New to the forum so hello guys/gals and thanks for having me.
I added some extra pictures in a post lower down. Still learning how to use this particular forum. Bear with me.
I designed this "bmw m3" style oil cooler for my vq35hr 350Z. The cooler you see is a 20k btu oil cooler from derale. I built that little block off plate. When I take the plate off at it drops the oil temp 10-15 degrees depending on speed so it does work. Runs at 200 even with the plate on which is what I wanted. Has a 180F thermostatic sandwich plate.
At my last track day I was still pushing toward 270F oil temps and it was 78F that day (I also installed a gauge so I know what it is now). It cools back down pretty quickly. Above 260 I don't really like.
I found a dual pass oil cooler that will fit in there. It's all aluminum. Do you think that will lower the Temps another 10-20 degrees? Ideally I wouldn't like the oil temp above 260 even on a very hot day.
Would hooking fans up to a relay be helpful?
Open to better ideas that still let me run at 200F when driving around town.
All responses will be read and appreciated. Thanks. 
Can you share any pictures of where the cooler is mounted and how it gets airflow? That's where I'd probably start.
Any significant engine mods? I went through all of this with my 318is before realizing it was right on the edge of pinging. Pulling 2-4 degrees of timing (4 degrees around peak torque, 2 up towards redline) dropped oil temperatures by 30+ (!) degrees. I don't know how big the + is because before the change, I would run a cooldown lap once I hit 280F. After the change, it stabilizes at 250F for the whole session.
I use a cheap ebay stacked-plate style oil cooler (this one to be exact). For us it's good for a 45* drop in oil temperature, verified when we had to bypass it at one of our races.
In reply to Keith Tanner :
Sorry, I guess the other pictures did not load. It it mounted right in the undershroud behind the front bumper. The high speed/low pressure area under the bumper draws air through the low speed/high pressure air inside the air dam that's in front of radiator.
In reply to gearheadE30 :
Just a tune and breather mods. I have a "Sunday special". My car, before any mods, can seemingly blow away all the other HR Z's. I must have gotten lucky.
In reply to ross2004 :
I have no idea what the Temps were before as I only have the guage installed now. That gives me faith in the dual flow ebay cheapo I was looking at though. From what I can and from what I know of twenty years of manufacturing experience is that those "cheap" eBay ones are the exact same a the mishimoto ones. I can guarantee they come off the same assembly line in China. So maybe not so cheap lol
Based on what I've seen of Mishimoto's understanding of aero (their fans for the Miata are a serious downgrade from stock), I'd take their claims with a grain of salt. In order to have a good flow of air from the engine bay to under the car, you should have an air dam at least. I believe Pontiac/Chevy used a bottom exit for their cooling setups in an F-body and it was quite sensitive to the use of the factory airdam. The point is that while your cooler is in approximately the same place as used on a BMW, aero is one of those places where details really matter.
It might be interesting to stick a camera on the car so it can see the core and put a few telltales on it to make sure you've got significant airflow - and even which direction it's going. Depending on direction, you might actually want to replace your blockoff plate with a scoop.
In reply to Keith Tanner :
Oh I'm not going off any claims by mishimoto. They don't even know the btu/hr rate of their coolers, ridiculous. I called them and asked.
This is not their setup, I made this. It works, I know that for sure.
You may be correct and the air could be going up, I doubt it though. From my limited understanding of aerodynamics the air would have to flow down due to high and low pressure areas trying to reach a homeostasis.
I could put a pink poof thing on a string and duct tape my phone in there to make sure lol. I might actually do that lol. It's pretty easy to reach down there with the hood open.
It works, which is great. But you want it to work better, and the easiest way to do that is to get more cool air across it.
Assuming it is moving air from the engine bay to under the car - is it post-radiator? If so, that's nicely pre-heated and the amount of heat transfer is directly related to the temperature delta between the air and the oil. If you can feed it fresh ambient air, you'll shed more heat than if you're feeding it engine bay air.
In reply to Keith Tanner :
It is pre radiator. Cool air. I considered making a duct from the grill direct to the cooler but I feel that will limit the flow as it relies on pressure differentials to work right now.
I think a dual pass in that spot will help it out and if need be, I can run the current cooler in addition to it. Will just have to come up with another clever mounting point that gives me access to block it off.
In reply to Keith Tanner :
I heard running two small cooler is better than running one big one? Do you understand the thermodynamic principles behind this? I, currently, do not.
