Diff and trans coolers
 

I thought it might be helpful to start a thread with pics of diff and trans cooler installations. Share ideas and what not. I'll start with Vegas.

Feb 2019 update:
We ended up with Aeroquip -8 hose, Genesis pumps https://www.hrpworld.com/GEN-GC1111-...1111.html.html
Trans I/O are neutral switch port and drain. John felt the fill plug was too close to the exhaust. With the ducting from the fender through the license plate area, we have enough airflow to have never needed the fans.
http://www.setrabusa.com/products/fanpacks/index.html
Overkill for S1. If we ever ran an enduro in hot weather we might actually turn the fans on. So I think one can implement either good ductiong/airflow or fans, but you probably don't need both. Much easier to skip the ducting, just stuff the core under the car somewhere
and run a fan. I think the highest temps we have seen were with the Quaife (sequential) at maybe 180°. The AZ6 runs much cooler, barely hitting 140° even with no fans. That makes me happy.

William also has no OEM fuel filter assembly on his S1 so that area ahead of the RR wheel is vacant. He plans to put his exchanger/fan there with just a shroud to keep rocks and dirt out, but otherwise unducted.


https://cimg0.ibsrv.net/gimg/www.mia...2b03c6eaa3.jpg

https://cimg1.ibsrv.net/gimg/www.mia...dda7db181f.jpg
https://cimg3.ibsrv.net/gimg/www.mia...9ca42cab62.jpg

Saw these on MX5 Mania's fb page (Australia). I know nothing about this car so ask them if you have any questions.
https://www.facebook.com/mx5mania/

https://cimg4.ibsrv.net/gimg/www.mia...3cf11d4eba.jpg
https://cimg7.ibsrv.net/gimg/www.mia...36e744022c.jpg
https://cimg8.ibsrv.net/gimg/www.mia...468cb06a06.jpg

https://cimg9.ibsrv.net/gimg/www.mia...6e077482df.jpg

Good subject. I will add that anyone following this thread beginning to wonder "should I consider adding trans and/or diff coolers?" should as a first step be installing temperature gauges in their trans and diff. Deciding to add the weight and complexity of such a system should only be done after acquiring data. If you don't know what temp your parts are operating at, you aren't prepared to make the decision.

Pics below show the sensor positions I chose for my trans and diff. If you don't have a logger dash or similar, standard oil temp gauges work just fine. Make sure the sensor location is below the fill hole so the sensor is submerged. Thanks to these sensors I happily discovered I don't need to add the cost/complexity/weight of coolers, but obviously my results don't apply to the Miata drivetrain.

https://photos.smugmug.com/LFXSwap/G...wm2a3lx-XL.jpg

https://photos.smugmug.com/LFXSwap/M...3yoqqnc-XL.jpg

Does one have to worry about pump life with the source being below the pump? Sorry if silly question, but wouldn't the pump run dry for a bit before it got any oil through it?

Depends on the pump. Some like Tilton are self priming and will pull fluid uphill several feet if need be. Others may need to be gravity fed.

Ah thanks. I should have googled first.

Cooler Pumps - Tilton Engineering

"Cooler pumps feature an internal bypass valve and are self-priming up to eight feet above the source from which it draws."

Who can find me an adapter to fit a 3/8"NPT GM sensor in the stock diff and 6 speed drain plugs?

I see all of the work that went into the cooler done by MX5 Mania and then read what Ryan said, which is to check it first before adding the complexity. I can't help but think that all of that plumbing and expense was done without first shielding that exhaust from heating up the differential. And the CV joint, for that matter. Hopefully some shielding was added after that picture was taken. The exhaust is probably adding a lot more heat than the cooler is capable of removing.

That's interesting about the AZ6 having aluminum shift forks and having shifting issues when hot.

I've intermittently had the issue going into gear (mainly 5th). It would always be during an afternoon session on a hot mid summer day. I replaced the clutch slave / master / rubber line and the frequency reduced, but it's never been completely solved.

This still happens even after installing the Blackbird competition engine mounts and poly diff mounts.
I've often thought maybe I'm just getting fatigued, but I can go entire weekends where there are no issues at all.

I haven't measured trans temp, yet, as this jalopy is still near stock output and I never thought 120-something whp could overheat the drivetrain.

As mentioned in the oil cooler thread (IIRC), oil temps are created primarily through (high) revs. I suspect it's the same with transmissions.

