Oil cooler tech
 

In the same vein as Emilio's cooling system thread, here's some tech info on oil coolers.

Why you need one
Oil coolers are an important addition to any car that sees track time. As oil gets hot, it loses viscosity and becomes less effective at supporting the loads placed on the bearings by the crankshaft and rods. Get it too hot and you scuff a bearing and things go downhill quickly (spun/seized bearings, broken rods, holes in blocks, tears). True high-end synthetic racing oils (Amsoil, Joe Gibbs, etc. – not Redline or anything you can buy at an auto parts store) are generally better at resisting this high-temperature degradation, but even they have their limits. Stock Miatas can exceed 300*F oil temps in hot weather, and no oil will tolerate that kind of temperature. Even if you are racing a stock-powered car, you likely need an oil cooler.

Where to measure temperatures
Measure the temperature of the oil in the oil pan/sump. The temperature of the oil in the pan is both the average temperature of the oil in the engine as well as the temperature of the oil being fed into the engine, so it’s the ideal place to take oil temperature measurements. If you can’t put a sensor in the pan, put it as early in the system as possible – another good spot is in a sandwich adapter before the oil filter.
Maximum allowable temperatures will vary depending on the quality of your oil, but if you are using quality oil (Rotella T or better), you should strive to stay under 250*F at all times. High-end racing oils (Amsoil, Joe Gibbs,etc) can tolerate more temperature than this, but it should be avoided if possible.

Sandwich plates and thermostat control
Oil that’s too cold is almost as bad as oil that’s too warm. Cold oil circulates poorly inside an engine and can inhibit proper lubrication. Mazda’s oil “cooler” on the 94-05 Miata actually functions primarily as an oil warmer, using the warm coolant to bring the oil up to appropriate operating temperature more quickly. Racing oil cooling systems use thermostats to restrict coolant flow when the engine is cold instead. Most quality systems have a bypass thermostat built into the oil cooler sandwich adapter. Others will use a separate thermostat installed in the cooler lines which allows oil to bypass the cooler before it has warmed up. It’s important to use a thermostat that allows a small amount of flow even when the oil is closed – if the oil cooler system is sealed completely, you will see system pressure fluctuations as the thermostat begins to open. Most automotive application oil thermostats are set for 180*F.
Sandwich plate adapters will typically foul the block on 1.6L Miatas. This can be solved by adding the longer stud and oil cooler/warmer from the 1.8L car. Leaving the OEM cooler/warmer hooked up will still allow the oil to warm up quickly, so leave it installed and hooked up whenever possible.

Hose size and type
Hoses must be sized to minimize pressure drop. The longer the hose, the larger the diameter that should be used. -8AN (1/2”) hoses are generally not large enough to maintain full oil pressure through the system. -10AN (5/8”) hoses are preferred.
There are two types of hoses that are commonly used in oil cooler systems. Push-lock hose is less expensive and can fail catastrophically if the fittings are not assembled perfectly. Braided hose is more expensive, but also significantly more robust and less prone to assembly issues. Stainless braid is the strongest hose available, but must be routed carefully because it will cut through whatever it touches (including things like aluminum brackets and wiring). Nylon braid is lighter and won’t cut through its surroundings, but it is not as robust as stainless. I prefer Stainless braid for oil cooler systems.

Core type and size
Inexpensive TruCool-style coolers do a poor job of actually removing heat from the oil. OEMs around the world prefer Setrab coolers, which have been the industry standard for decades.
Core size will depend on application. If you have more power, you need a larger core. Less airflow to the core will also need a larger core. Light-duty naturally aspirated track cars with the cooler in direct airflow can use a 10-row core. Higher power N/A track cars and all forced induction applications should use a 16-row core. High-power forced induction or limited airflow applications may need to size up to a 20-25 row core to keep things in check.

Core location and mounting
The ideal location for an oil cooler will depend on what other heat exchangers you have installed. If you have a naturally aspirated track car, you can simply place the oil cooler in front of the radiator and call it a day. If you have a turbocharged street car with A/C that you occasionally take to the track, things get a lot more complicated. The ideal placement for the oil cooler will vary significantly depending on intercooler size and placement. It’s up to you to determine the best place for your cooler. All the same requirements for radiators and intercoolers apply to oil coolers – maintain air gaps between cores, maximize exit flow as well as inlet flow, and duct the flow on high-horsepower builds.

