shanghai_todd

iTrader: (2)

Have this posted in the conversions section but have got no hits or feedback so trying my luck here.

Some of you may recall my build with the rear mounted radiator in a Porsche 911. The cooling results have been successful but now I am questioning the oil temp.

Here is the senario:
If I start the car and leave in the idle for 30min the water temp reaches 195~200F within 10min and remains steady at this temp

The oil temp raises to 250F within 20min and the climbs to 300F in 30min

Is it possible for the oil temp to be hotter than the water temp?

I am using a oil cooler block on the side of the motor and is where I mounted the sensor (see picture). I suspect that the sending unit may be bad and have ordered a new one from Summit. Looking at the pic I think I may have used the Porsche VDO sending unit and hope this is the problem.

Any suggestions?

BTW, I added a 25 Row oil cooler and get the same results

02*C5

iTrader: (1)

Is the oil cooler stock or after market and where is it placed. Would the placement of the radiator might have blocked the air flow over the oil cooler.

shanghai_todd

iTrader: (2)

Oil cooler is an aftermarket 25row and is placed in the rear fender away from the radiator. Air flow is not optimal in the fender as it is behind the tire. Have consider adding a fan

Darkman

iTrader: (2)

The operating oil temperature is supposed to be higher than the operating coolant temperature, but not 300F. Oil temperature sensor (and the asspicated ground) is likely the problem based how quickly you report oil temperature climbing.

shanghai_todd

iTrader: (2)

Darkman, are you saying I should run a ground wire to the oil cooler block to give it better grounding?

Darkman

iTrader: (2)

My reference to grounding was based on the usual causes of a false readouts from oil temperature sensors which include: (a) defective sensor; (b) defective wiring between the sensor and the guage; and (c) ineffective grounding of the circuit.

shanghai_todd

iTrader: (2)

Update:
Finally got around to changing out the oil sending unit and experimenting with my coolant system. As suspected I was using the wrong oil temp sending unit and once changed oil temp is staying steady @ 194F

In regards to the radiator and trying different combination's of anti freeze Vs distilled water here are the results:

50/50 Tap Water + Dexcool (GM Recommended Antifreeze)
First test: 30min idle time while sitting in the garage with no incoming air (Outside Temp 60F). Fan's pulling in air and pushing over the intake and engine. Temp range after heated up was 198~205F. Average coolant temp @ 200F.

Distilled Water
First test: 30min idle time while sitting in the garage with no incoming air (Outside temp 60F). Fan's pulling in air and pushing over the intake and engine. Temp range after heated up was 194~198F. Average coolant temp @ 194F.

Distilled Water + DEI Radiator Relief
First test: 30min idle time while sitting in the garage with no incoming air (Outside temp 60F). Fan's pulling in air and pushing over the intake and engine. Temp range after heated up was 192~194F. Average coolant temp @ 192~194F.

Conclusion:
Distilled water significantly reduces max operating temp by 7 degrees while DEI Radiator relief provides an additional 4 degree and safety for lubricating the system. Since I live in Florida and do not need to worry about snow, ice or freezing I see no benefits for using Dexcool.

Darkman

iTrader: (2)

Have you considered that coolant from Evans Coolant (dot com)?

Running with no coolant is problematic since its purpose is also to raise the boiling point.

shanghai_todd

iTrader: (2)

Never seen before but pricey.. I will monitor the performance on my setup for a couple more months and have to decide in the summer when the heat reaches 95F in Florida.

Capacity in my setup is only 1.6~1.7 gallons which seems kinda small.

Do you know what is the capacity in a Vete or Camaro?

Darkman

iTrader: (2)

The coolant capacity of a 2005 C6 vette is 12.6 quarts (according to a post in the Corvertte forum).

Lt1Porsche

iTrader: (6)

I have tried running distilled water plus an additive to reduce temps but like stated above the issue we ran into was the antifreeze does raise the boiling point of water and even with the benefit of the cooler temps, on the road course temps still got hot enough to boil and cause excessive air in the system which caused overheating issues. Now this was in a GR40 03 Cobra but we have since went back the factory coolant specs and have yet to experience a problem. I would recommend some dexcool.

shanghai_todd

iTrader: (2)

Outside temp a little higher today and decided to put some load on the engine with a couple of high RPM passes. Here are the results


Distilled Water + DEI Radiator Relief
First test: Temp range after heated up was 194~198F. 3 passes under acceleration and the temp raises to 205~210 then settles back down to 198F while in idle.

I am a bit concerned that in 98F degree Florida weather these numbers will raise 5~10F which is on the high side of my goal.

What do you guys think about a 160F thermostat?

I believe I have a 180F which I will need to confirm with RH

Darkman

iTrader: (2)

A 160 degree thermostat may not hurt anything in your particular application, but I do not believe a thermostat can reduce the operating temperature of a cooling system that otherwise has insufficient capacity.


http://www.carnut.com/ramblin/cool3.html

joecar

Since you're experimenting with coolant, have you tried these:
- 50/50 water and Prestone All/Extended,
- water and Redline water wetter.

I think you would be better off with a 180 thermostat.

What is the capacity of your cooling system (with the wing mount)...?

joecar

What is the intent/purpose of your car...?

I think your oil temp is getting a bit high... when does it get that high...? what oil do you use...?

Is there a way to modify the inside of the fender well to give your oil cooler more airflow...?

Darkman

iTrader: (2)

I think an oil temperature of 194 F (as updated) is too low, not too high. Operating oil temperature needs to run 212 F, at minimum, to prevent the accumulation of condensation/combustion-related water dilution. Am I missing something?

Marky522

iTrader: (8)

Coolant has very little effect on boiling point, at most like 10 degrees on a 50/50 setup. I agree that your oil temp isnt getting too high, at what temp are your fans set to come on, isnt stock like 212? IT sounds like your system is working pretty well actually.

Mark

joecar

What is the car doing when this happens...?

joecar

I agree the oil temp has to be sufficiently hot... but the op said it goes as high as 300F.

Water will evaporate at temperatures well below its boiling point... but the oil does have to get sufficiently hot to function correctly, but not sufficiently hot to get burnt.

See "Engine Oil Coolers" here: http://www.perma-cool.com/Catalog/Cat_page02.html

Darkman

iTrader: (2)

You missed the update in Post #7, 1st paragraph, the high temp went away with a new oil temperature sending unit.