I'm adding a cooler and pump to my transmission. These two pumps are similar in specification and both companies have been around a long time.

Tilton: http://www.summitracing.com/parts/TIL-40-524/

Mocal: http://www.racerpartswholesale.com/product...ial_Cooler_Pump

I know several of you run Jabsco Water Puppy pumps, but I see no advantage to it over the Mocal or Tilton.

Anyone out there with experience as to whether one is more reliable than the other?

I've never used either but I do read a lot of spec sheets ;-)

Ordinarily my personal preference would be for the Tilton over the Mocal, for no reasons I can readily quantify.

but a 265°F max temp limit for the Tilton would be scary, I think, for a track car (and if it's not a track car, why would you need a cooler?). The Mocal does claim 300°F max temp.

I've bought from both vendors with no issues so that's not a differentiating help either...

I haven't tested the transaxle fluid temps in my car yet, but today I'll point an infrared thermometer at it after several spirited runs up a local steep and twisty grade. just to get a feel, but 265°F degree transmission fluid scares me no matter what.

What track temps are expected with a clutch type LSD?

I agree, which is why I think it'd really suck if the pump died at 266...

If you figure a conservative 10% power loss in the drivetrain, it means if you 've got a 200HP engine, the transmission is making as much heat as a 20HP motor...

Also figure the transmission is aft of the engine and over the exhaust. I believe (but do not have the instrumentation to prove (yet) that mid-200's temps are common and 300's are possible.

Well, my 3.6L gives me 210hp to the rear wheels, not sure about brake hp numbers. But I know the LSD produces a lot more heat than either an open or TBD if I'm in the twisties for any length of time or on the track.

I've always wondered how much the exhausts contribute. They are well to the side and probably not a huge factor while moving, but as this is a street/track car, it does see some traffic lights. I'll be installing a temperature sensor because... it's obviously the right thing to do.

It's definitely an issue in the Southern USA.

I've read about cooling systems with spray bars inside the tranny, and others that tap into the side with spray emitters.

Can a cooling system be installed on a 915 box without removing it from the car?

transmission removal is trivial, unlike the engine, which is merely easy. Undo the shift linkage, unbolt the halfshafts, ta da. (Support the engine...) Deal with the speedo sender, whether it be electric or mechanical cable...

Pull off the tail cone, remove the gear stacks as a unit. do what you need to with no issues about whether or not drilling chips got inside. (Almost) anything _can_ be done, but it's so easy to pull the box and do this with relative ease on the bench, why make things harder on yourself than you need to ?

Thanks for the info.

I guess I'm more interested in whether it can be done without taking the box apart. Removing the box from the car is super easy on my car, but I have limited experience with the innards of transmissions.

This is something I might do later on.

I've been at the track a lot lately. It appears that after the boxes get hot (901 and 915) they get cranky. I see and hear the shifts at the beginning, and the end of 20 minute runs, and towards the end the drivers are shifting more methodically, whereas at the starts they are shifting quickly and easily.

Conclusion is a cooler box is a happier box.

You could do it if you ignored squirters on the gears, and perhaps used the drain and fill plugs for in and out of your fluid after the fluid was drained.

But with some finesse, you can take the transaxle out without taking the motor out. Then you can install brass/bronze bosses for your cooler system elsewhere on the case.

If you decide to install squirters, don't make the mistake of pointing the oil flow into the mesh areas of the gears and R&P. That makes for huge forces pushing them apart as they try to squeeze the oil out from the mesh.

