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simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

As is known I would very much like to convert the supercharged car to run with a turbo too.
However, at a recent event a guy with some expereince of the CGTS said that cooling was a problem on those models and reliablity suffered as a result. In most cases the hottest pot would fail, and as I think we might all know/suspect that means number 4 cylinder.

Has anyone else experience of this problem?
If I am to run much more boost (0.8bar now) then cooling must be good as a championship contender cannot be unreliable!

If it is at all dodgy then I will try and max what I have and go the route of less weight. I can speed the blower up a little to get another 1 or 2 psi or could possibly get a whipple blower that will make 15 or 16 psi. Its not just reliability that is the issue as pistons now have to come from the US and each order takes 6 weeks. So one failure a season means the car is history from a championship point of view.

A number of you folk with the turbo cars have tuned them to higher boost. How high can you go safely and have you done anything to improve the cooling?

I have a Davies Craig elec pump and no pump impellor or thermostat and it cools ok now. However that does not mean its ok with say 1.1 or 1.2 bar!

Cheers
Simon
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Lizard · Posted: Tue Jul 22, 2003 4:44 am Post subject:

I think the cooling system is fine on these cars, but if you have a worry of over heating, get a rad for one of the renagade hybreds, built for a V8 and then get a pair of high velocity electric fans for the car, and maybe consider rebuilding the waterpump, and use a low temp thermostat. that should cure the problem
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3 928s,

jpab924 · Posted: Tue Jul 22, 2003 1:44 pm Post subject: Re: Cooling issue

Joes924Racer · Posted: Tue Jul 22, 2003 2:37 pm Post subject:

Duh com-on you guys we all know these motors can get hot.
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1979 porsche 924 Na
1980 porsche Turbo 931GT Replica
Have u ever driven a turbo.

Lizard · Posted: Tue Jul 22, 2003 3:51 pm Post subject:

924RACR · Posted: Tue Jul 22, 2003 10:34 pm Post subject:

I have no heating problems on my racecar or turbo as long as everything's working properly. Cooling problems and high temps (on a stock or relatively stock car) indicate work that needs to be done.

Simon - you need to figure out how to reverse the cooling flow through the head. That's what was done on the GTR's, but I don't know any details of how they did it.
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Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

Lizard · Posted: Wed Jul 23, 2003 2:28 am Post subject:

78porsche924 · Posted: Wed Jul 23, 2003 3:34 am Post subject:

Why would u want to reverse the flow??? How would that help cool it better?
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90 944 S2
78 924 NA <---now sold and killed by new owner
snailshell trans
Bae turbo kit
to check out my 944 S2 http://www.cardomain.com/member_pages/view_page.pl?page_id=388139

Lizard · Posted: Wed Jul 23, 2003 4:14 am Post subject:

78porsche924 · Posted: Wed Jul 23, 2003 4:42 am Post subject:

Ah, makes sense.
_________________
90 944 S2
78 924 NA <---now sold and killed by new owner
snailshell trans
Bae turbo kit
to check out my 944 S2 http://www.cardomain.com/member_pages/view_page.pl?page_id=388139

78 924 N/a · Joined: 20 Mar 2003 Posts: 769 Location: Pacific N.W.

78 924 N/a · Joined: 20 Mar 2003 Posts: 769 Location: Pacific N.W.

Here's some reading about Chevrolet's development of the reverse-flow cooling system for use in the second-generation small-block. If you have an open-mind, and don't mind that it's not about Porsches, MAYBE you can learn something useful TO YOU.

It might take a sharp mind to figure out a way to reverse-flow cool the Porsche 924, and make it work correctly. But it is an idea THAT DEFINETELY has very high rewards and performance improvements.

http://www.theherd.com/articles/lt1_cool.html
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1978 924 n/a

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

Lots of good ideas.
One thing I have worked out is that the standard pump 'draws' down the line from the back of the head and heater and then pumps that back into the block.
This sems to be so because the standard impellor is 'inset' a litle into the face of the block and the retun port to the pump is effectively upstream of it.
I have removed the pump internals and fitted an electric pump in the line from the bottom of the rad. In so doing I am now filling the old pump housing and hence 'blowing' water up the old retun line from the head and heater.
I am not sure if this is better or worse though!

I think the GTR ran two pumps, one for the head and one for the block. The flow was reversed too.

What might work is;
1, Increase pump speed to flat out all the time (I have a temp control speed system on it now).
2, Open up the return line via an enlarged alloy block on the back of the head and increase the bore of the return line in some way.
3, Up the rad and fan size.
4, Use water wetter. This stuff really does work well.

I reckon all that will ease the temp enough to safely runa couple of PSI more on the existing blower setup but I think a more radical solution is required for the 1.1-1.2 bar twincharger setup.

Of course the ideal setup is an individual water flow for each cylinder. This would involve a new block and head design, sigh !

Cheers
Simon
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Blown is always best!

simsport · Joined: 06 Nov 2002 Posts: 573 Location: UK Warrington

It just struck me.............why not try it.

If I connected the output from the pump to the old return line out of the head and simply allowed the hot water to return to the top of the rad from the block how would it perform?

Ideally someone with a std road car and an 'itch' would try this to see if the temps are comparable under normal conditions first before getting brave and looking at race temps.....must find somebody!

I think for best flow the old thermostat block would need to be scrapped and a simple plate+pipe stub fabricated in a good bore size.

I dont think it would easily fix the temp of number 4 cylinder but it might help promote more flow from that end of the block via the old heater and return line block, which could also be replaced by a better flowing pipe and stub fabrication.

Cheers
Simon
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Blown is always best!

john h · Posted: Wed Jul 23, 2003 2:37 pm Post subject:

Maybe I've been lucky but I've run my GT Replica for about 14 years at boosts from standard (.07) to 1.2 bar.

I've removed the sealing strip in the engine bay to allow hot air out and I also run a 30% mixture of gycol and water. I run the standard trubo oil cooler and then have a secondary 8 row cooler mounted in the front of the car just below the bumper. I've found the car hasn't overheated since these mods were done. These were done in 1987 (80,000miles) and the engien is now approaching 260,000 miles and still runs between 1/2 and 3/4 on the temperature gauge on the track and on the road runs between 1/4 and 1/2.

If the cooling system and pump is in good shape and you keep the oil cool the the car seems to run OK.
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Remember a Porsche is not just for Christmas,

if you take it to pieces slowly it can provide anguish all year long!