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On my 90S4 and later models the engine oil cooler was taken out of the radiator tank and moved to a separate air cooler slung under the radiator. One thing I have noticed over the years is that even though I use a 20w50 oil, the oil pressure in the cooler season [i.e. now] my idle has no problem holding 2 barg as indicated on the dash display. On really hot summer days [ambient temp 44C] that indicated pressure can drop a little and if it can not hold temperature at idle then most likely it will not fare any better at load. At the moment when running above 3k rpms the indicated pressure is about 5 barg but during hot summer days it may be closer to 4 barg. I am always a bit wary bout believing such gauges and whereas 4 barg should be adequate I would feel that the system would be more under control if the readings were the same "hail or shine". My motor has always burnt what seems to be too much oil but with breather mods I did manage to improve the situation.
The above leaves me wondering whether I should do more in the oil cooling department. My currently fitted custom radiator has no cooler elements in either tank and I use the stock transmission cooler but without the in tank cooler part of the loop and it seems to work just fine but I change my ATF at 20k miles or every 4 years maximum. I have it in my mind that I have read previously about this type of situation with engine oil cooling. I have a very nice 928 Motorsports radiator sitting in my spare parts cupboard and that has in tank coolers fitted. I seem to have engine cooling well under control and I am wondering if the oil cooling circuit could be modified so as to take hot oil from the motor, into the tank and then into the air cooler.
I seem to remember reading something about this being done but wondered if any Rennlister has specific experience of such and whether it can/would make a positive difference noting that we do not want to "over cool" the oil albeit the thermostatic valve should prevent that from happening. Whether it would help reduce my oil consumption remains to be seen but for what it is worth, my motor after all my various efforts with ST2 and the exhaust, cooling etc seems to be running as well as it ever has at the moment. My instincts tell me the later external oil cooler is just not sufficient for my hot environment.
The below radiator oil cooler on my 93 GTS was useless in stop & go traffic, 110F weather here in TX. Even when using 20W 50. I added the radiator oil cooler and used a Greg Brown hose set so the oil flowed through both coolers before going back to the engine.
The improvement was marginal by the gauge. On the worst days I can still see 1 bar but the red light never comes on (it did before on one or two occasions of severe use in the worst ambient conditions). Although I can't give you empirical data that proves its is better my assometer says it is and that makes me feel better.
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Does it have the "Do It Yourself" manual transmission, or the superior "Fully Equipped by Porsche" Automatic Transmission? George Layton March 2014
928 Owners are ".....a secret sect of quietly assured Porsche pragmatists who in near anonymity appreciate the prodigious, easy going prowess of the 928."
The below radiator oil cooler on my 93 GTS was useless in stop & go traffic, 110F weather here in TX. Even when using 20W 50. I added the radiator oil cooler and used a Greg Brown hose set so the oil flowed through both coolers before going back to the engine.
The improvement was marginal by the gauge. On the worst days I can still see 1 bar but the red light never comes on (it did before on one or two occasions of severe use in the worst ambient conditions). Although I can't give you empirical data that proves its is better my assometer says it is and that makes me feel better.
Interesting- did you notice any difference in oil consumption during your hot weather season? 110F is close to the 44C we commonly see. On rare occasions at the end of May the temps can go to 49C but that is rare. In the desert away from the coast it can go bonkers.
Based on your post it would seem my oil pressure is not doing bad at all albeit I have the S4 motor not the GTS lump for whatever difference that makes.
A couple years ago, PN 928 107 212 00 Engine Oil Cooler went to zero stock at Porsche, and I knew owners needed to have them available because of the occasional impacts they receive. I set about making a new and better oil cooler that would fit in the same spot. Once designed, I contracted with Setrab (oil cooler manufacturer and supplier to OEM's) to make them for us. I had 15 oil coolers made... then the OEM part came back in stock! ****skee! So I shelved the project for a while.
I dug this product out last month and have been working on it. Quite literally YESTERDAY I took these pictures of the prototype mounted on my 1991 GT. My plan is to offer our Setrab oil cooler as a kit with SS braided -12 AN oil lines to and from the engine. Prices I got yesterday from Porsche for the oil cooler and the two oil hoses were $1700 at their suggested retail, I know we can do much better.
