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Author Topic: What is meant when I am told that I am overcooling my engine?  (Read 1627 times)

Offline frank mccune

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What is meant when I am told that I am overcooling my engine?
« on: August 06, 2020, 04:18:35 PM »
      What are the symptoms of this and how does it affect my engine?

       Tia

Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #1 on: August 06, 2020, 11:14:59 PM »
   I've had flameouts in manuvers & sitting on the stooge. I sometimes thought it was because of overcooling. Brett has spoke on this subject I refer to more than once, hopefully he will be able to help you with your question.
    John L.

Offline Brett Buck

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #2 on: August 06, 2020, 11:27:16 PM »
      What are the symptoms of this and how does it affect my engine?

   Not to disappoint John, but I have no idea what that means or how that theory was arrived at, or who told you that.  I think it is very hard to "overcool" an engine, at least a stunt engine. What is it doing wrong?

   Temperature changes do affect the way it runs, of course, and most of my engines run leaner when they are hotter and richer when they are cooler. For example, if I fly back-to-back flights, the heat and heat soakback from the run will almost always cause the engine to start leaner/faster than it ran on a cold start. After a few laps, it cools back down to normal operating temperature and runs the same speed as it did on the previous flight. I have checked it in these conditions, and found it to run around 3-400 RPM faster.

    Brett


Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #3 on: August 07, 2020, 08:14:49 AM »
   I'm probably describing "  loading up " .
            John L.

Offline RandySmith

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #4 on: August 07, 2020, 03:22:23 PM »
I have never  seen an  engine  that was  over cooled
Tells  us  why yours  is
Randy

Offline Tim Wescott

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #5 on: August 07, 2020, 03:36:02 PM »
What does it mean when you are told that you are overcooling your engine?  It means that someone thinks you're overcooling your engine, and they said so.

How does it affect your engine?  Not at all -- engines can't hear, and if they could, they wouldn't be able to understand.

Perhaps if you could describe the circumstance in which someone told you that you are overcooling your engine, and give us their stated reasons for why you're overcooling your engine, we can unwind what the conversation actually meant.

It's certainly possible to undercool an engine, but given how many profiles there are out there with the engine hanging out in the breeze, and probably getting better cooling than they would in almost* any sort of cowling arrangement, and running quite well, thank you, I question the claim that your engine is overcooled.

* I'm sure that some freaking expert at cooling air-cooled engines could do a better job with a properly baffled cowling than an engine just hanging out in the breeze.  But for most of us mortals, a cowled engine isn't going to cool as well.
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Offline Ken Culbertson

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #6 on: August 07, 2020, 03:56:57 PM »
When you find out, let us know.  I want to use it on my next IC.  The only thing I can think of at all was an OS35s that was long in the tooth and would have virtually zero compression after you landed.  If I had to fly again for at least 10 min I would flip it over and fill the case with fuel to cool it down (loading up?).  There was more to it that that but I suppose I could have overcooled it.

Could he have been referring to the plug?

Another possibility was that he was referring to how nice it looked LL~

Ken
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Offline Tim Wescott

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #7 on: August 07, 2020, 05:12:44 PM »
Another possibility was that he was referring to how nice it looked LL~

I'm getting out my aluminum polish and I'm going to "overcool" an engine!!
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Offline Dan McEntee

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #8 on: August 07, 2020, 09:18:40 PM »
  You know, I have been around this stuff for along time, as long as this forum has been around, plus Stuka Stunt and years worth of reading model magazines before that, but I have to say that I have never ever heard that term,  "over cooled."  But I'm going to go WAY , WAY out on a limb here and blame Randy Smith for this. Over the years there have been many discussion on the forums about getting good head temperatures for our stunt engines and the need to run hot plugs and such, and Randy has mentioned many times that to achieve this, he cuts "heat dams" in the heads of engines that he reworks to help keep the combustion chamber hot and head temps up where they need to be. So, someone has taken that information and figured that the opposite can happen, and you can "over cool" an engine. I am interested in hearing what the guy's solution to the problem is??
   Type at you later,
    Dan McEntee
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Offline RandySmith

