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But...
Does the increased internal system pressure have any effect on heat transference efficiency?
I think Haystack pretty well nailed it. Just to try to explain it in a different way, you have several factors going on in a cooling system. When you refer to "heat transfer efficiency" I see that as being a combination of several things. The inherent design of the engine block and components and radiator and how well it disperses heat. The coolant itself and whether it is water or glycol changes the BTU/pound of heat it can carry(glycol carrying something like 90% of pure water). How efficient the rad is in terms of overall airflow which gets into fan capacity and what the heat transfer of the cooling fins is per sq/ft or whatever. So all other components of the system being equal and back to "heat transfer efficiency", the increased pressure in the system increases the boiling point which reduces problem areas inside the block which would start to boil at a lower pressure. The increased temp of the coolant carries more BTU. That is what cooling is all about is removing the BTU. One pound of water raised one degree F is one BTU. So if the water temp is higher it is carrying more BTU so "heat transfer efficiency" will be greater. The higher the coolant temp in the rad the greater heat transfer to the air on a hot day. This is known as Delta T in the formulas dealing with heat transfer. For example in determining how many gallons per minute you need to cool your engine the formula is quite simple - gpm=total btu of water jacket heat rejection divided by 450 (factor for gallons per minute to pounds per hour x 90% for glycol) x Delta T. So if your coolant temp leaving the engine is higher, you get more heat transfer to the air(Delta T) . So for example if Delta T changes from 10 degrees F to 20 degrees F, not that hard to do, your gpm required is half and/or and ability to cool the engine doubles. So to reflect on your question, increased system pressure results in possible higher temperature without boiling, which can significantly increase the Delta T, so I would say that qualifies as increased "heat transfer efficiency".

I am speaking of this cooling system knowledge coming from a heavy equipment and farm background and more recently with an old boat with heating problems and more time on my hands. The engine is a 6D14 Mitsubishi NA in line 6 with 6.55 liters or 400 cid and 120 hp. It is keel cooled which means instead of a rad it has about 40 feet of 1 1/4" K grade rigid copper pipe in the sea water under the hull. I asked hundreds of people about where to start on this problem, including engineers at some of the heat transfer specialty businesses in Edmonton that build power generating and pumping skids for the energy industry. Without all the technical specs they would get from the design engineers for engines and cooling components, they just glaze over and do not have all the numbers to plug into the formulas and it ends there. So I started reading and compiling some of the key data factors in every cooling system. Start with the water jacket heat rejection number from the manufacturer. Which for my 6D14 is 138,000 BTU. But does that include the heat load from the water cooled exhaust manifold(required to lower engine room temps and therefore engine air intake temp etc etc.) and the transmission, and the hydraulic system cooler? I have learned that NO it does not. So I approach total BTU generated from how much diesel is burned per hour. So for my engine 120 HP, generating 16 hp hrs/ US gallon of diesel?? (all engines are in a range of about 15 to 18, newer higher tech being closer to 18) I come up with 7.5 us gal/hr. at EPL. Diesel has about 138,000 btu/gal so X 7.5 = about 1,000,000 BTU per hour. Average old school engines like mine disperse heat about 1/3 out the cooling system, 1/3 out the exhaust, and about 1/3 gets turned into rotary energy and friction. So if I have to get rid of 330,000 btu from the rad, plus say half of the btu from the water cooled exhaust manifold, plus 5-7% of the rotary energy in the transmission, and some % of hydraulic system heat generated, I am well over 500,000 btu total heat to be removed by the keel cooling loop. Vastly more than the water jacket heat rejection figure of 138,000 btu published by Mitsubishi and what I suspect my keel cooler was designed for. I got into several heated debates with keel cooler manufacturers and designers that only looked at the 138,000 figure. One guy told me "I have been doing this for 30 years, are you questioning me"? Well yes I am, and that is why my engine is overheating and always has. So I proceeded to build a test bench to measure the gpm flow of my water pump which is the other huge factor. After rebuilding and machining the impeller clearance to .020" it was really close to the manufacturers spec of 58 gal/min at 8 psi. So now I can do some flow calculations through my 1 1/4" cooler pipe with a dozen 90s and Ts and fittings and restrictions. Not even close!! It would take 40-50 psi to push 58 gpm through that maze of cooling pipe. The engine spec is 15 psi max internal engine pressure. That rules out a 9200 Hypro sprayer pump that could push 58 gpm but at 40-50 psi. And at those higher flow rates the maximum feet per minute flow rate in the pipe of 2-8 feet per minute is exceeded. So right there I know the existing cooling system is way undersized for handling 500,000 btu with 58 gpm and with total restriction on the system of less than 8 psi. So the only solution is increase the size of the plumbing to all 2" and shorten the length and restriction of the system. I have to install my new Fernstrum 2" diameter pipe keel cooler this spring so have yet to see if it will all work. Also I have determined that the factory thermostat and housing is part of the restriction problem so am building my own temperature control manifold patterned on an Amot temp regulator used in industry for this exact purpose - better control and full flow in bybass mode. I am using a 3406B 190 F thermostat for ample flow.

