have probablly been ask this before but, does octane booster prevent vapor loc? Thanks in advance! Jon
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I don't see how it could...
Typically, octane boosters act to raise the octane rating of the fuel in the tank (a measure of the precision with which a fuel burns). Vapor lock is typically caused by fuel boiling (not igniting) and today's environmentally friendly fuels (doped with alcohol) have a tendency to boil at lower temperatures....
Where I'm coming from is how does the addition of an octane booster somehow remove the alcohol that's blended into the gasoline? -
Re: Duke,I know that you..........
I'm not sure that it does, though some make that claim based on personal experinece. Most "octane boosters" consist primarily of a carrier fluid, which is usually either an alcohol or a hydrocarbon blend than is more similar to kerosene than gasoline. But even if the carrier is very low volatility, a quart of this material in 20 gallons of gasoline will have little effect on overall vapor pressure characteristics, and the culprits are still there in the commercial gasoline.
Modern gasolines have lower vapor pressure than blends from the sixties due to evaporative emission requirements, and modern EFI cars can handle lower vapor pressure and still exhibit good cold starting and driveoff. Gasolines from the sixties had a lot of aromatics, which are considerably reduced in current blends. Benzene, the smallest of the ring shaped aromatics has a boiling point of 176 F. The ethanol in today's blends boils at 173F.
One would think that today's gasolines should be more resistant to vapor lock, but that may not be the case, and Rochester FI engines, in particular, seem to be more effected. One person I've discussed this with who has expertise in gasoline issues thinks it could be the result of more mid range volatiles in modern blends, including ethanol, that can effect hot soak vapor lock on vintage cars.
Modern EFI systems maintain constant pressure at the injector (40-60 psi) and much more fuel is delivered to the fuel rail than needed, especially at idle and low load, and this excess fuel is recirculated back to the tank, so the fuel effectively functions as a coolant. Fuel metering is controlled by injector dwell time.
Rochester FI meters fuel by contolling pressure at the nozzles - from just a few psi at cranking speed and idle to about 200 psi at WOT max revs. Plus there is no circulation of fuel as on modern EFI systems.
At least on carbureted engines you can reduce heat to the carburetor by blocking open the heat riser valve and plugging the vertical passages to the "heat slot" in cast iron manifolds that allows exhaust heat right up to the base of the carbuetor under the idle circuits. Since we usually don't cold start these cars at below freezing temperatures, these features aren't really needed, and the engine should have good cold driveoff characteristics in mild weather with the heat riser valve open all the time and the manifold heat slot blocked.
The manifold heat slot can be blocked with Welsh plugs or you can thread the manifold and install pipe plugs. If you want no evidence the the heat riser had been tampered - like a visible wire holding it open - the valve can be removed from the shaft.
DukeComment
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Thanks Jack and Duke!......NM *NM*
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