ESE's works engine tuner

[wobbly]

We Know for a fact that on a 54.5mm stroke race engine lifting the Ex floor several mm made more power.
It was tested properly in a real back to back by Mr Thiel.
Blindly thinking lifting it more will automatically be better is a dangerous assumption, and could well end up like most assumptions
in just being an error waiting to be revealed.
Sure a longer stroke would need alot more, but how much has still actually to be tested properly.
TeeZee tested it on a cylinder that was a good one, he buggered that up in some way, then added a high floor or dam and made it better.
Not very conclusive or scientifically relevant to a non buggered up cylinder.

[husaberg]

Forget Ryger, forget homologation, the oil less aspect is real I can show that in a running example. The lack of fuel out the exhaust is also a reality with delayed port injection, also displayed in a running example (different engines) but the tech is out there now. 70 hp at 17500, well thats the problem, how? I have my "team" working on that now.

If the ring was retained so it could just stick out microns, to do the sealing job but not enough to catch in the port, you could have a huge "one" exhaust port. Remember the piston is not wearing against the bore any more. That would give a large exhaust port AREA. No oil carbon to cause the ring to stick.

Interesting times

Kaaden unsuccessfully tried ringless pistons. But his access to metallurgy was known to be poorer than the Japanese or Europeans. yet the Japanese and Euros never went this route either.
Your post there got me thinking about how one some of the tiny aero engines have no rings Secondly if anyone had ever tried a piston design with a Lab type combustion seal arranged of multiple grooved pockets.
Maybe with a better guided piston ring friction and the breaking of seal with tilting is not an issue and design can be different

I do however thing the limiting factor of high speeds breathing limitations was due to blowdown rather than total port area of the EX port. So it might be moot.

[TZ350]

Page 1260 ...

We Know for a fact that on a 54.5mm stroke race engine lifting the Ex floor several mm made more power. It was tested properly in a real back to back by Mr Thiel.

For comparison Honda Rs Scavenge

If you look at the porting from side on you will se why it is they are arranged like this.
The scavenge pattern is arranged to prevent short circuiting and have the rising columns colliding in such a manner that the they do not escape and are able to fill the cylinder both quickly and efficiently.

Frits from memory did a nice piece on it around xmas 2 years ago
http://www.kiwibiker.co.nz/forums/sh...post1130452977


Pretty sure I have pics of a cut up Honda cylinder.
http://www.kiwibiker.co.nz/forums/sh...post1130766509

Plenty of RS pics here
http://www.kiwibiker.co.nz/forums/al...id=4841&page=7

The KTM is worth a look pretty much a Honda.
http://www.kiwibiker.co.nz/forums/al...p?albumid=4857

One you posted years ago
http://www.kiwibiker.co.nz/forums/sh...post1129196083
http://www.kiwibiker.co.nz/forums/at...6&d=1241260771

There are a few clever enough people ( like Holzer at Modena ) working on kart engine design that I am sure enough R&D has been done to establish if the basic ideas behind Jans Aprilia scavenging works "better" than the current monkey see monkey do Hondarish arrangement.

Problem is that we are dealing with a very different apple to the GP Aprilia. It has a power valve and a mile of clever electronics - a KZ2 has neither.

I have replicated the actual port timing layout ( lower but with B,C opening first ) and this makes considerably better power from peak onwards,but what it gains in overev it looses way more down at 9000.

This is the rpm when exiting the slowest hairpins ( usually only once per lap ) but it is just way too slow at this point that lap times suffer excessively.

I also have replicated the Aux ports ground around to bore centre, and this also makes a HUGE gain in overev power and useable rpm. But in this case it looses some 1.5 Hp at 9000, and this can be got back with plugs in the small end pin.
This loss is easily offset by the fact we can add another tooth on the back and rev it alot harder ( 15,000 ) - lap times drop,so that is a worthwhile gain.

The extra rpm available also allows deleting several between corner gearchanges, again making faster lap times.

The other problem is that it is a big mistake to assume that simply replicating one small element of Jans concept will be a positive step for any old port arrangement.

I know others have tried to add material to the B duct front face, making the wide septum entry, but this then completely changes that front walls entry angle into the cylinder - and this for sure is doomed if the whole reverse stagger,axial angles scenario etc etc isnt used as well..

Those complex 4 stroke behemoths typically flow 70% intake to 30% exhaust, statically on a flow bench.Any ideas what the 2 stroke is statically (obviously pipe is doing quite a bit in the running model)

I can see a long winded answer emerging, Lifting the floor 3mm AND adding 3mm to the bottom corner rads by welding as far in as I could get ( about 20mm ) from the port added around 5% power everywhere in a 125 ie 1 in 20 at the bottom and 2 in 40 at the top,plus slightly more in the overev.

But I stress there is just as much to be had by optimizing the duct exit and spigot geometry.
You are right peewee, make it 3mm high, and add a fillet piece at 6mm high as a test.

The issue with any add in piece is that it wont be cooling the retained slug of A/F in the duct bugger all and this will detract from its overall performance..