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #9 on: August 07, 2020, 09:32:34 PM »
  You know, I have been around this stuff for along time, as long as this forum has been around, plus Stuka Stunt and years worth of reading model magazines before that, but I have to say that I have never ever heard that term,  "over cooled."  But I'm going to go WAY , WAY out on a limb here and blame Randy Smith for this. Over the years there have been many discussion on the forums about getting good head temperatures for our stunt engines and the need to run hot plugs and such, and Randy has mentioned many times that to achieve this, he cuts "heat dams" in the heads of engines that he reworks to help keep the combustion chamber hot and head temps up where they need to be. So, someone has taken that information and figured that the opposite can happen, and you can "over cool" an engine. I am interested in hearing what the guy's solution to the problem is??
   Type at you later,
    Dan McEntee

Possible  he way  thinking that  because of a  Cold Glow Plug ??

Randy

Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #10 on: August 07, 2020, 11:34:17 PM »
 A guy told me several years ago that I could ruin an ABC engine by running it too cool ( rich )  before it is truely broken in.
  John L.

Offline Ken Culbertson

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #11 on: August 07, 2020, 11:42:05 PM »
A guy told me several years ago that I could ruin an ABC engine by running it too cool ( rich )  before it is truely broken in.
  John L.
Did that guy sell engines?

Ken
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Offline Brett Buck

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #12 on: August 07, 2020, 11:46:22 PM »
A guy told me several years ago that I could ruin an ABC engine by running it too cool ( rich )  before it is truely broken in.
  John L.

  Not very likely with a stunt engine, maybe with a racing ABC, like a SuperTigre X29. Exception is the original GMA-Jett 50, that had FAR too much taper, that one you could damage with running to rich.

   "Loading up" means it starts to misfire, apparently rich. On stunt engines, it usually happens on inside turns with inverted engines. I doubt that has anything much to do with overall cooling, it probably does have something to do with where the incoming fuel/air charge goes inside the cylinder and what it does when it gets there. For instance, my engines load up and almost quit on inside loops when running 22% 50/50 oil but not with 25 castor/75 synthetic, also 22% total oil.

     Brett

   

Offline Brett Buck

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #13 on: August 08, 2020, 12:02:06 AM »
  You know, I have been around this stuff for along time, as long as this forum has been around, plus Stuka Stunt and years worth of reading model magazines before that, but I have to say that I have never ever heard that term,  "over cooled."

   I have heard that term occasionally over the years, usually from "local engine experts" that dispense various forms of such wisdom periodically. Ironically, stacking in half-a-dozen headgaskets or hogging it out to a "hemi" would actually help you if it really was too cool, because lowering the compression makes you run the engine harder and thus hotter - because lowering the compression *greatly reduces the power*. Great modification, eh?

   The combustion temperature *does* make a significant difference in the engine parameters. For instance, you get more energy for a given amount of fuel if you burn it at a higher temperature, which is very important for something like a team racer. Stunt planes probably waste something like 95% of the potential energy of the fuel already, make it 94 or 96, it doesn't matter very much. Thermal stability is very important, which is why you can slavishly copy the blowdown, exhaust duration, and crank timing of a good engine on a different engine and it might run completely differently/like crap anyway - because there are a host of other things that matter, too.

    Brett

Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #14 on: August 08, 2020, 02:06:10 PM »
 Yeah,
   Some times I have trouble knowing what someone is trying to tell me like " overcooling"   so I ask in detail.  Anyway I hope to mow the field tomorrow & fly Monday & Wednesday.
   John L.

Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #15 on: August 08, 2020, 02:10:41 PM »
   I spoke with Larry Barrikman from time to time , he told me the OPS .40s that George Aldrich set up for him ran hotter than the stock OPS .40s.... he " thought" it may have been because George rechromed the liners,, he  said he hadn't taken them apart so we never found exactly why.
            I always enjoyed Larry.
                          John L.

