ESE's works engine tuner

[jonny quest]

I've found cast piston make more power than forged pistons.

The link that Kel posted of the KTM is exactly what I was talking about. Great info by Wobbly too.

I've wondered why Frits and Jan didn't run that piston design, I feel it's the best.

[lodgernz]

Attachment 308848Attachment 308849

Start of the mighty Team ESE super RG50 project. Sketchy made this head insert for us to try, maybe we could have done it on the lathe but we wanted at least three the same with a variety of insert profiles. In the end CNC is the only way to get repeat ability and like Flettner, Sketchy makes a really good job too.

The drawings were done by Kel and are a copy of the Aprilia bath tub head, Kel has also drawn a RG50 head insert based on Wobs toroidal design. There will also be a 14mm and 10mm plug version so we can do a back to back test to see what plug size is best.

If anyone wants to try a head insert for their own RG50 then they are welcome to have Sketchy run one off using our drawings.

If you make inserts with 10mm plugs, don't forget to change the insert profile to keep the water near the plug. Otherwise it's 2mm further away on each side. Just sayin'...

[TZ350]

If you make inserts with 10mm plugs, don't forget to change the insert profile to keep the water near the plug. Otherwise it's 2mm further away on each side. Just sayin'...

Good tip, thanks.

[senso]

That is very interesting, virtually air cooled. I am trying to convert a water cooled cylinder to air cooling and would like to know more about the circumstances around how yours was being run, was it being thrashed? was there any water left at all or was it dry? I would love to know more.

Good morning TZ350, it was in fact an accident, my brother went for a ride with some friends(another 50cc bike and a 1980 kx250), the other 50cc guy got tired and went away, so my brother keep going and playing catch up with the 250.
He thinks that it was after a jump, the lower frame(the part that goes under the engine) broke, and the back engine mounts moved enough that the radiator tubes disconnected from the water pump, he says that he noticed the engine reving up slower, but he didn't notice any lack of power, so after at least 30 minutes after the said jump they arrived at my friends house and they noticed a horrible burning smell(it was the head gasket sort of roasting with the heat).

They connected the tubes, but as soon as a sit on the bike they would disconnect again, and the engine was still running so he came home ridding her(another 15 minute travel distance).

He arrived home, told me what happened and I didn't believe, but its true, the next day I still put the engine working, there was still a good compression feeling in the kick-starter.

I have some photos of the piston, that is burned a lot in one spot and the cylinder also got yellow/reddish in some places.

In the end, after pulling the cylinder off the engine he sort of dropped the cylinder in the work bench and broke the back(intake) skirt, also a lesson learned, I can't remove a lot of metal in the intake because the back skirt loses almost all its support.

[adegnes]

Something like this http://www.pit-lane.biz/t118p20-gp12...tiques-ktm-frr

Can anyone tell me what the acceptable minimum distance would be from spark plug to piston crown at top dead centre for a 50cc cylinder with 41mm bore?

Is 1.4mm from piston top to ground electrode enough?

[Frits Overmars]

Yeah yeah all very well. But what if you put some BIGGER injectors in there. Surely that must be better

Yeah, because putting in bigger main jets always makes more power, eh?

Right, like big-diameter exhaust ducts and headers and diesel-like compression ratios .

...the best power was had from a piston that had an angled squish ( at 7* ) then a flat top.... The idea of the angled edge came from the factory YZR 500 as this is what they used at the time, and was developed when they got themselves a Czech CNC anemometric flow test machine.

But the idea did not originate at Yamaha, Wob. The flat pistons with a beveled edge that you saw in the YZR 500, were designed by a friend of Harald Bartol, the late Martin Ziegler, who lived across the street from Mahle in Stuttgart. He supplied them to Team Roberts if I remember correctly, and in his office he had a certificate, thanking him for his contribution to the world title (from Wayne Rainey, I think it was).

I've found cast piston make more power than forged pistons.

We found the same outcome about cast versus forged pistons. But for the next ten years 'everyone' will still be convinced that forged is better.

