water oil cooler?
 

I see where people run water to air inter-cooler.. Well why not a water - oil oil cooler? for the engine oil

I was thinking if you wanted to get fancy use a marine oil cooler... already made for this application the only thing is of-course we don't drive in the water and we would need a radiator to cool down the water and a pump to cycle the water through the cooler.

Just thinking out loud since water is ~4 times more efficient at heat transfer .. has anyone done something like this to cool their oil? could this be an effective alternative to an air-oil oil cooler

http://www.ejbowman.co.uk/products/index.htm

http://www.ejbowman.co.uk/images/MarineOilCooler2.jpg

There is a company in AZ that installs an oil tank in the some what normal alum water radiator. Road race car system at something like $400.00 a couple years ago. Don't ask the name of the company because I would ned to ask a friend for the info.

Oil/water heat exchangers are quite common in motorsports.

http://www.crracing.com/custom_built...nal_heat.shtml

I like to call them Milkshake makers :)

Ahh nice, what am i a cave man? how didn't i know this shit? haha well that answers my question on weather it works or not but has anyone tried it on their rx-7 with personal experience? and does anyone know of any cons

The con is that the heat the exchanger pulls out of the oil needs to be removed from the water. Usually systems are setup so that this is accomplished by the single radiator. Meaning that all of the heat from the engine is then being rejected through the already highly taxed radiator. Setting up a water-to-oil cooler without regard for an upgrade to the radiator is asking for trouble. Then you need to consider that the inlet temp at the water-oil-cooler is only as cool as the outlet temp of the radiator. So the capacity to absorb additional heat is not so great and efficiency falls.

Just like a water-to-air IC you would ideally have a seperate exchanger and pump (more weight and complexity). Water-to-media coolers excel in powerboat applications where there is an endless supply of total loss, low-temp coolant and in drag race conditions where there is not enough time for the coolant to become heat saturated.

Here is a system ISC sells for road racing 2nd gens.

http://iscracing.net/2nd_Gen_Parts.htm

http://iscracing.net/images/2_n_d_gencooling.jpg

I'm planning on sticking a 13B into a VW Bug and I already have a huge 3 core radiator mounted in the front with 1700 CFM electric fan.
It's big enough to cool a 3 to 4 liter V6 or V8 and there isn't a lot of space or ideal locations in a Bug for air-oil coolers so using the extra radiator capacity to cool the oil would be a big help.

Q1 :
Is it ok if the engine oil temperature is the same as the water temperature?

Q2 :
What is a stock 13B's maximum oil flow rate?

ya can anyone answer the questions serge asked I'm curious as well

That depends on your coolant temps. :)

For the most part, thermostats whether for coolant or oil generally open about the same temperatures. So in general, yes it ok for those two to be the same.

Thanks, now just need to find the oil flow rates so that I can select the right size heat exchanger.
I should imagine that sort of info would be in an engine manual (which I'll buy when I get my hands on a 13B).

Just get the biggest one and make it easy! Its not an issue of flow, its the temp of the oil.

A guy I share a shop with had an exchanger that came off an ACRA car on his RX7 when I first started helping him with the car. He hadn't run the car very hard and hadn't tested the system. His thoughts were if it was enough for a V8 it should work on the little rotary. I put my vote in the "I doubt it" column. Well a hot weekend at Sebring proved my doubts. Oil temp got to 280F, he had to get off the gas the last lap and gave away a win. The car now has two stock coolers.

for a rotary I would suggest retaining at least one oil cooler in adition to the heat exchanger, Oil temps should be kept between 190-240.

1700 CFM seems kinda low for an e-fan cooling a rotary. I run a 3300 CFM fan with a Koyo radiator. I hope the size of your radiator core makes up for the low CFM.



On topic:
What size heat exchanger would be best to cool the water that is cooling the water to oil cooler? Would running a heat exchanger about the size of an upgraded FD oil cooler in one of the stock oil cooler locations be enough while the water to oil cooler sits on the other side of the bay around the secondary oil cooler location. Would this be any more efficient than a dual oil cooler setup?

Just checked - it's a 16" 2340 CFM fan.

You mentioned a secondary oil cooler - does the RX-7 use two in stock build?

The US Spec R1/2 models come with a secondary oil cooler. The automatic version of the FD has a tranny cooler in the location of the R1/2 secondary oil cooler. I'm not sure of the non-US spec models as to which ones do or don't have the secondary oil cooler.