B
mtk said:Also, a CR125 has an 8.6:1 compression ratio according to Honda's website. The CRF250 has a 12.5:1 compression ratio, again from Honda's website. That's a pretty significant difference and a long way from the 11.4:1 number you quoted.
Yet another "Cut and Paste:"
"Basically what all this means in the end is, averaged over time (RPM) the “fires twice as often” advantage of a 125 two-stroke is diminished to a large extent by the lower working pressures and the lower rpm it has to run at compared to a 250F, and thermal efficiency differences account for only a very small part of this."
XRpredator said:2 strokes still suck. so there :nener:
XRpredator said:okay, I been thinkin', and that's dangerous . . .
The argument is that a two stroke is cheaper to rebuild than a four. Now, my feeble mind tells me that (in general) a 4 stroke needs fewer top end jobs than a two stroke, so in my head the voices tell me that you are gonna spend about the same money in the same time frame.
Plus I save money not having to buy mix oil.
but then again, I'm me.
CaptainObvious said:Yes, two-stroke dirtbikes have fallen out of favor with the OEM's because of emissions. But truth be told the clean answer to the 2S emission problem is the direct-injection two-stroke (DI2S) engine.
The popularity of four-stroke dirtbikes has more to do with marketing than anything else. At the end of the 1990's, sales of 2S bikes had reached a plateau and it would have been difficult for the OEM's to move riders (buyers) from the current two-strokes to DI2S bikes. So they introduced powerful four stroke bikes to the buying public. As soon as the market is flooded with 4S bikes and sales begin to tapper off, the next "new thing" will be the 2S engine.
Two-stroke dirtbikes will come back in a big way. It's just a matter of time.
Rich Rohrich said:I It's funny to hear F1 and WSB engine guys talk about having to run 50 degrees of ignition lead just to get everything to burn as engine speeds reach above 15000 rpm.
mtk said:I recall reading once that the F1 guys didn't like the huge amounts of advance they needed to work at the RPMs they were turning, so they turned to their fuel suppliers for a fuel that would allow them to run more "normal" amounts of advance in their engines. Being F1, they threw HUGE sums of money at the problem and sure enough, came up with a fuel that would allow it. This was probably a decade ago or thereabouts and this was the era when guys wore HAZMAT suits to fuel an F1 car.
I ain't gonna, but I've seen it done. And I have a feeling Vic will last plenty long. As Rich said, there's the former 125 buzz bomb pilots that jump onto the 250F's and bang against the limiter. Then it's all the bike's fault, according to these goobers.Micahdawg said:In the case of an XR motor vs. a two stroke....in the end you will probably spend way more money on a two stroke than an XR. XR motors are low revvers and if properly maintained should last forever (low HP, low revving = happy conditions). BUT, you ain't gonna win races with an XR motor.
Micahdawg said:BUT, you ain't gonna win races with an XR motor.
Rich Rohrich said:I think that's what ultimately forced the rules makers to go with an RON limit on the fuel and a stipulation that only components that currently exist in road legal fuel can be used in the fuel. The fuel that Shell and some of the others produce for F1 is still pretty trick, but nothing like it was in the early 90s. The funny thing is, with current rpm levels they are forced to run compression ratios in the 12.5:1 range.
Micahdawg said:As for the superiority of the thumpers....I don't want to rub it in, but I did handsomly walk away from a 2004 YZ250F on my 1989 KX250...on the street, from a dead stop, all out drag race. He had a 50 tooth rear sprocket and I have a 47. Even with his tighter gearing I had him from the line.
yep, 2 strokes suck. :nener:Rich Rohrich said:Well that sums it up. :coocoo:
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