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914World.com _ 914World Garage _ Rear mounted oil cooler Part 10

Posted by: gereed75 Aug 7 2017, 08:05 AM

I wanted/needed an oil cooler on my six. The motor is a 2.4 essentially S. It runs very cool (180 - 210) under normal street driving but quickly heats up when getting on it for any significant intervals. Since I like to get on it (why would you build this motor and not enjoy it??) and want to be able to run the occasional track day, I needed more cooling.

I have been through all the threads and came away thinking the jury was still out. I looked at two options - under the trunk floor and under the engine lid. I choose under the floor.

My prerequisites were no cutting the car (original six) and it had to work. After studying everything else out there, I thought under the trunk could work but needed a better effort than what I have seen previously. The idea was to provide a plenum that would pull "cool" air from the passenger wheel well through the cooler using a fan. The plenum should also provide some heat protection from the stock six headers. So here is the cooler, plenum and fan "unit" that I came up with.

First is a mounting bracket. I used a steel sheet about .187" thick and fabbed/bent a mounting bracket that integrates with the passenger side tranny mount. This bracket holds two long arms (bolted) that hold the cooler unit cantilevered from the bracket. Attached Image

Here is the plenum unit. Fabbed from .032 sheet aluminum.

Here is the whole thing mounted in the car:

I control the fan using a solid state controller set for about 160 degrees.

Seems to work pretty well. Highway cruising on a warm day is about 180 - 200. Ran several 20 minute track sessions running hard. First track day was cool OAT's and never saw above 210 on oil temps. Second day was warmer - mid 80's OAT. Oil temps got to 225 and cooled immediately back to 180 after one easy lap. Pushed beyond that, it seemed to stabilize at about 225 and did not go above that.

Kinda wish I had a hotter test day, but for now, that is about it, seems to work - no holes in the car, the thing seems very solidly mounted and manageable oil temps. Me likeee but probably needs a hotter test day to be conclusive.

Posted by: gereed75 Aug 7 2017, 08:23 AM

Here is a view from the right rear wheel well

Oh yea, easily reversible bolt in installation.

Posted by: BillC Aug 7 2017, 09:38 AM

Very nicely done!

Posted by: Mueller Aug 7 2017, 09:52 AM

Nice, rivets are under appreciated at times.

Posted by: Krieger Aug 7 2017, 09:56 AM

I like it! Very clever!

Posted by: Andyrew Aug 7 2017, 10:25 AM

That is nice!!!

Posted by: gereed75 Aug 7 2017, 10:56 AM

Thanks all. Sheet stock and rivets work. It is a bit rough, the final result got two major changes from the original sketches I made so it is a bit cobbled together. Not my best work but functional.

Posted by: SirAndy Aug 7 2017, 11:04 AM

The big cup washer on your transmission mounts is upside down and above the flat round washer, both of which is incorrect.

The cooler looks good though ...

Posted by: gereed75 Aug 7 2017, 11:56 AM

thanks and thanks

Posted by: wes Aug 7 2017, 03:49 PM

Well done! Did you make a mock up? I've been thinking of something like that to get fresher cool air to the oil cooler and this looks better than anything I've seen. Which oil cooler did you use?

Posted by: maf914 Aug 8 2017, 07:36 AM

Very interesting!

I wonder if the air in the wheel well is noticeably cooler than the air under the rear trunk floor and if your ductwork will actually draw air from the wheel well area. Is it possible to extend the ductwork closer to the wheel well?

Posted by: PanelBilly Aug 8 2017, 08:44 AM

Really clean installation. I like this so much better than plumbing all the way to the front.

Posted by: gereed75 Aug 8 2017, 09:05 PM

I am pretty sure that the cooler I used was the Mocal 235 25 row. I mocked up a couple of different sizes and that was the largest that I could fit into the available space. It is pretty tight fitting the thing into that space.

AN12 lines.

I was trying to get a snorkel kind of end to get into the wheel well as deep as possible. One of the changes I had to make was to reduce the size of the snorkel - it was a pretty good fit with the suspension set at regular ride height, but with the car jacked up, the shock moves forward and interfered with the snorkel so it had to be shortened. A better solution might be a flexible snorkel that gets into the wheel well and allows some deformation when the suspension is hanging and goes back to shape at regular ride height.

I assume that whatever air is pulled from the wheel well is cooler than the air trapped above the header/heater boxes.