Conferences > International Scooterist BBS > Topic #34588
I am rebuilding my P200 engine.
at all times there is a thin boundary layer of gas that separates your piston's crown and hot expanding gasses. in fact there are boundary layers on your skin, water and essentialy anything and everything on this planet that is exposed to different temperatures! the boundary layer inside motors is what protects your components from harm, and it is the elimination of this layer that puts holes on pistons. when you get detonation the layer is blown away and the piston is exposed to the hot gasses that melt away, or sand blast away aluminum untill there is a hole.
regarding the second part of this reflection = cooling notion. heat is dissipated away from the piston to cylinder wall in two ways. one is that the fresh charge, that is dormant under the piston, absorbs some of this heat and the second is that heat moves from the piston on to cylinder wall (which is cooler on account of cooling fins). heat is dissipated on to the cylinder mostly via piston ring contact with the wall, in fact 80% of the heat is transfered this way. second transfer is via oil that is in between the piston skirt and the cylinder, but this method depends on how much oil is persent and how close the skirt is to the wall.
ceramic coating is necessary inside liquid cooled cylinders. in some cases liquid cooling is so efficient that too much heat is lost. there has to be some amount of heat for proper combustion/operation. so ceramic coating on the crown, head and inside the exhaust port is helpful heat retantion aid. vespas most certainly don't need any help in heat retention! a simple look at your piston's underside lets you know if you need more or less cooling. and in all cases i can bet you that you have a very dark brown/black spot or carbon build up on the crown's underside. btw, that brown spot means that things are getting so hot in there that the oil on the underside is starting to bake.
if you use a good synthetic oil at a leaner oil mixture you shuldn't worry about build up.
So Geoff, stop using Dino oil, and adding some oil premixed as well as the autolube and you'll be fine
Just remember this - in this country they drive on the wrong side of the road.
I run the profiled P.M Tuning head - covering a piston that has been ceramic coated. The piston passes a ceramic coated exhaust port wich is connected to a ceramic coated P.M Tuning pipe ( inside and out). The skirt of the piston is moly-lubed as well.
Not only is it fun to test and do a little R & D. It's science. The research I did was based on go-cart technology on air cooled two-stroke motors. Those guys seem to know what they are doing.
Ceramic coating the piston crown (not the inside of the head), exhaust port & pipe keeps the spent charge hot longer so when the exhaust port opens it exits faster - drawing the new charge in faster. It also helps keep the heat off the piston effectively keeping the temp lower and running more efficient.
It might be over kill for the simple design of the P210 motor, but mine runs like a bat out of hell. I've worked up a fairly solid formula and most of it is from existing sources.
Part of the enjoyment I get out of scootering is the modification and improvements we can work into our machines. It's cheap technology and it can be rewarding. So - call me a hack - but I can back it up.
I've already backed it up. The science works. When I get the time, I'll roll it on a dyno. 9.5hp stock P200 - I'm easily in the mid to low 20s and I'm running a 24/24e.
I just thought it was funny that you stomp on these guys and get all "annoyed". We're here to exchange ideas - not get our feeling hurt.
Take care -
in your initial post you made some reference to how ceramic coating has a theoretical advantage in go-carts, but you made no attempt to explain how this stuff is beneficial to a vespa engine, and even applicable. so since you shy away from actualy backing up what you claim to work, and hide behind kerr and grahm (who are both nice guys but irrlevant in this case) i'll take take the time to explain a few things, and not just for a pissing match but because there are other people reading these messages and they need to be educated.
ok, there are two basic reasons why you'd use ceramic coating. one reason is in drag motors that need optimal combustion temperature, and the second is in high output motors that need protection. drag motors need high temperature inside the combustion and inside the exhaust pipe to expel burnt gas as quickly as possible. these motors also need high temperature because the cylinder and the pipe are high rpm bias, which means no low end power and they have to use momentum to expel gas (and this is true in 4 or 2stroke applications). when you wrap a header, or coat is with ceramic materials you speed up the flow. this increased flow is very much needed on motors that are high rpm biased. as far as 2 strokes are concerned, the reason why this coating would be needed is because it gives the effect of a much shorter pipe, in other words pulses are generated back to the source much faster. if you want a high rpm pipe you make is short and if you want a mid range pipe you make it long (to delay/time the signal). now, these short pipes are needed on high rpm motors becuase they have a very narrow band where the motor is most efficient at expelling gasses and pulling the fresh charge in as well as being in sync with reed pettals and piston speed. and since the power band is at a very high speed you need a pipe timed to work at that speed. keep in mind that anything below the peak power is flat and there is no torque. to use coating on the piston crown (and yes the head as well), and the exhaust port is an extension of this attempt to contain high temperature in order to maintain high flow.
