ESE's works engine tuner

[fatbastd]

I concur with what Wobbly said - the HPC coating is very effective and I have used it in a number of applications to (marginally) reste piston/bore clearance where the old piston was sound but undersize, correct errors where restores have been bored/honed just that little too big and as anti-eizure protection. I have found the coating to wear a touch, but ant-sozure protection has been excellent - have never seized a coated piston (and (insert preferred divine entity) knows I've tried..)

[Gigglebutton]

During testing of pistons for the BSL we had endless trouble getting small batches made, with the small shape changes needed.
When we finally got it right we wore our last couple of sets out , after doing some 300+ laps when testing at Sepang.
They actually rattled on the overun into corners.
HPC coatings in Auckland applied a Moly based baked on coating, that they said would get us back running till replacements arrived.
The coating was thick enough that when first put together there was ZERO bore clearance.
I was super nervous about Steve Briggs being thrown down the road at Puke when running it in, but after a few laps he gave it death with no issues at all.
It did around 30 laps that day, and after pulling it down there was no sign of scuffing or the coating wearing away.
I put one piston into the single cylinder dyno engine that night, and it made just over 1.5Hp more in 56 repeatably.
Cheap method to retrieve worn pistons, and for sure the coating lasted well.

Some thing like this Wob

[seattle smitty]

lodgernz, the product I used is called "Gun-Kote." When Kal-Gard was selling a lot of it to racers, they relabeled it as Piston-Kote and Gear-Kote, but someone in the company told me it was all the same. They did have a coating you could apply to cooling fins that was supposed to increase heat transfer to the air, but I don't know anything about it. I also don't know whether anybody at the successor company can give first-hand info about the old days. I just went to the KG Industries website and see that they also sell a PTFE coating, which is new to me. I would tend to worry more about that coating bonding well to pistons skirts, but maybe it's fine.

The Gun-Kote used to come in spray-cans, but you don't use much at a time, so the can would probably lose its pressurization on the shelf before you got full use of it. So buy it in a non-spray quart can, stir it and shake it, and apply it with an airbrush or one of the modern paint sprayguns, whatever will lay down a fine spray. Find an old phonograph turntable before us old folk, who remember what the hell they are, all expire.:facepalm:

Be obsessive about prepping the parts, and keeping your oily fingers off them before coating. Get 'em hot and sweat out the oils as best you can. If you have access to a shop that does hot vapor degreasing, so much the better. Blast the skirts for further cleaning and to create a surface that has some "tooth." Don't clean pistons with glass bead blasting; various piston ring companies have put out service bulletins warning auto machine shops against this common practice. Bits of glass will impinge themselves in the aluminum surface, which you can actually see with an optical comparator. FWIW, never glass-bead an aluminum part to get it clean for welding, either, unless you follow up by removing a little of the blasted surface with a rotary-file, or you could drive your welder batty.

Instead of glass bead, blast the parts with soda or salt or possibly walnut shell (don't know how that would work out for this purpose). Right before I'm going to coat the parts, I apply some welder's aluminum etching acid, then wash it off. As stated, I then heat the part just enough to drive out any moisture. That's too hot to coat, so I let it cool toward room temperature. I want it warm, not hot, when I shoot it. Since I've been handling the part, while it is cooling down from driving off the moisture I give it a quick wipe with a lint-free rag that has some acetone on it. By the time I turn on the turntable and pull the trigger on the airbrush, that part is as clean and surface-prepped as I can make it in my home shop setting.

Oh, one other thing I do is set the can of Gun-Kote in a pan of hot water to warm up the contents so it sprays better. I find this to be a good technique to use when spray-painting of any kind; warm up the can of paint, especially spray-can paint.

This is a long description, but it makes the job sound a lot worse than it is; it's really not very much trouble.

