ESE's works engine tuner

[Larry Wiechman]

But we're more excited by the intellectual exercise than the vulgar prospect of vast quantities of unseemly torque.

Aren't we?

Ironic quote from a KTM 1290 SDR rider.

[Frits Overmars]

So, if capacity isn't constrained, is just another tuning variable within an open racing class then where is the likely optimum capacity point?
If any one of the current capacity limited racing classes had that constraint removed then what would the trend be? Towards slightly larger engines based on similar tuning factors because it's easy power with few comparative disadvantages, or towards significantly more capacity with all of it's associated mass issues and likely tuning discrepancies but hugely flexible power?
Or does that depend entirely on the track size and surface? Case in point: I think the difference between 250 and 400 MX lap times are negligible, more dependent on minor track variations than available power, and I think from track to track the respective advantages for each is close to 50/50.

You had me thinking about road racing until your last sentence directed me towards agricultural racing.
In MX the power of a 400 cc or 500 cc bike is probably more than you can use on most tracks. What you can improve with more cubic capacity is rideability: no power band as such, but always sufficient good-natured, finely-doseable rear wheel torque without the need for gear shifting or clutch fiddling.
Half a lifetime ago I tested the Husqvarna 400 Automatic (3-speed with centrifugal clutches; later they also built a 4-speed along the same lines). It made me a much better dirt rider. In other words: the concept worked.

Improving rideability is also what the boys in MotoGP are doing: far too much power that's only good for long straights (Mugello) and a complicated Engine Control Unit to keep the rider alive.
The FIM in its immeasurable wisdom decided that the sport was becoming too expensive if every constructor developed its own ECU, so they all had to make do with the Italian Marelli ECU. Honda threatened to withdraw from racing altogether if this decision wasn't revoked, but in the end they went along. Ducati was happy because they were already cooperating with Marelli. Yamaha suffered, and is still suffering: they can't seem to come to grip with the Italian ECU.
Now everybody is experimenting with spoilers in order to keep the front wheel on the ground. It's not a development I applaud.
I'd like to see a nice victory wheelie whereby the wind gets under those spoilers and turns the wheelie into a backflip .

[Ocean1]

Now everybody is experimenting with spoilers in order to keep the front wheel on the ground. It's not a development I applaud.
I'd like to see a nice victory wheelie whereby the wind gets under those spoilers and turns the wheelie into a backflip .

There's probably a solution to be found lying around the aviation industry somewhere, but I suspect the need for that solution indicates that you're no longer operating a motorcycle.

As for the capacity variable, I spent a bit of time playing with machines denied that option, and I did find that the lack of development in that direction detracted from my understanding of the benefits to be had, there. So when I started playing with bikes with little or no constraints I was delighted with what was available from simply minimising mass and maximising capacity.

From a dirt riding perspective I'm interested in your experience with that automatic Husky. With that capacity and tune and a well tuned auto I would imagine traction would be somewhat enhanced, and I'm wondering if most dirt rider's typical use of power to selectively reduce traction as a control tactic is a genuine advantage in a traditional dirt bike, or if it's simply making best use of a less advantageous feature.

Ironic quote from a KTM 1290 SDR rider.

Yes, the SDR rider is aware that several on board computers are often of the opinion that his request for more power should be denied. You can tell, the dash lights up, and you're not dead.

[Larry Wiechman]

Yes, the SDR rider is aware that several on board computers are often of the opinion that his request for more power should be denied. You can tell, the dash lights up, and you're not dead.

The SDR is my first experience of only having a vote, not the final say, on throttle opening percentage. Experiments with turning the Motorcycle Traction Control off have resulted in profanity flowing like poetry.

[Ocean1]

The SDR is my first experience of only having a vote, not the final say, on throttle opening percentage. Experiments with turning the Motorcycle Traction Control off have resulted in profanity flowing like poetry.

SuperMoto mode.

[Muhr]

Regarding previous discussions, I think I would give the opportunity for further discussion with the following statement.
The only state of motion the gas flow has is that it is pushed and thus completely dependent on what is happening behind to be able to be pushed into an area with lower pressure, by the atmosphere or local atmosphere (closed crank compression).