Since mounting is such a variable when designing a good oil cooling system, we've put together a DIY package which lets the end user mount the core in the ideal location for their location. You get everything required to assemble the kit, all you need to do is pick your mounting location and trim/assemble the lines. The 10-row cooler is shown below, which is $400. We also offer a 16-row cooler (our most popular kit, $430) and a bad boy 25-row for $475.

Attachment 239098

I've been waiting for this thread. What brand sandwhich plate do you recomend, you didnt specify it, Mocal?

And speaking of the stock oil warmer, it was brought up on another road racing board that it could be put on its own coolant loop with an electric pump and 250° thermo switch to make an air to water cooler setup. Its heavier, but has basically no chance of catastrophic failure and/or fire.

So what's the verdict on the stock oil cooler? Keep it or toss it?

Oo! I've been waiting for this one! in4knowledge

god damn noob! y u no read?! :rofl:

Happy for this thread. Sticky with cooling system thread.
Thanks for good info to keep our little cars strong and healthy!

Mocal is what I stock, yep. Also have all the correct BSP bits and Dowty seals to make it work like it's supposed to. I actually stock full DIY oil cooler kits, $430+ship for a 16-row Setrab, rubber-isolated mount, Mocal sandwich adapter, 10ft of -10AN hose, and all the necessary fittings.

Sounds incredibly complicated. Electric water pump, water lines, heat exchanger, all to feed coolant to the tiny little oil cooler. I seriously doubt whether it would make a large enough difference, and there's no way it's worth the additional hassle of the pump.

Great thread. I have a Miata-n00b question: How do all the SM cars get away with no oil cooler?

*edit*: Looks like Trackspeed has a oil cooler kit on the way, yes?

I personally saw a stock oil warmer develop a hole in it. The driver of the car saw the coolant temp rise above what the gauge always read and pulled over immediately. Looked under the hood and saw oil in the coolant.
When towed in I suspected head gasket. But I pulled the oil warmer and pressure tested the cooling system. Water began pissing out of a small hole in the warmer.

I replaced the warmer, flushed the cooling system and all is well.

I don't know how common this is but I have a first hand case. Could have been a defective warmer. I was thinking either this, electrolysis or some sort of cavitation in the warmer but nothing confirmed, just guessing. It had a stock radiator, so I would imaging that would have gone first if electrolysis. Also thought it more likely to find cavitation at water pump but I suppose it could still be a possibility.

Really not here nor there but the stock oil warmer can fail.

16-row DIY kits in stock.

Trackspeed DIY Oil Cooler Kit

Awesome thread/info and awesome kit from TSE.

The weak-point in my system is the TruCool unit itself. I've absolutely maximized the airflow for it to a point that it is able to do the job for my 200whp (oil temp maxed at 235* in 105* ambient), but with any more power I'd have to look into a better cooler, and I probably will move to a Mocal or Setrab eventually anyways, just to be on the safe side.

-Ryan

Is there a preferred order of stacking the factory oil warmer and the other sandwich plates. Maybe block/factory/sandwich plate/filter.

No other way to do it, yep. Block, OEM warmer, Mocal adapter, oil filter. 1.6L cars typically need a spacer or the 1.8L warmer (and stud) to fit a sandwich adapter. The fittings on the adapter foul the block if you don't space it out from the block using the OEM warmer.

Great write-up Andrew, I'm not a fan of adding an oil cooler due to all those new oil lines going around in the engine bay and so far, oil temps are around 230F (which is fine for my Rotella T6).. but I'll surely consider your kit if It ever get too hot.

Is there any thermostatic sandwich plate worth considering? The Mocal one is extra-baller, but a bit rich for my blood.

I was thinking something more like the $30 derale thermostatic adapter

One downside to that one is the 3/8 ports rather than the 1/2" ports of the Mocal. And the 180°F thermostat, IIRC mocal is available with the more appropriate 205°F thermostat, although something more like 230°-240° would be even better.

Can you please be more specific about this? What does the warmer accomplish by being in place? A lot of people have 1.8+ swapped into their 90-93. As I'm re-using my 1.6 oil cooler I'm sure others are too. I.E. I don't have the warmer . I do have a fancy glow shift plate. :party:

See, I took a look at the TSE kit, and thought "Do I want my oil thermostat to open at 180*? That seems low..."

Does anyone know if 180* for the oil is too low? Does anyone know what temperature range oil stays at during street driving with a stock setup(no cooler)?

Thanks
-Dustin

1.6's didnt have oil coolers. The 1.8 oil warmer spaces the sandwich plate out enough that the fittings dont hit the block. Maybe he's always done it, but Andrew has been using foul to replace the words interfere or intersect recently.

