Mocal vs Tilton oils cooler pumps, One better than the other? Options

[pcar916]

I've got a brass 1/2" female one way valve if you can use it....... (IMG:style_emoticons/default/shades.gif)

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

[pcar916]

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.

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!

[stownsen914]

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 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.

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

[pcar916]

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.

[Downunderman]

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.

[john rogers]

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.

[stownsen914]

Spraying on the individual gears is good, just not directly into the web where the two actually mesh together.

Ron,

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

Scott

[puff adder]

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.

[ArtechnikA]

Where is the cooler itself usually mounted?
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.

[pcar916]

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.





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/

[Downunderman]

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

[pcar916]

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

[maf914]

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.

[john rogers]

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

[pcar916]

Simple... fan underneath or scoop only?

[john rogers]

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.

[pcar916]

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...