Octane Supreme (formerly Lead Supreme)

[Johnny Horsepower]

I'm sold. Just ordered some. I run a blend of 110, 93 and lead additive now. We'll see how this works.

JOHN

[WILMASBOYL78]

Tried that link and no go....

wilma

[Xplantdad]

Works for me. Try shutting down and rebooting...or clearing your cookies...

[mockingbird812]

On a slightly different tangent: what has been your experience with a target octane, for example, on a 11:1 CR motor? My understanding is that you are wasting money with overkill, i.e. too much octane or running straight 110 octane racing fuel. Where is the point of diminishing returns? Is the lower end of this (i.e. too little octane) defined by detonation and or poor engine performance? Guess I am looking for a formula or procedure to determine target octane with an eye toward maximizing performance and balancing that with cost effectiveness. Any lessons learned out there?

Thanks!

[Chevy454]

That's a good point, Sam...99% of the folks out there have no idea what their *actual* CR is...unless you cc everything you're just guessing. I'd say the vast majority of the engines out there are well below where their owners think they are. And while running too much octane isn't as physically detrimental as running too little, it *will* hurt you performance-wise, and make your car temperature sensitive...been there, done that!

[mockingbird812]

[ QUOTE ]
That's a good point, Sam...99% of the folks out there have no idea what their *actual* CR is...unless you cc everything you're just guessing. I'd say the vast majority of the engines out there are well below where their owners think they are. And while running too little octane isn't as physically detrimental as running too much, it *will* hurt you performance-wise, and make your car temperature sensitive...been there, done that!

[/ QUOTE ]

Rob,
For what its worth, I have receipts from local shop which performed recent engine rebuild including specs on L78 pistons and have decent confidence in what my CR is. I am not sure I understand your comment: "And while running too little octane isn't as physically detrimental as running too much". I thot that running too little may lead to detonation which could be quite damaging to the pistons. I thot there was more room for error on the top end, i.e. too much octane was more of a waste of $ vs. potentially damaging.

[Chevy454]

Sam: you're too quick! I re-read it and realized I had it backwards (too early yet)...and wasn't pointing the finger at you directly...sorry if it came across like that!

But like a lot of folks, I used to *assume* that since my L72 was rated at 11:1, that it would in fact be close to 11:1...WRONG. I tore it down, did an ever so slight clean-up on the block & head surfaces, and put a set of TRW blueprint 11:1 pistons in it...then I broke out my cc'ing kit, and my jaw hit the floor...I had a WHOPPING 10.2:1 compression! Quite a far cry from the advertised 11:1 I was expecting, and this was after removing some metal and getting (what I thought was) a good set of pistons. I did some asking around, and it turned out it was common...Scott Tiemann had done a similar experiment on a Berger COPO, and came up with 9.8:1!!

Anyway, running in Pure Stock I saw everyone else at the track dumping in race fuel, so I automatically did the same...but I was at a T'n'T one night at MMP, and the car wasn't as sharp as I thought it should be. It was late summer, and had cooled off a bit (cool for Memphis, at least, which is my home track), and it finally dawned on me that I had mostly race fuel left over in the tank from Stanton. So, I pulled it out, put in some good ole 93, and ran a 12.7x (about .05+ quicker than before). But I've also hurt parts with too little octane...busted the ring lands off of a 454 I was cutting my teeth on in high school...all lessons learned.

[@wot]

If you are building an engine that will run on 93 octane, you need to cc the heads. Otherwise, it really doesn't matter what the compression is. If the engine is detonating (you hear it or check for signs on the plugs), you need to make some tuning/fuel changes. If your engine is in sound shape, and you like the timing and distributor curve the way they are set, you need more octane to resist burning too quickly in an engine that detonates. You may get away with lower octane if you are not driving hard

I have not had real good results with boosters, and still mix racing fuel with 93. The ratio depends on the ambient temperature.

[mockingbird812]

[ QUOTE ]
If you are building an engine that will run on 93 octane, you need to cc the heads. Otherwise, it really doesn't matter what the compression is. If the engine is detonating (you hear it or check for signs on the plugs), you need to make some tuning/fuel changes. If your engine is in sound shape, and you like the timing and distributor curve the way they are set, you need more octane to resist burning too quickly in an engine that detonates. You may get away with lower octane if you are not driving hard

I have not had real good results with boosters, and still mix racing fuel with 93. The ratio depends on the ambient temperature.

[/ QUOTE ]

Dean - By saying the" The ratio depends on the ambient temperature", I am assuming that the hotter it is the more octane is required. Is that right?

What has been your poor results with boosters?

Rob - checking plugs is a good idea.

Thanks,

[@wot]

The hotter it is, the more likely my engine will detonate. Boosters have never eliminated the detonation problem, and as stated above, leave some strange deposits on the plugs. My theory on boosters is this:

Any additive used to raise the octane works on volume. A 16, 32, etc oz can of any booster can't effectively change 18 gallons of 93 to 102 octane.