Offline RandySmith

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #16 on: August 08, 2020, 03:37:10 PM »
   I spoke with Larry Barrikman from time to time , he told me the OPS .40s that George Aldrich set up for him ran hotter than the stock OPS .40s.... he " thought" it may have been because George rechromed the liners,, he  said he hadn't taken them apart so we never found exactly why.
            I always enjoyed Larry.
                          John L.

Hi John   I would  doubt  that,  It must  have  been  some  other  reason, like  machining  the  head  out  to lower  Compression,  The  OPS  came  stock  with a  hard  chrome  liner, so   honing  the  new  hardchromed  liner out to strip the  chrome, then  re-chroming  the  liner, really would  make  no sense  at all.  I have  seen  a  few of George's  OPS engines, and  they  had  machined  out  head chambers

Regards
Randy

Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #17 on: August 08, 2020, 04:06:45 PM »
  Very well could be Randy.
   John L.

Offline Brett Buck

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #18 on: August 08, 2020, 06:50:00 PM »
Hi John   I would  doubt  that,  It must  have  been  some  other  reason, like  machining  the  head  out  to lower  Compression,  The  OPS  came  stock  with a  hard  chrome  liner, so   honing  the  new  hardchromed  liner out to strip the  chrome, then  re-chroming  the  liner, really would  make  no sense  at all.  I have  seen  a  few of George's  OPS engines, and  they  had  machined  out  head chambers

   I don't know about the OPS specifically, but pretty much every GMA engine I saw had the chrome stripped, great amounts of taper added, and then rechromed (because he had the means). Also in all cases, he lowered the compression *dramatically*, like, .060-.070 or more (with machined-out combustion chamber). To make up the power, he put in an enormous venturi. The GMA-Jett 50, as I recall, was .250 with a flush inlet. In some cases, with low-pitch props, the engines would quit right after release from fuel starvation from the acceleration. They all ran *extremely hot* by stunt standards, switched from 4 to 2 and back at the slightest movement, and had nearly no or "reverse" break, where the power actually seemed to go down when it broke.

     For an example, original GMA-Jett 50 VS PA61 compression. We were checking with the pressure gauge (not the best way, but representative), spin over the PA, 125-130 psi. Same speed, same everything, GMA-Jett 50 - 35 psi. It also had a tendency to squeak audibly when running rich, and was extremely prone to sticking at TDC, even with the plug in. In that case, while I wouldn't call it "overcooling", it was clearly set up to work with the head/liner at much, much higher temps to try to take out some of the taper. Unfortunately, it had to run the same 1/2 horse everyone else's engine.

   He told me he did that on purpose, because the first ABC engine he ever got, he ruined. ST X29 or some equivalent, the first ABC engine in major production, for rat. He turned it over, it squeaked and was tight over TDC, "obviously" too tight, so he stuck it in the Sunnen and "fixed" it. And of course ruined it. Since, he said that he was making darn sure any ABC engine had lots of taper and was really tight over TDC, like the X29, to avoid a repeat. Note that this was all over on the old RCO forum, anyone who was around can confirm.

  Of course, the X29 at full song ran with the head glowing dull red, and a GMA-Jett 50 in stunt trim runs much, much cooler. The Commissioner and a few others had all sorts of issues with them (like breaking cranks), later got Dub Jett to make new liners with conventional taper, and then they ran well.

   Brett

   

Offline RandySmith

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #19 on: August 08, 2020, 07:01:33 PM »
Hi Brett

YOu could  be right, some  .. of  his  OPS  engines  may  have been done that way, I however  got  3  of his  OPS  motors  and  they  were  NOT  re chromed, They had  the  OPS  made  special, low timed  liners, and  were  the  STOCK taper  from OPS,  the  Heads  however  were  milled out, and  compression lowered,  The  venturis  were  also large.    I make  a lot of these  engines  for  pilots  all over, Mine  ran the  best on the  stock untouched head, except  I machined  a  heat dam around the plug  to  help it run cleaner,  many of  mine  were  the  low timed  OPS liner, but most of the ones  I built  had  my  AAC  piston sleeve  setup in them.  Low  taper  as in my Aero Tigers

Randy

Offline Brett Buck

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #20 on: August 08, 2020, 08:15:34 PM »
,  the  Heads  however  were  milled out, and  compression lowered,  The  venturis  were  also large. 