[peewee]

wob about the aux windows extending into the wristpin cavity . have you ever tried to determine any power increase from extra sta vs any power loss from short circuiting ? assuming a tear drop shape to keep short circuit small as possible , along with good aux passage geometry

[SwePatrick]

Regarding previous discussions, I think I would give the opportunity for further discussion with the following statement.
The only state of motion the gas flow has is that it is pushed and thus completely dependent on what is happening behind to be able to be pushed into an area with lower pressure, by the atmosphere or local atmosphere (closed crank compression).

Don´t forget speed and the increasing inertia that follows speed.

[SwePatrick]

My 211cc kawasaki project?

I had a lot of issues.
Carb is shaking hard and foaming fuel, have been designing a balance shaft system, it works, but need to sent away to get hardened.
It broke the cylinder, the deckplate came loose, have been strengthening that, it works now.

So today i was curious if the new cylinder and pipe produced any power as it sounds amazing, no balanceshaft mounted as i don´t want to run the gears without heat treatment.
Yes, still have issues with foaming, but in the dynopull below i reached for the carb with my left hand and hold it to dampen the vibrations.
You can see on the curve, a huge dip, it started to make power instantly when holding the carb.
But,,,, either the clutch started slip hard or the tire spun on the roller, or both.
After the pull the reartire was quite hot.

Last year a pull took about 7seconds starting at 8000rpm and up to 13200rpm, this when producing ~68hp to the roller.
This year a pull took 2.97seconds starting at 8000rpm and up to 13200rpm(the same) but only produces 50.95hp
Datalog from dyno shows about ~150% slip at where peak power should be, 12600rpm

But in all the disaster i still see some light.
more traction and more weight on the clutch should do the trick.
I´m aiming for about 70hp to the roller

[wobbly]

There is a direct relationship between the available STA/power increase by extending the Aux around to the bore center , but its how you implement this that sets the
amount of port linking and thus the amount of short circuiting.
Assuming no pin plugs its a very tricky compromise.
The solution is two fold, one is the teardrop shape , this adds area at the top of the port where the pressure delta is the greatest , and thus the flow.
Then the second element is the depth of the Aux port " pocket " if you like at the top corner near the bore center.
Ideally a nice big deep radius would seem to be the best way to add flow , but all this does is dramatically increase the linking area , and the trade off is badly in favor of short circuiting reducing the trapping efficiency
and thus power.
So you juggle the height of the port at bore center, and make its exit into the duct all but tangent to the bore thus keeping the linking depth to a minimum.
This makes the best compromise and the best power with no plugs.

Re the previous question about B hooks - the radiused hooks Cd is so hugely superior that it always seems to make more power even keeping the same directional exit angle.
The optimum angle may in fact be quite different , but I have never had the opportunity to do conclusive tests that kept the Cd increase,and then made even more power by adjusting the angle and improving the trapping
and or scavenging ratios.

[Muhr]

Don´t forget speed and the increasing inertia that follows speed.

Sad to see that it went to pieces! On the positive side, you know that you probably have a cylinder pressure over 850 psi for that to happen
Do not know what you mean by that, maybe my english or rather my lack of it that is the problem. You may mean that I was un accurate about when you reach atmospheric pressure and crank compression begins and ends.

[1948rod]

Wobbly or others have you any experience with tuning aimed kf1 engines.

[1948rod]

Sorry spelling came out wrong. Should be Iame kf1 engines

[Makr]

Not at all. Mark used brute force to destroy one of his pistons to the extent that the piston pin was torn out of its holes, but the thread remained impeccable.
I have pictures but I'm not sure I'm at liberty to post them.

Yes you can share them.

I have redesigned the piston anyway with the dome and pin boss as one piece and the skirt that threads on.

[Frits Overmars]

Mark used brute force to destroy one of his pistons to the extent that the piston pin was torn out of its holes, but the thread remained impeccable. I have pictures but I'm not sure I'm at liberty to post them.

Yes you can share them. I have redesigned the piston anyway with the dome and pin boss as one piece and the skirt that threads on.

Thanks Mark. Here is that destruction picture I was talking about.


Are you going to combine that 'piston skirt that threads on' with Denver Lawson's inside-out L-ring that should make ring-guiding bridges superfluous?