For instance, the 5-speed is weaker than the 6-speed and many posit that the case is less stiff, which allows the gears to improperly mesh with the expected catastrophic result. As a data point, my Quaife gear set (installed in the 5-speed casing) will live indefinitely on the street but I've blown it up twice on the track (the second time it was a cold, rainy day). So, while a Spec Miata experiences the same case flex, 100-ish lb-ft is not enough to strip a gear, while 300+ lb-ft certainly is (no matter how robust the gearset).

And yet we still manage to regularly grenade 3rd gear :P

You're obviously a bunch of animals. However, I stand corrected.

DiscountHydraulicHose.com
Part #9235-18-06 | M18x1.5 Metric Male x 3/8" NPTF Female

I have confirmed it fits in the 6 speed oil drain plug. I will be confirming it fits in a diff hopefully tonight.

Attachment 228657

Diff and trans plugs are interchangeable so it should

Yep, but wanted to verify.

https://cimg0.ibsrv.net/gimg/www.mia...a7bc934eca.jpg

Well that makes it easy

What gauge are you going to run the sensors to?

i would presume wire to Log in megasquirt

Going to my MS. I am doubtful if I ever actually make a gauge in TS for it, more want it to review in logs.

Thanks for posting this info. Though did you just remove the magnet? I want to do this but am worried about not having the magnet. Potentially I could move the drain magnet to the fill port to keep it, though that's not ideal.

CSF has a new dual-pass 8 row fluid cooler that has the entry and exit on the same end. It should make for tidier installations.

Universal Racing Radiators - CSF Racing

Has anyone data logged temperature differences of diff or trans fluid with and without flat bottom undertrays that cover the entire unit? Or any tests with flat undertrays with NACA ducts specifically pointed at heat sink fins on the diff or trans?

All I know is that Brian from Goodwin Racing apparently said he got away without the use of any coolers, and that the general MT opinion was "the diff runs hot as is". I've not found conclusive DATA, but the top folks apparently do run designated oil coolers. Dunno, maybe it's a matter of local climate, or personal preference in which religion you want to believe in? Will additional coolers help? Likely. Is it worth the complexity IMHO? probably not, I'll stick with homemade NACA ducts. Because I'm a lazy bastard.

Updated the OP with some more data and info.

Parts sources

The Genesis (motorsports) pumps are much nicer (and more expensive) than the generic ShurFlo RV/Marine pumps. Tilton a few other companies make even higher end pumps but the Genesis seem like 80/20 to me.
https://www.hrpworld.com/GEN-GC1111-...1111.html.html

A few of the Setrab fanpack options. Other good heat exchangers out there but Setrab are world class and still affordable.
Setrab ProLine Fanpacks | susa

Are there any recommendations as to what size of cooler and fan is needed for say 280whp in a location with no airflow (attached to rear bulkhead on opposite side to fuel filter).

I'm not sure whether this would be enough, or something much bigger needed.

I know this forum doesn’t like to spoonfeed, but I’m having difficulty working out how to get the lines from the gearbox ports to the rear of the car.

The route to the front looks much easier, but the only place I can put it there is in the front right wheelarch, which is
1. More weight up front
2. The lines would have to pass through intake side of the bay, which is a bit of a crowded disaster on my RHD cars with a reroute, dual feed rail plus regulator etc

The route to the back is less straightforward. I saw the supermiata video that put the lines over the top of the 6 speed before the shifter, but this seems too tight on mine (drop mounts on the supermiata car? Mines stock height) and also I’ve still got the stock center console so all of the screws for that stick down and would destroy an oil line.

it looks like I could follow the PPF the whole way back and pass it through the rear subframe, but this puts the lines close to the diff flange (should be ok once secured, but doesn’t look ideal) and there’s a long length exposed to radiant heat from the exhaust.

Does anyone have a clever (or obvious!) routing I have missed? ( I blame my facilities, trying to do it laying on the floor in a 1 car garage with no lift:rofl:)

I'm currently building a new wiring harness for my car. In the process I'm also adding provisions for a transmission cooler setup. However, the solution is very complex and also uses two of my few spare ECU inputs (transmission oil temperature) and outputs (ECU signal to relay, which activates the pump at a certain temperature).
By accident I came across a very neat solution which might not even require drilling into the transmission housing: Setrab offers thermal switches, which can activate the pump at a certain temperature: Thermal Switches | susa

https://cimg8.ibsrv.net/gimg/www.mia...68e286f001.jpg
https://cimg7.ibsrv.net/gimg/www.mia...8d91648e60.jpg
So one could put an M18x1.5 to -06 AN adapter in the drain plug hole, attach a 90° AN fitting, add the male-to-male adapter with the thermal switch, run the oil line to the pump and cooler, and return the oil at the neutral switch or fill hole. The power wire to power the pump is routed from the main fuse box (plenty of spare spots available at least in my case; add a 10A fuse) to the switch and from there to the pump. The switch activates the pump at the preset temperature.