As to your posted question: "can we improve the cooling of the oil cooler?", I say YES. If you look at the stock oil cooler, you will see that it is a single-pass cooler, running the hot oil out in a tube in one direction and then back through the cooling core to the engine. I didn't want to go any lower to the ground, and you can't really go up either, but we were able to go back - and made our oil cooler a 2-pass cooler so it goes through cooling media in both directions. This is the reason I expect better cooling. I know when I changed the radiator on my race car from a single-pass to a dual-pass type, the improvement was significant.
The oil coolers are done and I'm just finishing up the steel mounts for it now. Hope to be to market in about 30 days. Fred, if you want to fit one and report back what your oil temps look like after its installed, I can give you a discount to do that.
Please understand that these photos are in the midst of the prototyping process... the parts are not finish-painted, the oil fittings will be black (not blue), and the mounts on each end will be steel not aluminum.
That stock cooler looks like my oil coolers twin brother that is also a bit creased after decking out on something- I guess there is a limit as to what your bash plates can protect against! It would be interesting to see how that cooler performs. The deeper matrix will add something to the duty but just be mindful that there is a law of diminishing returns in play as the air heats up passing over the matrix. Ideally you will need to know the performance of both the stock system and your modified system at given ambient temperatures.
My spare 928 Motorsports radiator has cooling coils in both tanks- have not tried it yet but it sure looks a neat piece of kit. The fact that it has the cooling coils in it tempts me to want to try using it in tandem with the stock cooler. To do that I would need the end connections from two earlier model hoses to get the hoses made up- that or get a pre-fabbed set as Roger indicated. My only reticence about that is trying to undo the connections from the block having read a number of horror stories about what happens if not counter held correctly. Given I have previously changed out the tranny hoses and power steering, I would like to have the security of knowing my hoses are good to go for another 20 years or so- logic suggests to do the job once and have done with it whatever the option selected.
The stock oil cooler is a single-pass cooler. Yes, of course oil has to go to the other end to come back, but in cooling parlance, that is not a "pass" through a cooling core.
See pics here - the single-pass cooler and our dual-pass cooler right next to it.
I have fittings in stock for your radiator or your engine if you want to make your own hoses. Then you could hook them together in series like you want.
The fittings are steel, and convert the metric thread to -12 AN so you can buy your hose ends anywhere and make up some nice stainless braided oil lines that route anyway you like.
Your cooler looks very elegant and for sure should improve overall heat transfer- the interesting determination will be by how much.
Be assured that having designed just about every type of cooler found in the oil industry I do recognise a double pass air cooled exchanger when I see one
I have fittings in stock for your radiator or your engine if you want to make your own hoses. Then you could hook them together in series like you want.
The fittings are steel, and convert the metric thread to -12 AN so you can buy your hose ends anywhere and make up some nice stainless braided oil lines that route anyway you like.
The AN system is brilliant in its simplicity and I would really like to go that way. The bit that puts me off is the way the stock fittings are bonded into the block. If I had the motor out of the chassis I would not be too concerned about putting a torch on the fittings to break the bond but trying to do that in-situ with the car on axle stands leaves me with a very cold feeling. On the other hand I have a very friendly hydraulic fittings shop who made my high pressure power steering line for me so reworking the oil lines should not be too much of an issue once I have determined the type of hose needed for exposure to engine oil at working temperature.
Rgds
The below radiator oil cooler on my 93 GTS was useless in stop & go traffic, 110F weather here in TX. Even when using 20W 50. I added the radiator oil cooler and used a Greg Brown hose set so the oil flowed through both coolers before going back to the engine.
The improvement was marginal by the gauge. On the worst days I can still see 1 bar but the red light never comes on (it did before on one or two occasions of severe use in the worst ambient conditions). Although I can't give you empirical data that proves its is better my assometer says it is and that makes me feel better.
The difference between 1 bar of oil pressure and the .7 bar of oil pressure is 30-40 degrees Fahrenheit. It is very common to see oil temperatures over 270 degrees in 90 degree weather, when stuck in traffic.
