mark kibort

pusher fans dont work that well. they naturally stall the air that they are pushig into the radiator. at speed they can work better, and certainly work better with pulller fans on the other side. (direcly on the other side) is there room for puller fans on the other side? that will work much better.

Cosmo Kramer

The OP has four 8" pullers and no pusher right now.

James Bailey

If Porsche had known that you could block off 20% of the back side of the radiator, add a blower which increases the drag on the engine and bump horespower significantly.......They would have made the radiator SMALLER ! Much as Ferry Porsche commented about the 911 engine when someone asked what he thought about that engine growing from a 2 iter to a three liter....He replied we should have made it smaller.

Point is the radiator was designed to be big enough for the job intended and removing the schroud means that the puller fans ONLY cool the area which they cover...The race cars which do not run A/C and the condensor which limits air flow do O K . Also worth mentioning the shift to the air to oil coolers as of the GT/1990 cars which reduces the load on the radiator.
About 1/3 of the energy used in making horsepower ends up as heat in the cooling system anytime you increase horepower or use more horsepower it must dissapate more heat.

dprantl

A pusher fan cannot be efficient with a shroud. The fan blades push the air in a general direction, not directly where you want it to go. This is why they are best when they are touching the heat exchanger, so that the air has nowhere else to go except throught the fins. If the fan were further away with a shroud, it would push the air and while the air would eventually go through the heat exchanger, it would first create a bunch of turbulence especially as you get further away from the blades. A puller fan is much more efficient because it creates a zone of low pressure in front of it... it doesn't really matter much that the air after it is blown straight or at an angle as long as it goes away from the fan.

Dan
'91 928GT S/C 475hp/460lb.ft

Z

The Murf stage-3 kits come with the pusher fan, but it's an option on the stage-1 kits.

There are a number of things that can contribute to a car running warm. Most of them apply to all cars, not just the supercharged ones. A system that's not operating as well as it could be might not be as apparent on a stock car as it is on a supercharged one though.

Personally, I'd suggest using one of the 75C thermostats and some WaterWetter in the supercharged cars, whether they're running warm on the gauge or not.

Assuming that the temperature gauge is accurate, some of the things that can contribute to warm running include:

Debris blocking the radiator. A lot of stuff can build up between the A/C condenser and radiator not really be that noticable if you're not looking for it.

Not having the aluminum air dam that's included with the supercharger kits installed on top of the radiator. It doesn't do much good if you drill a bunch of big holes in it either, like I saw was done on one car that did have it installed.

The sides of the radiator having openings that allow air to flow around it, instead of through it.

All of the fans that are supplied with the supercharger kits not turning in the correct direction, due to the wiring polarity being reversed on one or more of them.

Some people like it, and some don't, but there has been some testing done that shows the motorized air flap system that came on some model year cars increases underhood temperatures, even when it's working correctly, or the flaps have been permanently locked fully open.

Part of the spoiler/air directing system at the front of the car blocking the air inlet at speed. It may look fine when the car's stopped, but move at speed if damaged or not installed correctly.

The water pump impeller slipping.

Excess clearance between the water pump impeller and block, either from variance in manufacturing tolerances, or impeller to block contact having occured at some time.

A bad thermostat.

A bad seal behind the thermostat.

The radiator cap or some other cooling system component not holding the correct pressure.

An incorrect water to coolant ratio.

Not having the belly pan installed.

The inside of the radiator being partially clogged.

The effect of things like those on the engine temperature are cumulative. The more things that aren't working as well as they could be, the sooner the limits of the cooling system as it is will be reached, resulting in warmer engine temperatures. The outside temperatures that some of you guys have been seeing this summer sure wouldn't help the situation either.

