i think kens idea of swing valve is pretty good. seems like frits agrees also
Hardcore Biker
i think kens idea of swing valve is pretty good. seems like frits agrees also
Anorak
They appear to be very Honda like in layout......Originally Posted by Muciek
Maybe it's time to use ATAC now to get rid of that torque dip at around 7000?
KTM FRR cylinder pictures off Pitlane ( http://www.pit-lane.biz/t118p20-gp12...tiques-ktm-frr )
http://imgur.com/a/JNQy1/all . Someone with higher rank could upload them to KB I can do only 6 per post.
Then again I understand so were Bartol Yamaha cylinders............
Kinky is using a feather. Perverted is using the whole chicken
Forum whore
Yes it would be a good idea.
Anorak
Where is lozza
Kinky is using a feather. Perverted is using the whole chicken
Forum whore
Hi Chris, glad to have you thinking along.
Having the transfer floors flush with the piston crown in BDC is very important for power. But one of the purposes of lowering the transfers is to reduce the power,
so temporarily dropping the transfer floors below BDC is not a problem at all.
There are two reasons for wanting to lower the transfers:
1: Normally the blowdown time.area is such that the cylinder pressure has dropped below the transfer pressure by the time the transfers open. But if the revs are very high, or if the transfer pressure is low because of a partially closed throttle, spent gases will enter the transfers, heat up the fresh mixture and so provoke detonation. Lowering the transfers while leaving the exhaust timing alone will increase the blowdown TA and solve the problem.
2: At revs below the power band the exhaust return pulse arrives back at the cylinder when the transfers are still open. This pulse then pushes the cylinder contents back into the crankcase. That's the cause of the torque hole at 2/3 of maximum torque rpm.
Lower transfers close earlier, so the exhaust return pulse has less opportunity to cause havoc.
In the latter case lower transfers will give more power. This in turn will influence the necessary throttle position. Hence my idea to get rid of the inlet throttling altogether and control the engine power via the transfer height. Not direclty, but via ride-by-wire, because both the engine rpm and the required power have an influence on the optimum transfer timing, so a little help from some electronics may be welcome. My ideal would be a linear relation between throttle and torque.
No8 Wire Extraordinaire
Ahh from your sketch I'd though you intended to move the top section to close the transfers. See I told you I'd get the wrong idea.
Don't you look at my accountant.
He's the only one I've got.
Bucket Racer/Crasher
You said something about a concern that your moving sleeve with the transfer ports would end up lowering the exhaust port at the same time the transfers were lowered. If the sleeve was manufactured using CNC machining it could be made say 1mm thick in the exhaust port area. The exhaust port in the sleeve could be made tall enough so that it never protruded into the exhaust passage and therefore never altered the port timing or area. The only drawback would be a slot in the exhaust port roof where the sleeve has risen when on the power and the transfers need to be fully open in the raised position. Being only 1mm as proposed it might not be critical. The trick will be machining the 1mm semicircular slot.
Actually I may have got your drawing wrong. I was thinking the surface the piston runs on is stationary and there was a moveable sleeve which had the transfer ports in which was raised and lowered. A further 2nd thought is the moveable sleeve does not require an exhaust port, or perhaps extending up to the base of the exhaust duct when fully raised, and therefore would not effect exhaust port height or T/A at all.
Last edited by speedpro; 6th January 2015 at 10:58. Reason: 2nd thoughts
Fair weather rider
And can you keep the sleeve free to move after it as warmed up?
Or how to maintain a good thermal path to the water jacket?
Forum whore
I've been doing some sketching based on the comma idea. I can be done, but I haven't yet figured out where to put the actuator linkages. These would get in the way of the coolant passages that don't show up on the sketches, so I'm not done thinking yet.
The lowered yellow comma reduces the transfer timing from 130° to 60°. That is an 80% reduction in area and a 91% reduction in angle.area, which should be good for idling at about 2000 rpm.
The second picture shows how the lowered yellow comma fits nicely between the transfer duct sidewalls and the piston.
The blue comma on the left disappears into the transfer roof when it's completely up, but it will show some leakage at intermediate positions. I think I can live with that.
Hardcore Biker
There is a lot of area on top of the fingers for the blowdown pressure to act on. Do you think these would withstand a misfire or several?
Forum whore
In my sketches the fingers may appear thin, but remember that they are curved in two planes, so they are quite stiff.
The actuators may be spring-loaded so that any unforeseen pressure peaks can push the fingers either up into their recesses, or all the way down, where they can rest on the transfer floors.
Think of it: a misfire in the cylinder, for example because of a faulty ignition, may push the fingers down, so the misfiring will never reach the crankcase.
Forum whore
Is it just me, am I the only one who can't see the pictures you post Frits.
i'm a wanker
right click and go to open link
No8 Wire Extraordinaire
Just you Neil.
Don't you look at my accountant.
He's the only one I've got.
No8 Wire Extraordinaire
How about an expanding wax trapped in cavities actuating the commas like a thermostat?
As the engine heats up the performance gets better.
I haven't thought past the first corner, but I'm a big picture type of guy, the rider can surely work out the details.
Don't you look at my accountant.
He's the only one I've got.
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