914/RS: Re-build and Re-design: Engine and Cooling Options

[Cracker]

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]

The volume is not necessarily the same - the two circuits operate on completely different pumps and pick-up sources. I just do not understand where you are drawing that parallel from...we are installing what should prove to be a far more efficient radiator.

T

[jd74914]

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.

I'm surprised they didn't recommend the pressure side going something like tank>pressure pump>filter>oil cooler. This would give you the least aerated oil which would both help overall parasitic pumping loses since you wouldn't be forcing oil+air bubbles through a cooler and likely improve heat transfer. I'd be a bit worried about air collecting at a high point and effectively blocking some of the channels.

They definitely have more practical experience there, it's just interesting. Not what I would have expected for sure. I've only designed one dry sump system (it did work really well) and was not super impressed with the level of design data available from the pump manufacturer or heat exchanger manufacturers. Neither Aviad or Armstrong have much actual data on their sites. It looks like a lot of kits which culminated from BTDT. I'm not trying to say they are not very good at what they do, but its just very different than what you see when buying aerospace or industrial parts.

Slightly tangent, but the automotive aftermarket is a funny place. To date the only radiator/intercooler supplier I've talked to who can offer real engineering data is Bell-they actually deal with mass flows and energy dissipation requirements, not "HP". But maybe that's because of Gerhard Schruf?

The volume is not necessarily the same - the two circuits operate on completely different pumps and pick-up sources. I just do not understand where you are drawing that parallel from...we are installing what should prove to be a far more efficient radiator.

Sorry, confused there. Maybe I'm misunderstanding everything? I assume you have a number of pickup scavenge pumps>single outlet>tank and then a tank> pressure pump>engine. Then the coolant side uses a single pump/radiator with branch line through oil cooler?

You see the slower so it has time to cool story bandied about in the hot rod magazines too. It is not correct physically, but it sounds right. A lot of people who know a huge amount about engines aren't like me trying to figure things out going from college class to reality. As everyone knows, reality can turn around and bite you.

The slower thing just kills me-it's everywhere.

For sure, reality is tough. When you look at coupled systems, not a lot of stuff is very straightforward and sometimes it 'appears' to go against conventional physics. I think that's where some of these wives tales come into play. Then when you model the whole thing, the math shows deviation from physical expectations are caused by a bunch of factors acting against each other, etc.

Sorry to if I'm coming off as an armchair-internet-know-it-all. Just trying to share some of my engineering perspective and seeing what other people are doing is interesting. I've spent close to 10 years now designing/troubleshooting thermal management systems for power plants and high end aerospace/marine test systems and am almost finished with my PhD which focuses on aerospace combustion/heat transfer/fluids systems so I like to think I have some relevant experience.