Here's an interesting cooler set up, done on a 3.0 245hp engine running in cali heat with no issues. Done for an original /6 that the owner didn't want cut up for a front cooler.
What do you guys think?

BTW before you totally knock it it was done by Henry Schmidt at Supertec, so the builder does have some credibility.

Very nice, but doesn't the hot air go directly into the engine?

I'm not really an expert on these things, but that's a low pressure area with not much air flow... Maybe a fan would help though? It sure is a clean looking install though.

I'm one of those guys who thinks that if a little bit is good, then a lot is better.
Consequently my motor never has seen an oil temp of over 100C.

Getting the motor up to temp is a bit of a problem. I used to throw a towel over the GT style lid to get it warm faster.....blocking off about 80% of the air flow. Goose the throttle and the towel would quickly conform to the grid pattern of the lid.

You don't need an aux cooler till you *really* need it. Then it had better work, IMO. I've never had that problem. This set-up would seem to create a heating loop
that would not satisfy the *really* part.

That cooling fan pulls huge amounts of air through it. I do not think the oil cooler makes enough heat to effect the air temp in any significant way.

My thermostat opens at 185 deg F then the oil goes to the aux cooler. When it leaves the cooler the line is only warm to the touch. That gives the engine relatively cool oil. In this set-up, where does the extra 80 deg air go?

My question: Henry, wouldn't that pre-heat the cooling air?



Keep in mind this is a 914/6 street car and would also be using the stock cooler as well.

There's a missing number there. Mine was 100C (212F) under extreme usage.

This location is less than ideal. It is directly over the COOLING fan sucking really hot air (oil thermostats open around 200 ferenheight) and blowing it over your engine. A really hot day in the desert: 115 degrees.....Sure your oil temp is cooler, but

Oil cooler on a /6 should always be in the front.

Always.

Hey JP,, while you and I agree that if a little is good, too much is better. BUT when it comes to oil you really should let it get above 100c because that's when the moisture in the oil gets evaporated out of the mix. I would think an operating temp with slight load that hits 100c and spirited driving up to 120c would be a good range. It will prevent sludge build up, but then again I'm the guy with the rotary engine. I did stay in Holiday Inn before.

-Robert

I respectfully totally disagree. I've built at least two conversions with external oil coolers that were not in the front. Neither one runs too hot, both are still going strong one is 15 years on the conversion, and one is 8 yrs.

What is your basis for "always"?

Water will boil at 212F. It will evaporate down to absolute 0.
At 185F it evaporates very quickly.
I've never had a sludge problem but a mag case will turn to sludge (rhetorically) if it gets too hot.
I'd accept the lesser of 2 evils.

I don't like coolers above the engines. Oil drains down when shut off.

Mounting the cooler in the deck lid is not the best location but given our options it works very well.
The customers desires quite often offers some challenges but we were pleased to accommodate his needs.
We try not to let the "Perfect" get in the way of the "Good".
Cheers

BTW: only a small portion of the air used to cool the engine actually comes through the cooler.
Picture the ac condenser located on earlier 911 and 930 in the deck lid.

Nice clean install! Whatever works is the perfect solution. Sorry all you armchair engineers, but if it works fine and keeps the motor and the oil cool, then all your BS about 'perfection' is irrelevant. If you want to go down that road, then ditch your aircooled BS motors, because water is FAR FAR more effective for cooling motors.

Totally.

I have one of these coolers and I think it's a good solution. Maybe it's not for an all out track car, but for a Canadian summer car it's added protection. One of our members here is running a 3.0 with just the stock cooler with no issues.
For me this isn't California, I rarely drive in heavy traffic and maybe I'll do a DE/AX one day.... but I doubt it.

FWIW High Performance House likes to install the aux oil coolers on the engine lid.

Wouldn't be my choice but it's not my car.
However - I don't like forged 90º hose ends in any part of the oil circuit.
OK - space might be tight for that front one, but the back one needs a bent-tube 90...
But since it'a a compromise solution, and scavenge oil is basically foam anyway, probably not a big deal.

Why not just use a heat exchanger with the ports on the ends to start with, and avoid the 90's completely?...

