mcollinstn

The article Cuda linked to is a good one. It does, however, make a statement that is easy to misconstrue.

It says "But most of all, we discovered that our presumption that higher-octane fuels burn slower than lower-octane fuels (and therefore require more ignition lead) is largely incorrect."

This statement is misleading. The presumption mentioned IS correct, not "largely incorrect". It is only incorrect to apply it to any fuel when comparing only the octane numbers.

What I mean by this (and what they go on to illustrate) is that within a given "category" of fuels, higher octane fuel will give a slower and less powerful burn. But you gotta stay within that "category" of fuels.

Pump gas: when comparing pump gas fuels, you gotta compare the fuels available within a single region, as different climates or local regulations will have a dramatic affect on what additive packages are in that base fuel. This affects the way it runs..

High octane gasoline: avgas, 100LL, etc: These are always going to be "purer" fuels than the crap we pour into the tank of the Accord at Mity-Mart. The purity of the distillates will create a better chemical platform for combustion and better performance can be realized from it.

Race fuels: Race gas is designed for optimal burn characteristics. Period. There are more than one producer of race fuels so their internal competition for marketshare dictates that they produce "better" fuels. You will always get better performance from race gas even at low octane ratings - it's bacause it is made from the more preferable volatiles than the junk ones.

Exotic or "enhanced" fuels: There are fuels that are designed to be "liquid horsepower". Exotic cocktails that add oxidizers and such to the fuel can offer a fairly dramatic performance benefit. For example, a 10:1 Vee Twin 1000cc Suzuki TL1000R showed 6 horsepower improvement (over its 117hp) by doing NOTHING except pouring Nutec into the tank. I mean no timing changes, no fuel changes (okay, so we DID bump the injector timing by a click or two, but earlier tests showed that we DIDN'T HAVE TO), just pour it in.

Hey! why don't we run that in the boats? Cause it's about $7/gallon.

Anyhow, the article does a god job, I simply felt that at the bottom it was a little vague on standing beside the results.

Also, note that timing changes accompanied every fuel change in the test in order to optimize the combustion event...
hope this helps.

Downtown42

Good info...I always thought 93 burns cleaner though. I have 1993 502's carb, mags(stock) and have always put 93 fuel in. Maybe I'll reconsider.

dirtlawyer

Great article Cuda - could have used it two weeks ago - got into an interesting discussion at the Marina re: octane and additives. A guy who keeps his boat at a Marina I frequent for petrol made the statement that adding 104+ to the marina 89 was a waste of time and money and that it did nothing. I tried to politely (well as politely as possible after a few beverages) point out that he was incorrect; however, nothing doing....

I have see a few articles re: the effects of booster and none have indicated anything other than positie results - in fact I think that a report came out of USC or UCLA which confirmed the effectiveness...

mcollinstn

Dirt,

You didn't read the article very well, did you?

It showed a 1/2% (One HALF percent) increase in hp and torque on a 10.4:1 motor. It wouldn't show squat on a 8.5:1 motor. And that was with 87 octane, not 89.

Oh well, people seem convinced that booster is good stuff. Guess that's why every major brand sells a bunch of it.

dirtlawyer

your missing the point - while the octane boost may have not produced the HP, it did prevent detonation - I cannot always find premium fuel on the water and need to run 89 from time to time - at least with octane boost I will not risk detonation.

Shah Mat

Best quote of the article:


Wusz said, "An engine does not know what the octane rating of the fuel is, unless it is too low"

mcollinstn

Yes, dirt, I suppose I am missing your point entirely. And I guess I am still missing it.

If you have a motor that will run on 87 octane at 34-36 degrees ignition lead with no detonation, then there is no reason to run a higher octane fuel and no reason to run octane booster. I thought the article made that very very clear.

If, however, you are running a motor that requires 93 octane fuel to run with no detonation, and all you have available is 89 octane, then YES, you must run octane booster.

Otherwise, your friend was correct. No reason to use it - just a waste of money.

dirtlawyer

mcollinstn -

I completely agree with you - for the average boater, it will not help. Both my boat and the other boa in question have 525Sc's in them - thus requiring min 91 Octane - since there are only a few marinas that carry 92, we have two choices when we need gas and are not near the right marina - use octane boost or risk detonation. That was my only point.

Otherwise, I agree - no reason to use it.

mcollinstn

Yep. You need the good stuff.

You may want to look into buying toluene in bulk. Toluene's octane rating is 114. It's around $2.75 per gallon if you buy in 30 gallon quantities.

2 gallons of toluene to 10 gallons of 87 octane (12 gallons total) will yield 91.5 octane. 3 gallons to 10 gallons yields 13 gallons of 93.2 octane.

1 gallon of toluene to 10 gallons of 89 octane (11 gallons total) will yield 91.3 octane. 2 gallons to 10 gallons yields 12 gallons of 93.1 octane.

Lots cheaper than a bottle of 104+. Takes up a little more room, though.