Looking for dead 24Ve

[kko]

Could a change in transmission ratio fix that issue? It would seem that the right gear ratio with prop would work well. I would imagine a drop in top end speed would be pretty significant, but most of us care little about that anyway.

I think this could be the key. I am not sure what trans. the mastercraft I was in was using. I know the Yanamar dealer installed everything and they had done lots of testing over the years. But it might have benn using the factory trans. And maybe a different ratio trans woulkd make it better.

[IDBoating]

12MPG, our tige now burns 4.5gph at worst (that's with 89 octane, it burns 3.2gph with 87)

Why would octane make that much difference in fuel consumption? From what I understand (which is very little), octane increases the flash point of the fuel so it won't ignite due to pressure.

[MooseX]

there's a dead 04 24v somewhere in tahoe according to a freind. I've asked him a couple of times where I could see it but not yet have got an answer. I'll keep pestering him

[boatwakes]

MooseX, NICE! Please keep me posted on that one. WA, I did the comarisons the first time we went to Lake Mead because all they have is 89. We showed up with a full tank of 87, ran 8 hours filled up and kept an eye on the mpg. It tanked and my driving style didn't change so we took note and it did the same thing after the next 3 tanks we put through it. The computer has to advance the timing with higher octane and when it's programmed for 87 mileage will go down with higher octane. The new higher horsepower 6.0 and 6.2 engines I'm sure have an octane requirement that's higher but wither way diesel is better.

[shawndoggy]

Why would octane make that much difference in fuel consumption? From what I understand (which is very little), octane increases the flash point of the fuel so it won't ignite due to pressure.

That's exactly right. Higher octane fuel is less volatile, so you can advance timing farther without premature detonation.

[IDBoating]

That's exactly right. Higher octane fuel is less volatile, so you can advance timing farther without premature detonation.

Yes, I understand that, but:

The computer has to advance the timing with higher octane and when it's programmed for 87 mileage will go down with higher octane.

...this is the part I don't understand. The fuel being less volatile allows it to be safely used in higher compression engines, but if you're relying on a spark to ignite it why would you HAVE to advance the timing?

More to the point: Why would advancing the timing reduce the mileage? Wouldn't the same amount of fuel be injected, regardless of when the spark is told to fire?

Just trying to understand....

[shawndoggy]

probably the computer is "dumb" and advances till knock is detected.

[IDBoating]

OK, but advancing the timing - by itself - shouldn't change how much fuel is consumed, right? Fuel consumption is controlled by injector pulse width. Timing is a question of when the spark occurs relative to crankshaft rotation.

Hopefully someone will educate us....

[dom w. forte]

OK, but advancing the timing - by itself - shouldn't change how much fuel is consumed, right? Fuel consumption is controlled by injector pulse width. Timing is a question of when the spark occurs relative to crankshaft rotation.

Hopefully someone will educate us....

I beleieve clynder explosion effecietcy would change with a different octane produceing more or less energy to the crank with the combustion, normally we get better efficentcy with the timing retarded but clynder temperature rises and causes spark knock , however you would never here it because the knock sensor would catch it first and retard more .
Also lower octane will explode at lower compression and start the power band earlyer , injector puslse width will change based on map signal change if the pulses in the intake are changing speed, thats why its called a speed density system, however the test would need to be same condition , air temp , baro , etc.