ESE's works engine tuner

[peewee]

hey guys has anyone tried mounting some plastic inserts into the voids of a rz style crank ? seems like it would be easy enough to do, anybody know what type of plastic material the manufacturers use ? ktm been using that plastic stuff for sometime but i dont know what it is. it may need a very long rod to recover the lost volume. maybe 125mm rod or perhaps longer, which would bring on another hurdle because the lower rod pin on them long rods is bigger. thats one thing i always hated about these twin cranks is the huge voids between the crank cheeks

[TZ350]

More EFI

That unleaded 96 is bad stuff, I had been using AvGas on the dyno, and filling the workshop with smoke, with no problems but swapped to 96 to save some coin. After 20 - 30 hours work sucking 96 fumes I got real sick and have not been able to do any dyno work for a few weeks now.

Other guys at work who did a lot of petrol station gas compressor service jobs say they experienced much the same when the country changed to unleaded. Leaded AvGas is not great but 96 with its aromatics and toluene are even worse I think, from a health point of view E85 (mostly Ethanol) would be my pick of fuels to work with.

On the dyno it was relatively easy to set the EFI for WOT (main jet) runs but the lower throttle settings have been hard to get right on the dyno. The load experienced by the bike from a rolling road dyno is just not the same as riding it on the road, the engine does not react the same way on the dyno.

So the answer is to ride it, and the other day I got a small laptop (notebook??) computer from surplus traders that sits nicely on top of the tank.



On the Alpha-N map screen there is a yellow highlight marker that indicates the current active cell on the map. The plan is to get out into the fresh air and ride the bike around quietly to find the bad spots in the map and adjust them. The Ecotrons software allows you to make adjustments on the fly.

If it was a car you could have a friend drive while you tuned the EFI system but with the bike I will have to stop to make changes. Anyway I did a little test ride tonight and the idea looks promising.

[chrisc]

I like your style doc

[speedpro]

I wonder if the rules about texting and driving cover tuning your EFI and driving. Probably not as who would have thought?

I see it still as a moving target unless you can keep a more or less steady state and monitor numbers.

I may be able to use an inertia dyno which has a monster disc brake fitted. Just need to make a big bracket to mount the bike rear axle, dyno sprocket, and some chain. Then I'll be able to hold certain load and rpm points and monitor the lambda. Further investigation this weekend.

[speedpro]

hey guys has anyone tried mounting some plastic inserts into the voids of a rz style crank ? seems like it would be easy enough to do, anybody know what type of plastic material the manufacturers use ? ktm been using that plastic stuff for sometime but i dont know what it is. it may need a very long rod to recover the lost volume. maybe 125mm rod or perhaps longer, which would bring on another hurdle because the lower rod pin on them long rods is bigger. thats one thing i always hated about these twin cranks is the huge voids between the crank cheeks

I've seen where carbon fibre was used. A couple of screws were placed in each face and carbon string wrapped round them. Blanks were fitted where the CF was not wanted, then each wheel was placed in a mold and the glass poured in. A vacuum was applied to extract any air and once set each wheel was removed and finished off. Assembly was as usual. As far as I know it's been problem free.

[wobbly]

UHMWP is the stuff to use for filling the crank, with Csk screws thru into threaded holes in the wheels.
But in the RZ/Banshee I believe the positive effect of the long rods of increasing the case volume would not be helped much by
" smoothing " the wheel shape, as they then also decrease the case - ruining more than helping.

[Frits Overmars]

hey guys has anyone tried mounting some plastic inserts into the voids of a rz style crank ? seems like it would be easy enough to do.

Fitting inserts to smooth the wheel shape will reduce the crankcase volume, reduce the stirring that homogenizes the fuel/air mixture, shroud the big end bearing from that mixture, and introduce the risk of the inserts coming loose. Are you sure you want any of this?

[ken seeber]

Fitting inserts to smooth the wheel shape will reduce the crankcase volume, reduce the stirring that homogenizes the fuel/air mixture, shroud the big end bearing from that mixture, and introduce the risk of the inserts coming loose. Are you sure you want any of this?

Jeez Frits, that just adds a whole new meaning to the term "get stuffed"

[Martin1981]

But if the engine NEEDS the smaller crankcase volume? And the rsa engine also has smooth crankwebs that do not help stirring?

Edit: okay, if ANY engine needs the smaller crankcase volume? the banshee engine obviously doesn`t need it.

[husaberg]

But if the engine NEEDS the smaller crankcase volume? And the rsa engine also has smooth crankwebs that do not help stirring?

Edit: okay, if ANY engine needs the smaller crankcase volume? the banshee engine obviously doesn`t need it.

With the RSA/ RSW Most of the volume is concentrated in the transfer ducts. Then there is the volume inside the piston of course, and the 1 mm shear-avoiding clearance at all surfaces of the crank.
But that is not nearly enough volume. If you take another look at the Aprilia crank below, you will notice that the space between the crank webs is the same as the space needed for the big end bearing. In other words: the crank webs have flat insides, good for another 60 cc or so, if I remember correctly.

Additional benefits: the con rod has an easier time pushing the mixture aside as it moves between the webs, and the big end bearing gets a lot more cooling and lubrication because it is not shrouded in any way.
Because there are no overhung bobweights, the crank webs are stuffed with tungsten to get the balance factor right.
In the RSA125, the con rod was lengthened from the RSW's 115 mm to 120 mm to create even more crankcase volume.

