[Cloud9...68]

Before I start a thread in the cooling system section on the behavior of my car's cooling system (I have a few things I want to check out first), I'd like to hear from the racers as to how high their water temp gauge gets under extreme racing conditions. By that I mean on a hot (100+ degree day), full-on, very high rpm, full-throttle, take-no-prisoners racing. Also, how high does you oil temp get under these conditions? Thanks.

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[JWahlsten]

Does DE count? I typically see the upper white line, but never above. This was pushing at NJMP last summer during an open track day, so it was long sessions running with really fast cars.

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[Cloud9...68]

[quote name='JWahlsten' timestamp='1375799868' post='146655']

Does DE count? I typically see the upper white line, but never above. This was pushing at NJMP last summer during an open track day, so it was long sessions running with really fast cars.

[/quote]

Yes, I was thinking primarily of DEs, as this (or what are referred to as "practice sessions" at the local driving academy) are all I'll be running in the foreseeable future. Just want to get a feeling as to what's "normal" as the starting point of checking my cooling system to see if everything is functioning as it should. It's better than before the rebuild, as it's maintaining a reasonable temperature indication in stop-and-go traffic on a very hot (102 degree) day, but when I start flogging it, the gauge quickly climbs toward the 10 oclock line, so I'm afraid it will overheat during a full track session.

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[craigawoodman]

Mine used to get to the point of actually lighting up the warning light.



Since then, the second oil cooler, installing the missing radiator top shroud and the engine work have all meant that even under hard track driving, the needle does not get above the normal mark.



Make sure all the duct work in the nose is there, as is the top plastic sealing strip on top of the radiator - this makes a huge difference.



From memory, there is also a different thermostat that you can run to open up the cooling system earlier and bring the fans in.



Same for the lower engine tray, etc. are these in place?

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[Cloud9...68]

Craig,



Thanks for the inputs. But to tell you the truth, I can't say for sure whether I have all the shrouding in place - I need to take a look at the diagrams in the PET to make sure. I know I have that lower curved lower plastic piece in place.



I'll check the operation of the fan switch, and then I'll bleed the system again. It's acting like it isn't getting sufficient air flow from the fans, as the indicated temperature drops rapidly when I drive at a high, steady speed, but struggles when I do a lot of accelerating.



I've heard about the importance of the lower engine tray, but to behonest, I'm skeptical of the importance of this, because again, once I build up some speed (and therefore have to rely less of the fans to get air flowing through the radiator), it cools fine.



What oil temperature do you see at the track? Flogging it on the street yesterday afternoon, the highest reading I saw was about 210 degrees F. I also have dual oil coolers (from RS Barn) that I've built shrouds for, and they seem to be doing an outstanding job.

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[craigawoodman]

Cloud,



I think one if the biggest improvements was the plastic strip that runs along the top of the radiator. This stops air blending over the top of the radiator when it is not there (and hence unsealed). I am sure that the ceramic coating also helps now.



Prior to getting the trim strip, etc - the warning light would just start to glow and so e short shifting later, it would drop back. I think part of this was the lower opening temperature thermostat as well.



Check out 951 504 321 01 Air Duct ($17). It is shown in the Body section of the parts manual, for the front section of the car.



The lower plastic trays stop low pressure forming and dragging the air down below the radiator. I just looked at the engine parts list and the duct is for the oil cooler. There is another in the body section for the radiator 944 575 141 00 (and there is a (01)), but nothing to tell the difference.



Without the ducts and seals in place, I don't think you get the right air flow.

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[Dubai944]

Two traces for oil temperature and water temperature. Three figures on the right are low, high, average for the period of the trace. These are just snapshots of a couple of minutes, but typical.



First one is a practise session at a track day in Australia with ambient air temperature around 25 degrees C.



Second one is more extreme qualifying session in Dubai, ambient air temperature around 40 degrees C.



I have a PWR water/oil radiator combo. With water +water wetter coolant temps are always stable regardless of how hard I push the car or how hot it is outside. Oil temp can get higher on hot days in race conditions. Temps are in Celcius, you will have to convert to Farenheit.







Track Day in Australia Typical Practise Session







Qualifying Session in Dubai

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[Cloud9...68]

Dubai,



Thanks very much for this useful info. What diagnostic tool did you use to obtain this data?



My oil temperature seems to be very well behaved, and comparable to yours. The RS Barn dual oil coolers, with the large shrouds I fabricated for them, seem to be doing a very good job of controlling the oil temperature.



