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Carbon on Exhaust Valve

Old 06-15-2017, 06:46 AM
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Four Stroker
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Default Carbon on Exhaust Valve

Whenever a four stroke engine starts to run ratty it is carbon on the exhaust valve. I am now running a YS 80 on RotorRage 30% heli fuel. It started running ratty at WOT. I took it apart and it was pristine new inside. No deposits on the head or top of piston. The ring looked new - still black. I thought I had wasted my time but decided to take out the exhaust valve since I was there. It was coated with carbon on the seating surface. This is a pattern for me anyway. It's always carbon on the exhaust valve.
Old 06-15-2017, 09:14 AM
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Propworn
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Can you try a different fuel? The only time I have experienced build up of carbon is when there was castor or some other carbon based lubricant in the fuel. Even in small quantities the carbon based lube will leave carbon deposits on the exhaust valve/surfaces even the piston at times.

I have run Wildcat YS 20/20 pure synthetic in all my YS engines with good results. No sign of carbon deposits and engines have run flawlessly for many years.

Dennis
Old 06-15-2017, 11:32 AM
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airraptor
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YS recommends 100% synthetic fuel for this reason. They make more power and heat will build up the carbon fast on the exhaust valve. clean it and run 100% synthetic oil fuel.
Old 06-15-2017, 06:19 PM
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My saito with more than 50 hrs needed bearings . The exhaust valve had some carbon that was easily cleaned up with a scotch brite pad with the valve in a drill press . Not enough to effect its running . 20% oil with a 1/4 of that castor . Just saying is all .
Old 06-15-2017, 11:13 PM
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Saito engines do not make anywhere near the power of a YS just saying is all
Old 06-16-2017, 01:14 AM
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Propworn
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Originally Posted by the pope
My saito with more than 50 hrs needed bearings . The exhaust valve had some carbon that was easily cleaned up with a scotch brite pad with the valve in a drill press . Not enough to effect its running . 20% oil with a 1/4 of that castor . Just saying is all .
So many things effect the heat at the exhaust. Fuel mixture rich/lean, load on the engine etc. that it is quite possible to get away with a carbon based lubricant in the fuel for four strokes with little or no build up in carbon deposits. All that means is your running the engine reasonably loaded with a good fuel/air ratio. Congratulations your doing it right.

YS's recommendation of pure synthetic has more to do with damage to the silicon parts in the fuel regulator than anything. Yes it also helps reduce/eliminate those carbon buildups. I know that the team from Japan at the world scale championships could not get pure synthetic in a high nitro content so they ran theirs with synthetic/castor blend with 20% nitro and cleaned the regulator parts after each run with 10% pure synthetic.

The YS ran fine on the synthetic/castor mix but they did not want to chance leaving the blended fuel in contact with the silicon parts in the regulator.
Old 06-16-2017, 01:04 PM
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Prop you're correct they can swell up causing it to run poorly. I race all of my YS engines on anywhere from 20 to 75% nitro and no real build up of carbon on the exhaust valve like other engines do. The OS engines are the worst at this
Old 06-16-2017, 03:12 PM
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Originally Posted by airraptor
Prop you're correct they can swell up causing it to run poorly. I race all of my YS engines on anywhere from 20 to 75% nitro and no real build up of carbon on the exhaust valve like other engines do. The OS engines are the worst at this
I have seen as high as 40% nitro but haven't seen 75% nitro used in a YS engine. I have used as low as 15% and they run just fine. Nitro by itself does not add to the combustion process. At the low end nitro aids in a reliable idle but much beyond 15% doesn't do much to improve the idle. At the upper end the nitro releases an extra oxygen molecule which allows a bit extra fuel to burn during the combustion cycle. Since the YS is a naturally aspirated (engine vacuum) carb intake there is limited raw air that can be drawn into the motor. The extra oxygen molecule supplied by the nitro allows a richer fuel setting however once the saturation point is reached of available oxygen vs. available fuel any additional fuel/nitro is simply pumped out the exhaust. The only benefit at this point would be the cooling effect of the un-burnt fuel. Personally I doubt anything above 50% nitro would serve any purpose and simply be a waste of money.