In reply to Bmsluite :
Have the engine mods been significant? The thing is, after I had gone through all of this with my 318is, I realized that I had been pinging it for quite some time. Oil temperatures dropped by 30+ (!) degrees when the timing was pulled 2-4 degrees (4 degree timing around peak torque, and 2 degree timing towards redline). Previously, I ran a cooldown lap after reaching 280F so I don't know how big the + is. For the duration of the experiment, it stays at 250F after the change.
Adding ducting pre-cooler does not prevent pressure differentials. The goal there is to increase the pressure on the high side, really.
I haven't heard that multiple small exchangers are better than a single large one. Can't think of a reason why unless they're in parallel - then maybe you get more drop because more of the core is at the initial high temp. If they're in series, it would be the same as a big one of the same area.
What's your water temp?
How much oil do you put in the car?
Had a similar issue and it was from putting in just a bit too much oil. Had 285 degree oil temps after just a few laps.
Dropped about 1/2 quart of oil (down to 1/2 quart above full) and my oil temps are about 30 degrees hotter than water temps now.
In reply to Keith Tanner :
Did you mix up parallel and series in your musings? Asking not to be a douche but because I am contemplating running dual oil coolers and considering parallel vs series.
And it seems that parallel would simply be the equivalent of a single larger, while series might, in theory, work better??
"The air temperature difference also means that if we run two oil coolers, they should be plumbed in parallel, rather than in series. If you run two coolers in series, the oil in the second cooler would be cooler (closer to the air temperature) than the oil in the first cooler, making it much less efficient. Another bonus to plumbing in parallel is that it has the same effect as adding more rows to the cooler: Less flow restriction for an even happier oil system."
https://www.pegasusautoracing.com/document.asp?DocID=TECH00133
In reply to jfryjfry :
No worries about douchiness, it's an easy thing to get mixed up and I was trying to be pretty careful :)
Yup. It's all about that temperature delta. To shed the most heat, you want the highest temperature delta between the hot thing (oil) and the cold thing (air, in this case). On a big cooler, the delta drops as the oil moves through the cooler so the heat exchange slows down. Also, if you have a fat multi-core cooler the air heats up as it goes through the cores so your heat exchange drops off as well.
This doesn't mean that you'll always get better performance by using two small coolers instead of one big one with the same total surface area. It depends on how that big cooler is designed, but since most oil coolers are set up to be short and wide, I can see how it generally would perform better if you split it in half.
I think I just worked through why the original Miata radiators had their tanks on the long side :) Didn't work as well as a cross-flow with tanks on the short side, though, probably due to the fact that heat exchange takes time. I think I need to get the FLIR camera out and maybe pull out some of the Carrol Smith books.
I'm running a Derale 15660 25 row plate cooler on my G35, with their 190-degree inline thermostat controlling the fan. It dropped oil and engine temps significantly on the track. Most importantly, it stabilized them. Engine and oil temps stay pretty much rock solid throughout a 20-minute session where before I would have to do a cool-down lap every 3rd or 4th lap.
My setup is right in front of the radiator, hanging under the bumper. I'm also running ZSpeed's undertray so all the air that goes through the bumper has to exit through the radiator. It also extends far enough back to cause a low-pressure area in the engine bay. It alone helped a surprising amount in stabilizing engine temps.
In reply to Toyman01 + Sized and :
My current one is just the derale 10 row. I went off the advice to run the smallest cooler possible so you run at a good temp on the street.
Two questions: what are your Temps on the street just cruising?
What are your Temps holding at on track?
I wanted to stay away from mounting in front of the rad bc I previously had water overheating issues. Koyo rad fixed that. Rock solid at like 210.
In reply to wvumtnbkr :
Water tmep stays rock solid at 210 now. Koyo rads are amazing. No issues there.
It holds 6 quarts of oil with the new cooler and the giant oil filter that I have to use with the thermo plate. The engine itself holds 4.7 and the old oil filter held 0.3
In reply to Toyman01 + Sized and :
You've got the oil cooler set up with the fittings on the bottom. This means it will drain when you turn the car off. If you check your oil level with the car not running, it will be a quart low (or s0) as soon as you fire up. I'd recommend either checking oil levels with the engine running or purposefully overfilling by the capacity of the cooler.
Bmsluite, if you're running a thermostat plate, you can run a bigger cooler. That's the point of the thermostat. And taking heat out of the oil will also take heat out of the water.
