how hot should the head be?

[hugh hargett]

How do carbs like the CP zoom carbs with there great atomization play into cooling the intake charge?

 

[Jim Allen]

JIM!!!,.. you have a very good way of raising a topic, and posing it in such a way that really keeps me thinking about it.. I was trimming some plants,.. still thinking about this!!!

Spend less time thinking about it & spend more time learning how to make the necessary pieces. Do you remember the day you came to the lake with a 55 MPH boat & left with a 65 MPH boat? The propeller you used that day was your base line. If you do something to the engine to generate more HP, keeping the load the same, would the boat go faster?

 

[dwilfong]

If you would read the paper I posted it would put all this in perspective.

Most of the fuel is not even burned because it is in the boundary layer that is to cool to support combustion.

Read and learn!

All the thermal dynamics and efficiency finding are in there for a small glow eng.

I even has pictures for you to look at as it happens,

David

 

[hugh hargett]

Jim I dont know but why do we talk about hp and never torque? I cant asnwer that question coz to me without more torque which I feel would accelerate you faster or more rpm to turn the prop faster id say the extra hp means zero but more heat with the same prop(load) if it doesnt correlate to an increase in one or both of those catagories. Again I really dont know.

 

[Tim_Duggan]

How do carbs like the CP zoom carbs with there great atomization play into cooling the intake charge?

More importantly - what does Methanol do when atomised into air........

Ever noticed how much the inlet butterflies ice up on a methanol drag car vs a fuel drag car?

The bottom of the crankcase on our IC engines get very cold while running, even if the head is hot. Which raises the next question - what if that coolness in part of the case could be utilised better via thermal transfer or other means? At what point is the case too cold for the combustion chamber to really work efficiently? A practical example - OUTBOARDS!

Interesting comparison to a soldering iron in terms of wattage. If you made the tip of a 100W iron the same size and surface area as one of our engines / headers / pipes and exposed half of it to cold atomised air/fuel mix below zero degrees C - would it still melt solder?

 

[Andy Brown]

Most of the heat is absorbed by the nitro. Nitro must absorb much more heat than gas or methanol to reach ignition temperature. When it final does have enough heat in it the nitro will burn and all of that heat energy is released as cylinder pressure. Therefore Nitro itself is the best "radiator" your engine could have. That's why we go faster when we restrict the water and open the fuel valve.

Lose the water pick up and Dump in the Nitro! Yeah Baby! HORSEPOWER!

 

[hugh hargett]

How do carbs like the CP zoom carbs with there great atomization play into cooling the intake charge?

More importantly - what does Methanol do when atomised into air........

Ever noticed how much the inlet butterflies ice up on a methanol drag car vs a fuel drag car?

The bottom of the crankcase on our IC engines get very cold while running, even if the head is hot. Which raises the next question - what if that coolness in part of the case could be utilised better via thermal transfer or other means? At what point is the case too cold for the combustion chamber to really work efficiently? A practical example - OUTBOARDS!

Interesting comparison to a soldering iron in terms of wattage. If you made the tip of a 100W iron the same size and surface area as one of our engines / headers / pipes and exposed half of it to cold atomised air/fuel mix below zero degrees C - would it still melt solder?

I doubt it Tim of course more heat is realized in a small point but 12000 watts is alot more than 100 ya know? That also may depends on the type of solder. For devils advocates sake different solders have different melting points but I know what youre saying. Will a exhaust manifold on a car with it even with more surface area melt solder ? I understand but 12000 wats still seems alot to dissapate through the material thats there in our model motors. I can apreciate Andys explanation for where the heat goes as we sometime use richness to help with detonation on our turbo cars but to a point when we boost alot and increase the pressure there a point that achohol or water come into play to kill the KNOCK. Andy are you sayint that the nitro is a fuel cooling agent? I know at the strip the higher octane fuel does helps with knock in the higher compression engines. Andy for some reason your post and these motors make me think about diesels dragsters at the track.

LOTS TO CONSIDER!!!!!

Like working on my 20 psi 4 cylinder. I neglect daily fooling with these toys.

 

[Jeff Barnhart]

making the charge more dense needs to happen at the intake (i.e. getting more air and more fuel into the engine), then making sure you can get all the left overs out after it combusts. Problem is you can only fit so much stuff in a given volume of space.

The head can definitely be designed to give adequate heat transfer, though if I'm remembering correctly I don't beleive the calculation is necessarily simple and it requires some complex mathematics that most people don't have a clue about how to do.

