ESE's works engine tuner

[bucketracer]

Attachment 264100

The Red line is the smaller crank with 2mm clearance. (the original post is on page 155) I am not sure why the improvement is all at the bottom end and drops of earlier at the top.

Helmholtz frequency, my dear Watson. The smaller crank will give the pipe more crankcase volume to breathe from. This larger volume will also lower the resonance frequency of the inlet system, hence the drop at high rpm. It can be compensated with a shorter inlet tract, a bigger carb diameter and a later inlet closure.

To put it real simple: if you have more volume, you need more time to fill it.

Now that makes sense .....

[bucketracer]

Page 520 .... the last ten pages were mostly about what some wheels weigh, ATAC valves and crank stuffers.

More questions for the wise ones,
How good does the seal around the butterfly need to be : should there be clearance to allow for expansion of the flap ??
How critical is it to have the butterfly open into the ex, stream? ( mine is going to be about 5mm from the inside wall of the header when open and close to 10 when closed )

I am not wise but if you have a look on Ebay Cr125 about 1986 there are plenty. Remember it opens Parallel to the flow as well not into it.

IE with the butterfly offering as little as poss restriction to the flow as possible.
You can bet big money Honda did a fair bit on testing to come up with there configurations for the std bikes.The bottom one has a spacer to increase volume.


NS400r not so many around



Atac valves

To increase low end power Wobbly has pointed me towards the Honda ATAC system, he tells me that they had some success with the idea on the BSL500. He sent me this picture and some pointers on where to put it on the header.

Attachment 241414

"As close to the flange as you can, and get the throttle plate as close to the header as you can to reduce the ill effects when its closed at hi rpm......... Wob"

Other Bits and Bobs about the ATAC system that I scraped from the net........

ATAC System: The Honda Automatic Torque Amplification Chamber system works by effectively increasing or decreasing the volume of the exhaust system with a small butterfly valve located just before the exhaust connection.

A few pictures here:- http://www.scooterhelp.com/moto.barrels/honda.cr250.84_85.overview.html
A bit of YouTube of a guy working on his ATAC http://www.youtube.com/watch?v=tY7D0jLcfws

Atac and vtac differ very little. Vtac is a resonator chamber like kips, with only one inlet/outlet where atac is a bypass chamber with a in and out yet it doesn't block the main exhaust flow even when open so it very much acts like a resonator.

Attachment 241367 Attachment 241376

[ATTACH=CONFIG]241373[/ATTACH

The throttle plate or whatever you design must seal well.
I did a sliding flat plate with a hole in it design like they use in fuel injection throttle plates, that worked well on Champ winning jetski, as this got the plate real close
to the header and there was very little flow disruption when closed.
A small leak into the cavity will kill power real quick with an ATAC system.

Geee those bare wheels don't weigh much.

Std RS front 6 lbs or 2.7kg and rear 7 lbs or 3.2 kg.

Conversion assistant http://www.convertunits.com/from/lbs/to/kg

I weighed a set of RS wheels with disk tire sprocket etc.

RS complete Front wheel 8.0kg complete Rear wheel 9.5kg

compaired to:-

Wire complete Front wheel 9.0kg complete Rear wheel 9.5kg
FZR complete Front wheel 9.0kg complete Rear wheel 12.0kg


Complete RS swing arm 3.5kg and FZR swing arm 4.5kg.

Although I am not that convinced about the accuracy of bathroom scales for measuring anything, they at least give an indication of the wheels relative weights.

I might have a FZR400 front, I will dig it out and have a look.

Interesting clip on pipe building, I often wondered how they get those nice neat welds.

So this is where I am up to so far, Butterfly valve seems to be a long way from the header ID so plan B is to make up a spool valve like a Yamaha power valve and fit it in the same place as the collar which is currently on the header so that the OD of the spool is flush with the header ID when closed .
Attachment 263880Attachment 263879Attachment 263881

So TZ , say you were thinking of making your own barrel , engine or even spacecraft. You could read this thread http://www.homemodelenginemachinist....?topic=18727.0 and steal and adapt some of this guys rapid prototyping ideas.