Dennis
Old 06-17-2017, 10:34 AM
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Originally Posted by Propworn
So many things effect the heat at the exhaust. Fuel mixture rich/lean, load on the engine etc. that it is quite possible to get away with a carbon based lubricant in the fuel for four strokes with little or no build up in carbon deposits. All that means is your running the engine reasonably loaded with a good fuel/air ratio. Congratulations your doing it right.

YS's recommendation of pure synthetic has more to do with damage to the silicon parts in the fuel regulator than anything. Yes it also helps reduce/eliminate those carbon buildups. I know that the team from Japan at the world scale championships could not get pure synthetic in a high nitro content so they ran theirs with synthetic/castor blend with 20% nitro and cleaned the regulator parts after each run with 10% pure synthetic.

The YS ran fine on the synthetic/castor mix but they did not want to chance leaving the blended fuel in contact with the silicon parts in the regulator.
Please enlighten me, what is a carbon based oil?
What is it that you think will react in the castor oil with silicon? I mean, the fuel tubing can last for years...

Originally Posted by Propworn
I have seen as high as 40% nitro but haven't seen 75% nitro used in a YS engine. I have used as low as 15% and they run just fine. Nitro by itself does not add to the combustion process. At the low end nitro aids in a reliable idle but much beyond 15% doesn't do much to improve the idle. At the upper end the nitro releases an extra oxygen molecule which allows a bit extra fuel to burn during the combustion cycle. Since the YS is a naturally aspirated (engine vacuum) carb intake there is limited raw air that can be drawn into the motor. The extra oxygen molecule supplied by the nitro allows a richer fuel setting however once the saturation point is reached of available oxygen vs. available fuel any additional fuel/nitro is simply pumped out the exhaust. The only benefit at this point would be the cooling effect of the un-burnt fuel. Personally I doubt anything above 50% nitro would serve any purpose and simply be a waste of money.

Dennis
You do know that nitromethane is a monoproppelant, do you?
Old 06-17-2017, 01:36 PM
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Originally Posted by Nitrovein
Please enlighten me, what is a carbon based oil?
Should have said carbon based lubricant midnights will do that to ya LOL


Originally Posted by Nitrovein
What is it that you think will react in the castor oil with silicon? I mean, the fuel tubing can last for years...
I wondered the same thing when I contacted Central Hobbies and YS Performance and was told it gummed up and effected the silicon parts in the YS regulator. Since they are the sales/repair depot and have been at it forever I figure they have an idea what they are talking about. The team from Japan had a factory mechanic and he stated the same thing. Caster Synthetic blend was not good for the parts in the regulator.

Originally Posted by Nitrovein
You do know that nitromethane is a monoproppelant, do you?
Yes and those engines that run large ratios of nitromethane are purpose built to do so. Standard built engines, which our model engines are, run best with a methanol/nitro mix. With no mechanical overdrive to pack more air/oxygen into the cylinder a saturation point is reached and no amount of extra fuel/nitro will make more hp. Even the supercharged drag racers end up pumping raw fuel out the exhaust that is what you see as flames coming out the headers. Unburnt fuel. Our little compression timed engines have no timing adjustments, cams and cam timing is fixed. I doubt there is much advantage if any after 30 to 40% nitro. My opinion only.
Old 06-17-2017, 02:13 PM
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Originally Posted by Propworn
Should have said carbon based lubricant midnights will do that to ya LOL

I wondered the same thing when I contacted Central Hobbies and YS Performance and was told it gummed up and effected the silicon parts in the YS regulator. Since they are the sales/repair depot and have been at it forever I figure they have an idea what they are talking about. The team from Japan had a factory mechanic and he stated the same thing. Caster Synthetic blend was not good for the parts in the regulator.