Ids not saying 30 percent is wrong but in the future dont ever use wilkipedia as technical reference to be safe. Its not recognized by any academic institutions as reliable. Dot org's and Dot govs or technical journals and periodicals would be more accepted as factual info.

Hi Hugh, no. Absolutely. Hence the "finger in the air" disclaimer. It was just to illustrate the question of input vs useful output, vs waste - rather than absolute numbers. I also suspect that the right answer is probably a fairly wide range. Ian

As for an accurate engine efficiency, you need to consult a modern thermodynamics book that includes this material. Just because it is a .org or .gov says absolutely nothing about whether something is accurate.

Information is accurate if it is based on the relevant scientific laws and principles and is without errors.

not to debate but thats the point of dot orgs and scholarly journals the info is scrutinized by experts in the field (using scientific law etc.) before it put out there as the gospel wilkepedia does not. You wont write an acceptable grad paper using wilkepedia as a source you will quickly recieve an F if they even let you submit it at all use it if you choose but sooner or later you will be told something as fact on there that is wrong as the place the devil dwells.

Ant, Im with you does it want heat or not? The answer hasnt been made clear through all these diffrent threads that relate back to heat tranfer and such. It seems it doesnt matter as folks are going to do what they think will work regaurdless. "Ambiguity" certainly wont stop it coz the more confusing its made the less likely someone is gonna be willing to even worry about it theyll just try stuff til the boat runs faster and be satisfied not needing to know why,metallurgy,high level math, and all the other stuff it takes to clearly understand it.Its quite a confusing mess I agree 100 percent. Only eggheads will continue to unlock a eureka moment of understanding. All in all what seems to be more important to people for obvious reasons is, is it fast! There seems to be a unwillingness to try different technologies that are widely used in other forms of motorsport so Im at a lost with nitro rc boaters. A real good reason to go FE. Imagine if someone actually had the balls to try to builds a fuel injector and driver for these small motors. Seems we cant try anything new so it wont happen I guess. I based this on the non response to questions asked of the mebers of IW about water injection cold air induction and such. Gosh can we ever get outside the BOX or tunnel vision? If i could only get my hands on the equipment and had the skills that others do on here I could show how to live outside the box and I guarantee wed come up with something that makes the boats run better. OLD dogs are reluctant az hell to try new tricks. Without trying how do you know whats possible. Its Amazing to me.

Hugh,

I understand what you're saying about .org, etc. and for the most part that is correct but people need to be careful with the context of what is on them. My point is that if people want to go fast, they need to learn the concepts behind whats happening and how to apply them in different scenarios rather than just blindly accept something as fact because it is on a .org site.

Wikipedia is definitely not the most reliable place to get info because anyone can put it their.

 

[anthony_marquart]

As I continue to learn about these things I have a noticeable "gap" between thinking / learning about engine temp, compression, ignition,.. and all these things we talk about, and actually applying these concepts at the lake. I'm learning more and more about engines and boat designs,.. But to actually be at the lake and watch a boat run, listen to the engine, and actually be able to say,.. that motor is not running warm enough, ... or, the engine is maxed on rpm now load it with more prop,.. and maybe,.. the reason it's not warm enough isn't too much water it's too little load on the engine...

That is where I think the real knowledge is. Being able to apply these concepts is a whole different level than just understanding concepts and talking about it. I think also that I am personally to a point where my testing at the lake has to have more means of gathering data. I used to be happy with thinking or feeling that the boat is running better or faster,., I'm not so interested in going these days since I don't have a way to measure speed and RPM, and temp. And, there are no other guys to run run laps with!!!

 

[Jim Allen]

If you would read the paper I posted it would put all this in perspective.

Most of the fuel is not even burned because it is in the boundary layer that is to cool to support combustion.

Read and learn!

All the thermal dynamics and efficiency finding are in there for a small glow eng.

I even has pictures for you to look at as it happens,

David

Maybe you can explain to all of us, exactly how a thesis written about the characteristics of glow plug & HCCI combustion processes in a small volume at high engine speed applies to anything that has been discussed. The RPM of the glow plug engine used never exceeded 17,500 RPM & the fuel used was 10% nitro. Does any one think that the flame kernel patterns shown would be the same in an engine using 50% to 80% nitro running at 26,000 to 32,000 RPM?

