how hot should the head be?

[Jim Allen]

Is there a significant loss of HP that can result from to much cooling in the head? Photos posted on this site showing badly detonated squish bands & badly detonated piston crowns indicate inadequate removal of heat from some engines. Coolant head temperatures & exhaust gas temperatures will rise as engine load, engine compression, engine MSV, engine RPM & engine HP rise. Does boiling water or steam & vapor bubbles on metal surfaces within cooling cavaties help in removing the heat in the head button?

Can the head of the engine be designed to give adequate heat transfer, good rigidity & stability, while applying the things that give maximum HP?

 

[mark voorhies]

Seems like a Loaded Question Jim

Are you looking for an answer or a Disscusion ?

Greg

This part is loaded; Does boiling water or steam & vapor bubbles on metal surfaces within cooling cavaties help in removing the heat in the head button?

NO

 

[moparbarn]

i agree with that, solid water will transfer heat better than air & water. that's why i only restrict water at the outlet, not the inlet. having a smaller inlet than outlet can cause partial filling of the cooling passages. i like positive pressure in my cooling system. the best temp for any individual engine & setup will vary, but (imho) should be in the 200*- 210* range. that seems to be a good target temp for most any internal combustion engine out there, big or small.

 

[Jim Allen]

Seems like a Loaded Question Jim

Are you looking for an answer or a Disscusion ?

Greg

Nothing loaded about any of the questions. Since it is a fact that 1 HP = 745.699 watts of heat, where is the heat generated during 7 HP (5,219.893 watts) dissipated?

 

[ids987]

Seems like a Loaded Question Jim

Are you looking for an answer or a Disscusion ?

Greg

Nothing loaded about any of the questions. Since it is a fact that 1 HP = 745.699 watts of heat, where is the heat generated during 7 HP (5,219.893 watts) dissipated?

Are we talking about an engine which can transfer 7 HP to the load ?

If 7 HP is the output of the engine, then surely that 5,219.893 watts is the useful power transmitted to the load. The heat to be dissipated is the waste product. If the engine efficiency is (finger in the air), about 30 odd%, the heat output would be something of the order of 12,000 watts ?

 

[hugh hargett]

Ids how did you calculate 12000 watts? 5200 watts is closer 30 percent of 17000 no way its putting out that much heat think of a 40 watt soldering iron. 17000 watts? <_< Did you mean 6500 watts - 5000 plus 30 percent?

 

[ids987]

Ids how did you calculate 12000 watts? 5200 watts is closer 30 percent of 17000 no way its putting out that much heat think of a 40 watt soldering iron. 17000 watts? <_< Did you mean 6500 watts - 5000 plus 30 percent?

Hi Hugh,

No. If 5,219.893 watts is output (and assuming 30% efficiency), then heat is the other 70%.

So heat would be 12,180 watts.

If you add the two together, you get a little more than your total figure (just under 17,400 watts combined useful output + heat).

 

[hugh hargett]

got ya! I still dont think its sending out over 12000 watts of heat that would make for an extremely hot situation. Thats enough juice to support a hoseholds electrical needs like a 16hp generator.Thats like 300 times hotter than a 40 watt iron. Does it sound reasonable? I dont think so maybe not. You can calulate what it would take to dissipate that amount of heat. No matter what I dont think youd ever have enough FIN,water cooling, or just surface area to remove that much heat. If 30 percent is all you get out of it I wouldnt run a nitro period thats horrible efficiency seems like 1500 watts assuming 70 percent efficiency would seem more realistic i dont know :unsure: .

17000 watts would be over 26hp of potential if you could get it all so it just doesnt strike me as reasonable though im not a nitro guy.

 

[ids987]

got ya! I still dont think its sending out over 12000 watts of heat that would make for an extremely hot situation. Thats enough juice to support a hoseholds electrical needs like a 16hp generator.Thats like 300 times hotter than a 40 watt iron. Does it sound reasonable? I dont think so maybe not. You can calulate what it would take to dissipate that amount of heat. No matter what I dont think youd ever have enough FIN,water cooling, or just surface area to remove that much heat. If 30 percent is all you get out of it I wouldnt run a nitro period thats horrible efficiency seems like 1500 watts assuming 70 percent efficiency would seem more realistic i dont know :unsure: .

17000 watts would be over 26hp of potential if you could get it all so it just doesnt strike me as reasonable though im not a nitro guy.

