Which octane

[ducatiz]

I actually did back to back dyno testing with 91 and 89 in my 696.....

When we were developing the exhaust we were using 2 696's to get a baseline. My friends bike on 89 made 2 more HP than mine on 91.  I was pissed! So we drained the tank put in 89. Next day dyno again with 89 in my bike. Air temp and density was really really close to the previous day....poof! 2 more HP....Not only that but I have been consistently pulling 30 more miles out of the tank before the light comes on...So now I guess I'll try 87 on the dyno....

well shit, put some 87 in a gas can and let it sit for a few months and then try it...

[Langanobob]

well shit, put some 87 in a gas can and let it sit for a few months and then try it... Cheesy

I have an old 1941 CCKW military 6 by 6 with a 270 CID GMC  6 in it.  I hardly drive it and the gas in the thing has been in it for years and each spring it still starts right up.  The compression ratio is, and I'm not making this up, 4.6 to one and redline is 2700 RPM. 

[ducatiz]

I have an old 1941 CCKW military 6 by 6 with a 270 CID GMC  6 in it.  I hardly drive it and the gas in the thing has been in it for years and each spring it still starts right up.  The compression ratio is, and I'm not making this up, 4.6 to one and redline is 2700 RPM.  

yeah, but it has 12,000,000 ft/lbs of torque

sweet

[silentbob]

I have an old 1941 CCKW military 6 by 6 with a 270 CID GMC  6 in it.  I hardly drive it and the gas in the thing has been in it for years and each spring it still starts right up.  The compression ratio is, and I'm not making this up, 4.6 to one and redline is 2700 RPM. 

Mine was a multifuel and it burns 87 octane, diesel, jet fuel, kerosene, used motor oil, but not avgas.

[Razzo Bolognese]

A guy who no longer lurks on these boards builds & races Monsters.  He was a Master Mechanic at Honda (the cars, not the bikes).  He purpose-built a M620 and bored it to 800 cc's, just to win races.  He runs (ran.  I haven't spoken to him in a few years) 87 in his street bikes and his fancy-schmancy race-prepped bike gets Arco 89.

Jay at ECS had a conversation with me just a few months ago.  He TOLD me to run 87.  It wasn't a discussion.

-Dan

[Howie]

I have an old 1941 CCKW military 6 by 6 with a 270 CID GMC  6 in it.  I hardly drive it and the gas in the thing has been in it for years and each spring it still starts right up.  The compression ratio is, and I'm not making this up, 4.6 to one and redline is 2700 RPM. 

Maybe because you never ran out and refilled it with wonderful, reformulated gasahol.  That thing must be great fun!

[jasaretta]

FWIW I have always run 98 on advice from my Duc mechanic.

[DarkMonster620]

OK guys, so now I'm getting canne because of my use of avgas once? The manual says '95 oct' RON. I either can asume:1. Ducati made a typo or 2. they ment 91 oct MOZ...

PM me if you can explain why:1. my seat of the pants dyno says that with 95 oct my bike runs better and is more efficient and 2. how can this octane build deposits?

[junior varsity]

Seat Dyno is easy, its the placebo effect. If you are paying more for something, you should be able to feel a benefit. That alone sells more "performance" parts than anything else I believe.

[DarkMonster620]

Seat Dyno is easy, its the placebo effect. If you are paying more for something, you should be able to feel a benefit. That alone sells more "performance" parts than anything else I believe.

ato,

better milage and no sputtering and/or hesitation when using 'our 95 oct' instead of 'our 91 oct'; what better benefits?

[junior varsity]

I don't think gas is causing sputtering or hesitation, but rather you notice it when you use the lower octane.

Gas mileage should work conversely. The big myth behind octanes is that higher octanes release more power - thus requiring less gasoline to produce the same amount of work. Car & Driver, and several other publications have tackled this, showing that putting too high an octane can actually slightly hurt fuel efficiency.

Lower octane fuels are 'more combustible'. They require less energy input to go boom. Higher octane fuels are required only when compression ratio has caused pressure levels to reach the point that cause the lower octane fuel to prematurely ignite (everyone knows, blowin' it prematurely is no fun). That's engine knocking, dieseling, pinging, etc etc.

[DarkMonster620]

So in other words, start using '91 oct' when I get it back together? No additives? No mixing up with avagas or VP fuel? Just plain old 'our 91 oct'?

[junior varsity]

I don't know how your gas is measured in Panama. If you were in Panama City, FL, I'd tell you to get 87 in a stock 620, 89 on a crazy-hot day.

(If you increase the octane, it eliminates chances of knocking, as noted before, and knocking is more likely to occur when its hot as balls outside)

[DarkMonster620]

I don't know how your gas is measured in Panama. If you were in Panama City, FL, I'd tell you to get 87 in a stock 620, 89 on a crazy-hot day.

Temps here are more or less like Miami's between 85~95 during the day and 70~85 at night plus humidity hovering around 90%.

Gas is measured the same method as in the USA. So, 91?

[junior varsity]

With regular compression, I'd say 89 for day time riding where you might be in stop and go traffic.  But therein is the debate. I run 87 in my Monster with ... no issues. Runs great, good gas mileage (though I run it slightly rich since I rode it to Vegas and was worried about the heat and traffic).

The new 696 and its head design may operate differently, and would require something higher, no FHE.