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Question for Rich

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Posted by: Vic---------------------

Starting with a 250 two-stroke, how close could you come to simulating the powerband of a 250 four-stroke if you were willing to limit peak power to that of the four-stroke?


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by Vic
Starting with a 250 two-stroke, how close could you come to simulating the powerband of a 250 four-stroke if you were willing to limit peak power to that of the four-stroke?



Vic - Eric has gotten very close with the 265 and 310 big bore motors. On a stock bore size it's tougher. We got pretty close to that type of power with my stock bore 2001 CR125, so almost anything is possible.


Posted by: Vic---------------------

Does it require a custom pipe and/or ignition curve?

Did you ever have your CR on a dyno?


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by Vic
Does it require a custom pipe and/or ignition curve?

Did you ever have your CR on a dyno?


No and No

A pipe and ignition curve designed specifically this type of engine would certainly help but they are far from necessary. You can do an awful lot with time/area changes and compression ratios on a big bore to get this type of power.


Posted by: Vic---------------------

What would you estimate the peak HP of your CR to be?


Posted by: Okiewan---------------------

Quote:
Originally Posted by Vic
What would you estimate the peak HP of your CR to be?
About 92.


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by Okiewan
About 92.


But that's only with the Nitropropane in the tank.

Honestly Vic I have no idea what the peak horsepower was. I was working on getting a good usuable range for a small SX type track.

Jeremy Wilkey rode it a lot at Casey during DW01 and given the number of people he was passing on it I don't think it was all that slow.


Posted by: Vic---------------------

I was just wondering what you had to give up to get that type of power.


Posted by: nephron---------------------

Quote:
Originally Posted by Rich Rohrich
No and No

A pipe and ignition curve designed specifically this type of engine would certainly help but they are far from necessary. You can do an awful lot with time/area changes and compression ratios on a big bore to get this type of power.


Damn, Rich. I didn't know you owned a butt dyno. Hell, I never thought you'd get in the same room as one. Word has it around these here parts you're gonna be taking over Roland's column. True? (runtime errors won't let me bring up a smilie)


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by Vic
I was just wondering what you had to give up to get that type of power.


Vic - You'll give up some peak power, the torque will peak at a lower rpm, and it won't have the ability to carry the torque curve as far past the torque peak. In other words they will tend to flatten out at high rpm. A specially designed pipe and ignition curve could certainly minimize this but it would take a lot of specific development work . It would be tough to justify the huge expense for the potential gains IMO.

Quote:
Originally Posted by nephron
Damn, Rich. I didn't know you owned a butt dyno.


Hey Jack.


Posted by: steve125---------------------

Rich, Pete and I just spent the day dynoing the EGYZ 144. After a bit of pipe testing and got our timing set we focused most of the day on the intake, and learned alot.

We tested jetting, carbs, reed valves and reeds, different length and angle intake manifolds. I was very interested in the KTM and 05 YZ125 theory of the straight intake vs a angled one if it would show, and it did!

One big suprise was the airbox side intake boot, we did runs with it attached and with it removed. It was one of the largest changes on the dyno all day. With the boot removed, we lost .5hp on top and about 400rpm of over-rev. Seems this air direction thing(moving straight and forward) is a big deal at high rpm.

Also for fun we ran the PN and got nada. I hope to post all this up in a thread soon

Steve


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by steve125
One big suprise was the airbox side intake boot, we did runs with it attached and with it removed. It was one of the largest changes on the dyno all day. With the boot removed, we lost .5hp on top and about 400rpm of over-rev. Seems this air direction thing(moving straight and forward) is a big deal at high rpm.


Steve - I know that SFO and the MotoDynamics SuperMoto team spent a lot of time and effort "tuning" the boot between the carb and the airbox with good results on Doug Henry's bike. Maybe we've been looking in the wrong places all along.
If we could get that damn shock out of the way I'm sure we could find some additional power and range.

No surprise on the PN. Thoreau said "Men have become the tools of their tools" and it seems like the PN zealots have proven themselves to be complete tools


Posted by: steve125---------------------

LOL Rich, we even updated the PN with the bleed hole they recomend, still nada. This dyno shows even the smallest changes in jetting, timing,pipe length,reeds, fuels, ect...nada on the PN

The real scary part is now they have a new PN system. This one has the carb bell section as we have seen. In addition it has a wing in the front of the carb as well, the slide is now in the middle of the 2 blades.

So really who knows? this system seems like a good idea?? For now its only available for the 4 bangers. But at twice the money at 200.00 , I'll pass, on testing it this time around.


Posted by: Rich Rohrich---------------------

Quote:
Originally Posted by steve125
The real scary part is now they have a new PN system. This one has the carb bell section as we have seen. In addition it has a wing in the front of the carb as well, the slide is now in the middle of the 2 blades.


My favorite is the jughead who is touting his own PN derivative with 3 blades jammed in the intake. If one is good, then two must be better, and three should be just about right.

It's really sad to see what has happened to those kids who cut physics class to go smoke weed behind the dumpsters in high school.


Posted by: Vic---------------------

Quote:
Originally Posted by Rich Rohrich
Vic - the torque will peak at a lower rpm, and it won't have the ability to carry the torque curve as far past the torque peak. In other words they will tend to flatten out at high rpm.


Will it still rev as high even though the power flattens out?

Is max torque about the same?



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