Well, as you may have noticed from my 'living with a GTR' section, I've been struggling a bit with engine cooling. The cooling system is fine when I'm on the move, but at idle, the temperature slowly creeps up and the existing radiator/fan setup are insufficient to bring it down again. This isn't necessarily a consequence of the factory setup as (you may have read) I opted to lag the alloy coolant pipes which run along the cockpit sides. This has made the cockpit a nice and cool place to be sat in, but may have had an effect on the cooling efficiency of the system as the pipes would normally be able to radiate a bit of heat away (albeit into the cockpit - so a bit of a catch 22: hot cockpit or hot engine?). Additionally, the supercharger installation is much larger than a standard Chevy setup, with the consequence that it takes up much more space under the rear canopy. This has an effect on airflow and consequently, under bonnet (hood) temperatures.
After much discussion and research, it appeared that there were several options that I could go for. Firstly, there was some concern over the efficiency of the water pump at low revs. To put it into perspective, the Chevy ticks over at about 750rpm, so the mechanical pump isn't flowing coolant around the system at any great rate. To get around this, I decided to fit a secondary electrically operated pump in series with the existing one. This pump works at a constant rate, regardless of rpm, so would ensure that the coolant got pumped around effeciently, even at idle. I hoped this would help matters.
Secondly, I decided to install a high performance fan for the oil cooler in the engine bay. This would not only help cool the oil in idling conditions, but would also force air into the rear canopy, thus reducing the temperatures somewhat. So, the necessary phonecalls made and the parts ordered and delivered, I set about fitting the cooling aids!
I opted for the most straightforward fit first and that meant tackling the oil cooler fan. The fan is a Pacet 8 inch Profan which flows about 500 CFM of air. Fitting was easy enough, if a bit fiddly! Pacet made a quick-tie kit which consists of some plastic ties with use-once locknuts. Just thread the ties through the rad (a bit of persuasion is required as the oil cooler vanes are very close together) with the neoprene washers and slide on the locknuts. Job done save the wiring. I was going to wire the fan and the EWP (Electric Water Pump) to come on together with the fans. I already have a fan override switch in the cockpit, so this would be re-wired to operate the main fans, EWP and oil cooler fan simultaneously.
Next up, the rather more protracted process of fitting the EWP! The EWP is made by Davies Craig in Australia (but available through many local distributors). The technical data they supply makes for interesting reading and it seemed to fulfil my requirements of supplying a decent amount of coolant (about 22 gallons per minute which is equivalent to a Moroso billet pump), whilst not interfering with the efficiency of the existing mechanical pump, when used in series with it. The kit comes with the EWP itself, a 90 degree and a straight connector for the inlet/outlet side of the pump, some adaptor bungs and jubilee clips for different coolant hose IDs and finally, a short loom with a fused spur and operating relay. All in all, a decent quality kit.
Firstly, I had to find a position in which I could actually fit the EWP unit. Ideally, I wanted it on the radiator feed side of the system, which runs along the left side of the car to the top of the radiator housing. Inspection of the silicon link pipes at the radiator end showed this to be impossible without shortening the alloy pipes themselves. This was undesireable as it would mean cutting off the expanded end of the pipe which helps hold the silicon hose in place. Even if i had done this, things would have been VERY tight. So my attention turned to the rear of the car. Basically, I only had one option and fortunately, it's perfect! The existing 'standard' setup, takes a straight silicon link hose from the bottom of the swirl pot, into a short alloy connector and then onto a 90 degree silicon hose onto the alloy side pipe. By removing the downpipe and short connector from the bottom of the swirlpot, the EWP can be connected directly to the lower 90 degree silicon hose and to the swirlpot above via a shortened straight hose. With a bit of fiddling, the pump was in place. The loom supplied with the kit had to be extended to run from the fan override switch (on the rightmost side of the cockpit), behind the dash and through the passenger side (left side) luggage pod into the engine bay. I spliced a feed to the oil cooler fan so it would be operational whenever the EWP kicked in and the job was done. A dodgy earth caused a few moments of head scratching, but it served me right for trying to piggyback another one with a Scotchlock - useless things. Once a 'proper' earth was in place, the system worked a treat. I can be activated with the fan override (so I can continue to run the fans and circulate coolant with the engine off), or automatically with the fan's thermostat switch.
So - what happened next? Well, the car was run up to temperature to see if there was any improvement. In short, there was, but unfortunately not enough. The temperature rise at idle now takes a fair while longer as the EWP and oil cooler fan do their work, but it's still not enough :( I had already spoeken to the factory of my intentions and Ted had suggested upgrading the fans (this was after I'd ordered the EWP etc.). The factory supplied 10 inch fans pull a relatively low 575 CFM of air each (total efficiency therefore of 1150 CFM), whereas the pacet Profan of the same size pull 1090 CFM each! Therefore, I've ordered a pair of Profans and will try again. Hopefully, I can get it all sorted before the trip to Le Mans in a few weeks time. Wish me luck!
So, the new fans arrived. However, despite being the same basic design, one of the damn fans had a metal motor instead of the black anodised jobby - argh! Obviously I wanted them to match. A phone to the supplier revealed that they had no more stock - double bugger. However, all was not lost. The oil cooler fan (which is also a Pacet profan) uses exactly the same motor as the larger ones. So I stripped that one off and replaced the motor on the larger fan. It made no odds that the one for the oil cooler now sported the metal motor housing.
Anyway, this bit of faffing around done, I set about replacing the original fans. Amazingly, the new fans fitted straight on to the existing ally brackets with no modification! So it was a simple case of removing the 8 cap head allen screws and slotting the new fans in with the captive nuts. Job done. It's obvious by the motor size that the new ones are considerably more powerful than the old, but, they do rub on the grill somewhat. Still, test first and see what happens.
I ran the car up to temperature and the fans kicked in. The difference in airflow was damn good, you cool really feel the blast of air rather than the slight breeze of the old ones. I had also acquired an infrared thermometer to check the cooling efficiency of the radiator. With the laser sight locked on to the inlet and outlet of the rad. I saw a -10 degrees difference between the two which should be good enough. However, after about 40 minutes the temperature was again rising. In an effort to get maximum effect from the new fans I removed the mesh from the bonnet (hood) as advised previously by the factory. I had thought that the Stack reading was a little exaggerated, but further tests with the infrared thermometer showed that it was spot on! However, I became more suspicious of it once it passes 100 degrees as the radiator is much cooler. In fact, with the Stack showing 102 the fans cut out!!! This indicates that either the under canopy temperatures are abnormally high, or that the Stack sender is in an area of relatively dead flow (which I had been warned about). I continued the test by removing the EWP (an expensive test!). There was negligable difference (but it did run a little cooler) with or without the EWP, but fearing that it would be restrictive when the revs rose, I opted to remove it anyway. Finally, I richened up the idle mixture a little, this made my eyes stream a bit, but, with the car up to temperature, FINALLY, the fans cut in, the temperature dropped and the fans cut out again!! At last :)
So, I was finally ready to embark on the car's longest journey - to Le Mans! Read about our exploits in the Living with a GTR section
The build is complete, so to save doing the build diary as a series of monthly updates, I'll collate all the ongoing modifications into one page. Click the link below to view the ongoing development of the car!