On page 107 there is a discussion of the influence of inlet temperatures & hot residual gases on the performance of a mini high speed glow engine. This test was carried out at engine RPM's between 14,500 to 17,500. Conclusions of the test indicate no improvement of efficiency, a reduction in emissions & a decrease in the output power.

Exactly how would the information in this thesis help in building a reliable high performance two cycle engine used to power a model boat????

 

[lohring]

A little off topic, but these inertial dyno tests may shed some light on heat and detonation in engines of different sizes but with supposedly similar power. We did a series of Quickdraw tests on standard model boat nitro fuel. We could not get glow plugs to hold up for even one run, so we went back to standard ignition. The engine ran fine on up to 15% nitro, but melted the electrodes off the plug with 40% nitro. The electrodes dented the piston on the way out, but the engine was otherwise undamaged. There was no sign of detonation with a head button designed for gasoline.

Some years later we decided to test some 11 cc nitro engines. We immediately melted either the exhaust side or the center of the piston on 3 engines during the dyno run up. All the 26 cc gas and 11 cc nitro engines should develop between 5 and 7 hp. We have tested gas engines down to 3 hp and up to almost 12 hp with the same dyno wheel. I'm sure detonation killed the nitro engines. I bet that the nitro engines are at the edge of detonation and are under less load in model boats. A smaller wheel would load the engines less, but spin to a higher rpm. Marty Davis has done a lot of nitro engine testing with smaller dyno wheels, so he may have some answers.

The gas engines develop more torque since their peak power happens at a lower rpm. However, torque is a measure of the amount of work done while power is a measure of how fast that work is done. You can always find the torque by dividing the power by 5252 and multiplying by the rpm at that power. You can increase the torque supplied with gearing, but the work won't get done any faster. That takes more power.

Lohring Miller

 

[hugh hargett]

Loh, whats your unit of power in this EQ to find torque? I need to keep this in my notes.

Ant, I have an interview up in charlotte on the 15th of this month. Ill pm you and see if we can go out there and run. The beautiful pond that I was running at because of a jet ski supposedly has stirred up algae so no one is allowed anything there now but fishing. None of my boats have touched water in months . JIm Allen if youre around I might need to drop in on you too if you will be around.My twin jae is ready for prime but it wont likely make it in the water by the 15th. I havent recieved my turn fin yet. All I have to run is a 40 mono a sport 40 and the 1/8th scale which should be ready for a dip if I go on and tie up some minor loose ends.

Hugh

 

[Andy Brown]

A little off topic, but these inertial dyno tests may shed some light on heat and detonation in engines of different sizes but with supposedly similar power. We did a series of Quickdraw tests on standard model boat nitro fuel. We could not get glow plugs to hold up for even one run, so we went back to standard ignition. The engine ran fine on up to 15% nitro, but melted the electrodes off the plug with 40% nitro. The electrodes dented the piston on the way out, but the engine was otherwise undamaged. There was no sign of detonation with a head button designed for gasoline.

Some years later we decided to test some 11 cc nitro engines. We immediately melted either the exhaust side or the center of the piston on 3 engines during the dyno run up. All the 26 cc gas and 11 cc nitro engines should develop between 5 and 7 hp. We have tested gas engines down to 3 hp and up to almost 12 hp with the same dyno wheel. I'm sure detonation killed the nitro engines. I bet that the nitro engines are at the edge of detonation and are under less load in model boats. A smaller wheel would load the engines less, but spin to a higher rpm. Marty Davis has done a lot of nitro engine testing with smaller dyno wheels, so he may have some answers.

The gas engines develop more torque since their peak power happens at a lower rpm. However, torque is a measure of the amount of work done while power is a measure of how fast that work is done. You can always find the torque by dividing the power by 5252 and multiplying by the rpm at that power. You can increase the torque supplied with gearing, but the work won't get done any faster. That takes more power.

Lohring Miller

Lohring,

I suspect you were not feeding your test engines enough fuel. Nitro burns at over 4000*F. That is above the melting point of Platnium and near the melting point of Iridium. When using nirto we MUST pour in Excess fuel to keep the metal parts from melting. But I also see your point. The Wheel was surely too big for the 11 cc engine.

 

[anthony_marquart]

Loh, whats your unit of power in this EQ to find torque? I need to keep this in my notes.

As far as I know I will be around at that time.. I have a place where we can run..