I would recommend calling several shops that RACE vintage 911s and 914s with high revving engines and see what they use and recommend. I bought a complete setup from Jim Patrick in Phoenix as I didn't have a lot of time to run around and gather up all the bits and pieces. Several things to note:

- Yes you have to open the case so you can drill and tap for the nozzle over the ring and pinion as that is the heaviest loaded on a race box. As noted the limited slip also does generate a bunch of heat AND you do not want to have any chance of chips left in the case.
- The direction of oil spray is immaterial as any excess will splash off the gears and not cause any type of hydraulic locking or such. Just make sure one goes on top of the R&P
- You will need to add a closed vent run to your puke tank since you will be running an extra quart of trans oil (4 total now) to make up for the new plumbing, cooler, etc.
- Add a switch so you can turn the pump on/off or leave it run after you shut off the engine when done with a race group.
- Most 914s I have seen put the cooler in the floor of the rear trunk and vent air into it and out the botom. I added a small boat type axial fan to help out when it is really hot.
- Use stainless braided lines for the suction and returns since they are in a position at the rear that gets a lot of abuse from road stuff.
- Patrick sells a replacement plug for a temp gauge so you can see what the trans temp is doing, very handy to have.

I had run a cooling system for 5 years since putting the six in the race car and never broke a gear box and the ones that Wayne Baker, Frank Beck and Jim Patrick all raced never experienced any failures as far as I know.

If you are running a 6 a sportomatic pump off the back of the camshaft works well.

I have heard this elsewhere, and am interested knowing why it matters. If you look at a the oil level in a stock 901, the gears mesh very close to that point. It seems like the oil would be carried into the mesh area by the rotation of the gears. Why is it any worse to spray oil under modest pressure where the gears mesh?

Scott

The level is lowered during running since a lot of it is up in the gear train and on the top and sides.

Most of the oil is spun off anyway and a thin film is all you want. If oil is forced into the mesh a lot more oil can't spin off fast enough, and can't compress either, so the gears are forced apart more than they were designed for. With the R&P, this means at the very least, that the carrier bearings are loaded more than they should be. The other gears would be the same, higher bearing loads.

I don't know if it would be enough to break teeth, but it would certainly run hotter... and cool is good.

At worst I suppose a mag case could be compromised. This might make a difference in an early 915 case with a 2-piece bearing plate and an un-reinforced side cover. I have two of those transaxles. No racer would use them use them without the updated parts, but someone else might.

Downunderman...

- I have a power take-off on the back of this 3.6L where the power steering pump used to be. And I still have the pump and belt as well. That said

I'm not sure what the impact to the cam and chain would be with the added load. My flywheel is only 6.75# and I'm running an early clutch/pressure plate so it's all very light. I use the throttle to minimize the whipping of accel/decel but adding that load would make me nervous about snapping that cam in half.

If I wanted to go mechanical, I could mount a pulley on the inside transaxle flange at the cv and run a mechanical pump from that. If it doesn't run while I'm sitting still, so what?

John...

- What operating temps do you see?

- Excellent points that I'll follow on the install. I was going to put one squirter in the side cover pointed at the bottom of the ring. On the top would be easier and I wouldn't have to remove plumbing when the side cover comes off. I like that.

- As for the pump it appears that some racers use the Weldon 9200A.

http://www.weldonracing.com/product/54-7/9...e_Oil_Pump.html

Weldon is proud of it but it looks very good.

If you hook up the plumbing system you might be surprised and how little the actual flow is with any of the pumps. On the transmissions I setup and all the ones I have seen the outlets were on top of both the gear stack and also the R&P and essentially the oil just ran down on everything. The idea is two fold, first to get the oil cooled off and second to get as much as possible onto the gears to they will then cool off.

The highest temps I ever saw were at a race in Tecate MX when it was 96 degrees during the race and the trans got to about 275 or so. The temps were high due to the constant shifting and the tight corners making the GT limited slip work really hard. At the CA speedway when temps were 104 the temp only got to 210 due to the long run time on the NASCAR portion of the track. Less shifts mean less heat build up I imagine.

Excellent. I'll run the entire pump/manifold and squirters on a bench prototype first just to see what it will produce with the oil both cold, and at high temperatures. I have lots of -6 and -8 stuff around the shop so I'll just use what's here. As for flow, I'd rather have a lot of it at low pressure, but want the oil in the cooler long enough to maximize heat transfer. Wish we could add some PCB's (kidding a little bit).