There is a GM version with 1/2" fittings.
I was thinking of using it with a remote filter mount and block take-off plate.

That seems weird, like you'd end up with a bunch of hoses going everywhere. Why wouldnt you run an inline thermostat instead. Mocal even has one thats -10 male on all ends.

You would have 4 lines in total. Two from block to remote oil mount, two from thermostat to oil cooler. thermostat and remote oil mount are sandwiched.

as for mocal: I'm cheap.

Ports are way too small. 3/8" is equivalent to -6AN. -8AN is acceptable, but still reduces system pressure. -6AN is not big enough, period.

GM version is OK, although I vastly prefer the BSPP/Dowty seal setup that Mocal uses over NPT. I also don't see a GM-style 1/2" adapter in the proper M20 thread.

IMO, the added cost is worth it. Mocal is what OEMs use when they need a sandwich plate adapter. It's $122 including the adapters and Dowty seals, so we're not talking about a several hundred dollar difference.

The fittings on the Mocal plate contact the block if you just bolt the sandwich adapter onto the 1.6 without a spacer. The 1.8L warmer spaces the sandwich adapter out so there's clearance between the block and the fittings.

180*F is fine. Mocal does makes a 205*F version, specified for marine and aviation use where the oil being used is thicker than normal automotive-application oil. Running a 180*F Mocal adapter, I used to see warmed-up street temps in the 190-200*F range. You want to get the oil up to ~180*F, but it's less about viscosity and more about heating off the fuel and water that inevitably makes its way into the crankcase as the engine operates. Changing the weight of the oil you run has a larger effect on viscosity than the difference between 180*F and 205*F.

https://www.miataturbo.net/attachmen...1&d=1406833708

edit: Correction, 205*F sandwich adapters are in such low demand that Mocal does not stock them, so I can't get them without a large pre-order.

After using a cheap sandwich plate and then loosing oil pressure the extra money spend on a Mocal is totally worth it in my mind.

So n/a car with a/c it's preferable to mount the oil cooler in FRONT of the radiator? How come I saw Emilio put the oil cooler in the engine compartment BEHIND the radiator in his OGK car?

https://www.miataturbo.net/attachmen...0_motor_na-jpg

What about mounting the oil cooler to the steering rack like FLyin' Miata? Let's talk about oil cooler durability in the event of an off-course excursion.

What caused the oil pressure loss?

3/8NPT is the standard pipe thread for -8 (8/16=1/2") AN fittings. 1/2NPT is the standard pipe thread for -10 (10/16 = 5/8") AN fittings. 3/8NPT is not equivalent to -6AN.

Looks like they mounted it this way to warm the oil in the cooler . Some race engines run extremely to cold .

Never assume that something is preferable just because you saw it done on a purpose built race car. You'll also note the stock radiator used in that particular configuration of Crusher (not the OGK) as well as a flat piece of ABS to limit the airflow through that stock radiator. That motor was not a normal BP motor, and the 25 Hours of Thunderhill is not a normal race. Emilio can elaborate on the particulars of that engine if he so desires :giggle:

It's the only mounting location that is universal to pretty much all applications. It's also highly prone to damage if one were to go off-track. It's not a mounting location I would recommend.

I believe due to the configuration of that particular motor, there were troubles getting it UP to temprature. Notice how half the radiator is blocked off? That is not any sort of standard configuration, do not copy it. :bigtu: That picture has really fucked up peoples brains.

yarrr

I measured a -10AN hose end I have laying around and its 0.465" ID.
I haven't seen 3/8 NPT fittings go over 0.4" ID.

1/2 NPT would be better.
https://www.miataturbo.net/attachmen...ine=1406851045

I'm not saying they're right or wrong, but I'd be interested in opinions on their setup. Motoiq has their oil cooler mounted behind the radiator as well, but in a much different fashion.

Project S2000 - Oil Cooling

I had the oil temp sender in a sandwich plate and saw 230 pretty consistently. All warmed up driving down the highway in 70 degree weather on a bone stock '96 1.8L.
I saw north of 270 degrees on mountain roads in 80 degree ambient, driving spireted but certainly nothing close to track driving. (Same car)

My '99 had the same oil temp sender location ^ and similar oil temps before I put the blower back on. With the charger on, I back off when I see 280. I need an oil cooler soooon.

I could easily see how a stock miata on a track on a warm day would have dangerous high oil temps.