Yes and those engines that run large ratios of nitromethane are purpose built to do so. Standard built engines, which our model engines are, run best with a methanol/nitro mix. With no mechanical overdrive to pack more air/oxygen into the cylinder a saturation point is reached and no amount of extra fuel/nitro will make more hp. Even the supercharged drag racers end up pumping raw fuel out the exhaust that is what you see as flames coming out the headers. Unburnt fuel. Our little compression timed engines have no timing adjustments, cams and cam timing is fixed. I doubt there is much advantage if any after 30 to 40% nitro. My opinion only.
You could not mix RC fuel without carbon being present, it's what happens during combustion that matters.

I could believe that regulator can be gummed up from castor oil, but there is no reason why it should chemically affect any silicone parts.

If comparing larger engine, the only difference between a nitromethan feed engine and others are the ignition that's pretty stout on those.
The stoichiometric ratio doesn't change just because the engine changes in size or a blower is added.
With short exhaust like on a dragster, many gasoline or methanol engines will also spit flames. But most of what's seen on a Top Fuel dragster is hydrogen burning after the pressure has separated water.
They don't run any variable valve timing on those engines either, would be more then a handful to get that to work on one of those engines.
If you add more energy to a combustion, something is bound to happen.
Old 06-17-2017, 03:36 PM
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Last I checked, just about any oil that gets burned during combustion results in carbon and/or ash deposits. Kind of a given.

I don't run those YS jobbies... not my cup of tea; but the 4-strokes I do have only have a very light film of carbon on the exhaust valve and that's using 20% all castor oil in the fuel. I probably have 3-4 gallons through one of them. Not a spec of anything on the piston.
Old 06-17-2017, 09:32 PM
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Propworn I will say you are wrong when it comes to YS engines and you don't know what you're talking about. 75% nitro is not recommended and only a few have run that much. Some in the past have run 65% in the 91 and 120 engines. You say you have seen as high as 40% nitro used in a YS yet claim anything above that is useless lol take two airplanes same weight, same design and both with the same YS engines and the one running 60% will be faster than the one with 40%.

Know this I race these engines ........ so I have experience and knowledge on them
You have seen up to 40% this could mean you have seen other people run that high and not your self so either way your knowledge stops at 40%
YS four stroke engines have some level of super charging. They build up stored air under pressure and release it in to the intake port directly above the combustion chamber.
Old 06-18-2017, 09:57 AM
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YS made engines specificaly designed for nitro content up to 50%. The internals were modified to run this fuel. I doubt further increases in nitro would result in much if any increase in speed other wise everyone would be running it. Lots of people get in the mindset that more is better often passing the saturation point where any advantage can be gleaned but they firmly remain convinced otherwise.

I may not race these motors but have been around racing and performance engines long enough to know that if any one thing made as much difference as you claim everyone would be doing it not just a few of you otherwise the others might as well stay home. This goes for fuel, engine mods, frame or any other deviation from the norm. Anything that actually gives an advantage is adopted pretty quickly or there is no sense in taking the horse out of the barn so to speak. That only a few of you resort to such high nitro content means the advantage does not prove out on the race course. Just saying!!!!!
Old 06-19-2017, 12:29 PM
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You doubt which means you do not know yet claim that it is fact. So until you run one of these engines on different nitro levels and different prop what you claim is meaningless! But all good either way I know what works and you think you know. Not all run high nitro as it isn't needed for most applications the engines are used in. The YS115WS is designed for higher nitro of which I have ran 75% nitro on. This level is only for those well versed in the engine of which there may be 10-15 guys out there than can do it. 60% nitro however what some run on the WM airframes. The fact the engine will run with 75% nitro, 5% methanol and 20% oil shows me the engine can supply enough fuel for it with that the needle will need to be almost all the way out around on a well maintained engine. My last race this past weekend I ran 45% nitro with two turns out on the needle and 60% for one race was 2 1/8th turns out. This race was to much as I broke out and went to fast. Everyone doesnt run more nitro as it is expensive is why not that the engine will not see a gain in power lol So propworn quit trolling and try it for yourself I bet you will be surprised.....
Old 06-19-2017, 10:26 PM
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When self proclaimed experts start telling everyone how good they are or how they are better than everyone else its time to take what is being said with a grain of salt. Do others who are running lower nitro content break out? If so then it would appear the extra nitro you may be running just might be less of a factor than you are leading us to believe. In any case its wandered way off the original topic. One thing I know from being around other forms of racing is that cost is a common penalty of going fast. If a higher % nitro made that much difference everyone would be doing it.