You would lose the ability to read tranny temps, but would save a lot of wiring work and have more spare pins at the ECU. The switch is rated for 10A @ 12V, and the Mocal pump draws 7.5A.

Sorry if you have already known this for ages. I haven't, and I'm very excited.

I'm not convinced a sensor in a line will work too well. I saw those and was tempted for my build, but was worried about stagnant flow meaning that a true temperature wouldn't be measured. In the end I came up with the convoluted (and not quite effective enough) setup shown below.

The sensor is in the end of a banjo bolt, which feeds the AN6 feed line. The hex pictured is 18x1.5 on both ends and was used just to space the banjo out from the gearbox drain hole just enough that the line would clear the gearbox housing. I used a shorter one in the end. My thinking was that there's little distance between the temp sensor and the bulk of the gearbox oil, so it should be fairly representative.... (yes I know I had a major oil leak, thank the dodgy boundary front main seal for that....) Sorry for the photo size, I couldn't work out how to shrink them.

https://cimg7.ibsrv.net/gimg/www.mia...bf8fbe01ab.jpg
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As can be seen in the plot below, when the gearbox cooler activates at the 14m30 mark, the temperature jumps up nearly 30C as the sensor stops measuring stagnant flow and is actually drawing hot oil out of the gearbox. The same is almost certainly happening with my diff (OSG) temperature channel, as it didn't reach the 80C I had set the cooler switch point. This is all being measured and controlled by the ECU Master ADU dash in the car. Oil temp (top) and coolant temp shown to give a sense of how everything is heating up over time.

https://cimg4.ibsrv.net/gimg/www.mia...f9c8896a03.png


Maybe I can make some kind of clever maths channel in my ADU dash that will cycle the pump on for 10 seconds every 5 minutes or so above a certain temperature just to mitigate this effect, alternatively, just live with the hysteresis since accurate gearbox temperature control might not be critical, as long as peaks can be managed. I suspect my setup will have a lot less hystersis than an AN fitting out the gearbox with one of those AN run on sensor adaptors, so maybe then you could even have +40C, +50C of delta, but you'd have no way of knowing since it wouldn't be logging.

If I had the option to install the sensor straight in the gearbox oil, I'd do it.

Hard to say without seeing it, but if you swapped from a 45* to a 90* fitting going into that banjo it appears you could ditch the long spacer piece and get your sensor significantly closer to the sump. Is there a reason you chose spacer+45* instead of running the banjo straight down with a 90 and no spacer?

I assume your pump is not PWM but just on/off? Will the motor tolerate and do you have a spare PWM channel available?

I did consider this, but then the line runs closer to the ground and would be the lowest part of the powertrain, so could run aground.

The pump isn’t PWM, just simple power and ground wires. (Mocal EOP2). The heat exchanger is out of direct airflow so the output also has a little Spal fan in parallel to the pump. PWM control would be lovely for this. I’m not sure if the Ecumaster ADU5 can do PWM, but if it couldn’t I’ve got some spare MS3 outputs that might be an option.

Well, fair point. I think there are 3 ways to cope with this:
a) deal with it. Even with an initial Delta of 30°C oil temps wouldn't rise above 120°, which should be fine, before dropping to around 90°. At my last trackday (without cooler) I measured 155° at the non-exhaust side of the transmission housing
b) bring the sensor adapter closer to the transmission by mounting it directly to the M18-to-06AN adapter, before the 90° hose fitting is attached. Housing heat soak may suffice.
c) tap a single ⅛" NPT hole and mount thermal switch to transmission housing. Still an easy job.

