Yamato Fuel.

[JOCONNOR]

On race day,, everyone has their idea as to the "Perfect Fuel".. Any ideas on the benefits of different fuels and what would be the best fuel to go with the Yamato motors? I'm currently running aviation 99 octane fuel. $ 6 a gallon. Others are running AP C9 which is only 93 octane no lead no ethenol @ $12 per gallon.. I'm new to this. What Am I missing on the cheaper fuel?

[dholt]

93 unleaded/no ethanol pump gas is totally fine, no need for anything else

[fbref5269]

john mauch won the winter nationals in 350 mod hydro using 93 unleaded/ no ethanol pump gas

frank Novotny
52-E

[jeff55v]

A Yamato has low compression, and does not need such high octane. You could actually lose performance with such high octane.
Years ago, a snowmobile racer friend of mine gave me some of his super-duper 110 octane racing fuel to try in my A stock motor. Even with making spark advance and carburetor adjustments, I lost 3mph with the racing fuel.

[JOCONNOR]

Thanks for the help. I guess I'm going to try a batch of the VP C9 just to see if there is any noticeable difference between that and the avgas. Price on a 5 gal can of this stuff is $70. From what I understand avoiding ethanol has a lot to do with the performance because it absorbs moisture. This link I found is very helpful in locating good fuels with no ethanol and low to no lead. http://www.pure-gas.org/ . Does anyone know if their is a disadvantage to running the 100LL avgas? octane is a little higher but not too extreme.

[ZUL8TR]

The manuals for the Y80, 102 and 302 states 86 min octane ( they tested a lot). These are low compression engines (around 6.5:1 measured at the exhaust port release) and do not really need high octane. That said the manual does NOT state if this is a Research(R) or Motor(M) octane number or the typical average used of (R+M)/2. As you can see the average does NOT tell the proportions of R or M to make up the average (ex. R = 80 and M = 120 yields same average of 100 as R = 120 and M = 80. Per VP data more M is better in the mix based on the test engines used to determine R and M. However there is only so much energy per pound in the gasoline (expressed as BTU/pound) and it remains essentially the same as octane increases (at fuel stations there are season blends that slightly change the energy/pound but it is still essentially the same for 87, 89 and 92). Octane is only a measure of the anti knock index of the fuel not the available energy of the fuel. Thus the engine can't produce more energy/pound of fuel consumed than is available in the fuel, otherwise this would mean efficiency (output/input) greater than 100% - not possible.

Ideally the correct fuel is one that when ignited at the correct time will produce a flame burn that continues without violent explosions (causing unwanted knock) such that the most energy can be extracted from the fuel. BTW in a (SSBB engine) suck, squash, bang, blow we are lucky to get 30% of the available energy from the fuel to produce useful power to the prop a lot is wasted in heat, etc.

There are a lot of variables in the fuel to deal with and VP designs them in their fuels and you might get an advantage (if you can measure it?) if you play with: timing, plugs, mixture, etc and then these change with temperature, etc. And you must pass inspection for the fuel. So give it a shot. But IMO you will do just as well with Non Ethanol available at fuel stations (87, 89, 92 your choice) and not spend so much and hopefully allowed at inspection.

Tell us your results.

[Yellowjacket]

ZUL9R is right you're wasting time and money trying to use a use a higher octane fuel in an engine that doesn't need it.

100LL is only "low lead" in name only. That is, relative to the old 100 octane avgas it has lower lead content, but it actually has about the same lead level as the old 100 octane auto gas that was available in the late 1960's. In short, there's tons of lead in 100LL. I used to do the 100 hour inspections on my airplane and part of the job was to pull the bottom spark plugs and dig the balls of lead out of them with a dental pick, and then put them back into the top plug positions.

Lower compression engines don't develop as much heat and the lead in the fuel causes more spark plug fouling for that reason.

Using 100LL in an engine that doesn't need it is just going to cause a lot of plug fouling and not get you any performance.

[Racerkyle20]

89/93 octane non-ethanol. I wouldn't say you're wasting your time with more expensive fuel, doesn't hurt to try testing (unless you go slower with a higher octane, which you most likely will for reasons explained above) but you have two guys on this thread that are telling you you're fine running regular pump fuel that have won a few races. I'd go with what they're saying.....

[John Korbus]

There is a app that will find non-ethanol pump gas look for puregas.org it will fine the nearest station where ever you are

[Matt Dagostino]

Yep............puregas.org

[ricochet112]

another, buyrealgas.com

[raceboat61-S]

Back in the 60's when I started racing Tom Herbert (60-S) explained to me that 4-cycle engines especially high compression racing engines need to slow down combustion to get a long push to the bottom of the stroke until exhaust valve opens, hence, high octane. But a 2 cycle engine gets all its power in the top half of the stroke until the piston reaches the exhaust port. Lower octane fuel has a short violent explosion just right for our 2-cycle engines

[dwhitford]

Bud Wiget used to mix fuel for Cookie Fernandez's A-Modified (running in the alky class before we had a Modified Division) with 20% kerosene to further lower the octane and increase the fuel's heat yield.

Bud, incidentally, was a master fuel pro. He was a Cal-Tech trained fuel & lube expert for Shell in CA before he moved to FLA to race and run a boat store full time. He was under contract in the early 1960s to one of the vaunted Indy teams to blend their high-potency qualification fuel for the 500. The team would fly him up there for the qual and race week.

This was all recent history by the time I began working for Bud in 1966, so I don't have all the details, most of which would've been ''classifed'' anyway. But Bud did give me good schooling about how to mix my own methanol-based racing fuel.

[Yellowjacket]

Flame speed isn't related to octane rating. That is a very common misconception, but these are two different properties and they aren't related. In any engine you want as high a flame speed as you can get. This is because your addition of heat to the combustion gasses will take place at the highest pressure and your cylinder pressures will be higher and torque greater the faster the flame speed is. If you have slower flame speed in any engine you are losing power. You want high octane to allow you run higher compression ratio, but if the compression ratio isn't that high, then you don't need any higher octane..