PS my original 120 FS/SC's seem to work fine on 15 to 20% nitro don't think I need to try higher than that any time soon LOL

Dennis

Last edited by Propworn; 06-19-2017 at 10:35 PM.
Old 06-20-2017, 10:03 AM
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Originally Posted by Propworn
YS made engines specificaly designed for nitro content up to 50%. The internals were modified to run this fuel. I doubt further increases in nitro would result in much if any increase in speed other wise everyone would be running it. Lots of people get in the mindset that more is better often passing the saturation point where any advantage can be gleaned but they firmly remain convinced otherwise.

I may not race these motors but have been around racing and performance engines long enough to know that if any one thing made as much difference as you claim everyone would be doing it not just a few of you otherwise the others might as well stay home. This goes for fuel, engine mods, frame or any other deviation from the norm. Anything that actually gives an advantage is adopted pretty quickly or there is no sense in taking the horse out of the barn so to speak. That only a few of you resort to such high nitro content means the advantage does not prove out on the race course. Just saying!!!!!
you said you dont race these engine yet claim more nitro doesnt help
you said if it made as much difference as I claim everyone would be doing duh they do gold class guys run 35-65% for races depending on the location. In Sacramento lower nitro is required to run the numbers. In Redding (except this past race) 45-65% nitro was needed. At the NATS most guys ran 55 to 60% in gold class you keep talking about our racing and saying this or that yet you do not race in our races lol
Old 06-20-2017, 10:07 AM
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anyway done arguing with you as I don't want to confuse you anymore with facts since you have your mind made up.
Ok one last thing if dragsters use 80-90% nitro and it all goes out the exhaust then why do they do it if by your opinion 50% is all that is needed ? lol
Old 06-20-2017, 01:17 PM
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Originally Posted by airraptor
anyway done arguing with you as I don't want to confuse you anymore with facts since you have your mind made up.
Ok one last thing if dragsters use 80-90% nitro and it all goes out the exhaust then why do they do it if by your opinion 50% is all that is needed ? lol
Because the over driven supercharger provides the extra air/oxygen to keep the mixture correct for proper ignition even thought the cylinders are near hydraulic by volume. A stock motor could not even run the supercharger at these pressures/volumes. So there is no way that I can see how a two chuff cylinder displacement pressure system could come close to using that ratio of nitro efficiently. Look it up homey what ever they can't combust ends up out the pipes in flames.

The 2 chuff compression of air/fuel and oil barely qualifies as supercharging. Heck Shindiawa has been using this in their weed whackers for years. Used to be called C4 technology. Yes they use an oil/gas mix like a 2 stroke and it gives the 4 stroke the ability to run in any attitude without having to use sump oil for lube.

Believe what you want, more is not necessarily better. Since your one of the few running that high a nitro content I gather you consistently out pace the others and win most if not all your races. Must be a list of your accomplishments somewhere I'd like to look through it if you don't mind.

Here is a good read as far as nitro is concerned. Near the end they address nitro and naturally aspirated engines compared to true screw compressor supercharger. Remember the YS is a two chuff displacement style air/fuel pressurization system. Little better than the original 1 atmosphere of a naturally aspirated engine. It also doesn’t have the advantage of an adjustable ignition cycle/curve. Everything that is necessary to run high ratio nitro fuel efficiently is missing with these motors.

Dennis

Last edited by Propworn; 06-20-2017 at 01:20 PM.
Old 06-20-2017, 04:48 PM
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1QwkSport2.5r "Last I checked, just about any oil that gets burned during combustion results in carbon and/or ash deposits. Kind of a given."