   The extremely low compression and the associated huge venturi seemed to be most of the problem with power/performance. I mean, if it dies on the takeoff roll, that is not conducive to high stunt scores.

    Once we took the 3/64" worth of head gaskets and got a reasonable venturi, the GMA-Jett 50 ran pretty OK, and would spin up normally, although it was no match for a 46VF. I asked about it, and he made absolutely no bones about the fact that's what he was thought we needed, engines that ran instant and "soft" breaks. Fair enough, far be it for me to argue with George Aldrich. I went a different way and got a PA61 and promptly made the flyoff.
 
   Later Jett started making the liners the way he wanted, and there are no problems with them.

     Brett

Offline John Leidle

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #21 on: August 08, 2020, 11:01:21 PM »
  Brett,
 A lot of what you wrote about George's work  & theories sounds very much what he told me.
          John L.

Offline Brett Buck

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #22 on: August 08, 2020, 11:22:18 PM »
  Brett,
 A lot of what you wrote about George's work  & theories sounds very much what he told me.
          John L.

   I don't think any of it was a secret. This was during/after the time that Paul won 5 in a row to the point he got bored with it doing *the exact opposite*, so I went a different way.

      But when  GMA talked about something, it made sense to listen. *I* didn't invent modern stunt - but he sure did.

    Brett

Offline Ken Culbertson

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #23 on: August 09, 2020, 06:21:04 AM »
Off-topic, but was he the same George Aldrich who worked at NASA and who's work was to smell things? I may wrong. L
Somehow I think you already knew the answer to that one.

Ken
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Offline Chuck_Smith

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #24 on: August 09, 2020, 09:43:59 AM »
You can "overcool" an IC engine running on methanol, but this will only occur at low revs and only at the intake, not the combustion chamber. It's the rule rather than the exception to see frost forming on the injector hat of an alchohol dragster.  You do the burnout to heat the engine as well as the tires. Nitro dragster engines will overcool at idle too.

Having said that, cooling the incoming charge is actually a good thing for power. The reason we spray the de-icing fluid on before the run is to make sure the butterflies aren't frozen shut at the hit.

You can overcool a gas engine too. That's why cars have thermostats, and why radials have cowl flaps.

What's all this have to do with a stunt ship? Absolutely nothing.

For a model airplane engine I've never seen a problem. I'd expect that if it ever did happen at would be at idle on an RC engine, not on a stunt engine that's going pretty strong at takeoff. 

I've had a few stunt engines get too hot before takeoff though. When they lean out as you walk out to the handle that's a warning sign.


Try this: Next time it poops out on you before takeoff grab the spinner and see if it's warm. (Assuming you have a metal spinner.) If it's warm to the touch you are probably overheating on the ground.

YMMV, all opposing viewpoints considered.

Chuck
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Online Lauri Malila

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #25 on: August 09, 2020, 09:52:41 AM »
When an engine runs well in a hot weather, it's often a little too powefull in cold early morning air. Or at least the 4-2 shIft is more violent and not very pleasant.
I have found a couple of big silicone O-rings around head & cylinder fins cure the issue. So I guess it's running too cool. L

Offline George Fruhling

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Re: What is meant when I am told that I am overcooling my engine?
« Reply #26 on: August 09, 2020, 02:00:57 PM »
I saw a case of over-cooling once but it was with an rc boat.  Decades ago, at the pond in Memphis TN. a guy was having trouble tuning his Atlas Van Lines .60 engine.  Was running it with two cool clamps. One of the regulars told him to take one off.


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