I just got done putting my car back together. My coolant temps. are running a little higher than I think they should. I was hoping that some of the experts on this board could offer their opinion...
My Car: Stock Engine, 34,000 miles, typical bolt-ons (TA-49, Red Stripes, THDP, etc.), CAS V-2 Front Mount.
Cooling System: All new hoses, new 3-Row HE radiator, 50/50 coolant, RMI, stock water pump, stock radiator fan, 160F thermostat
My current chip turns the fan on at 185F and turns it back off at 179F. I am idling the car at 700rpm in drive and 775rpm in park.
On an 85 degree day in traffic, my coolant temps. were getting up to 190F with the A/C off (low-speed fan was of course on). When I drive at highway speeds, the car does not cool-off very fast. At 65mph, the coolant temp. will go back-and-forth between the fan on-and-off speeds (i.e. 179 to 185 then back to 179).
I think my high-speed problems are because I could not re-install the baffle that goes from the grill to the bottom of the rad (due to the front-mount). I did re-use my intercooler scoop by attaching it to the front of the lower rad support. The theory is that this will scoop air into the radiator when I am driving at highway speeds. Even at idle, I have measured the air temperature going into that scoop when the fan is running, and it is nearly ambient (about 85 degrees on an 85 degree day).
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So, I did a little experiment. Using an accurate digital thermometer, I measured the temperature of the coolant in the passenger radiator tank (near the cap) while the engine was hot and idling. My procedure was to let the car warm up for a long time (half an hour) in my garage. By doing this, the cooling system would reach a "steady-state" where the coolant temperature was not changing (as read by the temperature sender). Then, I would compare the temperature on the digital thermomoter (passenger radiator tank) with the coolant temperature sensor (CTS)(which is engine out, or the driver radiator tank). Here is what I found:
-In drive (700rpm), there was a 14-15 deg. difference between the digital thermometer and the CTS. This was with the low-speed fan running.
-In park (775rpm) with the A/C on, there was a 10-11 deg. difference. This was also with the fan running.
-In park reving the engine (about 1500-2000rpm), the difference was about 5-6 degrees. Again, with the fan running.
What I think this means is the following: At idle, my radiator is taking 15 degrees out of the coolant (pretty good). But, my engine is putting 15 degrees back into the coolant, because everything is at steady state. For example, at idle, my coolant was coming into the radiator at 183F, but going back into the engine at 168F. I do have some background in cooling system design, and it seems like a 15 degree temperature rise in the engine is too high at idle. 15 degrees is about what I would expect at WOT.
From these experiements, I am thinking that a higher flow water pump would help my idle coolant temperatures. By increasing the water pump flow, the temperature increase of the coolant through the engine would be lower. Of course, the temperature decrease of the coolant through the radiator would also be lower. But, I think the net result at steady state would be an overall drop in the temperature leaving the engine (what the CTS reads).
Well, what do you think?
Also, what's the best option for a higher flow water pump? Summit's pump? Tony DeQuick pump (where can I get one?)? Kirban's 10% overdrive pulley?
how about the dual fan setup from ram chargers?
does your stock fan have any weatherstripping around it to force the fan to pull air through the radiator?
I don't have a front mount, but by fixing my baffles between the grill and condensor, I did run cooler. Maybe you can engineer something.
http://personal.atl.bellsouth.net/mia/s/h/shawnco/projects/radiator%20seal/RAD.htm
I don't know anything about cooling system design, but I always thought that
>at idle speeds, the pump was not very efficient. The deltas you describe
>seem to indicate that's true. If that's correct, a high delivery pump seems
>the obvious choice.
>Years ago, I bought a high delivery pump for a Mustang, (My non-enlightened
>days) and the only difference was, the impeller had a sheet metal disk
>attached to the side of its vanes. I suppose its purpose was to eliminate
>pumping losses between the vanes and the pump body.
>If I had your background, I would try to design a vapor vent system that
>would return the vapors generated around the exhause valve guides and in the
>cylinder head steam pockets to the coolant reserve bottle. This would get
>rid of hot spots, cool the engine better, and help a lot of your fellow
>enthusiasts. I seem to remember the L98s had a tube mounted in a high spot
>in the intake manifold water crossover passage. It then ran to the coolant
>reserve bottle. The LS1 has vapor vents at each end of the heads that do the
>same thing.
Shawn,
What is the purpose of the piece of metal/plastic you have mounted between the intercooler and fan/radiator? The piece that blocks your view of the floor.
home made radiator air deflector...
http://personal.atl.bellsouth.net/mia/s/h/shawnco/projects/radiator%20air%20deflector/RAD.htm
Just as a follow-up to some of the comments I've seen:
I do have the fan weather-stripped to the radiator. It's amazing what you can do with a junkyard hood seal...
Also, I do not have my fan jumpered to go on "high" when the low-speed relay comes on. I would imagine that would help.
Once I put the car back together (had to fix tranny cooler leak - grrrrrrr), I'm going to try various baffling set-ups. I think that these will help me at highway speeds, but not at idle. The consensus seems to be that re-installing a baffle from the grill to the lower rad support is a good idea.
If I learn anything interesting, I'll post it.