Cams for Alcohol (E85-E98)

[delcrossv]

Anyone here familiar (or can someone point me to someone who is familiar)with any cam tweaks for burning alcohol fuels?

In poking around, I'm getting two conflicting sets of comments:

It burns faster so EVO should be earlier, and
It burns slower so EVO should be later.

(!!!)

[seajay]

Contact Hammer Performance.

[JB in NC]

Burn rate would have an effect on ignition timing, not cam timing. Consider the stoiciometric ratio, and the larger volume of liquid fuel in the intake charge. Might want to open the intake valve earlier in order to get that mass moving.

Jim

[delcrossv]

Originally Posted by JB in NC

Burn rate would have an effect on ignition timing, not cam timing. Consider the stoiciometric ratio, and the larger volume of liquid fuel in the intake charge. Might want to open the intake valve earlier in order to get that mass moving.

Jim

That too, but open the exhaust with the fuel still burning- not too good. Do fueley (nitromethane) guys run really early IVO timing? Stoich is almost 1:1 for those guys.

I do know you can advance the spark a good deal with ethanol. You get a lot of cooling also as the latent heat of vaporization is really high. Good Stuff.

Maybe an alcohol drag bike guy?

[JB in NC]

Stoichiometric ratio for nitro is about 2:1. For carbureted nitro, tight LSA, so yeah, early intake opening and a lot of overlap. (Keep in mind that nitro weighs about 9 lb./gal., compared to 6 lb./gal. for gasoline.)

But ethanol or metlanol is more closely kin to a gasoline motor, so nothing much from nitro will apply. I did a little racing with methanol, and the nice octane rating along with the cooling effect of the intake charge meant you could really jack the compression up (like 15:1) and then run a LOT of cam. And even at that, you might be running 40 degrees of spark lead. I built the motors just like a gasoline motor except for the fuel system. (But I was a novice with little understanding of what I was doing.)

Hopefully ferrous head will post up some good info.

Jim

[delcrossv]

Originally Posted by JB in NC

Stoichiometric ratio for nitro is about 2:1. For carbureted nitro, tight LSA, so yeah, early intake opening and a lot of overlap. (Keep in mind that nitro weighs about 9 lb./gal., compared to 6 lb./gal. for gasoline.)

But ethanol or metlanol is more closely kin to a gasoline motor, so nothing much from nitro will apply. I did a little racing with methanol, and the nice octane rating along with the cooling effect of the intake charge meant you could really jack the compression up (like 15:1) and then run a LOT of cam. And even at that, you might be running 40 degrees of spark lead. I built the motors just like a gasoline motor except for the fuel system. (But I was a novice with little understanding of what I was doing.)

Hopefully ferrous head will post up some good info.

Jim

Gotcha! We're about there now. 13.6:1 with tulip valves on both sides.