the second (general) reason that i mentioned is that ceramic coating protects parts. protection of parts is not really an issue on drag motors since they get to the finish line in seconds. so you have a bunch of these high power engines like snowmobiles and go-cart engines (which are essentialy dirt bike engines). one thing that they have in common is that they make huge power per liter, and the unwanted result is very high friction and heat. another thing they have in common is that they are kept on the pipe for sustained periods; snowmobiles because they have automatic gearing so you can keep them at peak more easily and go-carts because they can carry corner speed and there is no need to reduce rpms. you would not see ceramic coating on a dirt bike eventhough you would on the identical motor inside the go-cart. and the reason is that a dirt bike is not kept at peak rpms for extended periods. so because snowmobiles and go-carts undergo more abuse at high speed you need protection from meltdown. the boundary layer just can't protect the piston and these pistons undergo chronic meltdowns. go-carts aside, the reason you'd coat or wrap headers on a snowmobile is because it was found that snowmobiles lost power in the field. and the cause was becasue the exhaust pipes (that are in the front, and under the cowl) are exposed to very cold incoming air (this is a winter machine after all) and it is causing pipes to cool down. so ceramic coating or wraping is a solution to keep temperature inside the pipe.
so is this stuff needed on vespas, or even necessary and how beneficial is it? we know that drag racers use it and it works for them. we know that snowmobilers and go-cart racers use it and it keeps their pistons safe (eventhough ceramic coating is dicey and it does crack very often). here's what i think: whenever you look at other 2stroke advancements in attempt to improve vespas or lammys you always have to consider compatibility and relevance. it is the sum of all your internals working in unison that makes a fast and reliable engine. but if the internals are mismatched becasue they were designed for various incompatible engines then you get junk perfomance. for years i have been writing on this message board and trying to drive this point accross. so what if a gp 125 uses a 41mm carb. it doesn't mean that you can, and so what if a quad uses a 35 mikuni d slide, it doesn't mean that our engines can use those parts. there is a known limit that is set by design paramaters which can't be circumvent and you have to live with that or get a different bike. what i'm talking about is an engine's efficiency that is measured in BMEP (which in my mind is the most effective way of measuring engines). vespas are at the bottom of that tetem pole and gp engines are at the top. so why would you try to adapt technology intended for these ultra efficient engines? keep in mind that i'm not saying that we should just give up on improving vespas/lammys, but be realistic and improve them appropriately. we know, based on dyno results, that even highly tuned vespa 220s etc, are about as efficient as enduro motors (of similar size). so look to these machines when you want to improve your motor. copy their cylinder design and head design and transfer/exhaust durations. copy their carb sizes and exhaust design. you have to have a clear perspective and know what is applicable stuff and what isn't. i'd love to port my jug to same specs as a dirt bike but it won't work same on vespas because there are so many other design issues.
so does ceramic coating work on vespas. it's my opinion that at best it makes no difference, at at worst is detrimential. i say that it makes no difference because vespas don't generate enough heat to need that kind of protection (and if you melted a piston it's because your carb was all wrong or you had a sudden air leak or your timing was off). in fact, when you design pipes one of the crucial paramaters is exhaust temperature. and let me assure you that a vespa doesn't generate as much heat as a dirt bike or a snowmobile. in fact vespas generate very low mean temperature (compared to other 2stroke engines) so there is no need to worry about melted pistons if you build the motor properly.
and i say that at worst the effect of ceramic coating is negative because it alters your pipes design paramaters. i already mentioned that pipes are designed for different applications and most importantly speed range. all vespa exhausts are designed with mid range in mind and to complement existing transfer/exhaust specs. but if you want you can easily call up paul at pm tuning or mark b and they'll gladly design you a pipe to your specs, or you can have them optimize an exhaust for your target rpm/power. when you take a mid range bias pipe and then ceramic coat the header you are creating some kid of hybrid that is mid range physicaly (as far as cones and diamaters go) but high range wannabe because the headers are hotter and give the impression of being longer. and especially if you coat the header internally you are reducing internal diamater and altering the original design even further! pipes are designed with many paramaters in mind, many more then what kerr or grahm note in their books (ok, i shouldn't glorify kerrs pamphlet as a book). you have to consider temperature, rpm, desired power, and most importantly your actual transfer/ exhaust durations and physical size (the sum of the windows). when you start to mess around with header temperature you throw off all those things that were kept in mind.
look, i've read a lot and i've built many motors and had great success. i know what i'm talking about. i'm not insecure and i don't have to go on here to prove anything to anyone. shit i don't even ride vespas anymore but i post here becasue i like 2strokes and it's fun to help others understand better and get over the fear of imporving motors. but i do get annoyed when someone doesn't read my posts and gets things wrong and starts to blast me. i'm not egotistical. i'll read any post that challanges what i said, but please make the effort to at least write something pertinent that we can discuss, and don't twist what i wrote.