There is a bit more to a tubeless rim than just airtightness. A tire with an inner tube can move a bit in its bed without dire consequences because the tube will A: contain the air, and B: push the tire back into position. Tubeless tires do not have this luxury. Therefore a tubeless rim has humps at the inner sides of the tire bed to keep the tire firmly in place and sealed at all times.
99% of tube-type rims have no inner humps. If you fit tubeless tires on them, you are flirting with death. That is not an exaggeration; it has happened.
If you insist on wire-spoked wheels with tubeless tires, be sure to use dedicated rims with inner humps.

Dont worry I not one of them, why would the mixture come from round the spinning cranky things , there is nothing going on there to pump anything, my mental moddeling just has a blob of gas mix under and around the piston that gently bumps the mixture waiting in the transfers into the cylinder. With what frits says about the rsa and rsw ccv's , would indicate that the pipe is more involved than the crankcase compression in filling the cylinder

In saying that Wobbly is using some aluminium stuffers on my crank, i think this has to do with the paddle problem.

in this thread is the stuffing http://www.kiwibiker.co.nz/forums/sh...post1130142699

I've seen a crank in a bucket with screws into the crank webs and then carbon string wound all round them and then resin tipped in while the crank was in a mould. End result carbon-fibre filler for a full circle crank.

Good point, Dave; in fact several good points.
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 left, 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 right 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.....

Interesting about the Toroid head.

I have just re-checked, and Ooops I refered to the wrong post and graph.

Attachment 264100

The Red line is the smaller crank with 2mm clearance. (the original post is on page 155) I am not sure why the improvement is all at the bottom end and drops of earlier at the top.

Helmholtz frequency, my dear Watson. The smaller crank will give the pipe more crankcase volume to breathe from. This larger volume will also lower the resonance frequency of the inlet system, hence the drop at high rpm. It can be compensated with a shorter inlet tract, a bigger carb diameter and a later inlet closure. To put it real simple: if you have more volume, you need more time to fill it. But more time, i.e. later closure, has adverse effects at low revs. So my preference is a shorter tract (unless you go the 24/7-way and employ a reed for the low revs, and swing it out of the way at high revs).

[Frits Overmars]

To put it real simple: if you have more volume, you need more time to fill it.

Now that makes sense .....

Specific Time Area explained in 12 words. It's not yet as short as E=mc² , but I'm working on it .

[F5 Dave]

so if TZ is working with a 24mm carb restriction he has likely found the limit of crankcase volume. Fortunately my 100 will run any size carb I wish.

Thanks for the insights Frits, it has simultaneously confirmed\challenged\turned a few of my idea upside down.

So I'll have to think a bit more, but I definitely have some things to work on.

[Frits Overmars]

You're welcome, Dave.

so if TZ is working with a 24mm carb restriction he has likely found the limit of crankcase volume.

To the superficial reader that would seem as if the crankcase volume was too large. I would prefer to formulate it like this: TZ350's combination of crankcase volume, inlet tract length, inlet diameter and inlet timing is running out of breath at high revs.
I would rather shorten the tract, increase the diameter (if allowed) or lengthen the timing, in that order, and preserve (or even enlarge) the crankcase volume.

[TZ350]

interesting article:
http://motortecmagazine.net/article.asp?AID=1&AP=1

Far to many strokes for my liking; but horses for courses.

Thanks Bert, that was a very interesting read ....

[bucketracer]

TZ350's combination of crankcase volume, inlet tract length, inlet diameter and inlet timing is running out of breath at high revs.

I would rather shorten the tract, increase the diameter (if allowed) or lengthen the timing, in that order, and preserve (or even enlarge) the crankcase volume.

Increased inlet diameter (24mm taper bored carb) and shortening the tract length (short pumper cart carb) and inlet closing points as late as 85 ATDC have been tried and got worthwhile results.



TeeZee's idea of a plenum was to get around the restriction of a 24mm carb by allowing the motor to draw through an increased inlet diameter from a plenum full of fuel mixture.



Changing the length and diameter of the inlet runner is easyish.

I think TeeZee has plans to re visit this idea so he can increase the crankcase volume. Fuel dropout and guarantied lubrication were problems encountered with the initial efforts with the plenum.

[wobbly]

Back from forced holiday - happy to give you a 115 racing style RD400 rod to help increase case vol TeeZee.

[TZ350]

Back from forced holiday - happy to give you a 115 racing style RD400 rod to help increase case vol TeeZee.

I would be interested in looking at that.....

