924Board.org

[ideola]

The Davies Craig gear came in while I was on my parts run last Friday:

Davies Craig Electric Booster Pump (EBP) for water-cooled turbo circuit:


Davies Craig Electric Water Pump (EWP115)


Davies Craig 12" Thermatic Fan (12V)

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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[ideola]

I'm taking a closer look at reversing the coolant flow through the head first, based on some info posted here, and also in the thermal management section of Jeff Hartman's Turbocharging Performance Handbook. Bearing in mind the following characteristics:

• modified water pump housing
  
• modified thermostat housing (NO thermostat)
  
• modified rear water flange
  
• modified cross-over pipe
  
• heater-delete configuration (no heater core or associated plumbing)
  
• Davies-Craig electric water pumps (EWP115 for main coolant circuit, EBP for turbo coolant circuit)
  
• Water pump cycling will be controlled by the ECU
  
• 951 style coolant reservoir
  
• water-cooled bearing housing on the turbo

...here is the proposed reverse-flow configuration:

Any reason this won't work???
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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[ideola]

Bump ^^^ any feedback on the reverse flow topic?
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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[bass gt]

Dan,

Sorry for not getting back to you sooner, i've been on holiday in Mozambique it's tough, but someone needs to do it!!
Anyway, re the reverse flow thing. No reason at all why it won't work. in fact, i'm going to do this on my car once ready. It should result in head temps about 10 deg cooler, which really helps, as the ideal temp for a turbo engine is about 70-80 deg C.
keep us posted on your results. And if it's a no go, it's easy enough to revert to a conventional flow.

Steve
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Front Wheel Drive is the Devil's work.

[Martijnus]

Am I right about the following:

The stock pump pumps the coolant through the engine and the head...head has two exits, one at the front (thermostat housing) and one at the back (coolant flange).
The latter goes directly (through the metal tube on the outside of the engine) back to the pump, the thermostat housing goes also to the pump and to the radiator.

Correct?

Like the setup you designed Dan If I understand the coolant system correctly I don't see any problems too.
Only thing I noticed is that you pump coolant in the head from two sides, but normally that would be two exits so that's normal...but reversed.

Why is the head temp 10deg. lower? Because the coolant passes the head first before it goes in the block? Or is the stock system really restricting?

My head temp is always 80 deg. 85 worst case... but I'm not charging the intake
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)

924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment

[ideola]

The normal cycle goes like this:

lower rad hose -> water pump inlet -> block -> head

From the head, it splits off and comes out the back water flange where the TTS and CLT are located, and also the split for the heater control valve, as well as the connection to the stock cross over pipe, which tees back into the lower t-stat housing. In the front, it exits the head and goes into the lower thermostat housing. When the t-stat is closed, water circulates down the t-stat bypass connection, the little short hose that connects to the water pump, and goes back down into the block and continues circulating until the t-stat opens, at which point it proceeds over to the upper rad hose.

In my case, the t-stat is removed, as I will be controlling everything via the ECU. Also, the lower t-stat housing has been modified by welding shut the bypass and cross over connections. The water pump has the guts removed, and all openings except for the inlet from the lower rad hose welded shut. My welder is making up a custom rear water flange that have a ~30mm elbow outlet, with no take-offs for heater control valve (since there won't be a heater core). The theory is that the 30mm at the rear of the head, with same size hose to replace the stock cross over pipe, will equalize flow across the front and back of the head.

Now, to explain why reverse flow is superior, I'll quote from Mr. Hartman:

[tuurbo]

Very cool idea - so really, given the heat of these heads, Porsche should've engineered it this way from the start.
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1980 924 turbo, MSD, Meth. Inj, otherwise stock.

[ideola]

Well, on a street car, it complicates things a bit. First of all, you'd need a dual t-stat like what is mentioned in that LT1 thread. Then, you'd have to re-engineer how the water pump works, and then you'd have to pull the heater source post-head. None of these are insurmountable on a new engineering project, but given that the 924 was a parts bin car to start with, you can guess it probably didn't get much if any consideration.
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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[ideola]

OK, here are photos of my modified rear water flange:



And for clarity, here are photos of the modified water pump housing (be sure you don't miss welding up the weep hole!!!):


And finally, a photo of the modified lower t-stat housing:


The cool thing is, the upper t-stat housing from the 931 and the 924NA can be interchanged...one points to the front and the other toward the LHS fender, so depending on how everything else comes together with the intercooler, low pressure duct, radiator, and intake, I can select the most convenient part for my needs
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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[ideola]

Here is a nice, brand new 951-style coolant reservoir. Picked this up a while ago on a Rennlist group buy.

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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[ivan]

I've got a slightly off topic question, though it does involve cooling.

does anyone have any cheap solutions for a replacement expansion tank on a (future) street car?
So far my best solution at work (I work at a parts store) has been buy a pressurized expansion tank (which is like $30) and figure out a spot for mounting it....

...or the slightly more expensive option which is buy a new half sized radiator (I.E. mid 90's honda which is about $120) and just make a bracket so i have a new component that can rule out for failures, and i've already got a overflow tank laying around that i could easily mount.

[ideola]

Just buy a second hand 944 expansion tank, they routinely pop up on eBay. Come to think of it, I might have a spare I'd be willing to sell you. The 944 unit looks just like the above photo, but without the extra small port (which is the return line from the 951's water-cooled turbo) and it mounts directly on the fender rail. If you work at a parts store, you should have no trouble cobbling together a hose configuration that will adapt the stock 924 hoses to reach over that far.
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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form

[pocketscience]

+1 to what Dan says.

I bought a brand-new 944 style for ~$80 I recall. The new hose layout is easy-peasy...


G.
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Whoever said you can't buy happiness forgot about Porsche!
81 924 N/A, GTS lights, Saratoga, interior, headers, Integral cam, EFI (sold)
95 993
69 911

[Karlio]

[ideola]

hot side of the head.
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75 Fiat X1/9 | 80 US 931 '941' | 78 Poli-Form