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WSMC #51, CVRA #51
696 Posts
I'm running U4.4 and it's a good unleaded pump replacement without having to re map adds a couple HP but seems to accelerate better all the way through and a good price for the addition of oxygen and tetraethyl lead!!!

If you got the money run the new MR12 best fuel by far but you will have to re-map

there is no substitute for leaded fuel on the race track, I thought the "C" series was just high octane which really will be a waste and won't help make HP might as well run pump for half the price!

Here is some info I wrote on another BBS that may help.

The chemical oxygen in VP race fuels is derived from Methanol. Methanol will attack aluminium and o-rings. Its not enough just to drain your tank, you need to run the oxygenated fuel out of the bike and flush it with pump. Just siphon the race fuel out, add 1-2 gal of fresh pump and ride the bike for a min or two.

The reason for the chemical oxygen is simply to add a more dense air and fuel mixture to combustion chamber. If your fuel already contains 10% of the oxygen needed to burn you can add more fuel and stay at the same A/F ratio. The more air and fuel (some of the air contained in the fuel) you can burn the more power you will make. Thats how oxygenated fuels MAKE power.

Hi-octane fuels alone DO NOT make power. Mater of fact all else being equal you will lose power as you increase the octane. Many bikes make the most HP on pump 91 (unless its an oxygenated fuel). Only if you are running a higher CR then stock do you need higher OC. The reason for this is, 85% of the useful combustion pressures are extracted in the first 30 deg of crank angle. You want fast, complete combustion before the first 30 deg. High OC fuel resists detonation but burns slower. If your not running in to detonation with say 91 OC pump the slower burning 116 OC race fuel will not burn as completely before the first 30 deg. Some of that burn will just go right out the tail pipe as heat loss.

So, only oxygenated fuels will make more power then pump.
Only run as high an OC # as needed for your specific build.
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