Cooling system problems used to contribute to around 40% of engine failure problems. It all seems like a pretty big mystery at first glance, but when you break it all down to what one BTU is, it all starts to make more sense. And if the design engineers would allow a little more wiggle room in the capacity of cooling systems, we all would have a lot less expensive problems.
 

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In 1970 my cousin put an in-line 6 cylinder liquid cooled 2 stroke Mercury Marine engine in his Snow Jet for snowmobile oval racing. He quickly discovered that the water jacket design was meant to cool the exhaust exiting each individual cylinder port and required either a lake, or a radiator as big as a wall, or other complex engine redesigns.

This was all done as a ploy to beat my dad, who somehow in 1969 was able to procure an Arctic Cat from the factory racing shop that had hand built a sled using a two cylinder bottom end from a German engine used for small pipelines in the Canadian oil fields. For sleds they used larger 372 cc cylinders hand tooled to fit on it and the porting and heads were drastically modified for performance. Those engines were affectionately known as JLO 744’s. Ours was actually increased to 792cc, and all that were ever built had their fan cooling systems and kick starting systems machined off and just used free air cooling like an aircraft engine.

Oddly, in 1968 my Dad had put down deposits on a new 639 Ski-doo TNT and a Polaris 744. The 744 Polaris somehow became unavailable and was never delivered. Decades later after my dad had died, an enthusiast and amateur investigative reporter from California tried to find out how an engine, or a few of them, ended up at Arctic Cat that had been rigged together up the state at the Polaris factory?

The details of that are still sketchy. It didn’t really cool itself since the stubby little fins would brand your fingertips. That didn’t really matter either since it only had to last a few seconds to do 3-5 laps at a time in this region. Fifty years ago this month, I know for a fact, it was one of the fastest single engine snowmobiles in existence. They let me use it as a junior once before they banned it from the class. I lapped everyone on lap three.
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A little off track but I remember back in those days there was all kinds of ideas for racing snowmobiles and how to make them faster . There was a guy named Louis Caron who did all kinds of mods on sleds back then - even built a sled with another single banger at the back of the sled to get more speed ( think that was a Polaris ) . Ended up starting a dealership called Carons Cats was a wild time to think back then and what a farmer could rig up .He was a great family friend and I even worked for him for a while to pay for a used 650 king kat racing sled .
 

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As soon as you mentioned that name it rang a bell but I couldn’t have reconnected it with that dealership. I think maybe my dad and myself visited that dealership on the farm to inspect a 650 King Kat in either 71 or 72, which we declined to purchase. I can’t remember if that was just before or just after we bought and a few months later resold our 800 4 cylinder King Kat at the end of the 1971 winter.

It seems to me that a little later on, likely 73 or 74 we also looked over a 650 King Kat at Topnick’s Panther Cats. We probably came home with a 72 440 3 cylinder EXT that I used for a time, but my precise memory fails me. I wonder if there were originally two 650’s placed in Manitoba or if yours is the same one that made its way to Topnick’s in Stienbach?

My cousin told me recently that he speculated on a 793 triple King Kat replica built from parts with no serial plate. It went to New York State for $11,000. US, so I hope you know what you have there.
 

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There was no antifreeze required in those days. I believe Arctic’s first short production runs of free air cooling sleds would have been the the 71 King Kat’s, including the four cylinder Kawasaki 800 on the left in the photo and the twin cylinder 399 EXT on the right. We and most others who were racing had been building free air designs out of fan cooled engines considerably before then. The 76 and 77 Z’s ushered in liquid cooling for the brand. We ourselves didn’t get any production liquid cooled versions until the introduction of the 100% new and revised 6000 El’ Tigre’s, in 1978, which I had the pleasure of thrashing six of them right on into April in 78, 79, & 80. The 1981 model should have only had one gripe left if you could hold it wide open most of the time on a tank full of fuel. It’s CDI box was still bolted to the crankcase and they got too hot and were subject to vibration damage in spite of the fact the cylinders and head were antifreeze cooled by a big radiator and two under tunnel heat exchangers maintaining 120 degrees Fahrenheit.

