ESE's works engine tuner

[Frits Overmars]

I have scored the best 2T tuning job in the world. As after the World Finals in Vegas I am off to Pesaro to work at the TM factory with Franco Drudi on the next homologation design.

That is great news Wob . You'll be just 1400 km away then instead of 19000 km. Hope to meet you there.

[Flettner]

I have scored the best 2T tuning job in the world.
As after the World Finals in Vegas I am off to Pesaro to work at the TM factory with Franco Drudi on the next homologation design.

So ask me the same question next year.

So, great, now we will have You AND Franco posting on ESE
We won't tell anyone, we can keep secrets
I'm assuming you won't be Wrighting us off.
Good on you.

[teriks]

Mainly for Lightbulb, but anyway, might be of interest for someone else.

Work in slow progress, the crankcase for a rear intake version of the MB LS in the foreground. Behind it the standard front intake MB Profi.


PS: Congratulations Wobbly!

[Martin1981]

I am off to Pesaro to work at the TM factory with Franco Drudi on the next homologation design.

Congrats Wob! Maybe after the Work at TM is done you could help the Ryger Guys with their next Homologation Design.

[seattle smitty]

David Vizard (okay, yes, a four-stroke guy) got to wondering about shapes of add-on carburetor bell-mouths, and wondering if the favored shapes had more to do with pleasing the eye of the engine-builder than pleasing the engine, much as fishing lures may sell well because they look good to fishermen, though maybe not to fish.

Vizard tested a range of half dozen shapes, and you might be surprised at what worked best (not a bell mouth). The lovely cast aluminum trumpets I got out of Japan to go on some little Bings turn out to be nothing special, nor does the shorty plastic version (though each did have their own slight effect). See his book, "How to Build Horsepower, Vol 2, Carburetors and Intake Manifolds."

Be aware that the testing was in still air, so you might have to build a shield to keep any erratically turbulent wind blast from messing up airflow. Maybe this is not so much of an issue with most bikes, but in retrospect (decades worth!!) I think it probably messed with my racing outboards significantly. Who was it that suggested that the 2-stroke racers' universal symbol for T-shirts and hats ought to be a piston with a big skid mark down the side?

Too soon old, too late smart. If only I had access in the Sixties and early Seventies to all the huge volume of great info that's now available in print and on-line! Young racers have no idea how different the information situation was then. I remember sitting in the Univ. of Washington Engineering library (and I was majoring in History, long story) in 1966, reading a book on high speed 2-stroke DIESEL engines by some old German, hoping to find some clues. Maybe eight or nine years later, when Gordon Jennings' little red 2-stroke book came out, we felt like Moses receiving the golden tablets!! Of course, it would have helped if I had had some brains of my own then (hardly matters now).

[dark art]

David Vizard (okay, yes, a four-stroke guy) got to wondering about shapes of add-on carburetor bell-mouths, and wondering if the favored shapes had more to do with pleasing the eye of the engine-builder than pleasing the engine, much as fishing lures may sell well because they look good to fishermen, though maybe not to fish.

Vizard tested a range of half dozen shapes, and you might be surprised at what worked best (not a bell mouth). The lovely cast aluminum trumpets I got out of Japan to go on some little Bings turn out to be nothing special, nor does the shorty plastic version (though each did have their own slight effect). See his book, "How to Build Horsepower, Vol 2, Carburetors and Intake Manifolds."

Be aware that the testing was in still air, so you might have to build a shield to keep any erratically turbulent wind blast from messing up airflow. Maybe this is not so much of an issue with most bikes, but in retrospect (decades worth!!) I think it probably messed with my racing outboards significantly. Who was it that suggested that the 2-stroke racers' universal symbol for T-shirts and hats ought to be a piston with a big skid mark down the side?

Too soon old, too late smart. If only I had access in the Sixties and early Seventies to all the huge volume of great info that's now available in print and on-line! Young racers have no idea how different the information situation was then. I remember sitting in the Univ. of Washington Engineering library (and I was majoring in History, long story) in 1966, reading a book on high speed 2-stroke DIESEL engines by some old German, hoping to find some clues. Maybe eight or nine years later, when Gordon Jennings' little red 2-stroke book came out, we felt like Moses receiving the golden tablets!! Of course, it would have helped if I had had some brains of my own then (hardly matters now).

A few years ago I found prof Blair website with some good information. You might want to check the bellmouth article:

http://www.profblairandassociates.com/RET_Articles.html

[Lightbulb]

Mainly for Lightbulb, but anyway, might be of interest for someone else.