So the Mocal adapter has no ports for sensors does it? So would the preferred method to measure the temp and pressure with this kit would be to add a sandwich plate as well as the Mocal adapter?

Block - Factory 1.8 warmer - Mocal spacer - sensor sandwich plate - filter?

Seems crazy

The preferred method is a bung in the oil pan.

So in this case, it seems that the oil cooler doesn't affect the street driving temps dramatically, sounds like a good thing. I was concerned with 180* oil temps, but it's apparently not an issue.

Wow, spirited street driving seems to have a very large effect on oil temps, more than I would have guessed.

Here's an interesting thought from an uninformed source: Lets say your current car hits 260* spikes during track use with 10W-30. After you install an oil cooler, you only hit 220* during track use. At 220*, 5W-20 is the same viscosity as your 10W-30 was at 260*, so in theory, you could switch to the 5W-20 because you would be at the same viscosity as before, but at much safer oil temps. Would this help free up a little bit of power safely?

-Dustin

Free up power? Yes. Safely? Ehhhhh...

IIRC, there are spots on the Mocal adapter that you can drill and tap for a sender.

Another option is an inline AN adapter in the line going to the cooler. It won't read accurately until the thermostat opens, but you don't really care what the oil temp is below the thermostat opening point, right?

Here's an expensive pre-made one:

http://www.summitracing.com/parts/aa...0040/overview/

I have a 13-row Setrab on the FM steering rack mount with -10AN fittings. It works pretty well, but is definitely in a vulnerable location. One additional downside is that 13 rows is the max you can fit, I have a 19 row Mocal that I originally bought to use with it, but the fittings want to be where the sway bar is. On the plus side, the lines are nice and short. (Note that the kit FM sells uses -8 -- I agree that's too small, so I built mine with -10)

--Ian

Something in the cheap glowshift sandwich plate I had caused the oil pressure loss. Never pulled it apart enough to figure it out exactly as I was to pissed with the sandwich plate.

you can use this thing - its cheap ($13.97) and doesn't need extra fittings

http://www.summitracing.com/parts/rus-670360/overview/

https://www.miataturbo.net/attachmen...ine=1406905362

Or Fragola, in black
http://www.summitracing.com/parts/fr...8-bl/overview/

I really want to add a cooler to my car but I'm just not sure where I would mount it, my radiator/IC setup is boxed in and the space between my fans and engine is pretty tight too. Bah!

:rly: If someone has pics of this I'd love to see them

I'll have pics later this afternoon of the mocal plate.

Bitchin, thanks Curly.

I drilled a hole in my oil pan and welded in an 1/8" NPT bung, but it turns out I went full retard and its behind the motor mount. :facepalm:

Dont feel too bad. when I did mine I melted the 1/8"npt bung into an oval the first time and had to grind it off. And I put it on the drivers side in the sump for the sole reason that hustler said to put it there. After I put the engine back in I realized there was no fucking reason it shouldnt have gone on the passenger's side.

Oh it gets worse... the oil drain on the other side is almost directly inline with the hard lines that come out of the steering rack.

For those following along at home, this location:
https://www.miataturbo.net/attachmen...202_143118-jpg

When I go full retard, I go all the fucking way. :loser:

It's almost like we were surrounded by Miatas and just decided to not look at them and weld things wherever we felt looked good at the time. >.<

The Mocal plate:

https://www.miataturbo.net/attachmen...ine=1406932443

https://www.miataturbo.net/attachmen...ine=1406932443

Let me know if you want to see any other angles.

Doesn't this setup limit your ability to diagnose a faulty thermostat? If it doesn't sense actual temp until the thermostat opens then what happens when the thermostat fails to open and your actual oil temp is 280 but your gauge only reads 100?

When I put the temp sender in Theseus' oil pan, I was careful to locate it so that it wouldn't foul the motor mount. I then put the engine in the car and realized that it comes this close to hitting the subframe instead :brain:

That's the worst part. We had prety much no excuse, I don't think we were even drinking at the time.

It'll just force me to depower the rack. :brain: I'll bring over my spare and you can show me how to take it apart and get at the pinion.

My god, he is human! :laugh: This actually makes me feel far better about the whole thing.

Perrrrfect. Thanks again! Props.

Along the same lines what freedomgli was just asking about, that looks the the only space avalible for the sensor is after the thermostat. I believe Andrew had said there was "some" leakage around teh thermostat when closed, but is there "enough" leakage that the sensor can give an accurate reading for say, warmup?