You made some great points. One reason I got into to scooters is to learn about all this stuff. That said, you got a little pissy with Greyhound for no good reason. More friendly discussion, less drama.
In my VERY limited knowledge of automotive engineering I tend to agree with you. I can't see how a ceramic coating on certain parts would make an appreciable difference on a scooter engine performance.
Greyhound, can you post a link to any research on this?
It's warming up to 40 F today! I am going for a ride.
in my first post i said that, with regard to polished surfaces deflecting heat inside the engine, people who make these silly comments are hacks. and the reason that i say this is that a) this shinny surface is covered with a boundary layer so it no longer is shinny and b) when you have an object that is moving thousands of feet per second, as is the case with pistons, there is absolutely no time for any deflection to take place, if this even occurs. an informed 2stroke tuner would know this and would not make these silly suggestions.
in the second post (immediately following the first) i said that ceramic coating has a place in certaing engines, but is not at all necessary on vespa engines. somehow, in between these two posts greyhound got offended and started to defend his choice of ceramic use. unless, this same individual also purports that shinny stuff deflects heat and is commenting in general, but i don't know that since greyhounds reply was in reference to ceramic coating (to which i made no 'hack' references). so are we clear on this issue then???
again - the internet takes away any jest in a conversation.
I did think Nik was a bit harsh on the P.M. Tuning head comment and the hack comment, but hey everyone has both an opinion and an asshole!! : )
If anybody is interested in ceramic coatings - I have a great resource - they do a ton of cart stuff. I just did a run for a friend of mine who races water craft in FL.
My guys do pistions, jug ports, pipes and cosmetic powdercoating.
I'll have my website up soon.
I have had a successful run with coatings in regard to tuning a Vespa.
Also - the books mentioned about are excellent resources.
Have fun -
I'm getting ready to bulid a wicked T5 motor. I just wish I didn't weigh 200#.
Nope - that's 18 mos away - I have other projects in between!!
How's life? Have you joined the VCOA yet?
well, when you do get the time, you'll find that you are most dissapointed when your motor churns out a mere 17-18 bhp at the wheel..
not saying that the bike doesn't run great on the road, but huge power figures with the 24/24 are mythical at best..
it always better to set the expectations low and be pleasantly surprised!
very good observation.. in a few words, it's not the ceramic coating that will boost your power.. it's the tuning of the engine's components that gives you the power boost. at one point, your tuning will start pushing the boundaries of the component's stability, and that's when the ceramic coating comes into play, it make it possible to 'tune to the limit' in a 'safer' fashion and squeeze out those extra few hp's
i don't see the advantage of ceramic coating on a mildly tuned vespa engine, except of corse for the almighty 'i did it' factor, which our pal Nik seems to have completley overlooked!
haha! get back on a vespa and find your sense of humor man!
The other thing to realize - like Nik referenced earlier - a bigger carb does not always make your bike any faster / or more powerful. I've yet to even start looking at a Vortex set-up. I did some moderate intake porting and installed a cut crank. The bike gets plenty of fuel. Now it's a matter of leaning it to the right mixture to get the max power. That is why I think the hp is higher. It's night and day from a stock set up, and it runs away from a mildly tuned P210
I've been working on this engine for over 3 years. It has evolved into a "study" if I had to define it.
In an effort to increase the output, I looked into ceramic coating because as I lean the carb out for more power, the heat will rise. Containment of the heat is less fatigue on the engines performance. I'm certainly not claiming to reinvent anything.
This bike started as a street racer, maybe I'll get it on the track soon. I've done some rally ( New Orleans) drag racing and it was very competitive. If I'd had a heavier flywheel I most likely would have smoked the other two bike that edged me on a short run. I barely got into 3rd gear it was so short.
Anyway - as you see it - yes - the coatings are unnecessary and overkill. I'm doing it to see if it acutally does make a difference. Hopefully I'll get on the dyno soon and see the scientific results.