Once you have the stuff to do this coating, and have done it once, you'll find various odd uses for it. I once had a Datsun 510 station wagon and two dead L-16 engines. Each motor had piston damage, and I kept one piston out of each because one was a perfect textbook example of detonation (sharp-edged hole in the crown) and the other of pre-ignition (melted hole). They were such perfect examples that I ended up giving them to the local high school shop class last year. Anyway, between the two engines there were four undamaged pistons. I cleaned them and had the local machine shop knurl the skirts (an ancient technique from my father's time for re-using old worn pistons). Then I applied a thick (0.1mm) coating of Gun-Kote. I checked out both blocks, chose the one that was least worn, took the ridge out of the cylinders and honed them. New rings, gaskets, etc., came out with a rebuilt engine for about US$200. Sold the car, which has run and run for the buyer. I wouldn't build an engine for a keeper-car that way, but it pleased me to be able to get the car fixed up so cheaply.

(EDIT) On bottom of the last post at the bottom of page 1019, Frits gave us a link to a video of a trombone pipe. Take a look at the sliding sections moving open and closed: that is a good example of a place that you could apply the moly dry-lube coating (to take up some of the space between the sliding elements while having good low-friction qualities . . . ).

(another EDIT) If you screw up the coating of the skirt (with runs, for example), you'll have to get the coating blasted off before you try again. This should answer doubts about how tough this coating is . . . .

[Grumph]

Hot vapour degreasing = trychlorethylene bath. powdercoaters who can do work to ISO standard will have one of these.

Dangerously toxic so don't try this at home.

F5Dave - next time you're trying to weld cases, try getting them degreased at a friendly powdercoater.

[wobbly]

Yep, Giggle I have seen those pistons before somewhere.
Nice idea having the squish band angled with a flat top.
Must have been a clever bastard that designed them.

[seattle smitty]

It's pouring rain here in Seattle (aka Swamptown), a good day to sit at the keyboard and try to learn from y'all. So . . .

When I do a search here, as for "torroidal heads," I invariably am directed to several 2-stoke threads with ten thousand posts apiece, and no further suggestions as to which pages have the subject term. So I'll just ask here, and know that I HAVE tried to search first


What about those torroidal heads? Do they always work better (restricting my questions to high performance 2-strokes here)? Is this because they get the plug electrode closer to the piston crown or what? Should I assume they are generally used with modern-style fairly narrow squishbands?

Related question: A lot of times, a spark plug of a given heat range and electrode configuration can be had in both 14mm and 18mm types, or at least this used to be true in the '70s. Would it not be better always to opt for the 18mm plug, given that the additional volume around the electrode should give the A/F mixture a little better access to the spark, and a lower misfire rate? Dr. Christopher Jacobs, an ignition expert of some years ago said that even with the best of the available igniton systems and conditions there would always be a percentage of misfires, and the idea was to minimize these so far as possible. Did any of the top engine builders ever test 18mm vs. 14mm plugs of the same heat range?

[chrisc]

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[senso]

For some reason I always looked to those coatings as a marketing gimmick/wankery, all of them will just disappear when touched with wet hands(my experience is just with wossner, vertex and mitaka pistons, and some namuras that will loose the coating even inside the paper box from scratching).

[wobbly]

The coatings as used by Wossner/Vertex are purely designed as a "run in " coating.
The Moly coating as done by HPC is specifically formulated as a permanent slippy surface treatment.
They use it in Nascar, and have been told that it last longer than the pistons are used for = around 800 miles at 8,000 rpm.

Re proper Toroidal head shapes.
Bottom line is that the only real confirmed testing I know of, is that Jan developed the very flat topped wide bathtub at Aprilia with a domed piston.
I have done a huge amount of testing with flat topped pistons and the Toroid wins easily.
Yes getting the pug tip down into the path of the squish induced turbulence with its high speed flame front must be part of the deal.
The flat roof chamber with the dome probably has the same effect as that generated by the toroid and a flat top.
But as it stands there are plenty of very fast engines running domes and toroids.
One 125 kart World Champ tuner in Europe builds domes with toroids and the tech people finally agreed to allow it, as his engines must be ccd
with the cylinder sitting at a specific angle to allow the entrapped air out of the chamber.
He would not go to all that hassle if the toroid wasnt an advantage in those seriously deto prone KZ2 engines.
Its has been deemed illegal here in NZ, otherwise I would be doing it.
The squish MSV number is irrelevant to the discussion re the chamber shape - except to say that a theoretical 38M/Sec works on damn near everything.
This then becomes irrelevant also, when you run the piston/head clearance right at the limit of contact ( as you should be ) just past peak rpm - as zero
clearance would generate insane MSV numbers.
Having the theoretically correct setup in a 125 means you should be down at 0.65mm with a 50% SAR, but this has been found to possibly limit the peak overev
depending upon the fuel and atmospherics, and opening up the gap to 0.75mm solves that issue at 14500 if needs be..