There is no correlation to anything with the Ex area below transfer opening, apart from what I mentioned about reducing short circuiting from the A port.

EngMod cannot predict the effects on scavenging and or trapping efficiency when you change the Ex area below TPO, its not a 3D CFD flow visualizer like Fluent etc.

Re the flow regime in the transfer ducts and the Ex duct.
In good designs where everything is pretty much optimized you find that the areas of the ports ( and the intake ) converge.

In fact this is the first element to be looking at in the STA analysis from EngMod - check the 3 areas and go to work on the smallest first.

The Cd will be different but effective flow is way more like 50/50 than what we see in a 4T.

Let's assume a port width of 65% of the bore. Then you can calculate the vertical half-axis.



The minimum safe vertical half-axis becomes
0,7 x (port width / cylinder bore)^4,57 x cylinder bore
= 0,7 x 0,65^4,57 x cylinder bore
= 0,09775 x cylinder bore

Converting this half-axis into center and corner radii can't be done with a simple formula, so I'll do it for you, once-only.
center radius = 88% of bore
corner radii = 5,2% of bore

On the bridged port NiCasil MX engines that I still occasionally do, I send cylinder off with no port chamfering... and instructions for them to not do any chamfering. I only radius top edge of ex port. All other ports I don't even touch. I believe this helps with short circuiting, and a nice consistent transfer opening. Never had a problem with rings

[jonny quest]

Those complex 4 stroke behemoths typically flow 70% intake to 30% exhaust, statically on a flow bench.

Any ideas what the 2 stroke is statically (obviously pipe is doing quite a bit in the running model)

This may give some insight into single Ryger exhaust.

The RSA did what it could with a typical 2 stroke layout.

Very exciting to see this engine development completely outside the box. Basically changing 65 years of development work.

Could you imagine the impact this would have had 10 years ago on the industry?

[peewee]

wobbly im sure the most logical approach would be to start with the floor at bdc and raise until theres no more power but thats alot of work and without a way to measure power you (i) might as well piss in the wind. im still a amatuer with engmod but can it predict any gain from raising the floor ? if i grinded the floor lower i could bring it back up with a dam but anymore welding is out of the picture as the cylinder would just be warped to buggery once again. if nothing else i could just go straight to 2mm and call it good as i would probly see a benefit as well

[karter444]

We Know for a fact that on a 54.5mm stroke race engine lifting the Ex floor several mm made more power.
It was tested properly in a real back to back by Mr Thiel.
Blindly thinking lifting it more will automatically be better is a dangerous assumption, and could well end up like most assumptions
in just being an error waiting to be revealed.
Sure a longer stroke would need alot more, but how much has still actually to be tested properly.
TeeZee tested it on a cylinder that was a good one, he buggered that up in some way, then added a high floor or dam and made it better.
Not very conclusive or scientifically relevant to a non buggered up cylinder.

Big thanks to Wobbly for his advice on shortening the flywheel trigger lobe to fix our engine misfire , it worked . Did our fastest lap of manfield on our no 3 engine . 1.11.8 ,need to find another 1 sec improvement to our race pace , may need some help with that .
I was going to ask a couple of questions regarding exhaust port floor height , you have answered some in the previous post but I will ask some anyway
1. whats the relationship between the pipe , transfer opening duration and the lower half of the exhaust port
2,what is the limiting factor in closing the exhaust port much earlier ie same as transfer opening
3. you said power increased when the port was floor was raised , how much power do you think would be gained and where in the rev range
4. can this be tested on your engmod programme
5. would a alloy plate shaped to fit the port and tack welded into the port duct be ok to test this as welding a port completely may render the barrel useless
cheers

[wobbly]

I can see a long winded answer emerging, but I think less is more in this case as its Friday and we are working up to an AB win..
Lifting the floor 3mm AND adding 3mm to the bottom corner rads by welding as far in as I could get ( about 20mm ) from the port
added around 5% power everywhere in a 125 ie 1 in 20 at the bottom and 2 in 40 at the top,plus slightly more in the overev.
But I stress there is just as much to be had by optimizing the duct exit and spigot geometry.
You are right peewee, make it 3mm high, and add a fillet piece at 6mm high as a test.
The issue with any add in piece is that it wont be cooling the retained slug of A/F in the duct bugger all and this will detract from its overall performance..
There is no correlation to anything with the Ex area below transfer opening, apart from what I mentioned about reducing short circuiting from the A port.
EngMod cannot predict the effects on scavenging and or trapping efficiency when you change the Ex area below TPO, its not a 3D CFD flow visualizer like Fluent etc.

Re the flow regime in the transfer ducts and the Ex duct.
In good designs where everything is pretty much optimized you find that the areas of the ports ( and the intake ) converge.
In fact this is the first element to be looking at in the STA analysis from EngMod - check the 3 areas and go to work on the smallest first.
The Cd will be different but effective flow is way more like 50/50 than what we see in a 4T.

[speedpro]

#2 there would be zero blowdown.

[husaberg]

#2 there would be zero blowdown.