Work in slow progress, the crankcase for a rear intake version of the MB LS in the foreground. Behind it the standard front intake MB Profi.


PS: Congratulations Wobbly!

You did not mention about making your own case. It would really benefit from having an extra set of bolt hold down holes by the rear bearing, so making it a 6 hold down design engine.
Thanks for the picture. I know the work of making bar stock engines.
Neil

[F5 Dave]

Thanks for the NSR fi info and congats on the job Wob.

[FastFred]

The crankcase...

CNC'd crankcase, very impressive, I like your work.

[oldjohnno]

This connection pipe, together with the cylinder and pipe volumes forms a Helmholtz system; its length and diameters determine the frequency of this system.
The header length is rather fixed by the desired wave actions, so the header diameters must have a certain value in order to arrive at the desired frequency.

Please excuse me for dredging up an old post, but this is something that has puzzled me for a while.

I'd noticed that there doesn't seem to be a close correlation between cylinder volume and pipe belly diameter - a serious 125 has a diameter of maybe 120 or so, a 250 is usually not much bigger and even 400s are still much the same. I would have thought that as the cylinder (and port) diameter increased the big end of the diffuser would would have to be proportionally bigger in order to maintain the taper angles and pressure wave establishment?

I guess some of the discrepancy would be purely because of the state of tune, but even so there are some big snowmobile cylinders with fairly high BMEP. Does a massive belly lower the Hemholtz frequency too much, and if so, does this factor trump maintaining the diffuser angles?

I just don't see a lot of big cylinders using 150 or 175mm centre sections...

[husaberg]

Please excuse me for dredging up an old post, but this is something that has puzzled me for a while.

I'd noticed that there doesn't seem to be a close correlation between cylinder volume and pipe belly diameter - a serious 125 has a diameter of maybe 120 or so, a 250 is usually not much bigger and even 400s are still much the same. I would have thought that as the cylinder (and port) diameter increased the big end of the diffuser would would have to be proportionally bigger in order to maintain the taper angles and pressure wave establishment?

I guess some of the discrepancy would be purely because of the state of tune, but even so there are some big snowmobile cylinders with fairly high BMEP. Does a massive belly lower the Hemholtz frequency too much, and if so, does this factor trump maintaining the diffuser angles?

I just don't see a lot of big cylinders using 150 or 175mm centre sections...

You might find, most bikes can't accommodate those fat bellied pipes.

[Frits Overmars]

I'd noticed that there doesn't seem to be a close correlation between cylinder volume and pipe belly diameter - a serious 125 has a diameter of maybe 120 or so, a 250 is usually not much bigger and even 400s are still much the same. I would have thought that as the cylinder (and port) diameter increased the big end of the diffuser would would have to be proportionally bigger in order to maintain the taper angles and pressure wave establishment?

The belly diameter of a serious 125 cc is more like 130 mm, and bigger cylinder volumes should have proportional bigger bellies; you can find the relation in the concept drawing below. But when did you last see a serious (that is: tuned for power) 250 or even 400 cc engine? Most big singles are MX machines and their power out of the box is already too much for the average rider. Besides, as Husa said, you wouldn't be able to fit a real effective pipe on such a machine.

I guess some of the discrepancy would be purely because of the state of tune, but even so there are some big snowmobile cylinders with fairly high BMEP. Does a massive belly lower the Hemholtz frequency too much, and if so, does this factor trump maintaining the diffuser angles?

The best snowmobile engines hardly reach 2/3 the BMEP of a 125 GP engine. That's understandable because they are utilitarian products. If you want to extract more power from them, you'll need to fit bigger pipes.
A massive belly or rather a big pipe volume does lower the Helmholtz frequency but then the bigger header diameter raises it (and the bigger header length lowers it again). It's only right because at the same specific time areas for blowdown and transfer, a bigger engine needs a lower resonance rpm and corresponding frequency.

[oldjohnno]

Thanks for the replies.

I have to say though that in my little world even 2/3rds of 125 GP BMEP is pretty high

[ken seeber]

Johnno, in our Oz, there is a speedway class called microsprints, where they run 250 ccc engines. Tons of space, so you can fit any sized pipe that your heart desires.

[Greg85]

hello,
i am new to the forum,this is very good forum for two stroke!
i am interseted in a lot of karting engine ,now i am interested in working with the cylinder jaros bench is anyone really knows this system for well optimized
cylinderworked in what sense?
THANK YOU[IMG]img_3533.jpg[/IMG][IMG]img_3535.jpg[/IMG][IMG]img_3536.jpg[/IMG]