Cam profile will affect the cylinder pressure at least as much as static compression ratio. I don't have much experience with the addatives but I have used 100 octane avgas a lot. I wix it half with pump gas because it is supposed to be too "dry"(whatever that means). Also I had seen real tetraethyle lead addative advertised in Hemmings no more than a couple years ago. The vapor injection is another good trick that someone mentioned. We don't see it much in cars but those modified P-51 racers have to have it with the boost they run. I think one of those engines will live like 5 seconds under full throttle without it.
Every year when the EPA messes with the pump gas out here I make my own booster. Run it regularly in a 10.5:1 396. A 50/50 mix of toulene and Xylene with a touch (2-3 oz per gallon)of ATF thrown in. I use a 10% mix with 93 pump gas and have the advance set high. If you dont want to play chemist then consider an ignition that you can program to multi pulse burn over the full dwell. The Jacobs is one of the best. Several guys I know eliminated detonation with a Jacobs.
Here's some info on racing gas I found on the web sometime back. SUNOCO "GT Unleaded" Color...Natural Research Octane...105 Motor Octane...95 R+M/2 ...100 Specific Gravity...0.760 Reid Vapor Pressure... 8# Distallation temp, degrees F Initial...90 10%...150 50%...210 Final...230 SUNOCO "Standard" Color...Purple Research Octane...115 Motor Octane...107 R+M/2 ...111 Specific Gravity...0.725 Reid Vapor Pressure... 8# Distallation temp, degrees F Initial...90 10%...160 50%...220 Final...360 SUNOCO "Supreme" Color...Blue Research Octane...116 Motor Octane...109 R+M/2 ...112 Specific Gravity...0.715 Reid Vapor Pressure... 8# Distallation temp, degrees F Initial...90 10%...155 50%...215 Final...260 SUNOCO "Maximal" Color...Red Research Octane...118 Motor Octane...115 R+M/2 ...117 Specific Gravity...0.700 Reid Vapor Pressure... 6# Distallation temp, degrees F Initial...100 10%...150 50%...220 Final...240
Here are some formulas for octane booser I found on the web sometime back as well. I've not tried them so I don't know how well they work. MAKE YOUR OWN OCTANE BOOST How to make your own octane booster (this is the basic formula of one of the popular octane booster products). To make eight 16 ounce bottles (128 oz = 1 gal): 100 oz of toulene for octane boost 25 oz of mineral spirits (cleaning agent) 3 oz of transmission fluid (lubricating agent) This product is advertised as "octane booster with cleaning agent *and* lubricating agent!". Diesel fuel or kerosene can be substituted for mineral spirits and light turbine oil can be substituted for transmission fluid. Color can be added with petroleum dyes. Other formulas FORMULA 1 Toulene R+M/2...114 Cost...$2.50/gal Mixtures with 92 Octane Premium 10%...94.2 Octane 20%...96.4 Octane 30%...98.6 Octane Notes: Common ingredient in Octane Boosters in a can. 12-16 ounces will only raise octane 2-3 *points*, I.e. from 92 to 92.3. Often costs $3-5 for 12-16 ounces, when it can be purchased for less than $3/gal at chemical supply houses or paint stores. FORMULA 2 Xylene R+M/2...117 Cost...$2.75/gal Mixtures with 92 Octane Premium 10%...94.5 Octane 20%...97.0 Octane 30%...99.5 Octane Notes: Similar to Toulene. 12-16 ounces will only raise octane 2-3 *points*, I.e. from 92 to 92.3. Usually mixed with Toulene and advertised as *race formula*. FORMULA 3 Methyl-tertiary-butyl-ether (MTBE) R+M/2...118 Cost...$3.50/gal Mixtures with 92 Octane Premium 10%...94.6 Octane 20%...97.2 Octane 30%...99.8 Octane Notes: Oxygenate. Very common in octane booster products. Has lower BTU content than toulene or xylene, but oxygenate effect makes the gasoline burn better and produce more energy. 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. FORMULA 5 Isopropyl Alcohol and Tertiary Butyl Alcohol R+M/2...101 Cost...$0.60-$1.50/gal Mixtures with 92 Octane Premium 10%...94.5 Octane 20%...Not Recommended 30%...Not Recommended Notes: Similar to Methanol/Ethanol. Isopropyl Alcohol is simply rubbing alcohol.
A little O/T maybe, but will any of these home brew octane boosters harm a fuel injected motor? Thanks. -Jeff
That MTBE formula should be banned! That stuff poisons ground water and wells big time, even a tiny bit of spillage percolates into the soil. Our state has moved to ban it and the Feds are also looking at alternatives.
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