tsheehan

Just looking for feed back. I have been advised to run streight av fuel in a 3.6 with RSR grind cams and 46mm PMO carbs. It is running off a electromotive ignition system . The engine make 340 hp and I dynoed at 279 rear wheels. The engine is built with uropean pistons . Botom end is stock. It is set up at 7300rmp rev limit. The answer I got when I asked why av fuel was that it was labratory grade fuel with out aditives that I dont need.

Geoffrey

Aviation fuel is made for engines that operate at a steady state and at extremely cold temperatures, not an automobile engine which has a wide operating range with high crankshaft accleration rates and high temperatures. I would not use aviation fuel in an automobile engine. You will notice a performance loss and potential engine damange depending on how your engine was tuned.

tsheehan

Geoffrey,
If av fuel is not the prefered fuel what would you recomend for this race engine it runs track only 22 min sprint races.

regards
tom

Geoffrey

What are the engine design specifications? How has it been tuned alreday?

InTheAir

Avgas has lead. I'd stay away from it for your car.

tsheehan

Geoffrey,
I will look at what my low mid and limit timming settings are for my ignition. Here is where I am at The numbers on av100ll fuel the octain 100/130 the specific gravity .69-.715 the Reid vapor pressre 6.5
The numbers on a designer race fuel like VP Red racing fuel. octain 105 specific gravity .73-.745 the Reid vapor pressure 6.25

Now if I equalize the octain # by adding 8 to the av fuel or subtracting 8 from the racing fuel the are both going to be above what I need to prevent detonation.They both contain lead. The only drawback I see to the av fuel is the bromine compound added to av fuel to scavenge the lead residue from the engine. The residue when mixed with oil water and other metals is corrosive. Toluene and Benzol are added for knoking and to lower the freezing point. I am not sure what the engineered race fuel has added as they are not as open with the information. If any one can fill in the similarities or diferances I would like to learn more.
That being the case I realize the av fuel will go lean quicker than the VP red but I can adjust the float to allow for that. The cars oil is changed in 5hr incruments on the motor. So the corosive nature of the Bromide compound can be managed. I do not run o2 or any of the such emitions or smog ect. The price saving is 1.70 per gal. What am I missing. And I have my doubts believe me.

Regards
Tom

tsheehan

To all,
Ive decided that a couple bucks to save on what I felt is a wild card fuel choice is not worth the risk to preformance and engine life. I have opted out of av100ll and gone to VP Red 105 motor octaine fuel. Availability and only one person out of many recomended the av fuel made the choice easy.I was hoping for more feedback on AV fuel and its place or not a place in auto engines. I have herd of mixing it with reg unleaded and other fuels. I know of others who run the fuel both unmixed and mixed and am looking for their real likfe experiances as this may help out the next person with the fuel choice. I have made mine and will tune and base my engines performance on the VP racing fuel product.

Regards
Tom

bobafett

Leaded fuel is not a big deal in racecars. I looked into runnign a racecar on the roads (thinking it's easy to get 100LL at airports along the way). THe biggest issue with running avgas is that the specific gravity of the gas is considerably lower than motor fuel, even if the octane rating is the same. The applications are different and as a result you will suffer from irregular detonation, etc.

Good move on going wiht the racegas. There are plenty of suppliers out there, including some small shops who do their own.

--Dan