I've been told that both Swepco dino oil, and the Lubrication Engineer's synthetic are good lubes to use with this GT LSD that I've just put into this box. I'm leaning toward the LE for the EP rating and the longevity but I have to buy 5 gal. at a time. Guess I'll be using it for a while.

I talked to some local guys who follows NASCAR obsessively and the ~210F seems to be normal operating temp for those cars as well.

I guess I am getting old as I forgot to mention to make sure to install a filter in the pump suction. I forget the brand I used but it was one of the plate type and I would open it a couple of times a year for checking of metal pieces. If the transmission distructs it will catch the pieces and prevent the additional pain of having to replace the pump.\

If you set things up right you can use the the pump to fill or empty the transmission which I did and it is much better than using the drain plug.

I figured on a Canton Mecca canister filter inline so it can be checked without draining, and will protect both pump and cooler. Pump to drain huh? This mod just keeps gettin' better by the minute.

If installed as you suggested, the cooler will drain back into the transaxle every time the car is turned off unless there is enough tilt to keep the oil in the cooler, and/or an anti-siphoning valve is installed. I was going to position the cooling system to try and keep the stock fluid level in the box, even with the added capacity, just to perhaps avoid possible leaks.

I've got a brass 1/2" female one way valve if you can use it.......

I have been using the sporto pump for a couple of years now with no apparent adverse consequences; GE80 cams and VMax springs which have an open pressure of about 285 lbs. I think the pump has an internal pressure relief bypass from memory. I have also plumbed in a cartridge type filter to get rid of all the shiny bits and clutch material from the LSD which also has a pressure relief bypass in it. I am not using big revs though, about 7,200. No photos at the moment because i'm at work.

Thanks dude. I don't know yet 'cause I haven't engineered the system completely. We'll talk...

Interesting. I wonder how easy those pumps are to find. I'll put out a tendril or two while I'm in the design mode. Wouldn't life be good if it fit perfectly on the boss for the 993 PS pump and had the same cam drive specs?

Then again I like the idea of turning on an electric pump on to drain the system!

If this is true, then does it mean that there isn't any point in having a spray bar? It would seem that passive sloshing of oil would be the preferable lubrication method ...

Scott

Spraying on the individual gears is good, just not directly into the web where the two actually mesh together. At the very least cooling the oil, even if it's simply cooled and returned to the case, is useful.

I think a lot of testing would have to be done (more than is generally practical) to find the temperature differences in a transaxle with different cooling methods. But over time, and with methodical tinkering changing one thing at a time, a racer could get good empirical results.

Oil return into all compartments is even more important on inverted 915 cases. The large oil galleries cast into the (normal) bottom of the bulkheads aren't cast through the top of the bulkheads.

Ron,

You should be able to find a sporto pump laying around without much trouble. Any porsche mechanic will have one laying under the bench somewhere. The pump is a small gear pump and should bolt straight up to the to the back of the cam. You take the pulley wheel off for the power steering belt and put the bolts back in, which drive drive the pump. Here's what Armando did. http://www.pbase.com/9146gt/image/54417634 Mine is pretty much the same.

Remember, if the lube and cooler pump is engine driven then you will not be able to run the lube system to cool the transmission down after a race session and those exhaust headers will be adding more heat to the transmission while sitting still.

Ron,

Any suggestions on where I could read more about this topic? Thanks.

Scott

Where is the cooler itself usually mounted?

Did I read correctly that one could use the fill and drain plugs tapped for cooler lines for in and out?

This sounds like a step in the right direction, as i could install everything, and then install the internal spray bar later when I have the tranny out.

Cooling the oil without actually spraying it directly onto the gears still sounds like it would make a difference.

The very early racing 915's (a la 3,0 RSR) used an oil pump in the tailcone and a cooler in the left side rear fender scoop. I seem to recall the 2,8 RSR's (which did not have vented fenders) using a cooler in the left front fender, like the trombone coolers fitted on the right side for engine oil.

