Oil cooler

[rbp]

I have a type IV 2316 in one of my Porsches. The engine has a DTM cooling shroud with the on board oil cooler removed. The only oil cooler is the remote unit. It is presently in the engine bay and I want to move it to the front.

Does anyone one know what size a cooler (BTU HR) or some other system of determining what will do the job?

[John Rogers]

I would suggest getting the largest cooler that will fit in between the box sections at the front of the trunk and allow the oil lines to be connected. There are coolers where the fittings come straight out the side and others that have the fittings facing towards the front/back so there will be no oil line interference. As for the heat removal data, any cooler that will fit up there will work well as the more important issue is the ducting for the air inlet and even more important the hot air outlet.

[rbp]

Agree, am looking at Remote Mount : 19 Row Hyper-Cool Dual Cool Remote Cooler, -10AN but not sure if the capacity (heat rejection) will do the job. Is this one Remote Mount : 40 Row Hyper-Cool Extreme Remote Cooler, -6AN at 67,000 BTUHR better suited? The square shape just doesn't fit as well as the rectangular one which is rated at a much lower 37,000 BTUHR.

[John Rogers]

I bought my front oil cooler from Summit Racing and here is a link. I installed mine in 1998 so things have changed a tad since then but the attachment points are about the same as are the fitting sizes. I would suggest either a -12AN or -16AN size fittings and flex hoses as they have way less flow resistance and use Earl's braided hose run through the right side tunnel. Some folks run the oil lines right through the driver area but that is giving out a lot of heat and some racing organizations ban that practice.

In your examples they show fans which are not needed with our cars and as I noted duct the air out the bottom of the front trunk like the factory did it.

[Dave at Pelican Parts]

I figure the larger, the better. The fans can help if you do not have good air flow through the cooler naturally, such as when you are stuck in stop-and-go traffic. If you know you will always be moving, go without the fans; you will get better flow through the cooler at speed with no fans (but proper ducting!!) than with the fans in place.

Usually the cooler size is chosen with specific space constraints in mind. The GT-type setup needs to be short but wide, for example, to fit in the nose of the 914. That's one reason the RX-7 coolers are sometimes used, because they fit the space fairly well.

--DD

[rbp]

Maybe I should explain a bit. I have a 914 Type IV RAT motor installed in my type 550. As you can see from the picture the oil cooler is in the engine bay and discharges hot air under the rear clam which is then drawn in by the fan and the carbs. To avoid this I want to remove it and install it in the front behind the oil cooler face plate (6" x 16") visible in the pic below.


I am trying to determine to minimum cooling I will need. If I can get something to provide more cooling I will be doing so. I am going to install a bypass thermostat so when the oil is below the 180 set point the cooler is bypassed. From there use an oil temperature sensor to start the fans if the oil temperature rises above the 180 deg set point.

Since I have no benchmark to figure out what the minimum requirement is I am not sure the rectangular one with 2 fans will be enough. The existing one is a Derale but I don't know what model it is. I took measurements of it every which way and nothing they have matches up dimension wise.

[porschetub]

So you have no cooler in the fan shroud ???,IMO you will struggle to get anything to work as well as one in this location...the fan in there makes far more air than a cooler in the normal airstream even front mounted.
Would be a shame to cook that nice engine.

[John Rogers]

Can you post a picture of the front trunk area with the lid open please? The width of the cooler will probably be determined by those two small air inlets on either side of the grill opening. The height of the cooler will be about double the height of the opening since normally front mounted coolers are mounted tilted such as the one you have mounted over the transmission. I have half a dozen pictures of real 550s and RSKs and they all mounted the cooler where you have it if they have an external cooler. Remember these were race cars and were meant to last a few races at most and the engines one or two races.

As for the heat removal capacity, I don't think you need to worry about it since the capacity is going to be more than enough. I would suggest to not use a thermostat since the ones in the lines to a front mounted cooler are made for a 911 (flat six) which pushes way more oil than a four cylinder unless you have converted to dry sump? Remember to use large lines too. Here is a link to a website that shows what you want to do I believe: Porsche 356, 550 Spyder, Speedster Parts

[TheCabinetmaker]

Originally Posted by porschetub

So you have no cooler in the fan shroud ???,IMO you will struggle to get anything to work as well as one in this location...the fan in there makes far more air than a cooler in the normal airstream even front mounted.
Would be a shame to cook that nice engine.

Ditto that, the stock fan and cooler is very effective, hard to improve upon. you will certainly need an electric fan to maintain air flow when car is stopped or slow.

Much of the air under the 914 in the rear is already hot from the motor, and exhaust, so that location is not ideal.


You need lots of cool air flow al the time, good luck

PS I added a 92 plate EMPI cooler to my 914 under the rear trunk with a fan, I still have the stock cooler and the oil still could be cooler

[rbp]

As noted above the engine and DTM fan shroud are from Jake Raby so the engine is designed to have just the external cooler. Where is the stock cooler? I expect it uses the engine cooling fan similar to a stock VW bus.

The openings at the side a air ducts for brake cooling.

