Quote:
Originally Posted by TOOSTUBBORN2FAIL
Hmm, seems I need to wait until this summer, and then make sure the car is at final weight, and climb the grapevine with the ac on and see what happens temp wise. Then figure out how much radiator I really need. My only concern is that this is going to be a heavy car (33-3400lbs with driver).
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Hi TOOSTUBBORN2FAIL,
Obviously rear engine cars; VW, Fiat or Corvair..., had enough cooling. But when VW made a water cooled Vanagon they kept the rear engine but put the radiator up front.
Anyway, consider how much fan you'll need. If your 3300 lb car needs about 6 hp for rr and 12 hp for aero on the flat at 65 mph. Then on a 7.5% grade it will need about 63 hp total. Generally you can expect to dump out the radiator about the same hp as the engine is putting into the tires. And the temperature rise through the radiator should be less than 15°F.
The thermal capacity of air is about 0.00042 hp•min/°F/cu ft
63 hp/0.00042=150000 °F•cu ft/min
for 15°F temp rise you need about 10000 cu ft/min through the radiator.
If you have a thermometer you can measure the temperature across the radiator and get a better approximation of how much airflow you'll need. An
electric fan capable of blowing 10000 cfm through a radiator takes a bit of power. If your aero drag at cruise is 12 hp and the fan needs 1.5 hp, then your front end radiator must represent more than 12.5% of aerodynamic drag for there to be a benefit in moving the radiator.
But you are planning on moving the A/C condenser and using an electric compressor, so you'll need air flow for that anyway. You'll have plenty of electrical power (I assume) so you could remove all the original A/C stuff and build ducting for a
portable or window type room A/C in the trunk and plug it into an inverter. So I'm thinking the same as you, why not move the radiator too? You won't win or lose much mpg, but I think it is wonderful and crazy.
-mort