Quote:
Originally Posted by Jim Parsons
Darrell, regarding your question about pump gas being quicker than race gas this is my assessment based on study and some actual race experience. Race gas is really about “octane rating” to prevent detonation and not about being more powerful.
With the laws and liabilities limiting lead content the race gas companies had to start using lots of “additives” to boost the octane level, that’s also the sweet smell you get. Today there isn’t much “gas” in race gas, another reason it cost more. These additives hurt power in a couple of ways they burn slow during combustion which changes their pressure rise on the piston and spreads it over a longer period which helps with potential detonation but not power. You typically can run a little less ignition timing with lower octane fuel. Actually the biggest reason is lower octane pump gas typically has more BTU’s of energy per pound than our legal race gas! So in your case with relative low compression you don’t need the octane to counter detonation it then makes sense that it will be faster when used. I proved this to myself when living in Denver as I took race gas out of my stocker and replaced with pump gas and picked up a tenth! This was back before specific race gas’ was mandated by NHRA and the old pump gas was still legal.
Why then do we run race gas? A couple of reasons, when pump gas had to comply with clean air regulations and started adding oxygenated additives, i.e. corn alcohol + other things NHRA’s compliance testing at the time for fuel went out the window. By them restricting us to Race gas they could set tight standards for each and compare when testing at the track, that’s why we have to declare our fuel type and brand. The other reason I suspect is they saw an additional money $$ source from the Fuel companies as each has to pay to be on the “accepted” fuel list.
I'm not saying you cant add "stuff" to gas and make it more powerful such as ERC and VP does with some of there highly originated fuels but those are thankfully not on our approved list as they are harmful and more expensive.
Hope this helps and yes there is more to the story but this is my quick take on your question.
Jim Parsons
(Past FIA international Fuel and Lubricant Committee member)
FYI: I tried sending this to you as a private message but it said you box was full.
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The lower the CR the quicker a peak cylinder pressure will decay. If I can have a lower peak cylinder pressure but have it at a point farther ATDC it is possible to have the same if not more turning force on the crank. In many cases peak cylinder pressure is 10 to 14 ATDC where a good amount of that force is trying to push the crank out of the block. Remember how the rod crank angle plays into using cylinder pressure as turning force.
Stan