posted on August 08, 2011 11:00
Project S2000 - Oil Cooling
by Khiem Dinh
Khiem Dinh is an engineer for Honeywell Turbo Technologies at the time of this writing. All statements and opinions expressed by Khiem Dinh are solely those of Khiem Dinh and not reflective of Honeywell Turbo Technologies.
Tracking the S2000 and monitoring the oil temperatures has taught us one thing: it runs hot! Even with the reduced coolant temperatures afforded by the Koyo radiator, the oil temperatures were still too high for a car to be tracked for long-term reliability. This is occurring at completely stock power levels even (the more power an engine makes, the more heat it makes and consequently needs to reject). High oil temperatures lead to reduced oil viscosity and faster oil breakdown. Low oil viscosity can mean inadequate oil film strength and thickness with the end result being metal-on-metal contact between engine components. While low oil viscosity may not grenade your engine immediately, it will lead to accelerated wear of components.
I tried a band-aid approach of using high viscosity oil (15w-50) relative to the recommended fill (10w-30) for my track day in the summer heat of the desert. This approach may solve the oil viscosity and pressure issue, but does not address the issue of oil breakdown with excessive temperatures. Also, rod and engine bearings are made of relatively soft metals that don’t take well to being heated to high temperatures. Lastly, high oil temperatures mean a hotter running engine leading to a higher propensity for detonation.
|I decided on an Earl's Temp-A-Cure oil cooler. This line of coolers was designed for the typical air speeds and oil flows seen in automotive use. They're made of high grade aluminum and are furnace brazed to create the most thermally efficient joint possible between the tubes and fins. Earl's choice of fin density was selected to maximize heat transfer to the outside air. I'm using a 34 row cooler with a 10.5" height and 13" width. I also opted for the optional mounting bracket kit. My old roomie left behind a roll of rubber that had adhesive on one side. I applied the rubber strips to the surfaces that would come in contact with other objects when mounted.
The S2000 engine, along with other high performance engines, uses piston oil squirters. The purpose of the piston oil squirter is to spray oil at the back side of the piston and reduce the temperature of the piston. A cooler piston reduces the likely-hood of detonation. Spraying cooler oil at the piston is obviously better than spraying hotter oil at the piston.
So we can see that the benefits of running oil at its proper operating temperature are multifaceted. Doing so will extended the service life of the oil, reduce engine wear, and reduce the likelihood of detonation. Now the challenge was to figure out an oil cooler setup for the S2000 that fulfilled the role of both a daily driver and track day vehicle.
|Earl's -12AN Auto-Fit Ano-Tuff fittings use a military spec hard anodized coating for corrosion resistance and toughness. The fittings were paired with Pro-Lite 350 hose. When assembling the fittings to the hoses, remember to use either some motor oil or Earl's assembly lube. Installing the fittings onto the hose was a snap.
Monday, August 08, 2011 6:00 AM
Nice write-up and installation.
So you don't like oil-to-water oil coolers? I have heard of some people using them successfully on the track. Perhaps it depends on the motor and cooling capacity of the radiator?
Monday, August 08, 2011 6:28 AM
Are you sure you aren't making a mistake with the Spal fan. From my experience slim fans, even high quality ones like Spal don't move as much air as factory ones. Worse if the size is smaller.
Monday, August 08, 2011 6:53 AM
Nice writeup Khiem. Make sure to cover those hoses in split rubber hose and zip ties anywhere it might contact something to prevent abrasion on the hoses themselves.
Monday, August 08, 2011 6:55 AM
Oh yeah, keep an eye on that heater hose as well. I've had a couple of failures with that stuff when looped 180* like that. If you have a failure, either upgrade the hose to silicon, or run a longer length to reduce the angle of the dangle (which determines the heat of the meat, btw). :)
Monday, August 08, 2011 7:32 AM
@wrecked, I'm not worried about the fan at all. There are no problems keeping the coolant temps in check with the fans. When just idling, it takes forever for the coolant temps to come up due to the fluid capacity. Once the fans do kick on, it only takes a few seconds to bring the temps down. so the only downside will probably be reduced AC performance while stuck in traffic. Don't forget that there's still the factory driver's side fan. So only one of the two were replaced with the slim fan.
Monday, August 08, 2011 9:22 AM
Monday, August 08, 2011 10:05 AM
Good write up, where did you order the mocal sandwich plate from?
Monday, August 08, 2011 11:32 AM
@ dusty. I had thought about a laminova, but decided against it. It just transfers the heat load to the coolant making that entire system work harder and heating up the coolant. It also does not make the maximum use of the heat capacity of the air available.
@tony. I bought the mocal and spal from racerswholesaleparts.com. I think that's the correct name. Sitting on an airplane right now.
