914/RS: Re-build and Re-design: Engine and Cooling |
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914/RS: Re-build and Re-design: Engine and Cooling |
Cracker |
Oct 24 2017, 08:45 PM
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#1
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Advanced Member Group: Members Posts: 2,148 Joined: 2-February 10 From: Atlanta (area) Member No.: 11,316 Region Association: South East States |
Well, I have never posted a "build" thread in the past - it will serve as my re-build as my car has been running for some time. Something that might be interesting for the H20 folks is a performance based cooling system - oil included.
The silver lining associated with the engine down is I have been intending to make the cooling updates for well over a year now. Its such a PITA I have delayed engagement. LS engines are notorious for running high oil temps on track - GM will tell you it is ok - I believe it is not. Likewise, mid-engine cars have a notoriously difficult time controlling temperatures simply because of the location of the engine and cooling systems. This is exacerbated with additional power. I walked the pits of the Walter Mitty Classic at Road Atlanta last year and took a bunch of pictures. All late-model mid-engined prototypes used Water-to-oil heat exchangers in lieu of oil-to-air. It adds a serious layer of complexity since the coolant now has to carry the burden of dispersing allot of extra energy. That is what I will be updating: all lines, the radiator, shroud addition, coolant distribution chambers, etc. One of the benefits of this new system is the ugly-as-sin rooftop oil cooler scoop will be eliminated (not to mention the drag that thing is causing ~ slowing me down)! Just remember, along with most other members here, I ain't no "Tygaboy"! (IMG:style_emoticons/default/bye1.gif) Tony |
Cracker |
Oct 27 2017, 06:26 PM
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#2
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Advanced Member Group: Members Posts: 2,148 Joined: 2-February 10 From: Atlanta (area) Member No.: 11,316 Region Association: South East States |
Worn - The water to oil heat exchangers are more efficient...a unit measuring roughly a foot long (like my cooler) has the equivalent capacity of a 40-row oil to air cooler. The other benefit is what was pointed out in the last post - it is far easier to plumb oil to a cooler located in the rear of the chassis than to the front. All of this improved energy loss doesn't come free...my entire cooling system from lines, junction boxes, radiator and an improved shroud is all being replaced.
Another big difference between the two systems is the oil being cooled will be off of the scavenge circuit - not the pressure side. It will move slowly enough to give the cooler/coolant a better chance to pull the heat from the oil. I will probably then pass either the coolant or the oil through an liquid to air cooler with a fan pack after the first cooler. The coolant will rejoin the engines heading towards the radiator - the oil will then go the dry sump tank waiting to be sucked into the engine. I do not pretend for a moment to know the scientific explanations or basis but having gone through what doesn't work - I have learned quite a bit. Thanks for the thoughts... Tony |
jd74914 |
Oct 28 2017, 09:12 AM
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#3
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Its alive Group: Members Posts: 4,796 Joined: 16-February 04 From: CT Member No.: 1,659 Region Association: North East States |
Another big difference between the two systems is the oil being cooled will be off of the scavenge circuit - not the pressure side. It will move slowly enough to give the cooler/coolant a better chance to pull the heat from the oil. Sorry, but this is very incorrect. Slower speeds do not allow more heat transfer. You're actually decreasing the internal convention coefficients of your cooler (reducing it's overall "efficiency"), so you need more temperature difference to transfer the same amount of energy. The perceived "slower=colder" is because now you have less fluid mass to cool, so the energy balance works out that the outgoing fluid is cooler (assume the two flows are going in opposite directions). I will probably then pass either the coolant or the oil through an liquid to air cooler with a fan pack after the first cooler. The coolant will rejoin the engines heading towards the radiator - the oil will then go the dry sump tank waiting to be sucked into the engine. I do not pretend for a moment to know the scientific explanations or basis but having gone through what doesn't work - I have learned quite a bit. Thanks for the thoughts... If you are going to add a second air-to-fluid cooler, I would do it on the oil side. Putting it on the water side will be a less efficient use of components since now you'll be lowering the water temperature into your radiator, lower temperature difference between the radiator inlet and air inlet, effectively reducing heat transfer rates. It's just not the most efficient use of energy. On the oil side you can use it for fine temperature control, depending on what oil and and water temperatures you like. I wouldn't be surprised if some GT cars are built like this because water temperatures in their pressurized coolant systems are probably much higher than desired oil temperatures. Just something to think about. (IMG:style_emoticons/default/smile.gif) |
Cracker |
Oct 28 2017, 09:52 AM
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#4
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Advanced Member Group: Members Posts: 2,148 Joined: 2-February 10 From: Atlanta (area) Member No.: 11,316 Region Association: South East States |
Interesting. Aviad and ARE who both contributed to the construction of my dry sump system gave that "rationale" as to why they wanted me to cool the scavenge circuit. My existing cooling system is inadequate (IMO) to add the W2O cooler as it sits currently...time will tell which method is more effective.
Tony Another big difference between the two systems is the oil being cooled will be off of the scavenge circuit - not the pressure side. It will move slowly enough to give the cooler/coolant a better chance to pull the heat from the oil. Sorry, but this is very incorrect. Slower speeds do not allow more heat transfer. You're actually decreasing the internal convention coefficients of your cooler (reducing it's overall "efficiency"), so you need more temperature difference to transfer the same amount of energy. The perceived "slower=colder" is because now you have less fluid mass to cool, so the energy balance works out that the outgoing fluid is cooler (assume the two flows are going in opposite directions). |
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