Bolting electronic packages onto engine blocs is going to present some long term COSTS on depreciated machines. Mark my WORDS.
 

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The cooling properties of coolant only a part of what makes a good coolant. That part is a short term, at the moment thing. If it overheats, coolant type is likely the last thing I would be looking at. I see cooling ability of the coolant it self to only be a selling point to the ignorant. Might just need to fix your cooling system.

The cavitation, corrosion, and electrolysis prevention it gives the engine is the long term factors I would be looking at. Lots go into cooling systems. Unfortunately, keeping coolant from killing your pets has made a huge factor into types of coolant over the past 25 years or so. That likely has not improved the life of your engine.
 

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There was no antifreeze required in those days. I believe Arctic’s first short production runs of free air cooling sleds would have been the the 71 King Kat’s, including the four cylinder Kawasaki 800 on the left in the photo and the twin cylinder 399 EXT on the right. We and most others who were racing had been building free air designs out of fan cooled engines considerably before then. The 76 and 77 Z’s ushered in liquid cooling for the brand. We ourselves didn’t get any production liquid cooled versions until the introduction of the 100% new and revised 6000 El’ Tigre’s, in 1978, which I had the pleasure of thrashing six of them right on into April in 78, 79, & 80. The 1981 model should have only had one gripe left if you could hold it wide open most of the time on a tank full of fuel. It’s CDI box was still bolted to the crankcase and they got too hot and were subject to vibration damage in spite of the fact the cylinders and head were antifreeze cooled by a big radiator and two under tunnel heat exchangers maintaining 120 degrees Fahrenheit.

Bolting electronic packages onto engine blocs is going to present some long term COSTS on depreciated machines. Mark my WORDS.
Very cool pics! Yes pun intended on a cooling thread! I drove a Cat exterminator briefly in about 1971. That was the hardest pull on my arms I had ever had experienced. That thing just never stopped spinning the track!! I also owned a 80 1/2 Tigre that chalked up way more than it's share of wins across a field, down the river or up a mountain. Was it 1980 1/2 that the 500 Suzuki liquid cooled was put in as a stock engine? An upgrade from the 440. Head and shoulders above anything else in the class in the day. Mine was piped and ported and ran 9,000 rpm. The 102C Comet had a short life on that application and needed regular balancing! Still have a 1984 stock El Tigre that was a great sled. I bet you have a lot of good stories!!!
 

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Was it 1980 1/2 that the 500 Suzuki liquid cooled was put in as a stock engine? An upgrade from the 440. Head and shoulders above anything else in the class in the day. Still have a 1984 stock El Tigre that was a great sled. I bet you have a lot of good stories!!!
Both the 78 and 79 6000’s were a new 440 cc liquid cooled Suzuki. The 1980’s and 81’ 6000’s were 500cc liquid versions of the same engine family with a revision to the hood in the radiator intake area. The 500cc free air version in the beginning of the Suzuki era starting back in 1976 was badged as a 5000. I wasn’t aware that any 6000’s were ever referred to as 1/2 year models but I suspect if they were, in reality they were 1980’s that were certified as having had their mandatory updates done which included a larger diameter primary clutch, wider belt and newly available aluminum secondary. The other mandatory bulletin was to remove and return the entire, newly in house designed, hydraulic brake system and replace it with the previous cable brake assembly. Possibly an 80 1/2 was equipped with an 81 hydraulic brake which was vendor supplied I think? The expense of this recall and litigation surrounding it surely added to Arctic Enterprises Inc financial peril.

Yes I have lots of memories that could be expanded into stories, sometimes unbelievable, sometimes hilarious, and a few that are just hard to define.

I still have one of the pair of 1980 6000’s, waiting, in the heap of good junk against the wall.
 

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Come to think of it this might be an EI’Tigre record. This 79, 5000 won the C stock, B stock, and A stock Canadian championships over the course of a couple of hours when it was five years old. Granted, the throttle never lifted all afternoon. ;)
6000’s and other “A” stockers were much stronger. Edit: In fact I think the 500cc 6000’s and Centurian’s were likely not allowed in any class because of speed and displacement. Um, I hate to admit it but my old man and his Centurian kicked my bragging buddy and myself’s asses on our 6000’s in a race to the end of the ranch and back when he was 60 years old, and he was already in the house when we pulled in. Humm the very last time we raced he beat me! I never noticed the full throttle cut lines in the ice on the entry until just now. Haha, poor Earl is pointing his thumb at the ground for some reason. (He’s actually wondering WTF is that retiree punk doing in this class, probably hollering go home) Fun times!



