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 |
worn |
Oct 27 2017, 01:58 PM
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#2
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can't remember Group: Members Posts: 3,290 Joined: 3-June 11 From: Madison, WI Member No.: 13,152 Region Association: Upper MidWest |
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. I like your posts and builds. I figure if you aren't a Tygaboy you must be his cousin. I am trying to understand the physics here. The heat goes from the oil to the water to the air. How is this more efficient than oil to air direct? Sooner or later you are cooling stuff with ambient air moving across as big a surface as you can afford to have. The possibilities that I can think of are A) it easier to produce a larger water radiator than an oil radiator, or B) the heat transfer from oil to water and/or water to air adds up to better than oil to air - though I cannot figure why that would be true. If you could use the phase change from liquid water to steam, it would produce tremendous heat absorption. But only as long as you have water left, so I don't think that is it. Water has a higher heat capacity, so you can get more heat transfer with less flow with water. How does this work? I have to believe that these cars are built by people who know their physics a lot better than I do. |
jd74914 |
Oct 27 2017, 02:11 PM
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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 |
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. I am trying to understand the physics here. The heat goes from the oil to the water to the air. How is this more efficient than oil to air direct? Sooner or later you are cooling stuff with ambient air moving across as big a surface as you can afford to have. The possibilities that I can think of are A) it easier to produce a larger water radiator than an oil radiator, or B) the heat transfer from oil to water and/or water to air adds up to better than oil to air - though I cannot figure why that would be true. If you could use the phase change from liquid water to steam, it would produce tremendous heat absorption. But only as long as you have water left, so I don't think that is it. Water has a higher heat capacity, so you can get more heat transfer with less flow with water. How does this work? I have to believe that these cars are built by people who know their physics a lot better than I do. It's not more efficient since you have an intermediate transport process increasing entropy. There can be a few benefits: -You don't need to run oil lines all over the place so packaging is easier. I'm assuming they use engine cooling water for oil cooling (so no separate system) too like most bikes. -Plumbing weight is greatly reduced since you now can get rid of oil lines and a small increase in water line OD results in little overall weight increase. Oil-to-water heat exchangers are also likely pretty light since you don't need much heat transfer area due to higher overall heat transfer coefficients. -You can also better optimize your oil pump sizing since you don't need to worry about a viscosity change of 2+ orders of magnitude which greatly increases cold line pressure drop-a big deal with really long, essentially laminar flow, lines. -Possibly better temperature control, especially if you're using a booster pump on the water side to control flow through the heat exchanger. |
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