Opinion on Sunoco Cam 2 race fuel

[Michael W.]

Re: Opinion on Sunoco Cam 2 race fuel

I'll politely ask the question one more time- when people say their cars 'run better', in what way? The octane rating of gasoline affects one thing and one thing only. Conversely, what performance problems did any of the posters have with pump gas?

[Richard E.]

Re: Opinion on Sunoco Cam 2 race fuel

My 67/435 has no "run on" with c-12 and starts better.The car sounds like a high performance 427 and just all around runs better.I doubt the engineers at GM in 67 designed the compression for low octane fuel cut with ethanol.I have owned,crazy as it sounds, over 200 midyears and some ran ok on pump gas but most ran much better on 112...But then again i don't putt around with my cars i drive them the same way i did back in the 60's so that may explain the need for good fuel.

[Duke W.]

Re: Opinion on Sunoco Cam 2 race fuel

Michael,



This was proven by champion spark plugs in a demonstration proving the burn times of octane. Again their test was thru 50' glass tubes ignighting low& high octane fuels at the same time and having the lower octane beat the higher octane to the end every time.

DOM

Sometimes lab experiments and marketing demonstrations cannot be generalized to what's happening in an engine.

Laminar flames in cylindrical and spherical test vessels start out with a quiescent uniform mixture of vaporized fuel and air. Different common fuels or common fuel blends show some difference in flame speed that may be visible in a 50 foot long tube when it can be observed that one flame arrives at the far end before another.

But for simultaneous ignition times can you see a difference in flame location at about the four inch point?

In an operating spark ignition engine the biggest contributor to the rate the mixture is consumed by combustion is turbulence. The greater the turbulence, the quicker the mixture is consumed, and this more closely approaches the combustion at constant volume model, which is the most thermodynamically efficient of the various combustion models.

Lots of R & D has been done in the last hundred years to both make combustion chambers smaller and increase turbulence, and a modern combustion chamber's "flame speed" is one or two orders of magnitude above what is measured in a laboratory laminar flame experiment.

So the slight differences in the flame speed measured in the lab test end up as being noise level in an operating engine.

Typical peak combustion temperature and pressure in a spark ignition engine operating at WOT with something near a stoichiometric air-fuel mixture are about 4500F and 800-1100 psi. "High compression" engine's see higher peak cylinder pressure compared to "low compression engines", but not that much difference in peak temperature. If spark timing is adjusted for peak torque, peak temperature and pressure occur a few degrees after TDC.

Duke

[John D.]

Re: Opinion on Sunoco Cam 2 race fuel

Why ruin good Cam2 fuel or 100LL by mixing it with ethyl alcohol aka ethanol. Sorta defeats the purpose.
Sorta like putting steak sauce out of a bottle on a filet mignon.

[Ridge K.]

Re: Opinion on Sunoco Cam 2 race fuel

I'll politely ask the question one more time- when people say their cars 'run better', in what way? The octane rating of gasoline affects one thing and one thing only. Conversely, what performance problems did any of the posters have with pump gas?

Michael, my experiences would pretty much mirror Richard E's, but I would also mention reduced engine knock. I am not currently driving my big block C2 Corvette, but have owned and driven 396 Super Sport Chevelles since 1969. More Chevelles than I can count with this aging memory.

Perhaps a little of it is in my imagination. Perhaps a little of my putting high octane fuel in is some sort of silly under the surface feelings of love for my cars. Kind of like the fact that I save left-over rib eye steak scraps, warm them up the next morning, and put pieces on my dog's meal. The dog probably doesn't need those rib eye bites, but I love giving it to him. But none the less, I feel my big blocks have performed better on higher octane rated fuels.

But once again, I will admit at least a little part of it may be imagination.

Ridge

[Michael W.]

Re: Opinion on Sunoco Cam 2 race fuel

Thanks Richard and Ridge-

That's the sort of credible info I was asking for. There's enough sky-is-falling hysteria over E10 already without mixing in the potentially placebo effects of high octane and it's 'miracles'.