924Board.org

[Lizard]

Weasel,

I have read many things on the DC unit. Most arent that good. CSR is what I would use and just run it at full with an external thermostat (if street car). I have a good BMW unit that is perfect for this.

PM for more info (I dont check in here often)
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3 928s,

[Euro924S2]

Reading with interest also as I, like Carrera RSR will be fitting a newly rebuild 931 engine soon also.

To be honest I thought I had my plan settled on already but I'm keen to hear of other options before I fabricate it.

Personnaly I worry (maybe needlessly) about the catastophic failure if an electric pump failed. Also, those pumps are pretty expensive and if I reversed the flow then my heater would require some clever re-plumbing and would again be a restriction to flow.

Since I want to keep my car a practical as possible, any solution I use must atleast maintain the current heater performance, and preferably improve it.

I've discussed my plans on here before but my plan was to keep stock pump and direction. Then fabricate a new outlet flange for the rear of the head with an outlet pipe ported to outlet of the head (cant remember exact size but about 28mm IIRC). This larger diameter pipe runs all the way to the front where the funny rubber reducer hose is trimmed to accept the larger pipe into the pump. This front to back pipe however has a 3-way 'Y' splitter in it. 1 input comes from back of head, one output continues as the front to back pipe and the 3rd connection goes to the heater matrix. The heater return pipe rejoins the front to back pipe via another 'Y' splitter nearer the pump. (So far basically the same as the OEM setup but with larger pipe.) The main difference comes when I'll add two control valves. One in the heater matrix circuit, and one in the front to back pipe BETWEEN the 2 'Y' pieces. Like
(sorry can't upload proper diagram, ignore the ... they just keep the layout)

............................> OEM valve > Matrix >
HEAD > PIPE > Y ...................................... > Y > Pipe > OEM water pump
............................> 28mm valve -------->

The 2 valves are controlled via the same heater controls but so that as the OEM heater valve is opened the large diameter 28mm valve is partially closed. (Can be tweeked in car with the slider to maximise heater temp but with the minimum diverted water flow for given ambient air temp coming through the blower)

My hope is that during normal operation with heater on cold, the maximum flow of coolant (limited by the head appature) will exit the rear of the head. Then if the heater control is moved into the Hot position, some/ most of the flow is diverted towards the heater matrix. Even though this flow will be less efficient, I'm thinking the extra cooling of the heater matrix, coupled with the persistent flow of some coolant directly back to the pump will still be superior to whats there - agreed its not the 'ultimate setup' but should certainly be an improvement, without any significant drawbacks.

I hope that makes things clear - if a picture says a thousand words then my Iphone renders me mute!!!!

As always, your thoughts are welcomed!!!
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UK spec '83 N/A with 931 motor with Eaton MP62 'charger @ 15psi. EFI - 565cc inj. Standalone Adaptronic ECU. 951 FMIC. Ally rad. Twin throttle. Recirc valve. Custom manifolds and CAI. 232bhp

[Euro924S2]

Oh, one more thing. When I turned my new crank pulley from billet aluiminium to drive my 6 Rib supercharger belt - I made the 'V' belt the same 140mm diameter (can't remember standar but more like 110mm IIRC). This has the effect of overspinning the waterpump and alternator and whilst I can't be sure if it's the new all aluminium radiator (smaller as it's from a Honda Civic Type-R) or this modification - my car never moves above the 1st mark on the gauge no matter how hard I drive it on the road - with my previous NA engine and a 951 radiator it never ran less than 1/2 on the same gauge. Not very scientific I know but maybe worth a mention since increasing the flow rate has already been discussed. (that said I hope I don't throw a fin off the impeller with this new RPM range!!)

Ps the alternator is still rubbish - but thats because I still need to re-new the ground!!!
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UK spec '83 N/A with 931 motor with Eaton MP62 'charger @ 15psi. EFI - 565cc inj. Standalone Adaptronic ECU. 951 FMIC. Ally rad. Twin throttle. Recirc valve. Custom manifolds and CAI. 232bhp

[Euro924S2]

Yet another idea, then I promise to let someone else have a say!!

Thinking about the electric water pump used on a 944 turbo that normally supplies water to the turbo for cooling.