As far as the water temperature, I think I have a problem. When I first got the car, it seldom got above the 8 oclock line even on the hottest days, but that was before I started tracking it. Then, all of a sudden, it started running noticeably hotter under all conditions, especially in stop-and-go traffic, and especially when I turned the AC on, which is backwards of what should be expected, as I understand it. During the track car conversion project, I found several wires in the fan cooling system whose insulation have been torn off, causing them to touch, so I repaired these. Now, it's doing better than before the rebuild, in that it's maintaining a reasonable temperature in stop-and-go traffic, even with the AC on. But when I do a series of hard acceleration runs up to 6000+ rpm, the indicated water temperature rises rapidly, getting right up to the 10 oclock line, which I had never seen under any conditions when I first got the car. When driving it at steady freeway speeds after a series of hard runs, the temp drops back to about 8:30 (so a little below horizontal on the gauge) fairly quickly. Both hoses are hot (I haven't measured them yet, but even the fat hoase is very hot to the touch, unlike what I found back when I had a stuck thermostat, so I must be getting sufficient coolant flow through the system). And the fact the driving at freeway speeds at low rpm (so in 6th gear) quickly brings the temp back down also tells me there is plenty of coolant flowing through the radiator.



So, the first thing I'm going to check is whether the high speed setting of the fans is working. The low speed setting definitely is. I will also check to make sure the system is well bled.



Anything else anybody can think of that would cause a very rpm-dependent hot running condition? Thanks.

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[Dubai944]

[quote name='Cloud9...68' timestamp='1375880829' post='146714']

What diagnostic tool did you use to obtain this data?

[/quote]



It's MoTeC software. The ECU logs everything.

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[tamathumper]

I'm assuming the Durametric would capture these data points as "Actual Values"?

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[Cloud9...68]

[quote name='tamathumper' timestamp='1375889124' post='146726']

I'm assuming the Durametric would capture these data points as "Actual Values"?

[/quote]

I would think so. I was thinking that's what Dubai944 was using. But in my case, I believe my gauge. My engine's cooling system is doing OK under "normal" driving, but is struggling to keep up when I flog it.

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[Dubai944]

I'm using a Motec ECU which has logging capability. You won't get this from a Stock setup.

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[craigawoodman]

Cloud,



Could also be the water pump. At high rpm, the impeller may not be working due to load. Could be the second fan (A/C should cut this in from memory), it could be the thermostat and it could be the shrouding and ductwork for the radiator (including the under car panels).



It could be the radiator itself, or a blockage in the hoses restricting flow.

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[Cloud9...68]

Craig,



I've pretty much checked all the items you've mentioned. I checked the tightness of the impeller on the water pump, and even put it in a big pot of boiling water on the stove to check that it wasn't coming loose at temperature - tight as can be. I doubt it's the thermostat, because the lower fat hose is getting very hot. I had a bad thermostat once, and this hose stayed practically cool to the touch when the thermostat wasn't working, which makes sense. I also doubt it has anything to do with shrouding or ductwork, because the engine cools off just fine as long as there's air flow (e.g. at high speed). I've also had the radiator checked for obstruction (clean as brand new), and the hoses are all new. If it isn't the fan (particularly its high speed function), or a significant amount of air trapped in the system, I'm stumped.



From Dubai's data, his engine never got above 89 degrees C, which is only 192 degrees F. Flash said the 10 oclock line corresponds to 212 degrees F, so even after just a few hard acceleration runs up to 6000+ rpm (so nowhere near the stress the engine would see during an actual track session), my engine is getting significantly hotter than his. I didn't get a chance to check whether the high speed mode of my fans are working last night, but I should be able to tonight.

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[flash]

assuming that all of the under trays are in place, and the upper cover that closes off the radiator and is below the air box is in place, and the fans are working properly, then the issue you have could be timing. if your cam timing is off, you could be advanced too much and that will cause this. a chip that has a lot of timing in it could do it too.



a restricted exhaust can cause this too, though i tend to think you have already opened that up.

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[Cloud9...68]

No undertrays, but I don't think that has anything to do with my problem, because my car never had them, and it cooled flawlessly for the first few years I had it. Not saying they're not a good thing to have, but definitely not the root cause of my current problem. The car gets hot at high rpm/relatively low speed, but cools fine at high speed, indicating that when there is sufficient air flowing, it's getting routed well enough through the radiator.



I had thought about timing as a possibility. Given all the uncertainty associated with getting the cam timing right, I don't know how I would go about making sure it's correct, though. I know I ended up close to the center of the adjustment range on the adjuster, so I suspect that even if I'm off, I'd be surprised if I were off far enough to cause overheating, but who knows.



If I'm going to be brutally honest, I don't think the car has cooled properly since I replaced the water pump about four years ago with a remanufactured one from Paragon. It doesn't leak, but I'm wondering if for some reason it doesn't pump sufficient volume to remove enough heat from the engine at high stress (read full throttle acceleration on a very hot day) conditions. Does this make any sense? I'm still hoping it's my fan switch, but am beginning to think water pump...