The link that Kel posted of the KTM is exactly what I was talking about. Great info by Wobbly too. I've wondered why Frits and Jan didn't run that piston design, I feel it's the best.

I wonder why you think that Jan didn't. He tested everything you can think of, and then some.
Keep in mind that both the transfer layout and the combustion chamber shape have an influence on the results, so there were a lot of combinations to test.
From the tested shapes the flat top piston was worst; flat with a bevel, like Wobbly describes, was better; domed with the squish area turned conical was about the same; domed with the center turned flat was about the same; just domed was best.
Domed with an edge radius was unbelievably good on the flowbench but not on the dyno, probably because of the influence of the radius on port timings. I still want to get to the bottom of this but test facilities are not what they used to be. Didn't you have plans to look into this too, Wob?

[F5 Dave]

Yeah, because putting in bigger main jets always makes more power, eh?

Hmm, I hear what you're saying. It must be MORE injectors he needs.

[TZ350]

Good morning TZ350, it was in fact an accident, my brother went for a ride with some friends(another 50cc bike and a 1980 kx250), my brother keep going and playing catch up with the 250.

Thanks, leaves me feeling hopeful that I can make the RGV250 cylinder work as an aircooled one.

[adegnes]

Please excuse me for the OT, I just can't figure out what these weird things I found are, and thought I'd check if you guys have seen anything like it.

I found a box with ten of these under my porch. No marking on the box except for a "danger corrosive" triangle.




White plastic box with clear plastic fluid container on top. Says "push" on top of container, to let the fluid drop down into the plastic box I presume (added som black so it would show up on the pic) . One red and one black wire connected to the white box, pins with big head on the end of the wires sitting in a small piece of styrofoam.

Could it be some kind of weird battery with separate acid container, so that it can be stored for a long time without going bad, and when you want to use it you push the button, the acid drops down and the battery is ready to be charged?

[F5 Dave]

Heavy water?

WMDs?

[adegnes]

Heavy water?

WMDs?

Maybe call up the germans and hear if they still want some then...

I'm hoping it's a battery - need the sulfuric acid for anodizing.

[jonny quest]

Frits, did not mean to imply that RSA testing did not cover all the bases. But what makes the RSA like a dome vs other designs.

On a warmed over bridged exhaust YZ125, same CR, the chamfered edge flat top was worth a full HP more than a dome. That's huge on a 125.

And yes, just a traditional flat top I've found to put it subtle. .. shit. That little chamfer (with corresponding head design) is pretty amazing.

I'd hazzard a guess as to the rounded edge piston just traps too much fuel above the ring that doesn't get a chance to heat the air.

[wobbly]

Too many variables to make an informed idea about why the VHM flat top with edge radius design makes more power in a KZ2.
I know the head shape goes around the corner, so there is no extra trapped end gases in the ring crevis, but then
the piston is fully machined from billet material - so maybe as has been found when comparing cast with forged,its simply the alloy type that makes the difference.
And maybe the real difference comes down to the machining - because its the shape the piston becomes when its hot in the bore that is all important, and all the different materials will
have quite different expansion rates.

The radius edge piston is on the list of possible projects to be completed as a thesis subject at Canterbury Uni - just needs a candidate thats interested in using
Fluent as well as the dyno to validate the results.

[peewee]

The radius edge piston is on the list of possible projects to be completed as a thesis subject at Canterbury Uni - just needs a candidate thats interested in using
Fluent as well as the dyno to validate the results.

regarding flat tops. do you meen like the red line or orange ? then cut the outer corner of the head at the same shape ?

then use a head shape like the rsa, but with flat squishband ? (TZ350's RG50 head appears to be just that). should the band be paralell or have some diverging angle like 1 or 2 degrees ?

[F5 Dave]

At some stage there has to be a compromise between increasing flow over a sharp surface of a constantly moving port duct to chamber interface
vs the increase of port timing, decrease of blowdown, increase of squish area trapped at the bore edge.