Then the later 915's (915/67) used in the Euro 3,2 Carreras have a gear-type oil pump (like a VW T-I) in the side cover to route oil through a finned serpentine tube mounted in the airstream alongside the transmission. It's relatively light weight and efficient and works "well enough" to keep temps under control. AFAIK the G50 cars don't have or need this.

I have a 915/67 I'll be using in my RSR clone/homage 911.

Things to remember tho - in the 911, the transmission is well forward of the engine and the exhaust, so even though the airflow isn;t optimal, it is at least relatively cool. And unfortunately, there isn't room in the case for the pump _and_ a flipped R&P for midengine use. You could think about using this approach for an inverted box, but then you have to deal with plumbing the inlet to the pump, which is no longer in a convenient place at the bottom of the oil pool.

Excellent discussion and why I like this forum. I've decided the electric pump separate from the cam is the way to go. Not just because of the inertial issues, and those static cooling and draining advantages, but also ease of installation. Those PBase 914-6 galleries are superb.

The 993 PS pump pulley is attached to the cyl # 4,5,6 cam, not the cyl #1,2,3 bank like the Sporto pump. The PS pump itself is attached high, where our trunk bulkhead sheet metal is. On the 993 engine there is a sensor (cam position perhaps... too crunched to cruise my 993 manual this morning) where the Sporto pump would be.

Click to view attachment

Click to view attachment

Anyway, that's more fabrication than I want to attack since the electric alternative is so much faster to implement. Frankly, I love design and fabrication. But driving a good car that you've built yourself is the bomb!

Cooler mounting position:
I mounted my 2nd engine oil cooler (off of the sandwich adapter in the picture) behind the transmission. I initially mounted a fan but never had to turn it on, so I removed it. For this trans cooler addition, I'm considering a "cooler-sandwich" in the same position with both engine and trans coolers and a spacer in between them. The downside is that if I back into gravel I could get cooler damage and the day would be done, although I did it once at Texas Motorspeedway with no damage... I'm still embarrassed about that one...

A fan might be needed then... don't know yet until I can record some temps. I like ambient cooling if it's enough, since the power requirements are restricted to the pump(s).

John suggested mounting it high, like on the floor of the trunk with air ducted into it. That would be easier for certain, both for access and drainage. I'd lose some trunk space but perhaps not so much!

Links to engineering data:
I've not found a lot of empirical data out there in racing circles, and the folks who develop and package their cooling systems aren't motivated to share the data either. I like to think of it as a simple heat exchanger problem where I know the input heat and design enough cooling to bring the oil back to a desired temperature before returning it to the transaxle.

- This is about coil droplet size and cooling efficiency. The summary is likely sufficient for our purposes here, Makes sense... surface area is key in heat transfer, but the math is there if you're interested.

http://www.sciencedirect.com/science?_ob=A...1a181157c75e5be

Not on this specific subject but a lot on transaxles... The mid-engine crowd loves our Porsche 930 & G50s, inverted or not.

There is a lot of fabrication and neat stuff in the GT-40 world. i.e.

http://www.gt40s.com/

Here are some photos for posterity. Before it had the cooler installed.

You realize your car is far too clean right? Nice simple installation.

I remember reading in 24:16: Le Mans 24 Hours that one of Norbert Singers first projects upon joining Porsche was to figure out how to cool the transmission in the then new 917. The initial solution was to add scoops to the upper rear body work and duct the air directly onto the tranny case. I assume they moved on to oil coolers from there.

Here are a couple of picts of the setup I had and what a lot of the vintage racers run.

Simple... fan underneath or scoop only?

An axial boat ventilation fan was added after these pictures were taken in the vent supply line. It comes on when the lube pump starts. There is a baffle under the cooler outlet to provide low pressure when the car is moving and the air is supplied from an inlet in the front of the right rear GT flare.

I like the axial fan idea. I may even have one. Now to find it...