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Both the 78 and 79 6000’s were a new 440 cc liquid cooled Suzuki. The 1980’s and 81’ 6000’s were 500cc liquid versions of the same engine family with a revision to the hood in the radiator intake area. The 500cc free air version in the beginning of the Suzuki era starting back in 1976 was badged as a 5000. I wasn’t aware that any 6000’s were ever referred to as 1/2 year models but I suspect if they were, in reality they were 1980’s that were certified as having had their mandatory updates done which included a larger diameter primary clutch, wider belt and newly available aluminum secondary. The other mandatory bulletin was to remove and return the entire, newly in house designed, hydraulic brake system and replace it with the previous cable brake assembly. Possibly an 80 1/2 was equipped with an 81 hydraulic brake which was vendor supplied I think? The expense of this recall and litigation surrounding it surely added to Arctic Enterprises Inc financial peril.

Yes I have lots of memories that could be expanded into stories, sometimes unbelievable, sometimes hilarious, and a few that are just hard to define.

I still have one of the pair of 1980 6000’s, waiting, in the heap of good junk against the wall.
Pretty sure my 6000 was a 1980 because my buddy that found it for me had a 1981 which was a little different. I don't recall it having a hydraulic brake but that is a long time ago! You mention Centurion. The same guy that found the 6000 Tigre for me had lived in Bozeman MT for a number of years and lined up a trip for 10 of us locals in Feb 1982 to that area, including Yellowstone. Three of the Bozeman locals that we rode with were late 60's age enthusiasts riding sleds like a modified Centurion 500 3 cyl, modified 650 Polaris ??? and a Cat dealer riding a liquid cooled Cat independent prototype. We had to work really hard in the waist deep powder to keep up to those guys but we did win over their confidence and I returned many times over the next 15 years to ride with those old boys again. Some of my best ever snowmobiling memories! I have a picture of the 67 year old on his Centurion at the top of a 1/4 mile hill climb still going so fast he is airborne and all you can see is blue sky in the background! Right there I said I want to be doing that when I am his age!

yes Cat went through a hard time right in there. They had a poster that looked like a calendar with an X across 1982 and 1983 and "Gone Fishing" hand written across those two years. It was cool way of stating the obvious. And then came the growing pains of independent!
 

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Funny to mention the " independent " as I have one of the first independent sleds that artic cat made - a 79 trail cat with a 340 Suzuki . The year earlier they had made a cross country cat for racing more or less a prototype . just rebuilt it two years ago with new paint and all - looks really good but needs new shocks as the old ones freeze up .
 

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Here’s a couple of photo files from Boss Cat Legacy of the racing side that will bring back memories of that fast moving era Marshall. Arctic Cat really put an emphasis on the antifreeze system once the engines were designed. Shortly after this era, protruding radiators were banned. In the fall of 1977 when I saw the first photo that was released of the new 1978 factory team Sno Pro sleds, I knew I had to somehow get out of stock class racing and back into the super mod’s.

The Scorpion oval sleds were the same architecture as the Arctic Cats but with a different skin. One of the 1980 replicas of the 79 team sleds was built for us, but I had a disagreement with them when they couldn’t provide the engine that was in our contract in a timely manner, or at the agreed price. I had to go and get a new leftover 79 Ski-doo to get what I thought was a decently powerful 340 engine. I had hoped to pick up the Arctic Cat from the warehouse in Winnipeg later on just to get the chassis once I had the Rotax sorted out on a slough at home here, and then put the Rotax engine in the Arctic Cat. By the time I solved it’s puzzle and put an Arctic Cat ignition into the Rotax and made one flywheel out of two, the Ski-doo had too good of a win record in Saskatchewan and Manitoba to give it up. They were ecstatic over their dumb luck, and the next year that engine architecture got a newly designed high wattage stator and flywheel along with much larger ignition coils to get get rid of the weak spark and its jetting conundrum of misfiring unless it was jetted lean.


https://www.bosscatlegacy.com/acproto/racing/1978.htm

https://www.bosscatlegacy.com/acproto/racing/1979.htm



https://www.thecombineforum.com/forums/attachment.php?attachmentid=155649&stc=1&d=1574870655

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Here’s a couple of photo files from Boss Cat Legacy of the racing side that will bring back memories of that fast moving era Marshall. Arctic Cat really put an emphasis on the antifreeze system once the engines were designed. Shortly after this era, protruding radiators were banned. In the fall of 1977 when I saw the first photo that was released of the new 1978 factory team Sno Pro sleds, I knew I had to somehow get out of stock class racing and back into the super mod’s.