Yeah, methanol, nitro methane, and all oils are full of carbon atoms including silicone oils.

airraptor is one of the guys that warbird races the YS 80S and YS115WS. They both have dished pistons and allow high nitro. As Dave Schadel once told me, 30% ain't high nitro! 70% is high nitro. Rotor Rage 30% Heli is 100% synthetic oil.

If you are sputtering along at 5000 rpm, then a little carbon on the exhaust valve probably doesn't matter. I am running this engine in a helicopter at 12,000 hover and 14,000 idle up. A thin film of carbon effects the compression enough to make the engine sound ratty and give a noticeable drop in power presumably because the valve is not seating.
Old 06-20-2017, 07:00 PM
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Originally Posted by Four Stroker
1QwkSport2.5r "Last I checked, just about any oil that gets burned during combustion results in carbon and/or ash deposits. Kind of a given."

Yeah, methanol, nitro methane, and all oils are full of carbon atoms including silicone oils.

airraptor is one of the guys that warbird races the YS 80S and YS115WS. They both have dished pistons and allow high nitro. As Dave Schadel once told me, 30% ain't high nitro! 70% is high nitro. Rotor Rage 30% Heli is 100% synthetic oil.

If you are sputtering along at 5000 rpm, then a little carbon on the exhaust valve probably doesn't matter. I am running this engine in a helicopter at 12,000 hover and 14,000 idle up. A thin film of carbon effects the compression enough to make the engine sound ratty and give a noticeable drop in power presumably because the valve is not seating.
If that thin of a film of carbon is preventing it from seating, then I'd be suspecting your fuel as being a problem. On the other hand - It should take a LONG time for a model engine to build up enough carbon to cause valve problems.

One thing ive learned in dealing with high strung engines - they are picky about what glow plugs and fuel they use. Sometimes adjusting the oil package alone can have a significant effect on tractability. It sounds to me as though you need a colder plug. I run medium cold plugs in my picky engines - in some cases a medium filament/cold body plug.
Old 06-20-2017, 09:36 PM
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you are going to need more than just a big Swartz if you want to win races, 75% should help do it
Old 06-20-2017, 09:49 PM
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wasp....... guys only used 75% for our speed dash last year at the championship race. It was won by Richard with a 203mph run on my 13x18 prop.

guys hate all you want lol
propworn again your understanding is flawed YS has CDI engines from the 70 on up. They are fixed timing but can be programmed with an aftermarket ignition. This CDI with its fixed timing does allow a better needle over glow ignition that changes timing as you lean on the needle.

Most guys run high nitro so not sure how many times I have to say that lol. Also most guys try to prop the 115WS around the 10,000 to 11,000 on the ground. I like to see 11,500 to 12,000 on the course.
OP sorry this went in many different directions. If you have any other questions feel free to hit me up with a email.
Old 06-20-2017, 10:16 PM
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back in the early 90s I ran 50% in my OPS 45 Boat engine, I can only imagine how fast my boat would be if that OPS was setup to burn 70%

Jim
Old 06-21-2017, 01:23 AM
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No this is all relevant to my original post. Airraptor, I guess my question is how often do you take down a racing engine to clean it up ? As in the original post, the entire inside of the engine was pristine clean EXCEPT for the exhaust valve. I have tried CY 30%, CP 30%, and now have Rotor Rage 30%. At least these three carbon up the exhaust valve. AND yes in the summer especially I have changed to a colder plug. In winter (maybe 50~70F), I use the standard YS/OS 4-stroke plug. In summer (80~107F), I have tried an Enya #3,4,5,6. Last summer I used the Enya #4. Idling is not a problem. I have the SwitchGlo Pro the turns on at 1/4 throttle and below.

I think racing is close to my application. What oil do you use with 70% nitro?

The YS 80S has a short pancake piston with a cutout in the top of maybe 10 thou. It runs really smooth at 14,000 rpm. I have accidentally run a YS 70S fast enough to float the valves. Weird goose honking noise! Dave told me that people were running 18,000 on the YS 63 with stiffer valve springs long ago with 70%. What glow plug were they using ?

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