*2 would also result in about 128-136 degrees of Exhaust duration, Which would be number twos. At most revs above idle.

[ken seeber]

Ringless pistons. Of course rings add friction, but the trade-off is that they also provide the proportional sealing of pressures, up to around 90 bar (1300 - 1400 psi) at all sorts of rubbing speeds and high temperatures, not a trivial task. Should they fail, as we’ve all seen with a stuck ring; blowby, loss of lubrication and death.
In a small engine, say a glow plug, one seemingly can get away with it, mainly due to viscous sealing because of the typically 20% oil quantity in methanol &/or nitro fuels, and possibly lower overall temperatures inherent in small engines due to the surface area to volume ratio effect providing a much greater heat transfer rate, at the expense of inherent lower overall thermal efficiencies.
Another thing that has been demonstrated, is that the crevice volume, formed between the bore and the top land above the ring, can result in trapped mixture, leading to unburnt HC emissions. This is why rings have been become higher up the piston. This is not so critical in a stratified charge running condition where, hopefully, only air or burnt gases enter and leave the crevice volume.
I am personally of the belief that a large percentage of the heat from the piston is transferred via the ring and rubbing contact of the ring land (the hottest part of the piston) against the bore. This effect is greatest at the TDC and BDC, where the piston land and ring area have the greatest residency time over the cycle. It is for this reason that cooling of the cylinder is best directed at the very top and also adjacent to the BDC area, usually within the transfer passage cup handles.
If Harry is chucking out all that extra power, relative to current levels, then he will have to provide great attention to the piston cooling, does he have a piston?
As to bearing life, things are going to get tough. 100cc rotary / reeds used to rev to 21k, but there were issues. Sometimes big ends, but with the older vertical reeds aiming between the crankwebs, the big end got much better cooling and lubrication that the now current horizontal reed blocks. Mostly though, it was piston failure, leading to a rod, then unconstrained, scything its way through the crankcases, ignoring all the M6 screws on its way. A 90 mm rod, over the standard VM rod of 110 mm, is going to place more side thrust load on the piston boss area. Maybe if it is a wet sump, using the Honda aerated oil lubrication system and retaining the roller bearings, then this could help, bearing in mind that, with the 25 mm spacer plate, the crank/big end will be more remote from the heat source. If it uses plain bearings, then this pretty much implies some sort of high oil pressure system. Maybe there is no big end at all, but some other clever gizmo. Back to the piston or whatever it is that goes up and down, it will have to be strong to take 30k, but maybe its motion and forces were opposed or dampened, then strength might not be so paramount.
Many a maybe.
He might have done all this and the thing is a real goer with all the claims we have seen. Good on him if this is the case and maybe the world will be a better place. It will inevitably mean change and change means winners and losers. That’s life. But the good thing is that no matter what improvements have been made, things can always be improved. That’s what you bucketeers are all about.

[karter444]

I can see a long winded answer emerging, but I think less is more in this case as its Friday and we are working up to an AB win..
Lifting the floor 3mm AND adding 3mm to the bottom corner rads by welding as far in as I could get ( about 20mm ) from the port
added around 5% power everywhere in a 125 ie 1 in 20 at the bottom and 2 in 40 at the top,plus slightly more in the overev.
But I stress there is just as much to be had by optimizing the duct exit and spigot geometry.
You are right peewee, make it 3mm high, and add a fillet piece at 6mm high as a test.
The issue with any add in piece is that it wont be cooling the retained slug of A/F in the duct bugger all and this will detract from its overall performance..
There is no correlation to anything with the Ex area below transfer opening, apart from what I mentioned about reducing short circuiting from the A port.
EngMod cannot predict the effects on scavenging and or trapping efficiency when you change the Ex area below TPO, its not a 3D CFD flow visualizer like Fluent etc.

Re the flow regime in the transfer ducts and the Ex duct.
In good designs where everything is pretty much optimized you find that the areas of the ports ( and the intake ) converge.
In fact this is the first element to be looking at in the STA analysis from EngMod - check the 3 areas and go to work on the smallest first.
The Cd will be different but effective flow is way more like 50/50 than what we see in a 4T.

would you recommend going correspondingly higher with a 72 mm stroke

[karter444]

#2 there would be zero blowdown.

my mistake question 2 should have read
what is the limiting factor in having the exhaust port fully open by the time the tranfers just open
ie exhaust floor height at the same height as tpo

[Yow Ling]

Has anybody ever tried a labrynth seal instead of rings, just a row of piston ring like grooves around the top of the piston. Sounds too simple to work dunnit

[Ocean1]

Has anybody ever tried a labrynth seal instead of rings, just a row of piston ring like grooves around the top of the piston. Sounds too simple to work dunnit

Fairly high pressure differential for a labyrinth seal. But I'm trying to think how you'd organize a piston to work like a Tesla valve....

[husaberg]

Has anybody ever tried a labrynth seal instead of rings, just a row of piston ring like grooves around the top of the piston. Sounds too simple to work dunnit

I always thought I was invisible............Have a look at the top of the page Mike