The Scorpion oval sleds were the same architecture as the Arctic Cats but with a different skin. One of the 1980 replicas of the 79 team sleds was built for us, but I had a disagreement with them when they couldn’t provide the engine that was in our contract in a timely manner, or at the agreed price. I had to go and get a new leftover 79 Ski-doo to get what I thought was a decently powerful 340 engine. I had hoped to pick up the Arctic Cat from the warehouse in Winnipeg later on just to get the chassis once I had the Rotax sorted out on a slough at home here, and then put the Rotax engine in the Arctic Cat. By the time I solved it’s puzzle and put an Arctic Cat ignition into the Rotax and made one flywheel out of two, the Ski-doo had too good of a win record in Saskatchewan and Manitoba to give it up. They were ecstatic over their dumb luck, and the next year that engine architecture got a newly designed high wattage stator and flywheel along with much larger ignition coils to get get rid of the weak spark and its jetting conundrum of misfiring unless it was jetted lean.


https://www.bosscatlegacy.com/acproto/racing/1978.htm

https://www.bosscatlegacy.com/acproto/racing/1979.htm



https://www.thecombineforum.com/forums/attachment.php?attachmentid=155649&stc=1&d=1574870655

https://www.thecombineforum.com/forums/attachment.php?attachmentid=155647&stc=1&d=1574870655
Very purpose built. With a handle for only turning with speed in one direction.
 

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Very purpose built.

I’d like to see a Quadtrac with auxiliary radiators six feet high and a foot and a half wide angled back from the rear cab posts with nice stylized frames and screens on both sides of them. They don’t need fans, they can just passively do their job cooling and cleaning themselves which ever way the wind blows, so it wouldn’t have to run at 210 degrees because of wind direction, or for no good reason.
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Here’s a couple of photo files from Boss Cat Legacy of the racing side that will bring back memories of that fast moving era Marshall. Arctic Cat really put an emphasis on the antifreeze system once the engines were designed. Shortly after this era, protruding radiators were banned. In the fall of 1977 when I saw the first photo that was released of the new 1978 factory team Sno Pro sleds, I knew I had to somehow get out of stock class racing and back into the super mod’s.

The Scorpion oval sleds were the same architecture as the Arctic Cats but with a different skin. One of the 1980 replicas of the 79 team sleds was built for us, but I had a disagreement with them when they couldn’t provide the engine that was in our contract in a timely manner, or at the agreed price. I had to go and get a new leftover 79 Ski-doo to get what I thought was a decently powerful 340 engine. I had hoped to pick up the Arctic Cat from the warehouse in Winnipeg later on just to get the chassis once I had the Rotax sorted out on a slough at home here, and then put the Rotax engine in the Arctic Cat. By the time I solved it’s puzzle and put an Arctic Cat ignition into the Rotax and made one flywheel out of two, the Ski-doo had too good of a win record in Saskatchewan and Manitoba to give it up. They were ecstatic over their dumb luck, and the next year that engine architecture got a newly designed high wattage stator and flywheel along with much larger ignition coils to get get rid of the weak spark and its jetting conundrum of misfiring unless it was jetted lean.


https://www.bosscatlegacy.com/acproto/racing/1978.htm

https://www.bosscatlegacy.com/acproto/racing/1979.htm



https://www.thecombineforum.com/forums/attachment.php?attachmentid=155649&stc=1&d=1574870655

https://www.thecombineforum.com/forums/attachment.php?attachmentid=155647&stc=1&d=1574870655
I had raced one of these when at carons cats - jim Thompson was on it and it was a drag race out in the field besides the dealership . When we both hit the throttle he straightened out the handlebars when the skis were up in the air and when he came down the machine went one way and he went the other which made a really good laugh for all . On the second try I still kicked his ass but he was only 440cc .
 

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I had raced one of these when at carons cats - jim Thompson was on it and it was a drag race out in the field besides the dealership . When we both hit the throttle he straightened out the handlebars when the skis were up in the air and when he came down the machine went one way and he went the other which made a really good laugh for all . On the second try I still kicked his ass but he was only 440cc .

This photo was sent to me last week Marshall. It was the last time out on this sled, but a testing concussion from the month before wouldn’t cooperate and I declined to continue with qualifying because of dizziness.

I actually retrieved this 1991/92 chassis from a woodshed at a residence by a lake near Albertabuck’s hometown and restored it into this rendition for the last event.

I believe it had eight antifreeze injection nozzles to lubricate its two track systems to make it fast and prevent wear.

circa (1997)
6682E4F3-1634-47A6-BAE0-50FB379F880A.jpeg
 
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