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
On all of the 1990 and later engines, I see greatly increased cam wear at lower mileages than I see on all the other models. I attribute this to the greatly increased oil temperatures that occur, when a 1990 and later 928 sits in traffic. Oil temperatures of over 270 degrees Fahrenheit are very common, as I mentioned, above.
The change from having the oil cooler in the radiator (cooled by water) to having the oil cooler under the radiator (cooled by air) was an OK idea for driving down a highway at 60mph....but absolutely was terrible once there was no longer enough speed to force air through the cooler. And regardless of single pass, double pass, or the size of the cooler, once the car quits moving, the cooling of the oil stops.
My idea was to simply run the oil through both the stock oil cooler under the radiator and through a stock cooler in the radiator....the best of both worlds. (Note to all you people that live in cold climates, this also warms the oil up much, much quicker...reducing cold running wear on the engine.)
The stock oil cooler is a single-pass cooler. Yes, of course oil has to go to the other end to come back, but in cooling parlance, that is not a "pass" through a cooling core.
See pics here - the single-pass cooler and our dual-pass cooler right next to it.
The Porsche engineers that designed the oil cooler change were most likely not stupid...... and they certainly had dual pass oil coolers, so the questions is....why did they return the oil in a tube, instead of through additional oil cooler? Does increased oil cooler thickness restrict airflow, actually increasing oil temperature? (Certainly it will.....but at what speed is this an issue?) What happens to oil pressure with the increased restriction? I can think of half a dozen questions...really quickly.
Don't misunderstand me....I like your idea....and it might turn out to be a brilliant solution! This would be certainly more important, if Porsche quit making the stock cooler and there was no alternative, like everyone feared was going to happen. However, the reality is, the "price point" of your cooler is the price of the stock cooler from Porsche, compared to your entire kit....since the stock late model hoses rarely leak or need to be replaced and only the cooler needs to be replaced, if it leaks.
I just think you've got some serious testing to do, long before this product can be considered for sale. And how you test oil cooler efficiency in 30 days....in the middle of winter in Wisconsin....is way beyond me. I'd put 10 of these things in cars and test them throughout the summer, in different climates, long before I'd consider selling a single one.
For me, proof of concept only comes from testing.....
I have only 1 street-able 928 and 1 race 928. So, to get testing done, it is not uncommon for me to offer discounts to those who don't mind testing the new part, like I have done here. That way I get more tests in more conditions with more drivers on more different cars than I ever would if I installed it on my one car and said "it's tested". This is a good thing, not a bad thing.
What you should know from my posts above: 1) it isn't for sale yet, and 2) I will be testing it Greg, on as many cars as there are guys who want to try it out in return for a discount.
Last edited by Carl Fausett; 01-23-2019 at 06:24 PM.
I have only 1 street-able 928 and 1 race 928. So, to get testing done, it is not uncommon for me to offer discounts to those who don't mind testing the new part, like I have done here. That way I get more tests in more conditions with more drivers on more different cars than I ever would if I installed it on my one car and said "it's tested". This is a good thing, not a bad thing.
What you should know from my posts above: 1) it isn't for sale yet, and 2) I will be testing it Greg, on as many cars as there are guys who want to try it out in return for a discount.
Carl:
I'm not trying to "throw bricks", just throwing out logical thoughts.
Let's just say we have a different ways of doing business and leave it at that.
Anything below the radiator that depends on air flow is pretty useless on a hot day in traffic - even if you increase the capacity. I doubt it will make very much difference in that scenario (high ambient, hot engine, traffic stopped). That scenario is THE PROBLEM not a bigger air to oil cooler.
Either the cooler gets air from a fan or is water cooled. Personally I would get rid of the air to oil cooler before I doubted the ability of the water cooled oil in the rad.
The oil cooler from Porsche was undergoing a design change recently and as already been said is readily available again. I have yet to see one of the new ones but the part number did change so it may be different in some way.
At my price of $650 plus a set of hoses from Greg your looking at circa a $1000. Works for cars 87 to 89. On top of that if you have a 90 or newer car you will need a radiator with cooler on the left side. So add $595 and you are all in for $1600 with THE added bonus of cooling for the stopped in traffic, high engine & ambient temperature scenario.
01-23-2019, 07:08 AM
Later model oil cooler effectiveness
George Layton March 2014
