Gas Engine cavitation
- Thread starter PaxilPlease
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Exactly....was just going to say this!
Diesel cylinder liners get cavitation damage because the liners expand and contract when the cylinder fires. When it contracts the coolant on it boils from being in a low pressure zone.
Gas engines don't have that kind of compression that a diesel does so liner cavitation does not happen with those.
Gas engines don't have that kind of compression that a diesel does so liner cavitation does not happen with those.
This is fascinating.
Yep!! Better not run that hemi hard , or next post will be "how hard is it to swap hemi heads"
Deliberately running a cooling system un-pressurized will have the unintended consequence of driving automotive engineers to drink.
It may be hard to accept, but 99.9% of the time, having a shade tree doesn’t make you a master mechanic & smarter than the people who designed your car.
Z
It may be hard to accept, but 99.9% of the time, having a shade tree doesn’t make you a master mechanic & smarter than the people who designed your car.
Z
So you know more than almost 100 years of automotive engineering or you are a troll. This whole post sounds like absolute bullsh**. Cavitation is caused by low pressure reducing the boiling point of a liquid you are actually making the issue worse by running the cooling system at atmospheric pressure.
First you need to diagnosis the cause of cooling system that over heats. Then decide of the way to correct the problem. Water/coolant cavitation is not easy to trace in any engine as a cause of coolant temperature uncontrollably changing.
I did not catch anywhere that any member had this problem? And drilling a hole in a cap designed to maintain a controlled pressure? Why would you do that?
I did not catch anywhere that any member had this problem? And drilling a hole in a cap designed to maintain a controlled pressure? Why would you do that?
I had a Model A ford and it had no pressurized cooling system. I had several 1936 Fords and they had no pressurized cooling system even with 2 water pumps. I also have used a 7 lb casp when I had a leak I couldn't find. That works ok if its not too hot.
I've read that with some high RPM engines, the water pump will cavitate near redline. I don't know whether it's actually true, but it makes sense if the engine's water pump pulley ratio spins it faste enough to provide adequate cooling at 700 RPM idle, then spinning 10x faster at 7,000 RPM may cavitate.
Those are extreme numbers. Most engines don't have such a wide RPM range so cavitation would be less likely.
Years ago, I had a car with the Ford 4.6 Cobra V8 that idled at 600 with a 7000 redline. I installed underdriven pulleys for the water pump & alternator. It gained about 8 RWHP on the dyno (about 2-3%) and of course by slowing down the water pump relative to the crankshaft it also reduced any chance that the water pump was cavitating near redline. Of course, it may not have been cavitating with the stock pulleys.
Those are extreme numbers. Most engines don't have such a wide RPM range so cavitation would be less likely.
Years ago, I had a car with the Ford 4.6 Cobra V8 that idled at 600 with a 7000 redline. I installed underdriven pulleys for the water pump & alternator. It gained about 8 RWHP on the dyno (about 2-3%) and of course by slowing down the water pump relative to the crankshaft it also reduced any chance that the water pump was cavitating near redline. Of course, it may not have been cavitating with the stock pulleys.
Funny thing: I just looked up engine water pump cavitation and it looks like a whole 'nuther thing from cavitation I was thinking of, in reference to boat propellors. But it does look like the speed at which the pump spins is a contributing factor to both.
The main source of cavitation in an ICE is when air bubbles from steam pockets reach the impeller. Increased block pressure raises boiling points, reducing the chance for steam pockets (near the combustion chamber).
Before the Ford Model A is used again for an example of a no pressure cooling system, it bears pointing out that a common cure for Model A chronic overheating was to put washers, ie restrictions in the coolant flow to build pressure.
We’ve learned a thing or two since the Model A , and my dad were he alive would be the first one to criticize the Model A cooling. As he owned one when they were new
and was cussing it’s cooling system from day one .
Basically cooling 101 , and right out of the FlowKooler web site,
“…,,FlowKooler pumps build block pressure. Increasing the block pressure by as much as 22% helps reduces hot spots on cylinder walls, prevents the formation of steam pockets in the engine block and prevents the cavitation of the impeller…..”
flowkoolerwaterpumps.com
Before the Ford Model A is used again for an example of a no pressure cooling system, it bears pointing out that a common cure for Model A chronic overheating was to put washers, ie restrictions in the coolant flow to build pressure.
We’ve learned a thing or two since the Model A , and my dad were he alive would be the first one to criticize the Model A cooling. As he owned one when they were new
and was cussing it’s cooling system from day one .
Basically cooling 101 , and right out of the FlowKooler web site,
“…,,FlowKooler pumps build block pressure. Increasing the block pressure by as much as 22% helps reduces hot spots on cylinder walls, prevents the formation of steam pockets in the engine block and prevents the cavitation of the impeller…..”
Commons Questions about Hi Flow Pumps
Why make a Hi Flow Water Pump? Who needs hi flow rates in their engine and a bunch of other great questions answered from the company who pioneered hi flow water pumps way back in the seventies!
flowkoolerwaterpumps.com
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Yoh Gimp! Did you read my first post in entirety? If so, maybe you could have a reading comprehension problem. Did you read where I ran two cars doing the same thing with no long term issues? It seems like I touched a nerve with you. Calling me a troll because I asked a couple questions? Absolute bullsh**? We can all act tough and accuse people of things behind a keyboard. You certainly wouldn't do it in person. I assure you.
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Well....somehow I do 95% of maintenance and repairs myself and drive cars long enough into the ground. I may know a thing or two about cars and mechanics in general. Who knows - maybe I am smarter than you?
Smarter than me ?
maybe.
Smarter than every automotive engineer in the world who designed all the pressurized cooling systems in use today ?
No, not smarter than them.
Z
I’ve never heard of any of these issues being caused solely by a pressurized cooling system. Neglect and age are usually the biggest causes of these problems… especially the head gasket one, the sub 30psi of coolant pressure is absolutely nothing compared to the 700+psi found in the combustion chamber while under load.
The system really needs to be under pressure, even at a 50/50 mix the boiling point is only ~226F, a 5.7 Hemi will hit that easily in stop and go traffic in hot weather and cause boiling. At 16psi that raises to 267F, a much healthier margin.
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You seem to like to make assertions about me based off your assumptions. Not a really good thing to do, and you likely may have been bitten by it either professionally or personally. If you can't engage in a thread without resorting to petty sophomoric responses, then I would ask you not to reply. Have a nice day bud.
There are valid technical reasons why automakers went to pressurized cooling systems many years ago, some of which are listed in this thread.
This sounds familiar.
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