OOOOPPPPSSS I messed up my pole and do not see how to edit it, Andy, can you fix it? It should be 75% of the 93 Octane to 25% 110 Octane race gas.

My daughter wanted to do her science fair project on something to do with the bikes this year. We hashed around several things, she had pretty much settled on weights of the various bikes, but then we got speaking about gas and how I mixed it etc. so the Science project evolved.

You see the question.

The procedure will be to take the Pizza bike of John Isherwood fame. (never rebuilt to my knowledge) Ish? (02 Sherco 125)

Take the 4 samples of fuel all mixed at 64 to 1 with Maxxima K2.

Bring bike up to operational temp as evidenced by the operation of the cooling fan.

Do a straight forward Dyno run for tourqe and HP and print the graph.

Drop tank and drain, ride bike around with fuel line disconnected to drain carb, refill with next sample of fuel, run to operating temp again and redyno.

Probably run double runs to look for consistency in measuring while a particular fuel is there.

So,,,,,, What do you guys think the answer will be?

Edited February 10, 200521 yr by Alan Bechard

Alan

No changes will be noticed.

This is a very simple answer. The reason these fuel blends are manufactured is to afford someone to run higher compression ratios and some other engine changes. They can then take advantage of the mechanical changes by using a different fuel blend. Simply using a higher octane purely by itself with a stock engine will not provide any significant change in HP.

In fact it has been proven time after time using to high a octain can actualy rob HP on a stock engine

Cheers

BillyT

An interesting experiment was arranged in the 1970s by Dirt Bike (USA) magazine with a dyno and a two stroke air cooled MX bike run on premix. All the fuels tested used the same petrol (gas) and oil type but they varied the petrol/oil ratio in a series of runs with the ratio going from one extreme to the other. I'm not sure but I think the oil was bel-ray synthetic and the petrol was "regular pump gas" which in 1970s USA meant leaded gasoline bought from a car fuel station.

The results surprised quite a few people who had been advocating running as little oil as possible to maximise power. Contrary to this assumption, they found that the bike made more power each time they increased the oil to fuel ratio. I think they started at about 2% oil and stopped at about 7%.

There are a few obvious things that prevent us from assuming that this experiment would produce the same results today with our different fuels, oils and bikes. I only brought it up as it may be of interest to people who are also interested in bike fuels.

Differences from then to now

Our "pump gas" is more variable in density, viscosity, octane rating and sensitivity to shelf age.

Our oils are generally better at preventing carbon deposits and smoke.

Our oils can maintain good film strength at lower oil ratios and higher temperatures.

Our modern liquid cooled off-road two strokes are much less compromised on heat rejection at full power than a 1970s air cooled MX bike (ie a 1970s MX bike engine at full power would get very hot on a dyno even with huge fans blowing on it).

Oil also has greater BTUs than fuel

I'm with Billy on this one Alan. Using those parameters there should be no appreciable differences, assuming you are not using oxigenated fuel blends and the specific gravities of the various fuels are consistant.

The advantages of "race fuel" over pump sludge is more than jusut octane. Octane is only a single factor. Race fuels are consistant from batch to batch (not even close to true of pump gas). They eliminate the "car crap" additives. They also are able to tune the distillation curves to meet specific needs. Because of this, lumping all "race fuel" into a single category isn't very accurate and why you hear guys saying stuff like "I tried that racing gas stuff and it didn't do anything". The wrong fuel for the wrong application will put you backwards nenarly every time. Combine that with sloppy jetting and you will almost surely loose HP.

Now, running an appropriate octane level race fuel, with an appropriate distillation curve, and jetted sharply will most definitely make a difference, even in a bone stock machine.

Edited February 10, 200521 yr by JTT

OK, we did the runs to get the Science project done.

100 LL AVgas was added at the request of some others.

87 Octane produced the most HP at 7.5

The Avgas, 100 LL was the lowest Hp at 6.78 I think it was.

The others were in between.

So,,, what do we learn, probably not much to be honest.

We did one run on each fuel, I would have felt a lot better, and more scientific if I could have done at least 2, preferably 3 runs with each. Unfortunately, I was supposed to be there at 10, we ended up there at 2, the Shop was jammed with customers, and for some reason the Dyno kept loosing communication with the computer. It just figures sometimes.

Also thinking about it, the most HP may not be the actual critical factor, and the Dyno run is not really representative of how we ride. We get it rolling in 4th gear, then do a tap to wide open and then shut off and read max hp. While that gives an accurate represantaion of that test, it is not really how we ride. Things like knocking, pinging etc. did not really come into play as they would actually out riding in the day. And while you could probably eliminate or minimize most of that with proper tuning, jetting, timing etc. you would very likely loose the HP gain.

Anyway, ask away. It was fun, man is that thing rough on tires, it is a little disconcerting running that thing, but nothing like when they had the Hayabusa on there!!!!!

Glad to hear the science project came out OK.

I agree with you Alan, that in the real world, pure HP numbers don't mean everything. I can tell you that with running a proper race fuel, jetted sharp, that there is WAY less loading up between sections. Crisp all the time, with rarely (if ever) any need to do the "clean out" rev common before entering sections.

A little spooky hearing a motor scream to the moon on the dyno isn't it