If this was plumbed in line in the pipe that runs front to back and either run continuously, or via a simple temp switch, or via your ECU if desired, then would this 'scavenge' a greater flow through the back of the head and increase the #4 cooling flow, rather than coolant taking the current path of least resistance via the front of the head? I'm not aware of the pluming on a 951 - is this pump ok to pump 100+ deg C water or does it only pump cooled - post radiator - water in the 951??

I'll be quiet now I promise!!
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UK spec '83 N/A with 931 motor with Eaton MP62 'charger @ 15psi. EFI - 565cc inj. Standalone Adaptronic ECU. 951 FMIC. Ally rad. Twin throttle. Recirc valve. Custom manifolds and CAI. 232bhp

[WEASEL149]

[Carrera RSR]

As my car is a toy, hardly driven in cold or poor weather I am seriously contemplating bypassing the heater matrix on the rebuild and increasing the return pipe diameter, maybe ditching the 'y' pipe altogether as it appears to restrict flow rather than speed it up. Again no expert on these matters
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1980 931 - forged pistons, Piper cam, K27/26 3257 6.10 hybrid turbo, 951 FMIC, custom intake, Mittelmotor dizzy & cam pulley, H&S exhaust, GAZ Gold, Fuch'ed, Quaife
Now www.924board.org/viewtopic.php?t=34690
Then www.924board.org/viewtopic.php?t=31252

[Cedric]

[Carrera RSR]

[ideola]

Let's not forget this option:

[leadfoot]

in answer to this as I did exactly that on the last car, the cooling is more efficient, and doesn't affect the heating, it still cranked the heat out,

I changed the heating circuit this time around for a solenoid valve instead of the goofy cable pull valve...

BTW adding an oil cooler will change engine temps alot more than this mod alone, helps cure heat soak at shutdown and stabilises coolant temps at running conditions,
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[ideola]

[WEASEL149]

I've got some photos of what i did with mine. I'll post a proper reply when i get home from work.
Mine uses the OEM rear coolant flange and is not yet converted to EFI.

I'm in agreement over fitting a large oil cooler. I do think this is an area that has been a bit overlooked as we all tend to concentrate on the water circuit.
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1979 UK 932

[WEASEL149]

Here are the only photos I have of the coolant crossover pipe modification.
I can't just go out to the garage to take photos as I keep the car at my father's house, but I will be taking a whole lot more as the engine goes back together.

We kept the standard rear coolant flange, so this works with CIS (as it did before we pulled the engine out).
All we did with the flange was open the two waterways out more with a drill.
The standard heater pipes that go in and out of the matrix are also retained.

All we did was run a tee off the new circuit which goes to the heater, then returns as normal to the new crossover pipe.
Water flows at all times from BOTH small and large outlets on the rear coolant flange via a couple of silicon hoses that connect to the new crossover pipe.

I ran this setup on the road and can confirm that the heater worked as normal.









As you can see from the last photo, the crossover pipe has 3 inlets/connections. One from the heater and two from the rear coolant flange.

I hope this is of some help to anyone thinking of altering the circuit. This was done with the engine in the car. My father is retired so working on the cars keeps him out of trouble
... but he did say it was a royal PITA fabricating the copper pipe. It would be a LOT easier using silicon and various couplers/tees.

In my humble opinion it's imperative to improve the coolant flow from the back of the head. We all know it's a problem on these motors.

For the record, I will be fitting the biggest oil cooler I can squeeze in
That is, after the small issue of fitting the EFI
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1979 UK 932

[leadfoot]

Dan, as I did this originally on the N/A there was no oil cooler, hence the adding an oil cooler statement, although this was an automotion unit that came off a 944 challenge car and was about 2.5 / 3 times the size of the stock unit.

my config on the bypass pipe consisted of a staight pipe, same diameter as the larger outlet on the rear flange, running off a tee piece at the end, the other end of the tee was directed through a rubber elbow reducer to the heater valve in a closed loop circuit to the smaller connection on the coolant flange.

Not sure I understand fluid dynamics completely but no matter how big an entrance to a funnel is, it aint going to flow more than the exit allows,
so Weasel I think you might have been better off having a larger pipe connection from the water pump to the secondary run off to the coolant flange as it looks like the most your flow is limited by the size of the mid section of your pipe, please correct me if I'm wrong here...
Stu
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[WEASEL149]