Sure - though to be fair, it would be the sum of the heat - including the heat lost through the pipe and header, the heat going out of the end of the pipe etc. I pulled 30 odd% from Wikipedia, as the maximum for an I/C engine. I don't know how accurate it is, or where a two stroke glow engine fits into the overall picture of efficiency. Interested to see where this is going to go.

 

[Jim Allen]

If my thoughts after being out of school for 50 years are correct, I would have to agree with ids987.

In our example 12,180 watts of heat would go out the exhaust into the air. 5,219 watts of power would be absorbed by the prop. The exhaust is extremely hot, approximately 700* F, when generating 7 HP. I also agree that a two stroke is less efficient than a four stroke.

Assuming the engine is 30% efficient would mean 70% of the fuel used is wasted. How much of the total heat of combustion that is generated at 7 HP is absorbed by the coolant system? How much is absorbed by engine components?

 

[hugh hargett]

I cant answer that but I can tell you that a 12000 watt iron would get hotter than 700 degrees F and if all the extra goes out the exhaust pipe what happened to the heat you need for the nitro to run? 70 percent of the fuel wasted ? Sounds horrible and a big waste of money then as nitro aint cheap. I thought the consensus was you needed to keep some heat in the chamber to run better?

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.

 

[anthony_marquart]

not sure where all this is going.. we know that 2 stroke engines are not considered efficient. Are we pumping energy out of the engine with the coolant water? Is the heat in the engine that goes out the exhaust and out in the coolant wasted energy that could be used in some way to help turn the prop?

 

[Jim Allen]

In my engines, I want to remove as much heat as possible through the head & the upper part of the engine. The reason is to keep a high charge density & the high pressure which results. Increasing the heat transfer in the two areas allows the engine tuner to raise the temperature in the combustion chamber & end up with extracting more power than previously possible.

This is why I use the head designed in 1988 that is shown in the photos. Not only does the design give the maximum rigidity possible, it also gives the largest area possible to transfer heat out of the upper cylinder & head areas.

SWAG, computational fluid dynamics & advanced computer simulation programs can give excellent starting points in the areas of engine development. However, nothing is valid until "cut & test". Cut & test must be done because each engine is unique unto itself.

Jim Allen

 

[ids987]

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

 

[ids987]

In my engines, I want to remove as much heat as possible through the head & the upper part of the engine. The reason is to keep a high charge density & the high pressure which results. Increasing the heat transfer in the two areas allows the engine tuner to raise the temperature in the combustion chamber & end up with extracting more power than previously possible.

This is why I use the head designed in 1988 that is shown in the photos. Not only does the design give the maximum rigidity possible, it also gives the largest area possible to transfer heat out of the upper cylinder & head areas.

SWAG, computational fluid dynamics & advanced computer simulation programs can give excellent starting points in the areas of engine development. However, nothing is valid until "cut & test". Cut & test must be done because each engine is unique unto itself.

Jim Allen

Thanks - as always Jim, for sharing.

Ian

 

[hugh hargett]

Is a cold air intercooler possible? Water/alchohol (may not be legal) injection? Ram Air? maybe sounds far fetched but if someone did it and it worked it wouldnt seem so off the wall.Does fuel temperature before combustion play a part?

Ian I dont doubt 30% at all it just sounds terrible to me to get less than a third of the power out of fuel when youre paying the price as if to get all the use out of the fuel.

Jim you may play around with the intake/exhaust ports or an exhaust throttle to have an affect? Glass beading,dimples or diamond cuts to the exterior of the heads/pipes never polish them to have more suface area to dissipate heat???? Does stoic numbers change as nitro percentage changes? Lastly how hot do you think the head should be?

 

[anthony_marquart]

So,. keeping the engine cooler makes the fuel charge more dense. I understand this concept, cooler, denser air makes more power for sure. But I have found that in my very small engines, .12 and .21s they run much better with very little cooling. Of course it's difficult to actually know the running temps,.. but when right off a hard run and pull right in... the engines are very hot to the touch,.. and water steaming off the header etc,.. maybe "hot" is too relative of a term. At what temp does the fuel charge become less dense and less dense and less effective? The more I read,.. the less I know.. hmm,..

and as always,.. Thanks Jim for sharing your thoughts?

 

[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.

 

[hugh hargett]

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.

 

[anthony_marquart]

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!!!