Even if everything's not working as well as it should be, increasing the efficiency of even one part of the cooling system might be enough to raise it's capacity to the point where cooler engine temperatures can be obtained. I'd expect shroud's on the puller fans to help increase potential cooling system capacity to at least some extent. Whether it would be enough to make a significant difference on any particular car that's currently running warm is the question.

vinyl_tien

Hi SQLGuy
I have a theory about push fan, Push and pull fan too close will make air flow stop(or one fan work slow) ,if there any possible left push fan from Radiator a few distance(1~2 cm), that might help pull fan to pull more air, can you try that?

dr bob

Pusher fans are a marginal benefit except when the car otherwise has no airflow. Minus a shroud that's in firm sealed contact with the radiator, a large portion of the fan-moved air spills out the edges. The fan blades themselves can/need to be away from the radiator a little, but the circular shroud needs to be sealed to the radiator with soft weatherstrip or similar. This is what Dan is saying above.

Moving the radiator forward an inch or two would be ideal, leaving enough room for a full-coverage rear shroud that would funnel all air through a fan or fans. The Taurus two-speed fan setup is a nice package if it can be fit in front of the compressor, but the fan isn't in the right place for them to fit in there together.

If it were my car, I'd be shopping for a new radiator that's a little shorter top to bottom, thicker if possible, and with mounting flanges that would allow it to sit further forward at least at the bottom. The air seal at the top needs to be maintained with the hood, on the sides with the existing radiator sheet, so all the air passes through. Focus would be on getting an adequate rear fan installed with shroud, with no front fans at all.

SQLGuy

Not quite. I have four pullers (not sure of size, but now thinking 7" or so), and two 9" pushers. My original statement that they were 11" was incorrect. They are Zirgo ZFB9's.

SQLGuy

I'm not sure about that. The way I read Dan's comments was that a pusher would never work well with a shroud, period. I was planning on a sealed shroud to allow some gap between the hub and condenser.

On the other hand, these pushers are reversible, so they are not neccessarily designed to be optimum as-is as pushers. I tried calling Zirgo to get their opinion, but was on hold quite a while and didn't have time to wait longer. I'll try to call them again later in the week. I also looked at factory pusher fans on some current model cars and did not see the blades (or, especially, the hub) being right against the condenser... they had a bit of space.

SQLGuy

Good spec, but I am talking about simply not being able to keep the car cool enough sitting in traffic and probably making less than 100 HP, not racing, auto crossing, or anything like that. In other words, I don't think I'm running into an issue where the extra HP of the engine is overloading the cooling system, I think I'm running into an issue, where the reduced effectiveness of the cooling system is being felt even before getting above the stock HP level.

dprantl

There must be some safety clearance between the fan and the condenser. Everything has a manufacturing tolerance and you don't want the fan rubbing through the condenser tubes. IMO a pusher fan with a shroud would be worse than having multiple pusher fans as close as possible to the heat exchanger covering the same area as the shroud.

Dan
'91 928GT S/C 475hp/460lb.ft

David L. Lutz

+1, No difference here in Texas than when I lived in Florida. We are running +60 days now at +100 degrees.

I have tried every combination of fans mentioned here with the same result. Engine runs too hot in traffic with AC on. With AC off, no problems.

Currently I am using waterwetter, 16" Ultra Zirgo fan as pusher, new rad., etc.etc.

I have not tried a shroud around the 4 puller fans. Makes sense, Sounds like it might help.

vinyl_tien

Have any one try small pully for water pump, let it pump more faster?

Landseer

I have a normally aspirated 85 32V car.

It needed a viscous fan recharge + removal of an ancient radar detector sensor.
Improvement, but still ran much hotter than an identical car here.

Turned out it was lean.
Lean because of partially blocked injectors.

I replaced them and the cooling issue went away immediately.
A lesson for me.

May not apply to your special setup, but I haven't seen this mentioned before as a potential cause and feel certain it caused excessive heat on this 85.

SQLGuy

Mine runs pretty close to stoich through most of the range, but is very rich open loop... to the point that it blows a nice black cloud when I hit the throttle hard. Run's 10:1 or richer during warmup. Definitely no lack of fuel from the 42lb/hr injectors.

Thanks, though.

Paul