[Guest]

What octane and brand of fuel seems to run best in your bike?

I know that the manual suggests 89 octane fuel for U.S. bikes, but I have found that Amoco Ultimate 93 octane (from Amoco/BP stations - NOT regular BP stations) seems to run noticeably better in my bike than any other brand. As expected, it really doesn't like ethanol blends.

I am interested in mapping a fuel curve for E85, but it is not available in the DEEP South, in the USA. Perhaps things will change. I need to check the fuel system to make sure it is alcohol compatable.

 

[kuhlka]

Yeah, be really careful with Ethanol because it doesn't really like aluminum. You might find your motor getting eaten by it. Do LOTS of research on it before playing with it. 89 octane from BP or Sunoco seems to work fine for my bike. All the higher octane fuel does is prevent pinging from predetonation, aka the higher octanes are more stable fuels. I'll pump in 93 or 94 every once in a while for the extra cleaning agents they add to it, but until I get a turbo, I'm not going to waste the money.

 

[Guest]

kuhlka is right. No need to waste your money. Higher octane is only needed for increased compression or advanced timing.

 

[Guest]

The advanced timing in my bike (with Tuneboy) may be a big part of why this fuel FEELS like it runs better on this one fuel.

 

[kuhlka]

Aha, well there you go. I'm wondering how far the triple motor could be pushed with regard to compression before one would need to swap out for stronger rods and pistons... The turbo kit would probably be a lot safer for the motor, but speaking hypothetically, I have to wonder...

 

[Guest]

Compression or even boost are not really that hard on connecting rods. It is RPM (aka: Ruins Peoples Motors) that stresses rods.

ie. The Buick Grand National engines with stock internals can handle high boost levels, but the rpm is fairly low. Rally cars do the same - 50-60 psi of boost at low rpm with boost bled off at higher rpm.

I would be shocked if the 955 or 1050 engine could not take a 60% increase in power through boost with the stock internals.

The biggest issue I see with many turbo kits for bikes is that compression is lowered with thicker than stock head gaskets. This reduces squish velocity and quench action at the same time - a bad idea for detonation resistance.

I would like to find a source for a THINNER than stock gasket - more compression and more squish and quench. The stock chamber design could use both.