saleach

Thank you everyone for the replies, after reading them and talking to some of the mechanical engineers at work i think i have figured out why my ac is so taxing on the system.

A recap of datalogging yesterday:

• Start car and let it warm up to idle, coolant is at 175F, oil is <200F.
• Drive for about 10 minutes with no AC, ECT gets to 207.
• Stop and let car idle for 5 minutes with no AC. ECT Temps stabilize to 190F. Oil temps are now at 250F.
• Drive car again for 5 minutes, no AC, temps reach 202.
• Turn on AC with no recirculation, temps reach 220 after 5 minutes of regular driving. (45-60mph, 3-5k rpms)
• Turn on AC WITH reciculation, temps climb to 230F within 5 minutes of regular driving.

Now, at idle after first start my AC blows super cold. Once the car is warmed up and driven and the oil temp is up i notice it is not nearly as cold. The reason that I have such a high spike when i turn on the AC is because my oil cooler is mounted on the driver's side in front of the AC condenser. (See figure 1 below) The fan is effectively pulling 220F air coming off of the oil cooler through the AC condenser and the radiator. So the 190F ECT is not being cooled, it is being heated up. With the AC off, the passenger side fan (based on ECT values) is pulling air that is opposite of the oil cooler, and much closer to ambient. However, I still have not figured out why recirculating the air causes ECTs to increase even further. It seems that recirculating cabin air would be less taxing on the condenser, but according to the data that is not the case.

Now, i am going to try to test this theory by dismounting the oil cooler and laying it flat on the under tray behind the bumper. Theoretically, there should be much less ECT impact once the AC is on and the ECTs should be lower overall. I will datalog and see what the results are and report back. I also plan to run a datalog of the car warming up from an idle and monitoring what happens to the temps as each fan kicks on and off, with different AC options.




If my hypothesis is correct, then relocating the oil cooler is a must. I think the best option would be a V-mount design. That way, the oil cooler is further away from the radiator, the air is directed up and away from the radiator, and move air is entering the front bumper around the oil cooler and heat exchanger, increase pressure and flow through the radiator.

Thanks to everyone who has contributed thus far!

MorngWoodStewie

Very nice talk through and conclusion. On some of your data it still seemed high for such a small quick drive. I would still check for air, you could always mount your oil cooler to tge side and throw a nice little spal fan on it works wonders with a in cabin rocker switch.

i think you can also conclude the pressure drop from just the heat exchanger in front of the oil cooler is not enough with oil climbing so fast. I would take it out of the equation altogether and give it room for a fan to draw air. I think i have a thread up in the under hood section. I mounted under the headlight crossmember with two SS hurricane mounts from ACE and some rubber bushings and a properly sized Spal fan.

saleach

Good point. I had a smaller oil cooler mounted to the side of the radiator and ducted from the bumper opening. However, there was not enough air to make a difference. My current oil cooler wouldn't fit, but i could rig up a spal fan with the vmount setup. I do have a spare 7" heavy duty that would fit nicely. Once I do some more testing I will report back with my findings.

In the meantime, does anyone know the reason behind the ECT increasing further when the re circulation is on?

spdracerut

What are your oil temps once you start driving? So in the test case where the car idled for 5 min to bring the ECT to 190F and oil to 250F, what did the oil temp drop to after driving for 5 minutes? If it dropped significantly, then I'd say the airflow is potentially adequate and the coolant needs more bleeding.

But you are correct in that you very hot air coming off the oil cooler, hitting the A/C condensor, then getting to the radiator.

In my testing: coolant at 190F, ambient at ~75F, air was coming off the radiator at ~120F. Oil temp was ~170F; the air going through the oil cooler went from 120F to ~150F. No A/C running.
Project S2000: Part 23. Testing Air Temps Through Coolers and Vents

So in your case, ambient of 90F and oil temp at 250F, the air coming off your oil cooler may well be around 170F or hotter. This is assuming you're staying out of boost so the air doesn't pick up any heat going through the SOS heat exchanger. Then the air would go through the A/C condensor and pick up a little more heat, maybe reaching 190-200F before getting to the radiator. Well, knowing what the oil temp is during steady state highway cruising will help clear up the picture a little bit. If you oil temp during highway cruising with 90F ambient is around 210F, I'd lean towards there just being an air bubble left in the coolant.

Maybe before going through the trouble of unmounting the oil cooler, just go for a drive tonight with the windows down, heater on full-bore, and do a bunch of small accelerations to get the engine speed up and down and try to burp the system. Also checking that the heater is in fact blowing hot air continuously. I have had it where I would be driving and the air would be hot then cold as an air bubble got into the heater core. Then hot again once the bubble got pushed out. If the heater blows hot continuously, then the system should be bled and then go down the route of changing the mounting of the oil cooler.

One weakness of the S2k is the lack of frontal open area for cooling. Look at any factory turbo car (WRX, EVO, GTR, Porsche, etc), and the intercooler will occupy one frontal opening and there's always another opening that has a clear shot to the radiator. I have seen pictures of guys with boosted S2ks where they made cutouts to the sides of the front emblem to create more frontal opening area that gives a clear shot to the upper half of the radiator. Not unlike the openings used for the JDM ram air setups.

saleach

Good point, i will look into getting that cleaned out as well. I have the original condenser/ heat exchanger and it could be pretty beat up.

MorngWoodStewie

"what did the oil temp drop to after driving for 5 minutes? If it dropped significantly, then I'd say the airflow is potentially adequate and the coolant needs more bleeding."

This, x2

MorngWoodStewie

think you may be misunderstanding the foam. The foam is very thin strips (3/4" high by 1/4"wide) and it is only located on the outermost perimiter of the fan hole cut (like a circle) Airflow still can pass through the cutouts and through the radiator where the steel is still closed off. That way, air is forcibly pulled through the radiator when they kick on, but it is still allowing free flow through the rest of the holes at speed.

yes but now the rest of the fins have to cool from the very pressure dropped flow from everything else in Front of it. Never stack double negatives (1: pressure drop, heat stack) i dont have pictures anymore but i made a air dam under the car that can re route fresh air up and in between condenser and rad.

i have a fully enclosed rad shroud and have no problem cooling in cruise or abuse. With a iirc 3.5" thick 800-850hp fullblown intercooler that fully and more covers the entire front opening but no oil cooler but do have an ac condenser in front of a mishi rad. Edit: but my intercooler isnt really "releasing" heat tho.

Just fyi, hope you find some answers, sometimes you just have to start back at square one. Your heading in the right direction though deffly with acknowledging the heat stack you have in front of the rad.

saleach

Very good points. When i have been driving i haven't really been driving with the heat on. (it's 99F today and heater with a black car just doesn't sound fun/safe). I will try that as well and see what happens. It makes sense that driving it would force more air out and without the heat on any air in the heater core stays trapped.

MorngWoodStewie

^^^^ gotta do what ya gotta do lol

Mrsideways

Wait a sec, your oil is 250f after casually driving around for a few min WITH an oil cooler. Correct me if I'm wrong but that sounds way high to me. I could see that with you beating on it and no cooler. But with a cooler and normal driving. That just sounds high to me.