Also, I wonder how important the radiator fans are, and if a simply bigger cooler (13 rows) isn't enough. Here's a pic from a BMW M1 Procar that I took when I visited the collection:
https://cimg9.ibsrv.net/gimg/www.mia...4c0480ac70.jpg

FWIW, the little Setrab diff & trans exchangers with integrated fans on Vegas never need the fans to turn on. We manage to get enough airflow with our ducting that just moving the lube through keeps everything below 210° regardless of ambient temps or load. If packaging on your build doesn't allow air flow improvements in airflow, then you have to deal with a fan control circuit and tstats. 3rd page on our MXG dash shows those temps. Manual switch on dash turns on both pumps. We pretty much turn pumps on any time the car is moving.

Tapping a hole does seem the nicest solution, but I would be wary about what is on the other side. NTC sensors usually stick through quite far. I'd' say get a low temperature switch, eg 60C and have a switch on the dash that disables power to the pump so it doesn't turn on during a long road cruise.

This looks OK. Only available in AN10 but 1/8npt switch can be removed https://www.t7design.co.uk/products/...e-40-150c.html

I bought the pull version of this along with an appropriate tiny Setrab (note, it took some fettling to fit a Setrab, perhaps get the Mocal which should fit better but the coolers aren't as nice)
https://www.t7design.co.uk/products/...hroud-kit.html

I'll post up how capable the system is once I've done a warm dry trackday. The data above was from a 12C ambient day, but it was damp so %WOT was low. I've just booked Destination Nurburgring 23 in May and that seems as hard a track as any on gearboxes with the extended high speed running....

Packaging on my car is tight. I drive the car to events and need to take tools, an overnight bag, a helmet and a jerry can, so could not sacrifice boot/trunk space therefore none of the pumps could go inside. Below the boot floor are pumps for gearbox oil, diff oil and a water injection pump. With a full size backbox, this didn't give much space, so that t7design shroud and setrab cooler is mounted below the battery (NA) and draws air from just below the battery. There is effectively no passive flow through the core.

Looks like I didn't get a good picture when it was done, but I got this one as I was mocking it up and everything ended up roughly where shown (and a heatshield added to protect from the exhaust).


https://cimg7.ibsrv.net/gimg/www.mia...6da7afebdd.jpg

Good insight, thanks. But then again your car is a pure race car, whereas I need to retain the license plate and boot
Funny, I had already checked out the T7 stuff before I made the first post. I'm pretty much in the same boat - typical dual duty gentleman driver. As for the radiator location, I had 3 spots in mind:
a) front right wheel well, right after the bumper. Designated duct from the GV lip intake or mouth to a narrow (115 mm) 19 row oil cooler. Bleed hot air into wheel well
+: maybe no fan required (if pressure testing confirms sufficient pressure differential)
-: a crash or off-track excursion might damage the radiator, leaving me stranded roadside. Might still require a fan

b) in front of left rear wheel, in front of rear subframe.
+: crash-proof-: will require fan. Especially with a fully flat underbody. Effectiveness uncertain because it might draw in hot hair from the transmission tunnel. Maybe needs an Emilio memorial duct from the rear wheel well

c) behind left rear wheel, similar to b. Maybe more prone to stone chipping, and might interfere with a yet-to-be-built diffuser

Do we have any long term results yet? Did cooling stop 6spds from destroying themselves at higher (300whp+) power levels and track driving?

Thanks






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Two things

1. We already know that running your transmission at 300 degrees is not as good as running it at 200 degrees. Viscosity and lubricant general protection quality is degraded at higher temperatures. Metal becomes weaker at higher temperatures.

2. A common problem is trouble shifting with higher transmission temps in the AZ6 variant used in the NB, which is the only variant with aluminum shift forks. I have no conclusive proof of this but my theory was the aluminum would expand more than the steel around it and cause the shifting to bind. The symptom was being harder to shift into 3rd or 4th gear after several laps in warm weather. Next session after the car cools down, it would shift into those gears fine until the transmission heated up again. Added a big transmission cooler and the problem vanished.

While that correlation does not guarantee causation, it's good enough for me.

Has anyone tried fitting the shift forks from other AZ6 variants (of similar era) into Miata boxes?

Don't fit/not compatible. We have made CAD models of the OEM shift forks but there just isn't a viable product there for us to pursue. Its possible to build a really nice AZ6 that
ll shift awesome and cope with 350 lbs ft, it just costs more than most are willing to spend and there are only really a handful of folks that are interested at any price. Best bet right now is a built box from Walter Motorsport.
That's what we run.

Bummer. Walter Motorsport is likely going to handling a spare I have sitting around for a rebuild/improvement.