Ant, I have an interview up in charlotte on the 15th of this month. Ill pm you and see if we can go out there and run. The beautiful pond that I was running at because of a jet ski supposedly has stirred up algae so no one is allowed anything there now but fishing. None of my boats have touched water in months . JIm Allen if youre around I might need to drop in on you too if you will be around.My twin jae is ready for prime but it wont likely make it in the water by the 15th. I havent recieved my turn fin yet. All I have to run is a 40 mono a sport 40 and the 1/8th scale which should be ready for a dip if I go on and tie up some minor loose ends.

Hugh

 

[lohring]

We weren't really serious with our nitro tests since gas engines are our focus. However, the 11 cc nitro engines were run with the needle setting they ran in the boats. We didn't get the chance to play with the needle since the engines didn't live long enough. We did run a series of fuel tests on a modified Zenoah. There we found that the more ethanol in the fuel, the more the needle needed to be opened. Tests with methanol and nitro needed even more fuel flow.

We haven't really done testing on the effects of temperatures on power. We always warm up the engine before a run as well as make several back to back runs. There doesn't seem to be any power improvement from the first to the last of 3 runs, though. However, inertial dynos probably aren't ideal for this type of test. I am always amazed at how quickly (seconds) the pipe gets hot enough to change color. We run plenty of cold water flow to the head, but it still gets as hot as it would in a boat during one pull.

Lohring Miller

PS the units in the torque formula are British engineering units - foot pounds, and 33,000 foot pound/minute horsepower

 

[John Finch]

Nitro engines........I like the touch and look method of getting the right engine temperature. If the fingers can stay on the engine for more than 3 seconds the engine is too cold. If you can't touch it for more that a split second it is too hot. If the plug is dull when the temp is right a dull plug is too lean a shiny plug is rich and a slightly dull plug is just right. If the plug is mangled the load is too great or the compression too much. Would rather up the exhaust timing and keep the low head clearance. Adjust nitro content according to piston diameter and oil content to type of rod bearing/bushing. AND IT ALL depends on the boat the engine is in. So the lake dyno is different for each setup. Did the land/shop dyno for years but the lake dyno works better for actual racing conditions. Not to say playing with the dyno is a bad thing, because you can learn some good things, but it does not tell the practical side of the ever changing load on the model boat on a race course. Just an old farts opinion.

 

[Terry Keeley]

Nitro engines........I like the touch and look method of getting the right engine temperature. If the fingers can stay on the engine for more than 3 seconds the engine is too cold. If you can't touch it for more that a split second it is too hot. If the plug is dull when the temp is right a dull plug is too lean a shiny plug is rich and a slightly dull plug is just right. If the plug is mangled the load is too great or the compression too much. Would rather up the exhaust timing and keep the low head clearance. Adjust nitro content according to piston diameter and oil content to type of rod bearing/bushing. AND IT ALL depends on the boat the engine is in. So the lake dyno is different for each setup. Did the land/shop dyno for years but the lake dyno works better for actual racing conditions. Not to say playing with the dyno is a bad thing, because you can learn some good things, but it does not tell the practical side of the ever changing load on the model boat on a race course. Just an old farts opinion.

Experience counts for much in this game I've learned, just another "getting to be an old farts opinion". :lol:

Some of the best tuners in drag racing still look at the pistons and plugs, even with all that fancy logging equipment.

Exactly what I do BTW...

 

[moparbarn]

agreed, terry. the parts will tell the real story - good or bad. data can be useful, but parts don't lie. old school? i still close my eyes & lay one hand on an engine to adj. mixture on a 4 stroke engine . tachs & co meters are good, but sound & feel work for me .i can usually feel an engine start to lean misfire before a tach will show the drop in rpm.

 

[hugh hargett]

When just talking "engines" the boat plays no part. Thats the point of the dyno. When youre talking a race boat - thats a vehicle with an engine in it. The dyno is for testing the motor and its output limits and such not how it runs in the boat. Thats the point that some have been trying to make. Like real motorsport teams they design what they think will be a good motor test it on a dyno then put it in the vehicle and get the vehicle to perform around the good motor that was dyno proven for an increase in performace. In any type of real motorsport a dyno is a valued and used piece of equipment. If you notice most top level engine builders at least down here in nascar country have a dyno in house. If you had a "dyno queen" and it didnt run good in the vehicle id check the vehicle not the motor. I dont think anyone in the persuit of a good motor would be upset if they ended up with a "dyno queen" whatever that is...... if its a motor that kicked back great hp and torque numbers and could turn k's with minimal vibration id be excited to put it in my vehicle boat or whatever. I believe either its a good strong motor or it aint especially with a direct drive. If it aint it aint gonna run good in the boat if it is then it will but the boat might limit how fast that motor can make it go.

