Cooling
- Thread starter Campbell
- Start date
Eric Parham
New member
Two main issues for the cooling system. The first is sufficiently cooling the water in the radiator, and the second is using that cooled water to cool the engine.
I've tried with and without return from end of head. No noticable difference with 1.8 head, but blocking that return caused #4 to run hot (inferred from knock-sensor ignition monitor) on 1.5/1.6/1.7 head.
Stock oil to water cooler probably helps overall engine cooling, slightly. A better solution is a real oil cooler.
For good cooling, consider cleanliness of all passages (block, head, radiator, etc.), efficiency of water pump (plastic impeller often spins on shaft when hot, tin impeller usually okay, cast iron impeller best by far -- use magnet to be sure since some plastic impellers really look like cast), correct type of thermostat (must block bypass when open unless you've plugged the bypass, and most of us use 80C).
I tried saving HP by spinning the water pump slower (pulley size), but found that the car wasn't cooling well enough. This was on a Scirocco 2 (small grille). Others have had different results with different models.
For even better cooling, consider thicker radiator (from Rabbit w/ AC), wider radiator (from Golf w/ AC) or even copper rad if you don't mind the extra weight (from some diesels).
Also consider sufficient grille area and proper shrouding (sometimes the stock plastic or cardboard is missing so air flows around rad, or just gets moved so air flow is partially blocked).
I've tried with and without return from end of head. No noticable difference with 1.8 head, but blocking that return caused #4 to run hot (inferred from knock-sensor ignition monitor) on 1.5/1.6/1.7 head.
Stock oil to water cooler probably helps overall engine cooling, slightly. A better solution is a real oil cooler.
For good cooling, consider cleanliness of all passages (block, head, radiator, etc.), efficiency of water pump (plastic impeller often spins on shaft when hot, tin impeller usually okay, cast iron impeller best by far -- use magnet to be sure since some plastic impellers really look like cast), correct type of thermostat (must block bypass when open unless you've plugged the bypass, and most of us use 80C).
I tried saving HP by spinning the water pump slower (pulley size), but found that the car wasn't cooling well enough. This was on a Scirocco 2 (small grille). Others have had different results with different models.
For even better cooling, consider thicker radiator (from Rabbit w/ AC), wider radiator (from Golf w/ AC) or even copper rad if you don't mind the extra weight (from some diesels).
Also consider sufficient grille area and proper shrouding (sometimes the stock plastic or cardboard is missing so air flows around rad, or just gets moved so air flow is partially blocked).
Bill Miller
New member
I've never seen any solid evidence of the OE 'oil warmer' actually doing anything to lower oil temps. I've run cars w/ an w/o one and never seen any difference in oil temp. If anything, I think it would kick your water temp. up.
As was suggested, use a bigger radiator, make sure you've got good shrouding around the radiator. You can run an external oil cooler (not a bad idea anyway), and I would also add some Water Wetter.
As was suggested, use a bigger radiator, make sure you've got good shrouding around the radiator. You can run an external oil cooler (not a bad idea anyway), and I would also add some Water Wetter.
Those ever-reliable laws of thermodynamics pretty much assure that the oil/water heat exchanger will move heat energy from the oil to the water. The question then becomes whether or not the water/air heat exchanger can move that energy from the water to the air efficiently enough to stay ahead of it.
In typical fashion, we've done something a little different with our Golf. We maintained the oil/water intercooler and added a nice cast aluminum oil sump. (I've seen more than a few aftermarket oil/air coolers get squashed or holed during long races so I worry about adding another set of potential failure points.) With a new, big OE radiator and ducting extensions attached to it to close up the cracks in the nose, we had fine temps at the Summit 12. Oil ran 250-270 all day, which with synthetics is no problem. Water temp needle was straight up.
We had what looked like an overheating issue earlier in the year at a roaster at CMP but when we addressed it during preparation for Summit, we discovered that we had (a) an overly coolant-rich mixture in the system, (
a lean condition, probably resulting from unmetered air getting in through an intake leak, and (c ) less-than-optimal cam timing. We worked out the engine issues on the dyno, went to a Water Wetter solution, and added the radiator shrouding and we were back to where we were last year.
K
In typical fashion, we've done something a little different with our Golf. We maintained the oil/water intercooler and added a nice cast aluminum oil sump. (I've seen more than a few aftermarket oil/air coolers get squashed or holed during long races so I worry about adding another set of potential failure points.) With a new, big OE radiator and ducting extensions attached to it to close up the cracks in the nose, we had fine temps at the Summit 12. Oil ran 250-270 all day, which with synthetics is no problem. Water temp needle was straight up.
We had what looked like an overheating issue earlier in the year at a roaster at CMP but when we addressed it during preparation for Summit, we discovered that we had (a) an overly coolant-rich mixture in the system, (
a lean condition, probably resulting from unmetered air getting in through an intake leak, and (c ) less-than-optimal cam timing. We worked out the engine issues on the dyno, went to a Water Wetter solution, and added the radiator shrouding and we were back to where we were last year.K
For the A2 I race I run a 16v with ac radiator, and a 23 row oil cooler using a thermostatic plate and got ride of the oil heater. Having lots of VW heat problems with the cars I tracked that heat exchanger is the first to go. I am also running a 170F thermostat. In the heat of last weekend I was holding 190F water and 230-240F oil temps. Last month in 80F weather, I was 170F water and 215F oil.
Bill Miller
New member
VWs are notorious for running high oil temps. My VR6 Corrado used to see 240* oil temps on a regular basis. Got as high as 260* once. And I agree w/ Kirk, you want the oil over 220* to flash off any condensation.
A guy in NW Region had an SSC MkII GTI, back when they were new, and he put an (illegal) oil temp gauge on it, behind the radio blanking plate...
It would regularly run 310-320*F.
I put a gauge on our Renault Cup car when we first converted it to ITC and discovered - to my horror - that we were seeing the same kind of numbers with its puny little 1.4 pushrod motor. We put a big oil/air heat exchanger on it and promptly over-cooled it. I'd typically run with essentially the whole grill taped over, like a Nextel Cup car in qualifying trim...
K
It would regularly run 310-320*F.
I put a gauge on our Renault Cup car when we first converted it to ITC and discovered - to my horror - that we were seeing the same kind of numbers with its puny little 1.4 pushrod motor. We put a big oil/air heat exchanger on it and promptly over-cooled it. I'd typically run with essentially the whole grill taped over, like a Nextel Cup car in qualifying trim...
K
x-ring
New member
I don't remember much about VWs. I haven't owned one in a long time, and I have never raced one, but in racing radiators, as far as I'm concerned, there is only one name: Ron Davis.
He made me a double pass radiator for my Z (notoriously hard to cool) that took the coolant temps fom 250 degF (!) to 190-200 degF at our high altitude, high ambient temperature tracks.
They're a work of art, too.
http://www.rondavisradiators.com/
He made me a double pass radiator for my Z (notoriously hard to cool) that took the coolant temps fom 250 degF (!) to 190-200 degF at our high altitude, high ambient temperature tracks.
They're a work of art, too.
http://www.rondavisradiators.com/
RSTPerformance
New member
What is an illegal oil temp gauge?
Raymond
Bill Miller
New member
Since all the Mk2 GTIs came with the MFA that has an oil temp gauge integrated into it, that sounds like a weird move.
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Are you sure about that Chris? I had an '85 GTI for a brief period of time, and don't recall it having an MFA. But that was many years (and brain cells) ago, so I can't say for sure.
Ron Davis radiators are top notch, as are Griffins.