Quote:
Originally Posted by robert campbell
Racing fuel could make a huge difference if you tune the car to it, and then use it consistently. Octane booster could have the same effect to a lesser degree.
The key word is consistently. A perfectly tuned to 92 octane 10 to 1 compression motor would ping all over itself on racing fuel. Racing fuel is much more volatile, explodes more quickly, and produces much more “power per given explosion” in the cylinder. You would need to retard your timing, recurve your distributor, and maybe rejet on the carb.
Rob
Yep, David, that's consistent w/my understanding if "racing fuel" = higher octane. As the octane rating increases the tendency for the fuel to detonate from the heat of compression (before the spark plug fires) reduces. In that sense higher octane is less volatile. So for high compression engines low octane fuel causes pinging. For lower compression engines using higher octane is just a waste of money. There is no more energy/gal in higher octane fuel.
BTW: For those of us living in CA where the highest octane is 91 (which is marginal on a 10:1 compression engine) there are some (only a few) Union 76 stations that do sell high octane gas. Two in the south bay area as far as I know. The racing fuels that 76 produces are...
http://www.ggoil.com/racing.htm
Otherwise if you use 91 octane gas you end up having to tune the engine away from its optimal operating point by retarding(?) the spark a bit. But this retarding of the spark means less performance and poorer gas mileage as it is not optimal for the design of the engine (someone please correct me if I'm off base with any of this). But it stops the pinging with the low octane gas.
James
Originally Posted by robert campbell
Racing fuel could make a huge difference if you tune the car to it, and then use it consistently. Octane booster could have the same effect to a lesser degree.
The key word is consistently. A perfectly tuned to 92 octane 10 to 1 compression motor would ping all over itself on racing fuel. Racing fuel is much more volatile, explodes more quickly, and produces much more “power per given explosion” in the cylinder. You would need to retard your timing, recurve your distributor, and maybe rejet on the carb.
Rob
Yep, David, that's consistent w/my understanding if "racing fuel" = higher octane. As the octane rating increases the tendency for the fuel to detonate from the heat of compression (before the spark plug fires) reduces. In that sense higher octane is less volatile. So for high compression engines low octane fuel causes pinging. For lower compression engines using higher octane is just a waste of money. There is no more energy/gal in higher octane fuel.
BTW: For those of us living in CA where the highest octane is 91 (which is marginal on a 10:1 compression engine) there are some (only a few) Union 76 stations that do sell high octane gas. Two in the south bay area as far as I know. The racing fuels that 76 produces are...
http://www.ggoil.com/racing.htm
Otherwise if you use 91 octane gas you end up having to tune the engine away from its optimal operating point by retarding(?) the spark a bit. But this retarding of the spark means less performance and poorer gas mileage as it is not optimal for the design of the engine (someone please correct me if I'm off base with any of this). But it stops the pinging with the low octane gas.
James
