ESE's works engine tuner

[husaberg]

https://www.kiwibiker.co.nz/forums/a...hmentid=309051
https://www.kiwibiker.co.nz/forums/a...hmentid=309050

you can also attach a image as a address of the net instead of off your files

[ceci]

This is the first version i tested, to get the valve as close to the port as possible i removed the power valve, to get it running on the dyno it needed a lot of clutch,we learn as we go.
The camshaft i made had a lot of dwell, valve fully open when piston opened the port, stayed open until BDC then fully closed when piston was half way up the port.That was my theoretical
plug, it was not a bad guess going by the sound of the engine running.Obviusly this is were
R&D time must be spent.By having a solid close of the exhaust valve will allow for additional
inlet pressure to be added and will also stop fresh fuel mixture escaping.
Now version two is nearly ready for a run.

Excuse my impatience.
From reading the description of your mechanism, I liken it to that of this other one.
They may be similar

[folke]

Post no longer wanted

[ceci]

the advantages of using a cam mechanism are that you model the times more appropriately, in the mechanism that I showed it has more limitations, in the BDC the exhaust port does not remain completely open

[Frits Overmars]

My hand is shaking as I write this , consumately aware of being stabbed in the eye with one of your intellectual forks by contradicting you Frits, but there is an easy way of incorporating a starter motor into a dyno setup as well as a safety sprag overun clutch for the spinning inertia mass.
The left hand chain comes from the sprocket and direct drives the secondary shaft.This has the starter motor flex plate on the RH end, so when the starter sprag engages it drives the test motor for firing it up. The PTO tractor sprag is internally connected to the jack shaft, and its outer is connected to the central sprocket/chain that drops down to direct drive the inertia wheel.
Whenever the inertia drum rotational speed exceeds the output sprocket speed, the sprag overuns, in effect allowing the engine to stop instantly.

The starter motor flex plate might object to that sudden stop. It may have much less inertia than the flywheel, but it may still be enough to grind the engine to grit.

The Corona virus seems to affect us in curious ways. In your case, it apparently stimulates a literary vein that I never suspected in you, Wob.
Stabbing you in the eye with a fork, it could have been written by Shakespeare.
You do know, don't you, that I have the highest regard for you. I would never puncture your eye, at most a tire from your chair .
See? That is what Corona does to me. The deprivation of social contacts seems to be turning me into a monster. Normally I am the gentlest guy out there. I would never intentionally hurt a tire.

The camshaft i made had a lot of dwell, valve fully open when piston opened the port, stayed open until BDC then fully closed when piston was half way up the port.That was my theoretical plug, it was not a bad guess going by the sound of the engine running.Obviously this is were R&D time must be spent.By having a solid close of the exhaust valve will allow for additional inlet pressure to be added and will also stop fresh fuel mixture escaping.

This begs for some form of supercharging Folke. Something like this, maybe?

Your asymmetric exhaust timing would enable real four-stroke-like supercharging, which could make Formula 1-two-strokes feasible, and we could substitute our bulky expansion chambers with a small after-the-turbo muffler. Or in the case of F-1 no muffler at all; they want noise. Well, two-strokes are your friends.

Come to think of it: if we use a mechanical compressor instead of a turbo, we no longer need crankcase pumping to start the engine.
That allows for another four-stroke benefit: pressurized lubrication for all crankshaft bearings. F-1 is coming nearer and nearer, even without opposed-piston technique, because I doubt (sorry Flettner) that an OP-engine would tolerate so much phase offset that the exhausts would close well before the transfers.

Instead of a camshaft plus valve, did you ever consider using a rotating drum parallel to the crankshaft? I think the drive could then become noticeably simpler.
Maybe a hollow drum (# 4) rotating around a stationary core (# 10 + # 11) like MZ was planning in 1960 (lack of funds prevented MZ from actually building it).

[Pursang]

Technical Puzzles for the Socially Isolated. #1

I'm prepping a 1984 Maico 500TE for general off-road use.
A very rare beast , air cooled, reed valve, compliance plated for road legal.
Very little info available for this year anywhere on the net, and then only the SC(MX) model.
Hopefully someone here has knowledge & experience with these.

Pulled the barrel to check for wear. Oversized 88mm piston & bore, still in spec.
(though looks and feels like the ports weren't chamfered/dressed at last rebore).
No holes in piston for reed valve use, but Boyesen style ports into the transfers.
Does this seem correct or does it have an earlier 490 non-reed piston?

My major problem is this: At BDC and with top of piston flush with floor of exhaust port, the piston lip is above the transfers bottoms by close to 3mm.
The step looks like a serious impediment to transfer flow. (This is very strange and I wonder if it was perhaps a dodgy way to de-tune the SC for enduro use)
If I pack the bottom of the cylinder, to lift the transfers flush with the piston, I will be increasing Ext duration from around 188 to 196!
One of the main benefits of the 500 is the amount of instant torque at low revs.
Is the increase of transfer flow likely to balance the earlier opening and extra duration of the raised exhaust? ie. no nett loss of lower RPM torque
I'm happy to leave the new 3mm step at the bottom of the exhaust port.

