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turbolarry
07-20-2010, 03:12 PM
A 50/50 mix of water and meth raises a fuel's octane by approximately how much? At 21 psi, full spray, full pressure etc., 91 octane is more like...what??? 100 oct.? 110? 95?

ultraflip
07-20-2010, 03:38 PM
simple question that can definetly be put up for debate...

The amount of real world octane increase is very small. Remember you usually injection aprox 15% water/meth at a 50/50 mix. So lets say 7% of what your injecting is meth and this is what going in the motor. Now usually 10% of the whole amount is going to dissapate in the intake track. So your going to end up with aprox 2.5% of your fuel as 116 methanol. Now this can greatly vary depending on setups. How much heats in the intake track etc. The majority of the kr resistance and power thats achieved from the alcohol injection kits is the cooler intake air temps.

ultraflip
07-20-2010, 03:44 PM
something i dug up


FORMULA 4
Methanol or Ethanol
R+M/2...101
Cost...$0.60 - $1.75/gal
Mixtures with 92 Octane Premium
10%...94.3 Octane (Methanol)
10%...94.7 Octane (Ethanol)
20%...Not Recommended
Notes: Methanol is wood alcohol. Ethanol is grain alcohol and found in Gasohol in 10% ratios. Both alcohols are mildly corrosive and will eat gas tank linings, rubber and aluminum if used in excessive ratios. Main ingredient in "Gas Dryers", combines with water.

ultraflip
07-20-2010, 03:48 PM
stolen from the dsmtuner forum...

As a general rule a 5% mixture of methanol will raise octane by about 1 - 1.5 points. So a 50/50 mix should equal about 100 - 105 octane (figuring 91 octane premium). The true octane could be much higher though...Reason below.

It's pretty hard to narrow down an actual octane rating for methanol or ethanol since the way they calculate octane is based on gasoline. Alcohol fuels have intake temperatures that gasoline fuels will never see. While octane measurements of alcohol fuels put octane between 100 - 110, the actual octane is much higher due to the higher cooling properties.

If you don't believe me, remember this: Running straight methanol (I know you're talking about meth injection) will cool your intake charge so much that you can run without an intercooler. Lets see any C16 race gas do that.

lemmonhead
07-21-2010, 04:36 PM
this is exactly why water injection will give you more power than 100% meth injection or any mixture of meth/water. This is why the Department of Defense used water injection NOT any mixture of it!!!!!!!!