Octane and HP talk...

SayTen · Post by **SayTen** » Mon Mar 02, 2009 10:46 pm

Ok, So I was experimenting with the octane of fuel I am using in the old war machine. I have come to see that 89 octane pump gas may just be burning faster and not really giving me any sort of boost. Or is it? I've tried 86 octane for starters. And ran quite well on it. So I have just been questioning if upping the octane and if it is really doing anything.

Is it bad? is it good? For the motor, Speed, etc.

So I've come here. For the wisdom of high tech scooter folk to get some of these questions answered.

Does upping the octane give me more HP? Is it wrecking things I don't know about? Am I just wasting my time?

I trust your judgment. Every bit of advise I've gotten from this forum has been dead on. And very helpfull.

So what's the skinny on pump gas in my scoot?

SprEE*MP* · Post by SprEE*MP* » Mon Mar 02, 2009 11:36 pm

Well, I'm pretty sure it will burn cleaner, also hotter.....it probly increases perfomance, but by so little that you wont notice.......try racing-fuel....

SayTen · Post by **SayTen** » Tue Mar 03, 2009 12:14 am

So 109 octane it is.

But seriously, Does anyone have any idea what if any the HP gain would be from an octane boost?

scooterwerx · Post by **scooterwerx** » Tue Mar 03, 2009 2:09 am

none, really, octane is only the measurement of how resistant to detonation a fuel is. you could run 112 octane and all that would happen is the thing would smell good! high compression, lots of timing, boost, etc, all make more power, and lead to bad things like detonation. high octane fuels allow higher comp., more timing, more boost, etc., without detonating. that said, im running 100 octane vp street blaze in my aero, it is probably not necessary, but i dont wanna find out! i am running the high compression malossi head with no base gasket...plus it trips people out when a scoot blazes by smelling like race gas!!! i do run the cheap stuff in my stock elite e, though.

ALOW1 · Post by **ALOW1** » Tue Mar 03, 2009 4:06 am

Common misunderstanding - totally implied by the oil companies in their advertising, is that high octane gas will pep up your car and is "better for it". Fact is, all the gas grades have the same protective additives. The oil companies just want to sell more expensive gas to the masses who don't know any better. Higher octane gas has NO more power and actually has less.

But... you may ask, "Why do high HP cars use high octane?".

The answer is actually simple. "Octane" is a measure of how fast a certain blend of gasoline will burn, or more precisely, it's ability to avoid "engine knock" or detonation. The oil companies actually have a standardized, single cylinder engine that they run their gas through. If the engine "pings" or detonates, the gas has a lower octane.

So if high octane gas has less energy by volume, why do we need it? Again the reason is suprisingly simple. High performance engines - as in fast cars like Cobras, Corvettes, LS1's, etc., are tuned to make much more power than the usual car. The main ways of doing this are A) designing the engine to have relatively higher compression ratios ("normal is around 8:1, while "performance" is closer to 10:1 or more, and B) running the engine at higher speeds. However it's the cylinder pressures which dictate the need for the correct octane.

It's "A)" which is the major issue. High compression/high HP engines will suffer from major detonation due to the very high compression ratios (cylinder pressure) if the gasoline ignites too easily. In fact, engine knock is caused by the mismatch in timing between the spark, the piston position, and the speed of "explosion" [the wavefront] of the gasoline.

Allowing any engine to run with constant detonation will kill it much faster than normal and possibly, very quickly.

The solution is to use a high octane fuel which burns slower, or in other words, explodes less easily, but also has less energy for a given amount of fuel.

In the end, though you might be putting the lowest energy, slowest burning gas in your tank (which the lovely oil companies charge us MORE for), when used in a high compression engine tuned for high octane, you end up with more power at the wheels. In other words, the more extreme the engine design in terms of compression/cylinder pressure, and spark timing, the higher the octane (slower burning) is needed in whatever fuel is being used.

As an extreme example, Indy cars, and funny cars - using huge superchargers to force air into the engine which raises the effective compression or cylinder pressures - make huge amounts of power. As a result, they need a fuel with a very high octane rating; a "very slow burning" fuel. One example of a high octane fuel would be simple EToH, or ethanol... Vodka if you will, though methanol can also be used.

Even though alcohol has roughly 2/3 the amount of energy as gasoline, the cylinder pressures in engines needing high octane, more than make up for that loss of energy and can produce very high power outputs. I'd imagine if someone accidently filled up an Indy car with "low-grade", 87 octane gasoline, they'd be rewarded with nice engine block full of shrapnel and a totally destroyed engine.

So, bottom line: Your 50cc scooter not only does not need anything higher than "regular" gas, it will also run better and scoot better compared to running "premium" gas.

Unless of course you have higher compression.

evilone · Post by **evilone** » Tue Mar 03, 2009 5:26 am

What Alow1 said. I've always been told to run higher octane till engine knock or ping goes away, if you have no knock or ping then you can run lower octane.

qaz · Post by **qaz** » Tue Mar 03, 2009 8:29 am

The only thing you will get from the high octane gas is a lighter wallet. Few if any of the high compression engines built useing the kits bought as package deals have enough compression to require more octane. In the 70's Yamaha built a DT 400 that had enough compression that they were notorious for blowing their tops, and they still ran on regular gas.

chevyguyjay · Post by **chevyguyjay** » Tue Mar 03, 2009 8:34 am

ive ran 110 octane turbo blue in my aero. only thing i noticed was a better throttle response and it smelled good. no gain in top end.

scooterwerx · Post by **scooterwerx** » Tue Mar 03, 2009 10:44 am

hey CGJ, speaking of all this, how did you change the timing? im thinking about welding up the timing tooth on the flywheel, and then turning it on the lathe, did you increase the duration too, or just advance the timing? or did you move the pickup?

chevyguyjay · Post by **chevyguyjay** » Tue Mar 03, 2009 10:56 am

i cut the two holes on the pick up coil. u can move the pick up coil forward and backward to advance or retard the timing.

scooterwerx · Post by **scooterwerx** » Tue Mar 03, 2009 11:08 am

aha! the easy way! thanks mang!

Kenny_McCormic · Post by **Kenny_McCormic** » Tue Mar 03, 2009 4:10 pm

ALOW1 pretty much hit the nail on the head, except methanol is a power adder.

SayTen · Post by **SayTen** » Tue Mar 03, 2009 7:55 pm

Really helpfull! Thanks.

The big thing now is finding out if any there is a way to run my scooter off of grain alchahol! LOL!

*, If it makes it any greener the better

wikked_spree57 · Post by **wikked_spree57** » Fri Mar 06, 2009 6:35 am

I was going to post a question like that in here, because I threw a whole bottle of STP "barely legal" octane booster in the Elite E I had and for some reason by GPS I got 34.5 vs. 30-32. Throttle response was better, but now that I know it won't hurt anything like two of my friends say it will, after I get my Elite going I'm flying my * out to Sunoco for some 110 octane.