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.