cam would work or wouldn't work in a non conventional, 600+ cubic inch, BBC injected on methanol. I would love to see a spread port or 20 degree 600+ cubic inch injected BBC on methanol with 14.5:1 or lower compression to see how it performed.

quote:

Originally posted by Triple Nickel:


Getting the mix to be perfect to me seems to be a function of the compression raito and the camshaft. I've seen the methanol injected 20 degree motor be very finicky and touchy on the dyno only liking 1 or 2 number moves on the main pill. Going from 110 to 130 picked the motor up from 988 to 1122. Same thing with timing, 2 degrees up or down from 30 killed 80 HP.

My theory is that all of these big cubic inch non-conventional headed motors have very high static compression ratios (15:1 or higher) and they don't seem to be methanol friendly in that the tuning window is extremely narrow. I haven't proved this theory, but my thoughts are it's about flame front speed vs. cylinder pressure. Camshaft design could help drop some of that, but that's over my head at the moment so don't have any idea what cam would work or wouldn't work in a non conventional, 600+ cubic inch, BBC injected on methanol. I would love to see a spread port or 20 degree 600+ cubic inch injected BBC on methanol with 14.5:1 or lower compression to see how it performed.

A few things here. I do not build my motors gas or alcohol to have extremely high compression and HUGE cams. I tend to go a little more conservative there because I think it does make the tuning window small and possibly more sensitive to weather changes.

On the article written about the fuels at 7,000 RPM gas puts out 27,600 BTU's
Alcohol 35,055 BTU's of energy
NITRO 65,200 BTU's of energy.

That is basic math and simple facts.

Now we all know NITRO will make more power. Fact. Yet you can not just put NITRO in a gas motor and expect it to live. And the numbers prove alcohol should make more power than gas. May just be as simple as we have not found the right combination for it.

To argue that a Pro Stock motor makes pore power on gas per cube than a 410 sprint car motor does on alcohol is not a apples to apples comparison. And if that was right then the 410 would make more power on gas to. Pro Stock has had 50 years to get the gas combination perfected and get every bit of power out of it. And they have, they are making good power for sure.
Pro Stock runs gas because they are REQUIRED to. I bet (and I could be wrong) but I bet that if Pro Stock was allowed to run alcohol that very quickly those combinations would be be faster with alcohol assuming that the NHRA allowed them to run adequate fuel systems. Right now one of the ways NHRA is regulating the Pro Stockers is Pumps, injectors and throttle bodies.

We may never know but if you look at raw numbers the alcohol motors should come out on top.

Smokey said:
"At compression ratios of 15:1 and above, alky can produce a roughly 5% HP increase."

Sprint cars run alky because they have very small cooling systems, and in the case of extended distance races, they run gasoline because they don't stop to re-fuel, not for HP.

Just my observations.