[TZ350]

It's pouring rain here in Seattle (aka Swamptown), a good day to sit at the keyboard and try to learn from y'all. So . . .

When I do a search here, as for "torroidal heads," I invariably am directed to several 2-stoke threads with ten thousand posts apiece, and no further suggestions as to which pages have the subject term. So I'll just ask here, and know that I HAVE tried to search first

You might find these search tips useful.

Some may find this useful. Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add

site:www.kiwibiker.co.nz

for example

Frits priceless site:www.kiwibiker.co.nz
or
Frits pisa site:www.kiwibiker.co.nz

the same will work for other sites with the appropriate site address

Mick

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[husaberg]

You might find these search tips useful.

Another way to filter the wheat from the chaff is to click on the user name of the person and either view attachments by user or forum posts.

[peewee]

hey wobbly in engmod is the Yam12 scavenging model the one i need to use for a banshee cylinder ? it appears to be the closest match from what i can see

[wobbly]

A stock Banshee is closest to Yam1, as that porting was a very a good system for a road bike in its day.
A well modified one with the axial angles reversed and a lot of epoxy becomes Yam 14.

[Frits Overmars]

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Thanks Chris. I didn't know that.
I played a little with it and amongst other things found this link for seattle smitty:
http://www.kiwibiker.co.nz/forums/sh...post1129962543

Smitty, I think that first we need to establish what a toroidal head really is.
For Wobbly it is a head whereby the center zone, containing the plug thread, bulges down towards to the piston.
I have a slightly different definition. For me a toroidal head is a shape whereby the center of the combustion dome is off-center from the cylinder bore center line.
That can lead to Wobblies shape; it can also give a head shape whereby the center zone around the plug thread is flat instead of bulging down.
I haven't considered 18 mm plugs; I'd even like to step away from 14 mm plugs and use 10 mm plugs like KTM is doing. And I'd prefer to use surface-gap plugs (no empty volume inside the plug at all). These 'conceiled' (from the viewpoint of the scavenging stream) volumes provoke detonation.

[Frits Overmars]

Here's some help on searching in these forums.

Top right hand corner of the screen, click 'advanced search'
Click the blue box 'search single content type' at the top.
Scroll down and select the forum area to buckets which is right near the bottom of the list.
Scroll down and select the dot next to 'posts' in the criteria called 'show result as'.

Another handy tip is under thread tools (near the top of this page) click view thread images. Very! Helpful on the ESE thread

Thanks Chris. I didn't know that.
I played a little with it and amongst other things found this link for seattle smitty:
http://www.kiwibiker.co.nz/forums/sh...post1129962543

Smitty, I think that first we need to establish what a toroidal head really is.

For Wobbly it is a head whereby the center zone, containing the plug thread, bulges down towards to the piston.
I have a slightly different definition. For me a toroidal head is a shape whereby the center of the combustion dome is off-center from the cylinder bore center line.
That can lead to Wobblies shape; it can also give a head shape whereby the center zone around the plug thread is flat instead of bulging down.

I haven't considered 18 mm plugs; I'd even like to step away from 14 mm plugs and use 10 mm plugs like KTM is doing. And I'd prefer to use surface-gap plugs (no empty volume inside the plug at all). These 'conceiled' (from the viewpoint of the scavenging stream) volumes provoke detonation.

the additional volume around the electrode should give the A/F mixture a little better access to the spark, and a lower misfire rate.

True, and the best way to create a big volume around the electrodes is to move them to the center of the combustion chamber. I used plugs with an extra-long thread (meant to be used with sensor rings). I ground away the part of the thread that intruded into the combustion chamber, leaving just some support for the mass electrode. So the spark was right in the middel of everything. It worked, especially on the overrev.

Christopher Jacobs, an ignition expert of some years ago said that even with the best of the available igniton systems and conditions there would always be a percentage of misfires, and the idea was to minimize these so far as possible.

True again.