Moral of the story: When drilling into the oil pan for bung placement, mark the desired locations of said bungs before you take the motor out?

This is why I'm at MT.net, I'm here to take notes of other people failures, and try to avoid the headaches.

Thanks for bringing up your failures!

If you look carefully at the design of these thermostatic sandwich plates, you'll notice that the only thing the thermostat does is open a bypass passage when cold. It doesn't close off the openings going to the cooler at all. The bypass passage itself isn't all that big, certainly not nearly as big as a -10 opening. So, the bypass passage reduces flow to the oil cooler but never positively seals it off. So . . . there is plenty of oil flow there to give an accurate reading regardless of thermostat position.

BTW, what drives oil temps is RPM. It seems much more driven by high RPM operation (even at partial throttle settings) than by throttle position/load. I noticed this when I was doing some VE tuning and trying to hit high RPM/low MAP regions. Oil temp still soared in that condition.

Was it for a turbo oil return or to put a temperature sensor ?
How temperature will differ from let say the oil drain location using VDO unit ?(323-055: Temperature Sender: 300F/150C - M14x1.5 - Screw - Single , by VDO - eGauges.com)

I mean it will see oil going through the pick up tube so maybe a little cooler but is the other way better ?!?

The above image was my oil return for the turbo. I mean it'll work, but I need to use it with a depowered rack. I posted pics of the temp bung location somewhere as well, but I'll stop crapping up Andrews awesome thread with my failures.

Speaking of the VDO drain plug sender, what are people's current thoughts on this? I read a very old thread on miata.net where one guy said it was very slow to respond. Too much latency. He ditched it for a different sender attached to a sandwich plate for better response. Still the case? Or are people happy with the VDO drain plug sender?

That's fine when you are light load like cruising the freeway. Up the load and oil temps will increase to the 220-240° range where you want them. The tstat is there to make sure it doesn't drop below 180°. That said if you have a really well ducted 20 row cooler cruising the highway on a 50° day, it may not reach 180° oil temps ever. In such rare combinations, it's a good idea to block off part of the cooler during winter months for light load usage. Few will ever have the problem of overcooling though.

Edit: Just realized it's alreday a 3 page thread and this was already answered. doh

That's Crusher, not the OGK. Anyhow, as Andrew alluded to, that motor and everything about it was anomalous, especially it's cooling systems. Unless you like building $10,000 145whp enduro engines, you're not likely to need nor want to duplicate anything on that puppy. O/C in front is preferred.

I was having packaging worries about my cooler and put this together over the winter. It is a Setrab with some home brewed braided lines and a glowshift sandwich plate with no thermostat. I would not do this with a street car but mine is only run on the track so here were some of my reasons for the path I chose:

1. My heat exchangers are very heavily boxed and ducted so routing oil lines in front of the stack was problematic.
2. I wanted a sandwich plate with two bungs for sensors - one for temperature (pre-cooler) and one for an oh shit idiot light to compliment the NA6 pressure gauge. The NA6 sender is too thick for a traditional T.
3. Lacking a thermostat in the sandwich plate, I figured warmer air from the radiator would help warm the oil more quickly to a reasonable temperature.

https://www.miataturbo.net/attachmen...ine=1406969741

https://www.miataturbo.net/attachmen...ine=1406969741

The lines were the perfect length before my crossflow rotted out and I went with the fleabay cheapie that is much thicker. I didn't have time to make new lines and it is hard to cut 1/2" off the braided stuff to slightly shorten the length so I'll need to order a few more feet and start over. Some guys just stick a big RX7 cooler up under the bumper support with no airflow and let it act like a big heat sink so an oil cooler behind the radiator with some airflow had to be at least as good.

I ran one track day (50* ambient) with this configuration but the cooler line just looped and saw the oil temps hit 250*. I was on the track Thursday in Portland in ~90* ambient with ~280whp and turning consistent 1:27s on clean laps. The oil temperature never got above 210* while the water temps were solid at 205*. 90* is about as hot as we ever run in the PNW so I'm perfectly happy with these results. I've been on the track on much cooler days in this configuration and gotten similar temperatures so the cooler in this location is shedding a bunch of heat even taking in the hot air off the radiator.

This was my exact idea of how i wanted to setup my cooler. I may make a block off plate with a cutout in it and then mount the cooler on block off. So more air can make it through the oil cooler. I can afford a little less cooling through the radiator with my current setup im sub 180 degrees at cruise