Here's the setup. Oil cooler mounted at the front of the car. A/C condenser mounted on the trunk floor. Fan mounted on top of the condenser. Air flows in through the oil cooler and out through the condenser. Do I need a puller or a pusher fan? My guess would be pusher, but I really don't know the difference. Help? Thanks!

You need a pusher, because the fan is pushing air through the thing it is mounted to.

sounds like you need a pusher....pushers are more efficient than pullers too (better to blow than to suck?)

QUOTE (goose2 @ Dec 15 2005, 03:16 PM)

sounds like you need a pusher....pushers are more efficient than pullers too (better to blow than to suck?)

Puller fans are about 15% more efficient than pusher fans in a typical automotive setup.

You need a pusher for what you are doing, though.

I would be concerned with preheating the air going into the condenser, you could see some really high pressures with everything hot and limited airflow such as in traffic.

QUOTE

Puller fans are about 15% more efficient than pusher fans in a typical automotive setup.

That's news to me...a friend recently installed some fans on a hotrod and the documentation that was packaged with them specifically said that they would be more effective as a pusher. Perhaps it depends somewhat on the application, shrouding, and the blade configuration? Also my (admitedly ancient) primary experience with fans has been in the HVAC field, so I'll defer to your expertise.

QUOTE (James Adams @ Dec 15 2005, 12:40 PM)

QUOTE (goose2 @ Dec 15 2005, 03:16 PM) sounds like you need a pusher....pushers are more efficient than pullers too (better to blow than to suck?) Puller fans are about 15% more efficient than pusher fans in a typical automotive setup. You need a pusher for what you are doing, though. I would be concerned with preheating the air going into the condenser, you could see some really high pressures with everything hot and limited airflow such as in traffic.

I planned on having a very large condenser and a very large fan. Probably going with a 16" fan at least. Still worrysome? I have absolutely no idea how hot condensers get or any idea how hot air coming off a hot oil cooler is. I realize an oil cooler is probably at 200-215 degrees, but the air isn't going to collect all that heat, so what's the realistic temp?

911s ran a fairly small condenser mounted in the fender, sideways with only a fan moving air through it. Seems like a condenser that's triple the size would be a little less stressed.

QUOTE (McMark @ Dec 15 2005, 04:28 PM)

I planned on having a very large condenser and a very large fan. Probably going with a 16" fan at least. Still worrysome? I have absolutely no idea how hot condensers get or any idea how hot air coming off a hot oil cooler is. I realize an oil cooler is probably at 200-215 degrees, but the air isn't going to collect all that heat, so what's the realistic temp? 911s ran a fairly small condenser mounted in the fender, sideways with only a fan moving air through it. Seems like a condenser that's triple the size would be a little less stressed.

It's worrysome to put any hot air in front of the condenser, especially with the limited space and airflow. A 16" electric fan is not "big" in the world of good AC with 134a refrigerant.

The 911 oil cooler was in the fender with a small fan (Carrera), but the AC condenser was across the front and exposed to cool air, and combined with a second condenser over the engine the 911 still had crappy AC.

If you are running it in Norcal you may not have the heat load that I have experience with living in Florida and Texas, so it may work out OK.

Now I have to see if I can come up with a better design. If not I'll do it and see what happens.

It's not that the condensor gets hot, it's that you're trying to cool the vapor as much as possible to (hold on to your hamburger) condense it. So by putting pre-heated air through it you might really be compromising the effectiveness of the A/C system. That's why in "normal" cars the condensor is always in front of the radiator.

Goose, some fans are made as pushers, some as pullers, and some as both (with slightly less efficiency). Your friend's might have been one of the latter kind so that his particular fan was more efficient as a pusher.