Monday, August 08, 2011 11:53 AM
I would have ditched the A/C altogether and place the cooler in front of the radiator instead.
With the S2K you can always remove the top :)
Monday, August 08, 2011 12:56 PM
It's been over 110° here in OKC quite a few times already this summer. I think I'll keep my A/C, thanks. :P
Monday, August 08, 2011 1:15 PM
"A good temperature for oil is around 100C "
Really? That may have been true a few decades ago, but not so today with modern synthetics. Extensive testing done for the Corvette Z06 (C5) showed no significant degradation in performance of Mobil 1 up to 300° (aka 149C). I am pretty sure GM Corvette team published the results through SAE.
You likely aren't going to hurt anything at 212°, but you certainly have a lot of room above your target and still be in the safety zone of any decent oil. In fact, you have a lot more room above than below that temperature.
Monday, August 08, 2011 2:28 PM
The oil is good for 300°, but the soft bearings (and basically the entire engine) ain't gonna like those temps?
Monday, August 08, 2011 4:49 PM
Bearings start to loose load bearing capacity at around 260 f. 300 is really pushing it. @ 300 degrees the bearings start to actually degrade.
Monday, August 08, 2011 7:00 PM
I really need to install an oil temperature gauge!
Monday, August 08, 2011 7:15 PM
@JDM, the ladies don't like the lack of A/C. And I don't want to have to wear sunblock all the time. And showing up to work sweaty isn't highly looked upon in the office. Remember, this car is my DD, not a pure track car :)
@teamDFL, while Mobil 1, Motul, etc might be okay up to 300F, why push it that high? There's no benefit at all to running oil that hot. Even if the oil were perfectly fine at 300F, that still means the rest of the engine is running hotter including the pistons. So there would be more heat load on the coolant system and a higher propensity for detonation.
Having watched my oil temp and pressure gauges, the oil pressure starts to level out around 80C and doesn't change much as it reaches 100C. On cold start with an oil temp around 20-30C, the oil pressure at idle is over 6 bar. At 80C, it's down to 2.0 bar or so. Pressure at idle with a temp of 100C is around 1.5 bar. All these measurements are at the oil filter of course and the readings may differ at a different location such as the stock oil pressure sending unit.
Considering Honda engineered the car to run around 100C in normal operation, it's logical to assume that's a good operating temperature. Beyond that, one of my old car buddies said 100C is good in order to boil off any water in the oil. I actually wanted a thermostat that opened up at a higher temperature, but Mocal only had 180F in the sandwich adapter design.
Monday, August 08, 2011 9:25 PM
I'm pretty sure that the additives in oil degrade rapidly at higher temperatures as well.
Tuesday, August 09, 2011 4:56 AM
I am not advocating running the oil at 300°, what I am saying is that there is no need to panic if you are unable to maintain your stated target of 212°. The oil can take a lot more than that. Yes, you will probably seem some acceleration in loss of additives, but a shorter OCI is a requirement for a car driven on track anyway.
Perhaps the S2000 engine has a particular weakness to elevated temperatures; I do not know and would not have assumed so based on Honda's reputation. As stated, detonation is the biggest concern here.
Clevite TriArmor are rated to 500° continuous use. I am surprised that Honda bearings would start to degrade at only half that temperature. In an engine that goes to such high RPM, it is difficult to understand why they would cut corners in that area.
I have a run a Ford Zetec at 300° for many hours, blowing fast the factory redline by more than 750 rpm. Was it the best idea? No. Would I tell someone to do it? No. But after 3,000 track miles and 120,000 street miles, the bearings were still looking good with only light evidence of elongation of the big end bores. The point isn't that you should run 300°, but the idea that somehow high oil temperatures will drastically shorten engine life is no longer true. My own experience and extensive testing by GM have shown this to be true. Many modern cars run at 240°. Today's oils are built to survive that.
Tuesday, August 09, 2011 8:03 AM
@teamDFL, I agree that today's oils are better and 240F is considered acceptable for endurance racing. For another reference point, I think Nissan's 370Z does not cut power until 280F and does not engage full limp mode until 300F.
However, there's still no reason to run temps anywere 250F+ if it can be avoided. In a race car such as GM's Vettes where they are limited airflow for cooling and also weight, they can decided to make the trade-off of reduced cooling for reduced aero drag and vehicle weight. In a daily driven street car that is tracked often, why not avoid the high oil temps?
Regarding wear, components in the head may also be adversely affected with cresults such as accelerated cam wear. Evos have shown signs of this and they come with oil coolers stock.
Anyways, you and I are both basically saying the same thing. I'm just saying, why reduce the life at all or run hotter risking detonation? This poor car only gets fed 91 octane.
