That pic labels the exhaust ports correctly.
Modding the liner is easy in terms of machining/dremelling but if the usual zenoah mods are applied to this motor then it may not respond well.

So do you cap off the other 3 ounce you decide on the one your going to use?

JA wrote:

>I have used chromed cylinders bores on my QD cylinders for several years. There have been
>no chrome flaking or peeling issues as yet. Works very well for piston ring seating & is
>much more wear resistant than the original hardened liner surface. Proper honing is still
>required.

Not trying to say chrome is bad - it has many wonderful properties.

Chrome flaking has been a bane for many model boaters ever since the first chrome plated
aluminum cylinders hit the market. Chrome adheres much better to some base materials than
others. We also know making chrome adhere well is very process sensitive. Where it has proven
reliable, by all means take advantage of it's features. Where it has not proven to be so
reliable (like using it in Al cylinders) maybe it's time to consider other possibilities.

While the sleeve's iron surface is not as durable as if it were chromed, a much higher
percentage of iron sleeves will yield a full service life (eventually wear out). There will
still be a significant number of chromed aluminum cylinders that go in the garbage due to
flaking.

If you are claiming that chrome adheres to sleeves much better than cast aluminum cylinders
(sure looks like you have evidence that it does) then I would agree that using chromed
sleeves is best practice and those who continue to run chromed cylinders must accept the
risk they are taking - especially after they start cutting them with Dremels, etc.

whitefish

CC wrote; "Chrome flaking has been a bane for many model boaters ever since the first chrome plated
aluminum cylinders hit the market. Chrome adheres much better to some base materials than
others. We also know making chrome adhere well is very process sensitive. Where it has proven
reliable, by all means take advantage of it's features. Where it has not proven to be so
reliable (like using it in Al cylinders) maybe it's time to consider other possibilities."

CC,

There is no doubt that chrome received a bad rap from what took place by certain engine builders who attempted to use the process on aluminum sleeves. I can positively assure you that if the process is done properly, the chrome will adhere to brass, aluminum & steel without flaking, peeling or blistering. Every Nelson engine presently manufactured uses only chromed aluminum sleeves & this has been done for more then 20 years. I am honing aluminum chromed sleeves & assembling pylon racing engines every day. There just are not any problems unless you try to take some shortcut. The chroming bath has very poor throwing power & therefore requires a long time to put the chrome on. The chemical balance & temperature of the bath are critical in plating chrome that is hard. Much more to this simple process has not been talked about.

Jim Allen

Just noticed that GIZMO's description of this motor claims the liner is steel. With Dave
thinking it's iron, I'm back to being confused. A steel sleeve would wear an iron piston
ring very rapidly, wouldn't it?

www.gizmomotors.com/index.php/...o-engine-detail


JA: What would be the simplest non-destructive test which would determine if these sleeves
are iron or steel?

CC,

The quickest & cheapest way to tell if the sleeve is iron or steel is with a spark test in a slightly lighted room. There is a great deal of information on the internet with videos of what to look for when comparing iron to steel. With that said, I'm fairly sure the sleeve is not iron. This would work, even with the ductile iron ring. However, it's life would be very short at the RPM's we run at without the use of an oil ring.

As far as any wear problems with a nitrite hardened steel sleeve that is properly honed & a ductile iron piston ring, there are none. In fact, the chrome platting would be even harder than any nitrite surface, but this causes no wear problems either.

JA

Does any one have any valid information on the thermal coating used on the piston of this engine? Is this a proprietary coating or the standard stuff tested by many high performance two stroke tuners that have resulted in inconclusive results?

I ask this question because any thermal barrier on the piston's crown would surely reduce the amount of heat that could be absorbed by that piston crown. Therefore, where does the heat, that the piston crown would absorb, go to? IT CANNOT & DOES NOT JUST DISAPPEAR! I would think that the upper surface of the coating must be nearly the same temperature as the temperature of the combustion chamber. If the piston's crown is not absorbing or is absorbing very little heat, will the coatings upper surface, that is absorbing the combustion's heat lessen or contribute to more detonation? The heat that the piston previously absorbed must now be absorbed by the remaining parts; the cylinder; the cylinders head & the piston ring in contact with the cylinders wall.

Many unanswered question here??????????????????????????

Jim Allen

I think you answered it yourself in a previous post in this thread and I quote
" I have found that the best method to prevent the combustion's heat from heating the surrounding metal materials (piston crown, head, cylinder walls) & reduce high surface temperatures is to polish these surfaces that are in contact with the radiated heat. This works well since the heat is reflected."

Dave,

Maybe I should explain further. My tests with coated pistons (usually .002" to .003" of a proprietary thermal blocking material applied by an unnamed company) did not help to eliminate detonation or increase the engines HP. The coating was intended to provided characteristics found in a good thermal insulator; very little heat is transferred through the coating; the surface temperature of the coating on the heat source side is very high; the temperature on the underside of the coating is very low. When replacing un-coated polished piston crowns with thermal barrier coated piston crowns on the same highly tuned engine, the engine's performance was always decreased.

So, the question is, why are the pistons in this engine coated & with what material? Was the coating done to mask a problem with very high piston crown temperatures? Is the coating done to prevent the piston crown from caving in? When using a coated piston how does the coating help the combustion heat reach the cooling system?

I believe that polishing the piston's crown does not improve the heat transfer to the rings & the cylinders wall, but it does decrease the amount of heat absorbed by the piston crown. Reducing the heat absorbed by the piston crown reduces the amount of heat that is passed through the piston rings to the cylinder walls.

JA

It's my understanding that highly polished/thermal coated surfaces within a combustion space, are there to reflect heat and hold it for power production. The coatings offer no increased strength to the parts. The hotter the combustion pushing on the piston ( more expansion ), the more power is made, but only up to the point of detonation. Therefore, we need to increase the available octane to take advantage and for protection. There's no question in my mind that such an extreme engine will go through rings like crazy, but these are VERY HIGH OUTPUT assemblies that need constant inspection. Keep in mind that a lot of combustion heat is being pulled/chased out of the chamber by a cool rush of incoming fuel that is also washing over the piston crown, by the tuned pipe on every revolution. On a polished/thermal coated assembly, it's possible that water cooling will need some upgrading.

I highly doubt that a coating alone on one of these little engines pistons, will show much of anything on a dyno by itself.