3mm seems a lot to remove from the top of the cylinder as it will be cutting away the lip at the top of the liner! (Or 2mm if I eliminate the original head gasket)
Does it sound reasonable/ sensible / practical to machine the alloy cylinder and leave the liner lip proud, to form a spigot? (Bultaco style, with a matching recessed groove in the head).
Or is it better to just shorten the cylinder and leave the head and gasket stock (+/- squish clearance adjustment)

Any advice will be appreciated,
cheers, Daryl.

[Frits Overmars]

What would raising the cylinder by 3 mm do to the transfer timing Daryl?

If you raise the cylinder, I'd prefer to modify the head so it intrudes into the bore. Finding a head tends to be simpler and cheaper than finding a cylinder. And welding additional material to the head, if done carefully, can be undone.

[F5 Dave]

Daryl, many engines are as you describe, which is not ideal but raising the exhaust port to crazy for a 500 is unlikely to make you happy, or increase your crank life. If it makes you feel better every engine spends most of the time with the piston in a worse position than that.

You could consider filling the floors but transfer floors are the devil to work on. 88mm bore is a luxury not encountered mind.

I'd sew it back together as is and spend my attention replacing that Bing with a nice new Keihin.

[Frits Overmars]

F-1 is coming nearer and nearer, even without opposed-piston technique, because I doubt (sorry Flettner) that an OP-engine would tolerate so much phase offset that the exhausts would close well before the transfers.

Me and my big mouth. This will teach me not to express an opinion without first checking whether it is correct.
It dawned on me that I have an easy way of checking: the HCCI program that I wrote some time ago for you, Neil.
Here's what I did: 130° transfer timing , 140° exhaust timing, with the exhaust crank 30° advanced relative to the transfer crank, so the exhausts will open 100° before transfer-BDC, which gives a conventional 35° blowdown angle.
And the exhausts will close 40° after transfer-BDC; 25° before the transfers close, so there is 25° available for supercharging. And it could easily become even more, if need be.

[Frits Overmars]

The 30° phase offset in the above example is much less than what I'd expected to be necessary. It made me think of a DKW opposed-piston bike of 1949,
the US 250 (nothing to do with the United States of Trump).

[Larry Wiechman]

What became of the Beare Six-Stroke? Death by lawsuits? http://www.sixstroke.com/index.html

[yatasaki]

Napier deltic had 20° advance on exhaust piston. Opening exhaust before scavenging (transfer)ports ( it is a diesel) in adittion with 20° resulted in exhaust closing before...transfers. So transfers became supercharging ports.

[Flettner]

Me and my big mouth. This will teach me not to express an opinion without first checking whether it is correct.
It dawned on me that I have an easy way of checking: the HCCI program that I wrote some time ago for you Neil.
Here's what I did: 130° transfer timing , 140° exhaust timing, with the exhaust crank 30° advanced relative to the transfer crank, so the exhausts will open 100° before transfer-BDC, which gives a conventional 35° blowdown angle.
And the exhausts will close 40° after transfer-BDC; 25° before the transfers close, so there is 25° available for high-pressure supercharging. And it could even become more, if need be.

Frits, I should never have forsaken the uniflow concept . Im convinced its the way ahead, now, with revised transfer scavenge and the ability to HCCI relatively easily plus crank phasing.

Im committed to building this single cylinder uniflow engine for some experiment and off road use. BUT Im also now keen to get back to building an Autogyro twin cylinder uniflow using this new scavenge system but still the ''cross transfer'' , two crankcases into one cylinder. After all it work so well on my now 25 year old uniflow boat engine.

But first I have to get this 360 going.

[Pursang]

What would raising the cylinder by 3 mm do to the transfer timing Daryl?

If you raise the cylinder, I'd prefer to modify the head so it intrudes into the bore. Finding a head tends to be simpler and cheaper than finding a cylinder. And welding additional material to the head, if done carefully, can be undone.

Daryl, many engines are as you describe, which is not ideal but raising the exhaust port to crazy for a 500 is unlikely to make you happy, or increase your crank life. If it makes you feel better every engine spends most of the time with the piston in a worse position than that.

You could consider filling the floors but transfer floors are the devil to work on. 88mm bore is a luxury not encountered mind.

I'd sew it back together as is and spend my attention replacing that Bing with a nice new Keihin.

Ah Ha! Raising the cylinder flattens the transfer flow and increases the transfer port area by 17% (at the short end of the sta). But it also lifts the transfer timing from 130 to 140.

An 88mm piston bouncing at the revs required to work with 196 ext and 140 transfers is probably not something that should be put between your legs!
My Crank Life is precarious enough at the moment anyway!


I think I will follow Dave's advice, a new carb will improve the reliability and rideability and that's what this thing needs, most of all.

Thanks Frits & Dave for the reality check, Hang in there everyone, during these most interesting times!

cheers, Daryl.

[ceci]

This is the first version i tested,
Now version two is nearly ready for a run.

the photos are from the 1st or 2nd version.
The truth that his approach has made me see details in other prototypes that had escaped me, Frits showed photos of one with a rotary valve on the exhaust, the details that I see are that an artificial negative pulse is created caused by the Zhukowski pulse.