Got a few things to do first though, I am away all of next week to Greymouth, when I get back I want to get the Beast running again and test a 30mm carb in back to back tests with the 24. If the 30 gives more power, ie the 24 has started to choke then it will be worth giving the plenum another shot.

On the side I am building a completely new motor with a much bigger inlet, I would be interested in running the RD400 rod and some Mallroy slugs for ballancing in that.

[Yow Ling]

While I was messing around with this other engine, I realised it would be possible to use it to experiment with Frits's 24/7 concept.
As it has both a reed induction system and a rotary valve, I figured it could be made to work if it was possible to control the slides of 2 seperate carbs independently without too much brain strain for the rider. I tried thinking of mechanical means to do this but failed miserably.

So if we had 2 carbs and one twist grip why not use 2 servo's one for each carb and a potentiometer connected to the throttle control.
ther would be no rv where one used to be, but that carb would stay closed untill the engine was making power, when the servo controlling the other carb would close the reed carb slide and another servo could open the rV carb.

Its not really any different than the fly by wire throttle on some motoGP bikes. might be a bit tricky to manage the transition
Could use stepper motors instead of servos

[TZ350]

While I was messing around with this other engine, I realised it would be possible to use it to experiment with Frits's 24/7 concept.
As it has both a reed induction system and a rotary valve, I figured it could be made to work if it was possible to control the slides of 2 seperate carbs independently

Thats clever thinking, I am impressed ......

[husaberg]

While I was messing around with this other engine, I realised it would be possible to use it to experiment with Frits's 24/7 concept.
As it has both a reed induction system and a rotary valve, I figured it could be made to work if it was possible to control the slides of 2 seperate carbs independently without too much brain strain for the rider. I tried thinking of mechanical means to do this but failed miserably.

Why can't you use a split cable with a cam to control the opening with another ramp or linkage like a XR250 RE/RF or a control box like a Twin Carb Starmaker?
Failing that plenty of cars have old 2 and 4 barrel equipped have mechanical secondaries.

The fly by wire is cool as you could program in the feel and adjust for trottle response say slower in lower gears or wet (traction control) etc. A lot of cars have them Falcons etc

[Yow Ling]

Why can't you use a split cable with a cam to control the opening with another ramp or linkage like a XR250 RE/RF or a control box like a Twin Carb Starmaker?

Because by doing it with electronics you can control the overlap etc easily , using a cam means having lots of cams to try and get it right

[husaberg]

Because by doing it with electronics you can control the overlap etc easily , using a cam means having lots of cams to try and get it right

Look above (ie the last line of my post) I think you replied why i was looking for a picture of the Starmaker set up.

You of course need not have to make so many cams just ones with a lot of holes on differing radius and he transition could be controlled with cable adjusters. Not as trick obviously as electronics.

Talking with Yow he said of course he wants to totally shut the first carb when the second will open (when switching over to the disk induction.)
I was trying to think of a linkage that works like that that like a trigger on a rifle or a overcetre on a wind up toy etc.
when i thought why not a ratchet mechanism like a kick start. For the primary carb?

[Frits Overmars]

While I was messing around with this other engine, I realised it would be possible to use it to experiment with Frits's 24/7 concept. As it has both a reed induction system and a rotary valve, I figured it could be made to work if it was possible to control the slides of 2 seperate carbs independently without too much brain strain for the rider.... There would be no rv where one used to be, but that carb would stay closed untill the engine was making power....

You might want to take a look here: http://kreidler.nl/forum/viewtopic.php?f=5&t=38866 . Don't be put off by the writing; that is what Dutch looks like.
Never mind, all pictures are in English and so is the video ( http://www.youtube.com/watch?v=tMDJcSqpImM ).

In the video the piston-controlled carb is set for a high idle. The second carb is opened much too early but nevertheless you can hear it is contributing to the revs.
Getting the carburation spot-on may become a nightmare though. Closing the first carb while the second one opens, will not make much difference so you may as well leave the first one open. But clean carburation is essential for lap times. That is why I want injection (is that allowed in bucketracing?)

The above example with a piston-controlled inlet plus a permanently open inlet is one of the options I considered over the years. But I think he simplest solution is my present approach with just one inlet, just one carburetter (until the injection becomes available) and a simple reed that is swung out of the way (can be done by the powervalve-servomotor).