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[flash]

don't make any assumptions. you have done a lot to the car. symptoms like these are often a result of small changes.



absolutely it could be the trays. this car is incredibly sensitive to engine bay airflow. i can tell the difference when the third tray (the metal one) is missing. negative pressure zones are everything. your theory about "having enough air" is flawed. what you have is too much air, but in the wrong place, at the wrong time. you need positive pressure in front of the radiator, and negative pressure behind it. when you get up to speed, you are picking up too much air under the car and it is entering the engine bay, without first passing over the radiator. that is bad



put the trays back on and then test it.



then, when you have eliminated that variable, look to the timing. verify that your cam timing is correct.



different chips have different timing curves too. for example, the racer x chip has a LOT more timing advance than the autothority chip.



restriction in the exhaust can cause this too.



it can be a sum of issues too. for example, when i was running the racer x, and i had the stock exhaust, i would heat up rather quickly under load. when i opened up the exhaust, that eased up. when i changed to a chip with less advance, it eased up more (though i lost some upper end snap)



this does not rule out a bad or less efficient pump. there were two different impellers out there too. one of them works better than the other.



start by establishing a baseline.

install the belly pans

verify that the fans are working.

verify that the thermostat opens at the correct temperature. it should open at about 8:30 on the gauge.

you should have the low temp fan switch. the low speed should come on at just about 8:30 and the high at a bit over 9:30.



then, finally, read the coolant temps at the hose coming off the head (not the metal parts though) with a laser thermometer. after the thermostat opens up, they should be roughly 100 degrees F above ambient, or 15 above the thermostat, whichever is higher. forget the gauge.

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[Cloud9...68]

Thanks for al the inputs, but I have a few issues with implementing some of them. First of all, I don't have any of the pans - they haven't been on my car since I've owned it. I agree I should get these, but it never made it on my priority list because my car had always cooled so perfectly, even in the summer at the track, until it suddenly developed symptoms about four years ago (so before the recent project). Darryl has a center one he told me he he'd be willing to sell me, but we haven't closed the deal, so I'm panless at the moment.



Same problem with the cam timing. Short of driving the car to your builder, I don't know how to guarantee if I got it set perfectly. Not sure how to proceed with this one - any suggestions are welcome.



I need to buy an infrared temperature thermometer, but I can definitely say that the fat hose is getting quite hot. I've had bad thermostats on this car before, and that hose barely got warm, so I'm reasonably sure the thermostat is opening. I agree that it would be good to determine the temperature at which it's opening; how do you recommend doing this?



I do have the low temp fan switch (at least the previous owner told me he had one installed).



I installed an RS Barn cat back as part of the project, and I have a Racer X chip, which the car came with. So it cooled perfectly for many years with the Racer X chip and the stock exhaust.



I also have a question about the hose temperatures. Shouldn't the lower fat hose always be cooler than the one coming off the head, since the lower hose is (I believe) downstream from the radiator?



I am seriously worried about my water pump, but of course changing it is a huge job.



So, given my current limitation in terms of the pans and the inability to absolutely confirm the accuracy of the cam timing, I need to focus on what I can impact at the moment, which is limited to:



1. Verify the fans are working properly

2. Make sure the system is properly bled.

3. Check hose temperatures with an infrared thermostat.

4. Measure the temperature at which the thermostat is opening



This a depressingly short list, and if I can confirm the fans are operating correctly, my suspicion is that the reman'd water pump is somehow at the root of the problem.



As far as the pans, I'd be very interested to see how many people have at least the front apron/splitter and the middle pan. Anecdotally, I get the impression that an awful lot of these cars don't have any of the pans aft of the apron, but I'd like to confirm. I think I'll start a poll, because I think it would be a useful piece of information for the community.

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[Cloud9...68]

Re: the pans. A supplier of equipment to the company I work for has a 968, and I've emailed him asking him to check if his car has the belly pans, so I can borrow it/them to see if it makes any difference in my car's cooling behavior. If his has it/them, are there any "tricks" associated with installing it? For example, do they need some sort of special fasteners, or just ordinary sheet metal screws? I have the D1R splitter and RS Barn dual oil coolers with the oil lines that run horizontally across the car right behind the splitter. Do I have to do anything special to get the frontmost pan to fit given these circumstances? Thanks.

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[flash]

M6 hex head cap screws and 2 phillips head screws to catch the louvered side covers



the pans fit fine with the splitter. not sure about the cooler hoses



you absolutely will see a difference. it will run cooler, and you will gain front downforce



p.s. - all of the performance car manufacturers now run full belly pans for exactly the reasons i cited

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