Tuesday, August 09, 2011 9:04 AM
this article doesn't seem to mention oil pressure, with these kits you can see a pretty noticeable drop in oil pressure sometimes by up to 1/5th. You may want to check that.
Tuesday, August 09, 2011 9:05 AM
I would have also used fittings with a shallower angle like 45 degrees instead of 90
Tuesday, August 09, 2011 1:18 PM
To each is own I guess. I deleted my A/C long time ago (on my daily). I roll down the window, and bring some water with me :)
BTW, I live in South San Jose. In the summer we see temperature that get close to 100 degree, not much off from you guys.
If girls bitch about the heat, tell them to ride a bus !
As far as getting to work and stink....haha, bring some deodorant and an extra shirt :)
Tuesday, August 09, 2011 1:34 PM
@circuitsports, read the caption on the first picture of page 5 and also the first two sentences of the first paragraph on page 5 :)
While the 45 degree fittings would have less pressure drop, they would not work with my packaging constraints. To make them fit would require either of two things: either a shorter/smaller oil cooler or getting rid of the airbox snorkel.
Tuesday, August 09, 2011 1:35 PM
@JDMized, we must date different types of girls :)
Tuesday, August 09, 2011 2:45 PM
@ JDMized: Or, leave the AC on the car. :)
Once upon a time, I almost never turned the AC on because it sapped power and made the engine respond slowly.
Now it's a definite WTF moment if its above 75* outside and I'm in a car without AC. As you age, you tolerate such things less. Khiem and I are graduating into "old balls" status. Soon, we'll complain about how the weather changes makes our joints hurt, and the loud music them damned kids are always blasting... :)
Tuesday, August 09, 2011 3:17 PM
If the temperatures aren't triple digits, the A/C is off and the windows are down.
But then again, I run the A/C when I get in a hot car that's been sitting in the sun to cool it off. Then when it's cooled off, I turn off the A/C and put down the windows. :-P
Tuesday, August 09, 2011 3:42 PM
Graduating to old balls status? Already there buddy. Hell, I can already tell you that a thunderstorm is coming 30 minutes ahead of time.
Tuesday, August 09, 2011 4:26 PM
@ Khiem: Yeah, I'm getting close. My back generally hurts. Knees are going, but not gone. Too many contact sports... :)
@ Dusty: I just run the AC. Looking at Dash Command, fuel consumption is slightly lower with the AC on than with the windows down, and it's quieter and more comfortable.
Tuesday, August 09, 2011 5:57 PM
When we did the oil cooler on Project 200SX we were worried about the 4 90 degree fittings in our install. We used the constant radius 90's instead of the 90's used here and we were unable to notice any pressure loss in the system before and after on our gauge.
I think many people are cautious and like to point out the potential issues with using too long of lines and 90 degree fittings however until you actually install it and take readings it's just cautious speculation.
Nice write up Khiem install looks clean, well except for the painters tape ;) Maybe you could put a hella functional sticker on the painters tape....
Wednesday, August 10, 2011 11:33 AM
The difference is you took those measurements for oil pressure pre and post and that's missing from this article. It's a pretty safe assumption to say any oil cooler is going to cool oil unless it's placed next to something that is hotter than the oil. But assuming the oil pressure isn't going to drop isn't a good idea and I have seen engines where they lost enough oil pressure for damage to occur. And many more where it was dangerously low. All I am saying is this article should be amended at least with post install readings for oil pressure.
Wednesday, August 10, 2011 1:46 PM
@circuitsports, patience young grasshopper! The reason for going with -12AN (largest possible with the Mocal sandwich adapter) was to minimize pressure drop. Trust me, it's on my mind and I'll be keeping an eye on the oil pressure per the advice of my co-worker that road races his Nissan (he also recommended shimming the oil pump to get more flow/pressure). However, I do feel relatively comfortable as people have run the Greddy oil kit which is front mounted (longer lines), uses what appears to be only -8 or -10 line (smaller diameter), and also at least one if not two 90 degree fittings (big pressure drop considering how small they are compared to the -12AN!).
So far I've only had the chance to crank it up and check for leaks (the car is on jackstands in my garage pending some suspension rework). I did let it idle for around 10 minutes, with a few blips up the rev range, but the oil temp wasn't even close to getting hot enough to open up the thermostat (only around 50C) and I think I was starting to piss off the neighbors. And I didn't want to get carbon monoxide poisoning.
Anyways, I have some track time scheduled to test out the oil cooler and revised suspension setup, hence the "stay tuned for performance numbers". And yes, I'll be reporting the oil pressure with the thermostat open, don't worry :)
Tuesday, September 06, 2011 12:18 AM
If the bearings are degrading or starts to have higher wear, would it show up in the result of Used Oil Analysis?
Tuesday, September 06, 2011 8:54 AM
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