Another link to this topic: http://www.jrcbd.com/showthread.php?t=65871

 

[John Finch]

When just talking "engines" the boat plays no part. Thats the point of the dyno. When youre talking a race boat - thats a vehicle with an engine in it. The dyno is for testing the motor and its output limits and such not how it runs in the boat. Thats the point that some have been trying to make. Like real motorsport teams they design what they think will be a good motor test it on a dyno then put it in the vehicle and get the vehicle to perform around the good motor that was dyno proven for an increase in performace. In any type of real motorsport a dyno is a valued and used piece of equipment. If you notice most top level engine builders at least down here in nascar country have a dyno in house. If you had a "dyno queen" and it didnt run good in the vehicle id check the vehicle not the motor. I dont think anyone in the persuit of a good motor would be upset if they ended up with a "dyno queen" whatever that is...... if its a motor that kicked back great hp and torque numbers and could turn k's with minimal vibration id be excited to put it in my vehicle boat or whatever. I believe either its a good strong motor or it aint especially with a direct drive. If it aint it aint gonna run good in the boat if it is then it will but the boat might limit how fast that motor can make it go.

Another link to this topic: http://www.jrcbd.com...ead.php?t=65871

Ok, no one biting on this one, so I will try to add a little for thought. A car race team has a dyno and sets up an engine that will go in a known vehicle. The pavement does not wrap around the car when at rest. Things are pretty consistent from start to wide open as far as where the engine hits the road. A model boat is not consistent. Every boat is different. Every type of boat is different, and everyone sets them up different. Water conditions change where pavement is pretty flat most of the time. Point is.........an engine that performs great on the dyno may never get to the RPM thet it did on the dyno because of the boat, prop, or water conditions. Not to mention a lean setting because the prop is a bit slightly too large or the temperature on that day is in the 90s and the dyno test was done at 75 degrees so you lose 8 percent of your power because of temperature of incoming air density to the engine. I could go on and on with this. Take a mono........you set it up on a calm day. Water like glass. The engine runs hot because the boat is totally wet. You reset the trim to air the boat out and then you go to a race and the water is rough as there are 6 boats out there. Now the boat blows off the water. How should you have set up that boat. It is an ever changing lake dyno, so you need to set the engine for the boat and water conditions you will be racing in. Nitro engines have many variables that are affected by the boat setup, water conditions, and air density. Those variables cannot be duplicated with the dyno unless you do a ton of empirical testing and apply it to the load characteristics of a dyno. I don't think anyone could live long enough to accomplish that feat.

On the other hand........dyno testing can help determine many things about the engine as you said.....strictly engine testing. I did some dyno testing and found out how much nitro I could run in my engines before detonation occurred. I could actually hear the engine detonating and it sounded like someone hitting the engine with a hammer when I used too much nitro. I reduced nitro content until the hammer stopped and that is what I ran for that particular engine. I was able to measure pipe heat and determine pipe length for certain applications etc. Even enlarged carbs and went so far as to blow holes in the pistons just to see what the cause and effect was. So, there are two sides to the coin. Just want to let you know dynos can yield good answers to questions, but not the end all to the end game of effectively getting an engine to max out in a model boat. The bottom line is........ to be on top of your game with nitro you can use the dyno and lake testing, but because of all the variables you need to be able to tune on the fly at the races and fully understand how all the variables affect each other. I think we are way off topic now.......applying this to the topic......on hot days the engine will have less power because of less air. To make the proper air to fuel ratio you need to lean the needle. Then there is less fuel/air delivered to the engine and less horsepower. Don't let the air density fool you into having other issues. On a hot day you may not swing the prop you had on the boat in the Spring and the engine might over heat. Down size the prop if you are over heating to see if it helps. High altitudes equal less air and less horsepower also, because there is less air density. Air density is a big variable you need to learn to adjust for in keeping the engine in tune and running well. You may need to lengthen the tuned pipe to get launched or to move the power band to a lower rpm when there is less air available for the engine to make power. Just throwing more water to the head is not always the best solution. There! back on topic.