Also keep in mind that many do delete the original oil cooler. Note the one offered from Tangerine http://www.tangerineracing.com/engine.htm

[Dave at Pelican Parts]

The stock cooler is on the side of the crankcase, with ducting to ensure that cooling fan air blows down through it. As you say, it ain't there in your setup.

Cooling should be roughly proportional to area, so if you get a cooler that has a total area of about what yours currently has, you should be OK. Maybe add 25% or 50% just to be safe, and see what dimensions of cooler are available with roughly that size, or more.

But one very important thing is to make sure that you can get a cooler that fits the available space. You obviously have an inlet (the slatted one in your photo), but it's important to have an outlet as well. And the outlet should be roughly double the area of the inlet for good flow. Ideally, it should be located in a low-pressure area that doesn't put air under the car. And, of course, you need to have ducting to make sure that the air coming in does not simply go around the cooler. Making estimates of what that all will look like, in the space you have currently, will give you a ballpark for the largest cooler you can fit. If the area is roughly equal to or larger than your current cooler, you should be fine.

--DD

[rbp]

I agree. My existing oil cooler will keep the oil at around 210 when cruising at 3500 RPM on the freeway. What would be the ideal temp in this situation 80 - 90? What do most of you see fort oil temp when driving for long periods on the freeway at around 3500 RPM? I think I need more cooling but maybe I'm wrong!

[John Rogers]

If all you are doing is cruising and using synthetic oil such as Mobile 1 then your existing cooler is fine. I believe the cooling system Jake sold/sells is not meant to use a stock crankcase mounted cooler? with the stock cooler there is some restriction to the cylinders down stream of it and overheating can result.

Remember this was a race car, no ducting (extra weight) and meant to go as fast as possible. If you were in a slow moving caravan in the Phoenix AZ area today then I would worry but you're not.............

[Dave at Pelican Parts]

I believe that the best temperature for oil is 212F, the boiling point for water. That's in part because the specs for motor oil are written in large part with the assumption of a 212F temperature (the "warm" viscosity rating, for instance), and in part because water is one of the major contaminants of engine oil. Water will outgas at lower temps than 212F, but it takes more time.

That said, some very knowledgeable people prefer to see 180F. I feel anything below that means the oil is not really at operating temperature, though.

If your oil is at 210F, I figure that's pretty good. If you want the temp to come down, moving the cooler should be a good way to do it. But I'd personally leave it where it is, at least based only on oil temps. Heck, my temps have gotten perilously close to 250F even with my cooler. That's very bad for your oil, BTW... But it was pulling up hill in the middle of the Nevada desert in late June, so it is a bit of an extreme case.

--DD

[Tobra]

That 550 is a tubeframe, n'est pas? If you run the lines to a front cooler, you will want to protect them, secure them to the top side of a "frame rail" perhaps. Air into, and very importantly, out of the oil cooler matters. You can put a flap, like a Gurney flap, in front of the outlet if it is on the bottom to create a low pressure area that will draw air, as was done on the later 914s. Where to put the oil cooler will depend on where you can best manage air flow.

Sweet car, bet it is quick as greased lightning.

[John Rogers]

Looks like one of the Thunder Ranch cars? We used to go visit Tom's company in El Cajon and drool over some of the car that he was working up for customers.

[porschetub]

Originally Posted by rbp

As noted above the engine and DTM fan shroud are from Jake Raby so the engine is designed to have just the external cooler. Where is the stock cooler? I expect it uses the engine cooling fan similar to a stock VW bus.

The openings at the side a air ducts for brake cooling.

Also keep in mind that many do delete the original oil cooler. Note the one offered from Tangerine Tangerine Racing Engine Products

Ok, I thought those cooling system shrouds had the cooler standing up on an adaptor hosed from the original pressure/return, to clear the air away from shadowing the nearest effected cylinder and offset more to the rear of the motor like the first doghouse VW's were ?.
I still think the lowest temp you can get on your oil is best as DD pointed out, if too low then it can be controlled by an inline thermostat .
When the oil temp rises too much in an aircooled engine that extra heat has a follow on effect to the rest of the engine...its not a good one.
Contact Jake and voice your concerns (but you may get a bill for his time,or Chris @ Tangerine will help I'am sure ,seems like a decent guy.
I've never run an engine like this without an internal cooler so I don't know.......

[rbp]

My 550 is from Vintage Spyders in Stanton CA. Mine weighs 1,200 lbs and produces 200 HP and 200 ftlb of torque (approximate).

Mobile 1 is ok for hydraulic valve train but I need high Z & P levels in the oil so I use Swepco or Brad Penn.

Thanks for that info Dave, I didn't know that. If the oil temps are ok when in the 80 - 100 deg, C (180 - 212 deg F) range then I should be ok and will leave it as is. I had thought that the intent was to keep the oil at around the 80 deg C so getting to 100 - 110 was way too high.

It would be an easy run for the lines. The oil lines connect to the engine on the passenger side close to the firewall. The lines would simply run in the enclosed rocker panel located under the passenger door sill. From there the lines would enter the foot well inside the car and would need to be protected, fastened and hidden to some extent. From there they would simply exit into the area where the cooler would be installed. Not really a lot more line length then when installing in the rear, maybe 4' per line.

[donporfi]

Follow Dave's suggestion