Next Question! Fuel Injectors - Crazy CO values

[devimau]

@ least 80% were, but the higher the octane the more resistance to detonate and the quicker it'll burn, would that be the opposite?

[ducpainter]

I'm not certain for the 100% of them but @ least 80% were, the higher the octane the quicker it'll burn, should be the opposite, shouldn't it?

AFAIK the higher the octane the slower it burns.

That's the way high octane controls detonation by slowing the burn. My understanding is that high octane fuel in a low compression motor does nothing but create carbon, cause poor overall performance, and empty the riders pocket.

That's why I was asking. Perhaps the burn is so slow that some goes unburned and causes the cylinder washing you saw.

[devimau]

talking with vp people while back to choose the fuel for our race bike we came to the same conclusions: the higher the octane the less will detonate (you can compress it more, it won't start an explosion due to compression) but the front flame of the fuel when ignited will be @ an higher rate, that's why we didn't want higher octane on ours, we wanted low octane oxygenated.
in other words, you can compress it more but the explosion will be quicker and more violent.
what's AFAIK?

[ducpainter]

We should stop jacking the OP's thread.

[2 Wheel Wanderer]

Jack away , this is good info...

[ducpainter]

talking with vp people while back to choose the fuel for our race bike we came to the same conclusions: the higher the octane the less will detonate (you can compress it more, it won't start an explosion due to compression) but the front flame of the fuel when ignited will be @ an higher rate, that's why we didn't want higher octane on ours, we wanted low octane oxygenated.
in other words, you can compress it more but the explosion will be quicker and more violent.
what's AFAIK?

Jack away , this is good info...

OK 

AFAIK=As far as I know...

So they claim oxygenated fuel is less susceptible to detonation?

And what is the oxygenating agent? Not ethanol I hope.

[2 Wheel Wanderer]

One more question guys, so final air flow doesn't really matter if you've already done a TB sync, as long as you get the same CO from each header, each cylinder is making equal power and all should be smooth. This sound right?

[ducpainter]

One more question guys, so final air flow doesn't really matter if you've already done a TB sync, as long as you get the same CO from each header, each cylinder is making equal power and all should be smooth. This sound right?

When you say final air flow are you asking throttle position?

[devimau]

The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality; burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates.

To give you a good example of this, we contacted Jim Wurth from Sunoco Race Fuels. He explains, "A perfect example is Sunoco Maximal, which is our fastest burning fuel, and coincidentally one of Sunoco's highest octane fuels at 116 (R+M) / 2. A lot of Pro Stock teams rely on Maximal for those sub-seven second runs. When they are turning 9,000 rpm or more, the fuel has to burn pretty quickly to achieve complete combustion".

from here http://www.nsxprime.com/FAQ/Miscellaneous/FuelAdditives.htm

[ducpainter]

The burn rate of a fuel is a measurement of the time required for complete combustion of the air/fuel mixture. The notion that octane ratings affect the burn rate of fuel is about 180-degrees from reality; burn rate is a function of several variables, and the two are completely independent, although there is generally a correlation between octane ratings and burn rates.

To give you a good example of this, we contacted Jim Wurth from Sunoco Race Fuels. He explains, "A perfect example is Sunoco Maximal, which is our fastest burning fuel, and coincidentally one of Sunoco's highest octane fuels at 116 (R+M) / 2. A lot of Pro Stock teams rely on Maximal for those sub-seven second runs. When they are turning 9,000 rpm or more, the fuel has to burn pretty quickly to achieve complete combustion".

from here http://www.nsxprime.com/FAQ/Miscellaneous/FuelAdditives.htm

Let's leave race fuels out of it, because none of us are using it on the street. I don't use it in my stock motor 996 track bike either.

What is the relative burn rate of pump fuels? Is it related to octane, and do the higher octanes burn in a more controlled manner or 'slower' and do low octane fuels give that violent explosion or 'faster'.

