- Jan 8, 2000
- 3,331
- 1
Did I make a joke?
Crf250 Fuel
- Thread starter phazerrd
- Start date
slodsm, there are big differences between a bigblock and a CRF250. The CRF250 has a much shorter intake tract with much less heat for starters, not to mention that it also runs at much higher rpms.
In short (this isn't the Rich tech version!) what happens is that a lot of that pump fuel isn't vaporizing completely because of the high temperatures needed because of the distillation curve. This effect occurs more an high RPMs where the time to vaporize isn't as great. The C12 vaporizes more effectively because of it's lower distillation curve (more suited for the application).
In your bigblock the intake tract is long and the relative heat is high so it will have more time and heat to fully vaporize the pump fuel.
To add another one up for the C12, it is much more consistant than the pump fuel could ever dream of being.
Now, I know that I screwed that one up somewhere...I'm sure that Rich will fill in for my mistakes! :)
In short (this isn't the Rich tech version!) what happens is that a lot of that pump fuel isn't vaporizing completely because of the high temperatures needed because of the distillation curve. This effect occurs more an high RPMs where the time to vaporize isn't as great. The C12 vaporizes more effectively because of it's lower distillation curve (more suited for the application).
In your bigblock the intake tract is long and the relative heat is high so it will have more time and heat to fully vaporize the pump fuel.
To add another one up for the C12, it is much more consistant than the pump fuel could ever dream of being.
Now, I know that I screwed that one up somewhere...I'm sure that Rich will fill in for my mistakes! :)
TreeTalker
Member
- May 8, 2004
- 161
- 0
OH hell, after all that it still boils down to this.......SHUT UP AND GO RIDE!!!! At least that's what my wife tells me when I complain I have been working to hard....lol Guys it doesn't matter what fuel you use or what bike you have. Just get on the damn thing and ride it. If you were RC or Bubba or anyone of those guys who gets paid the big bucks to ride then I could see how it would matter. But for us everyday average Joe's it's all about the smile on your face at the end of a great ride. So with that said I am off to bed to dream about the next ride, hope you folks are too....Lee
Not sure .... but!
I'm not sure who actually wins the Jerry Springer noob posting war, but with regard to certain fuels.....
I have a fresh teardown CRF250R head in front of me that ran U4, and the intake valves have approx. 2mm of pink crust on their faces apparently from the U4. The valves were installed ten hours ago. I don't think it would rob too much power, but when you get into the discussion concerning valve float at RPM, I'm sure the extra mass of the valve+crust= more float susceptability and shorter valve life. You know; that "Honda" problem?
I'm not sure who actually wins the Jerry Springer noob posting war, but with regard to certain fuels.....
I have a fresh teardown CRF250R head in front of me that ran U4, and the intake valves have approx. 2mm of pink crust on their faces apparently from the U4. The valves were installed ten hours ago. I don't think it would rob too much power, but when you get into the discussion concerning valve float at RPM, I'm sure the extra mass of the valve+crust= more float susceptability and shorter valve life. You know; that "Honda" problem?
ACGUY said:
Is that U4 or U4e?
I just got a 04 CRF250X. Steady diet of pump gas. The original head had 400 miles+ of race action. The valves are crusty, Very. There is an new 05 head/cam on it. It had a few hours on pump gas. I started to run VP MS109 it is Oxygenated and unleaded. Rich seems to feel the lead in U4 may not be the very best for the Ti valves but the jury is out on this.
My only contention is that the added mass (of the crust) would naturally amplify the high rpm valve float problem. I am not sure if the fuel is U4 or U4E. It sure does smell strong though. There is also a heavy pink crust layer around the top ridge of the cylinder. I have never seen this much residue leftover from pump gas. Assuming jetting has been set, that is.
GhostRider32
Member
- Feb 10, 2004
- 473
- 0
Okiewan said:
Damn Okie, I knew Al Gore invented the internet but high octane fuel too. WTF.......If I'd known how smart Gore was, I'd have voted for him.
LOL...I think to win, or even participate in a war, you must have at the very least, some ammo.ACGUY said:
slodsm, if nothing else you are all the wordsmith. :blah:
(not that there's anything wrong with that...it's all good! :) )
A friend of mine found this while googling one day and asked me about it. Funny what’s hiding in the dusty corners of the web.
I got a good laugh from it and it lead to an interesting lunch discussion. From that lunch discussion the following seemed worth repeating.
For what it’s worth, I made my first 9 second pass on a turbocharged drag bike in 1978. It was an air cooled Suzuki GS750. Turbocharging and air cooling is a tricky environment to keep combustion stable in. I broke my share of parts back then, but for my trouble I got a priceless start to my continuing education in combustion engineering. It certainly didn’t make me any sort of expert, just a ravenously curious truth seeker. The drag strip is Mecca for unproven bullshit and opinions in my experience. But it’s super fun anyway.
In his defense Slodsm did indirectly raise one important point that’s worth always noting as you try to advance your knowledge of subjects that matter to you.
Eminence is NOT evidence, so don’t let some “expert” blow smoke up your ass no matter how familiar they might be to you. Question everything if it doesn’t sound right.
Our old friend Dr. Richard Feynman said it much better than I ever could:
“Science is the belief in the ignorance of experts”
“The first principle is that you must not fool yourself, and you are the easiest person to fool. “
and lastly
“STUDY HARD, what interests you the most, in the most undisciplined, irreverent and original manner possible. “
Dr. Feynman was one pretty clever cat.
I got a good laugh from it and it lead to an interesting lunch discussion. From that lunch discussion the following seemed worth repeating.
For what it’s worth, I made my first 9 second pass on a turbocharged drag bike in 1978. It was an air cooled Suzuki GS750. Turbocharging and air cooling is a tricky environment to keep combustion stable in. I broke my share of parts back then, but for my trouble I got a priceless start to my continuing education in combustion engineering. It certainly didn’t make me any sort of expert, just a ravenously curious truth seeker. The drag strip is Mecca for unproven bullshit and opinions in my experience. But it’s super fun anyway.
In his defense Slodsm did indirectly raise one important point that’s worth always noting as you try to advance your knowledge of subjects that matter to you.
Eminence is NOT evidence, so don’t let some “expert” blow smoke up your ass no matter how familiar they might be to you. Question everything if it doesn’t sound right.
Our old friend Dr. Richard Feynman said it much better than I ever could:
“Science is the belief in the ignorance of experts”
“The first principle is that you must not fool yourself, and you are the easiest person to fool. “
and lastly
“STUDY HARD, what interests you the most, in the most undisciplined, irreverent and original manner possible. “
Dr. Feynman was one pretty clever cat.
I'm damn sure stealing that and calling it my own. Sue me.
I have a poster of that hanging in my living room. It’s some of the best advice I’ve ever followed and it’s made me incredibly popular with the used technical book sellers on Amazon lol
Similar Topics