I've got to agree with Perry on this one. My 3.2 never got above 210 this year even during the hot-ass Kentucky Summer we had. I regularly drove it at 80+ mph on the highway, and my aux oil cooler is tucked up under the right rear fender. If I were tracking it, than it would probably be a different story.

Click to view attachment

Ok, that's enough. One post per year is all I'm allowed at this point....

Dion

Hey Dion! That's right where I put the oil cooler on my very 1st 6 conversion.

Works very well there without 20 feet of hose and cutting access holes. It also preserves one of the best things about a 914, the front trunk is totally intact.

Everyone seems to be assuming that air will be flowing downwards through the cooler - which it will be with the car at a standstill (ref JP Steins test with a towel) - but when the car is travelling forwards the area behind the rear window will be at low pressure and will therefore draw air up through the grill and oil cooler from the engine bay. As long as the cooler is hotter than the air from the engine bay - which at 200 degs it will be - the cooler will have an effect.
Looks like a tidy, effective and elegant solution to me.

Henry,
Good to see you here! I l like the install. For those of you that don't know Henry, he is a highly respected member on the bird board, and is a top-notch P-car mechanic. He does an oil-pump modification for sixes that is the schnitz. I just put one of his modded pumps in my 2.7RS build. Let's all hope he hangs out here more... There's tons of info in that brain, especially for us six guys...

Per Anderson's 911 book, the 911 fan delivers between 1390 and 1500 liters of air
*per second* (I'll assume that's at wide guts) depending on which ratio fan pully is used. Since the engine is sealed off pretty well from all other sources by the engine tin, just where do you think that air is coming from?

Any rational answer is acceptable to we armchair engineers. We ain't near as smart as professional hammer mechanics.

Cool, I may need to find out the specifics of this mod. I'm just starting to accumulate parts for my 6 conversion.

Will this myth never die ?

Why do you think the '73+ cars got deflector flaps _under_ the car ? What is the purpose of the airseals around the engine? There is a reason the intakes and cooling fans (/4 or /6) are above the airseals...

The area behind the window has "lower" pressure than some places but it is not lower than the air pressure _under_ the car.

Air does not flow up.

(Some folks with water conversions have forced bottom-up airflow with scoops and modded (i.e. removed) airseals. We're not talking about them...)

I stand corrected - I forgot about the tinware and seals.
Thanks for the friendly explanation.

a 200 degree surface can put out about 320 btu's an hour per sq/ft.

figure the surface area of the cooler, calculate the cubic ft. per hour going through that fan, figure the heat transfer/delta T equation taking into account the pressure and water content of the air and you will likely find that the amount of btu's transferred per second won't even be enough to get you 1 degree of air tempertaure increase.


i've sized a few heating systems in the past year, meh

speculation is fun. well thought out theories based on what we think is happening based on more speculation is also fun
I had alot of thoughts similar to those presented here but the data pointed out reality.
lid mounted coolers in 2.0, 2056, 2270 type 4 lowered oil temps on extended freeway runs, AX, DE and time trials. average reduction was about 20 deg. no fan
Lid mounted cooler on a 2.7 six was less dramatic but prevented temps from running away while up at willow running 30 min run groups.
head temps did not care a bit. I saw NO difference.
there are other racer-members here who had similar rusults.

The only problem I can see with a lid mounted cooler, is pre-heating your cooling air.

Part of the oil cooling is just running the oil through the "radiator" of the oil cooler. Just like the brass trombone coolers and the 21 row brass coolers, it's the heat transfer running through the tubing that cools the oil.

You get into a problem when you get to the extreme thermal efficiency of the oil cooler, and that's where you need the extra air flow over the cooler. I was able to direct mount a 7" spal fan right on the oil cooler, similar to the set up that Dion shows in his post.

Here's a pic of my front cooler. Feeds at the bottom and expells at the top, all lines are well below the normal running full line of the tank, all 90 deg fittings are of the radiused type..no hard 90s here...there are 5 of them in the system I feel the is a sound reason for doing all this detail stuff but won't bore you with any armchair engineering. The thermostat was also the best available.....a pic of that also. This is no place to skimp said the CSOB.

BTW, all this stuff including a stock oil tank with fittings is now for sale.

Did you sell the motor only? PM me the details if the conversion bits only are for sale (since I already have a motor but nothing else).