Oil Cooler - Rear Trunk, How I did it. Options

[MAD914]

First off, I wanted to say a big "thanks" to everyone who takes the time to post stuff. I've solved a lot of problems by searching the site. I've mainly been lurking and working, but I thought I'd do some posting of my own to solicit some opinions before firing up the engine. Please be gentle in case I've screwed this up deluxe.

After seeing what had come before me, I wanted to mount the oil cooler so that it would have cool air from the top of the car, instead of hot air from the bottom of the car. I wanted to take advantage of the same "roof-suck" effect that theoretically draws air into the engine compartment. The downside is, I have to sacrifice the rear trunk. No big deal really - I'm not going cross-country in the car.

Anyway, here is what I came up with:



I'm using a Canton filter that's mounted in the engine compartment where the battery tray used to be:




As for the oiling system, I mounted a Setrab dual-fan cooler in the rear trunk, and I'm using a 2-quart cable-actuated Accusump. I wanted the cooler to have cool air from the top of the car instead of the hot air from under the car, so I made holes in the trunk wall to the engine compartment. I've also installed a 180-degree thermostat (the fans turn on at 190 degrees). The lines from/to the engine itself are AN-8, but the system plumbing is all AN-10 to add volume and reduce flow resistance. The canister filter is positioned so the oil enters from the side, and air is purged out the top. Likewise, the cooler fills from the bottom so air is purged out the top as the oil rises up the slope of the trunk. Check valves are installed to stop oil drain-back into the engine, and to prevent the discharge from the Accusump from going “backwards” through the cooler and filter.




Here's how I laid out the installation of the cooler:



And the rough placement:



I'm hoping this might help someone, and I'd also like to hear any words of warning from folks who know more than I do (it's a large demographic).

Thanks!

[MAD914]

Oops. I forgot to post the photo of the cooler mounting taken from underneath. The red wire goes to the thermoswitch at the inlet of the cooler.

[Bulldog9]

Nice setup....... I see you have a Tangerine Exhaust too, or it looks like the Tangerine Exhaust stubs.


How/where did you have your hoses made up?

[FourBlades]

Looks pretty sweet!

I was unable to keep my big type iv engine cool on track with an oil cooler mounted under the rear trunk so it'd be interesting to see how well yours cools.

John

[MAD914]

Yup - it's a Tangerine 1-5/8" street package with an Evo-II muffler. I made the hoses myself with Aeroquip stuff I ordered from Summit.

[screenguy914]

I appreciate you're thinking out of the box and expect it should work in your application.

However, I would have more doubts if the cooling bits were attached to a large displacement (+2.7 liter) flat six. Some thoughts come to mind with admittedly more experience with 911s than 914s.

- At speed, air pressure is highest at the center-front of a vehicle, less so anywhere else. Any change in air flow direction (and turbulence) diminishes air flow to the cooling equipment.

- -12 AN hose/fittings should be the minimum ID for air cooled engines, especially if long runs are employed (reduces oil pump wear). While many 911 owners use -12 hose for add-on external coolers, the factory oil cooler hard lines are closer in size to -16 hose ID. Historically, external coolers were deemed necessary on 911s once engine displacement reached 2.7 liters and/or when engine output reached the 100 HP/liter threshold.

- I think fans in the "push" mode are more effective than fans that are in a "sucking" position, but I'm open to more data regarding this. In addition, the fan housings themselves pose their own restriction to clean air flow through the cooler, esp. when the fans are OFF.

- Not sure the difference in "hot" air near ground level is that much different from air temperature 2' higher that eventually flows over the hood>roof>trunk.

Admittedly, the cooling requirements between these engines are probably different enough to render my suggestions as mere "nice-to-have" rather than mandatory features. Therefore, this is one of those FWIW thoughts.

Sherwood

[MAD914]

It's mostly the hot air discharge off of the engine that I was trying to avoid - and to a lesser extent, the hot air rising off the asphalt. Maybe neither is that much of a concern "at speed".

AN-8 out of the pump is what was spec'd when the engine was built, so I'm gonna have to go with that. AN-10 for the cooling circuit was actually Chris Foley's suggestion, and I'm definitely going to defer to him. It's a 2270, so I'm hoping for the best. I'll post temp data after I run it.

[Dave_Darling]

The passages to and from the oil pump in a 914 are more like 3/8", as I recall; maybe 1/2". So you wind up with part of the system being -6 or -8 anyway. Larger lines are in general better, but I think you hit diminishing returns faster with the four-cylinder oil system than you do in the six-cylinder one.

The fittings in the "sandwich plate" adapter are 3/8". I used a mix of -8 and -10 hoses for my cooler setup, which is in a similar location to the OP's, but is all under the trunk floor. One nice thing is that the bend radius of the smaller hoses is tighter, so they're easier to route.

--DD

[Cap'n Krusty]

It gets hot enough inside the rear trunk to fog photographic film, and that's pretty hot. I, for one, thinks it's a less-than-good idea to put an oil cooler in an area that's not that much cooler then the oil you're trying to cool ...

The Cap'n

[Woody]

Nice setup. I am currently in the process of putting together the plumbing for my new engine. Mine will be dry sumped though. I'd be interested to see how it turns out. My cooler will be mounted next to the trans with a fan.

[MAD914]

Cap'n:

It's my hope that by adding additional ventilation holes (and uncapping the "roof-latch" holes) between the engine compartment and the trunk, it's a little less of an oven in there.

[Porschef]

Interesting. I'm planning on installing a cooler within the next couple weeks, but I don't want to cut anything. I've seen the cooler/fan assembly installed attached to the engine lid, I'm wondering if that is more efficient at receiving cold (er) air than a location under the rear trunk. If I had to cut anything, I guess sacrificing the rain tray would be about it.

Curious to see what kind of decrease in oil temps you get.

[patssle]

Very nice. I was considering that for my /6 but ended up mounting it below the trunk - I didn't want to take away any airflow that was entering the engine bay as it is indeed a low-pressure zone. Can see my setup here: http://www.914world.com/bbs2/index.php?sho...=249484&hl=

[MAD914]

I've seen the engine-lid mountings too, but was afraid I'd just be dumping heat back into the engine by heating up the air in the engine compartment that goes to cool the cylinders.

[Jetsetsurfshop]

Do you plan on running this car at the track? I assume so with the accusump that you installed. I bet for the street you'll be fine, though.
I have a very similar engine (so does four blades) and are cars ran fine with the rear cooler till we tracked them.
I spent a lot of energy trying to make a rear cooler work. The simple fact is that the clean air up front is a different world. I actually got to thrash my car, lap after lap, without looking at the damn temp gauge.
Now, I didn't do mine like yours. I bet your works better. Cant wait to see some data.
Here's my thread from my oil cooler fiasco.
http://www.914world.com/bbs2/index.php?showtopic=227027
(IMG:style_emoticons/default/driving.gif)

[stugray]

The simple fact is that the clean air up front is a different world.

This is also brant's advice for the track.
That is why my foglamp vents now house dual oil coolers

[MAD914]

It's really a street car, but I'd love to take it to the track if I get the chance. I really wanted the Accusump to minimize wear on start-up, and increase the overall system volume for cooling purposes (SoCal summers get pretty hot). I've painted the bottom of the trunk a reflective silver, and removed the rubber seal from the trunk/engine compartment sheet metal in an effort to keep this area as cool as possible.

Gonna have to try it to really know. I'm getting close to starting it up.