I believe that is the case.

[2 Wheel Wanderer]

When you say final air flow are you asking throttle position?

After you've done the sync and locked down right side TB screw and set your base degrees setting (2.7 for my bike).  So after I have done this is when I start adjusting the air bleeds. When I adjust them to match the CO and put on say a carbtune the air flows go off. From what Brad is sayin it doesn't matter as long as the CO is set the same.

I guess I'm over thinking this. For some reason I have it in my head that air flow and CO from each cylinder have to match all the way around.

[ducpainter]

I'm not sure which is more important.

[Howie]

Let's leave race fuels out of it, because none of us are using it on the street. I don't use it in my stock motor 996 track bike either.

What is the relative burn rate of pump fuels? Is it related to octane, and do the higher octanes burn in a more controlled manner or 'slower' and do low octane fuels give that violent explosion or 'faster'.

I believe that is the case.

Zakley!  Highly oxygenated race fuels are another species and have little in common with our alcohol laced fuel. 

Devimau, you are correct that octane is resistance to burn, not burn rate, particularly with race fuel, but since legal pump gas meets government standards burn rate between grades is fairly standard.  4.5 - 6% CO on pump gas is just fine.  If you run premium E10 unnecessarily you will develop carbon, and because it doesn't like to vaporize you might have some cylinder washing in extreme cases.  Premium that is not E10?  Mostly wasting money.

[devimau]

After you've done the sync and locked down right side TB screw and set your base degrees setting (2.7 for my bike).  So after I have done this is when I start adjusting the air bleeds. When I adjust them to match the CO and put on say a carbtune the air flows go off. From what Brad is sayin it doesn't matter as long as the CO is set the same.

I guess I'm over thinking this. For some reason I have it in my head that air flow and CO from each cylinder have to match all the way around.

that's right, close them all the way to sync them, after that forget about sync and remove the syncronizer, hook up the gas analyzer and set your co's evently (.5% max difference) and also if everything is good the air bleeding screws should not be more than 1/2 apart from each other ( one @ 1 and the other @ 1.5 max lets say)
also the more you open them the less hc readings you'll have, the healthier the idle speed but becarefull with hanging idle issues, I personally like them between 1.5 and 2 turns out, 2,5 max.

[devimau]

howie, ducati recomends 2 to 2.5 co % on stock bikes and 3.5 to 4 co % MAX on units with high performance exhaust systems and air filters/ open lid mod.
IMMO  richening up the trimming feature will have the same effect than putting a bigger pilot jet on a carburated bike, on efi units this trimming feature will be good up to 3500 rpm or 40% of throttle opening, after that is all up to the ecu's own mapping and you'll be distortioning the whole map with unburned fuel @ higher revs until the engine clears it up and that will make your bike run lazy and not sharp, that's a fact.
remember in the old days the whole secret on carbs was the relationship between main jet and needle shape, the pilot it's important but you don't want to mix the functions, and putting a bigger pilot was not the solution for a best running engine.
pump gas is tricky since the gas stations will cut it to have more to sell and actually you are not getting it as pure as you might think, all depends on what they use to cut it with, you can buy 91 octane and analyze it with 87 and if the level of alcohol in the 87 is greater (which is always the case) than the 91, you'll end up with a less octane gasoline that burns slower.
gas pump is not consistent, also I know people that'll add propane to bump up the octane and that causes the same effect, it accelerates the burn rate.
now, if you analyze this for a second typically to any engine the higher the compression the more revs it's capable of doing and @ higher revs  the fuel has less time to burn so it'll make sense  for those engines to have a gas type capable of avoid being ignited by compression forces and burn quickly, and I'm not talking about a race engine, I'm talking about an stock gsx'r 1000 @ 11k with 91 octane pump gas in the tank.
I know that there's a lot of contradicting info on the internet, some people say white and some people say black and I'm talking about chemical engineers.... is very confusing sometimes.