The paddling is a mixed blessing; it creates aerodynamical drag but it also greatly improves the homogenity of the mixture.
Smooth, full-circle crank webs have the advantage that there is little mixture hiding in nooks and crannies. An example of it's importance: in a certain engine there were 20 mm spaces between the crankshaft bearings and the seals. these ill-accessible volumes acted as pneumatic dampers on the crankcase pressure fluctuation. Filling those volumes with plastic bushes gave a measurable improvement.

Summary: you need a large crankcase volume. Ideally all of this volume should be situated in the transfer ducts. In real life you will also need to lodge part of this volume between crankshaft and piston, i.e: use a long con rod. Avoid nooks and crannies. Crankshafts should be small and smooth. Big end bearings must never be shrouded by recesses in the crank webs or by stuffers.

The picture below shows, wait for it, an RSA125-crank with stuffers...
After Jan Thiel went into retirement in 2008, some geniuses at the factory grabbed their chance to 'correct' the errors that Jan left behind, without even testing the result because 'everybody knows the smaller the crankcase volume the better'. But they never could understand why a 2011 RSA125 was slower than a 2007 model (just look at the 125 cc top speeds on any GP-track). O, the joy of working with Italians.....

Frits Overmars 2012

.....

In theory enclosed cranks are good. Jan Thiel did some experiments at Aprilia with a kart engine that had its reed valve at the front: the incoming mixture had to move against the direction of crank rotation. And although the crankcase stretched over the crank webs, reversing the direction of rotation brought another HP. So the crankshaft does have an influence.
But in practice, if you reduce the distances between crankshaft and crankcase walls to less than 1 mm, the viscous friction of the mixture between the surfaces really costs power at high rpm. And if you make the clearances so tight that lubricating oil can no longer reach the big-end and crankshaft bearings, it will also cost engines
Another negative aspect: any volume with a narrow 'entrance' between the crankshaft and crankcase surfaces acts as an hydraulic damper on the Helmholtz-resonance in the crankcase.
Aprilia has avoided this by making the space between the crank webs as wide as the big-end bearing. As a result the crankcase volume of the 125 cc RSA engine at TDC is about 650 cc,(or 675 maybe) so the exhaust pipe really has some volume to breathe from.
So much for the fairy tale of high crankcase compression

Crank stuffers? An Aprilia RSW125 has a TDC crankcase volume of 650 cc. An RSA125 has 675 cc and a bit more power. See where this is going?

Frits has also mention previously that the Reed Valve Derbi that produced 49 (I think) HP after some work by Jan had an even larger crankcase volume than the RSW and RSA.

I remember Jan saying that the crankcase volume of the Derbi reed valve engine was even larger than that of the rotary engine. And after Jan had laid his hands on it, that reed valve engine was the strongest 125 cc reed valver ever.
You see, the volumes of the transfer ducts and the volumes between the crank wheels and inside the piston are largely equal, and the volume of the reed cavity is a lot larger than the volume of a rotary inlet duct.

When Jan Thiel went to Derbi to design the bike we now know as the Aprilia RSA125, he encountered the 125 cc reed valve Derbi ridden by Lorenzo the previous season. Jan played around with the reed valver as well, because he wanted to find out the differences between reed valve and disk valve power. He managed to extract 2 HP more from the reed valver than anyone else had ever done before (never mind the fairy tales of reed valve 125s producing over 50 HP; those Horses must have been Shetland ponies, probably measured at the piston ring).
My graph shows the power curve for the Aprilia RSA, the Aprilia RSW and that best-ever reed valve Derbi. It's not quite in the same league as the rotaries, hmm?

EDIT: Shame on me; I discovered that I posted a wrong graph (and I do not have the correct one at hand here in Holland). Power curve DERBILOR shows the reed valve Derbi as Lorenzo rode it. After Jan finished playing with it, it had 49 HP. Still, the best-ever disk valver produced 10 % more power than the best-ever reed valver.

Well 41 or so of the words are mine.
I wonder if there is any job opening for a Physicists secretary.
Click on the pics to make them bigger

[Martin1981]

Husa, thanks for your post. a rotary valve engine needs a big crankcase volume, i know that jan thiel and frits told us many times. but ask wobbly if a reed valve engine also needs the bigger the better crankcase. and the banshee engine IS a reed valver.

[husaberg]

Husa, thanks for your post. a rotary valve engine needs a big crankcase volume, i know that jan thiel and frits told us many times. but ask wobbly if a reed valve engine also needs the bigger the better crankcase. and the banshee engine IS a reed valver.

Reed the last couple of paragraphs of my previous post.
About the Derbi.

[Lef16]

For sure bigger case volume is better,but I think Jan Thiel said on pitlane that you need the most of the volume to be on the transfer ducts on the cyl and case transfers,will bigger volume between the crank webs help on BDC??
Plus,can tranfers like the RZ's handle a very big volume in the cases and also a fat Aprilia type exhaust?
Cheers

[Martin1981]

Ok, so what do you think wobbly? i am about to put my 1986 cr 125 engine together again. should i use the stock crankshaft with the sheetmetal tins that are "wrapped" around the crankwebs to reduce the crankcase volume or should i take the other crank that has the tins removed by me because thinking bigger crankcase is always better because Jan and Frits said so? i don`t know....

[Muciek]

You need to shoot for actual ccr number. ( They were mentioned earlier here , for membrane engine with good duct's , average, and rotary valve) And It was 1 post above that You want most of the volume above the crank wheels, with the crank "being without holes and empty spaces"...