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Could be running too lean also. Main circuit.

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See my original post....its anything but lean at cruise...pretty fat...

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fan is worthless after 25 to 30 mph....natural air flow takes over....sounds like the car is lean as it "should" be its coolest when running down the road or the waterpump (high volume?) is pumping water too fast that it doesn't cool properly at highway speeds

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thats a myth

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so a fan pulls more air than natural airflow at 55 mph....I think NOT

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Terzmo, there are some things you're not considering.
Air flow at 55 mph isn't like sticking your hand out the window. The grille stops a bit of that air flow. The radiator stops a BUNCH of that air flow. Yes, it's designed to pass air but it is also designed to get in the way of the air so there is enough contact with the radiator fins and tubes to strip the heat.
There is far less air flow behind a radiator than you would think.
A factory style electric fan will move quite a bit of air. If that fan is used on a car that has a much larger grill opening than it was designed for the shroud will block air.
He is using a fan set from a Concorde.
Here's a Concorde:



See that large grille opening? Guess what? Most of it is blocked by a big fat bumper bar and foam energy absorber. There is relatively little open area. How do I know? I OWN a 2002 Concorde.
The air not only has to pass through a restrictive radiator but it also has to go through an equally restrictive A/C condenser.

When you blow on a radiator (vehicle speed) the air will stack up in front of the radiator and some will spill out through other openings or even push it's way back out around the grille and go over the body of the car. Having a tight fan shroud will only make it worse since that adds even more restriction.
If you get a strong enough fan it will be able to pull the air through the radiator.

Here's a test. Take a plastic or paper cup. Poke a few small (under 1/4") holes in the bottom. Turn your bath tub water on wide open. Stick the cup under the flow and see what happens.
If the cup can't flow enough water the excess will fill the cup and spill over the sides.
The same thing happens with air.

You must match the fan power, shroud size, and grille opening.

I've been going down the electric fan road for 13 years. 11 of those years had a monster heat generating twin turbo setup.

Chances are that his fan shroud is simply too tight for the air flow he's getting. A couple trap doors in the flat parts of that shroud would probably relieve the issue.

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fan is worthless after 25 to 30 mph....natural air flow takes over....sounds like the car is lean as it "should" be its coolest when running down the road or the waterpump (high volume?) is pumping water too fast that it doesn't cool properly at highway speeds

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thats a myth

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so a fan pulls more air than natural airflow at 55 mph....I think NOT

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Terzmo, there are some things you're not considering.
Air flow at 55 mph isn't like sticking your hand out the window. The grille stops a bit of that air flow. The radiator stops a BUNCH of that air flow. Yes, it's designed to pass air but it is also designed to get in the way of the air so there is enough contact with the radiator fins and tubes to strip the heat.
There is far less air flow behind a radiator than you would think.
A factory style electric fan will move quite a bit of air. If that fan is used on a car that has a much larger grill opening than it was designed for the shroud will block air.
He is using a fan set from a Concorde.
Here's a Concorde:



See that large grille opening? Guess what? Most of it is blocked by a big fat bumper bar and foam energy absorber. There is relatively little open area. How do I know? I OWN a 2002 Concorde.
The air not only has to pass through a restrictive radiator but it also has to go through an equally restrictive A/C condenser.

When you blow on a radiator (vehicle speed) the air will stack up in front of the radiator and some will spill out through other openings or even push it's way back out around the grille and go over the body of the car. Having a tight fan shroud will only make it worse since that adds even more restriction.
If you get a strong enough fan it will be able to pull the air through the radiator.

Here's a test. Take a plastic or paper cup. Poke a few small (under 1/4") holes in the bottom. Turn your bath tub water on wide open. Stick the cup under the flow and see what happens.
If the cup can't flow enough water the excess will fill the cup and spill over the sides.
The same thing happens with air.

You must match the fan power, shroud size, and grille opening.

I've been going down the electric fan road for 13 years. 11 of those years had a monster heat generating twin turbo setup.

Chances are that his fan shroud is simply too tight for the air flow he's getting. A couple trap doors in the flat parts of that shroud would probably relieve the issue.

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fan is worthless after 25 to 30 mph....natural air flow takes over....sounds like the car is lean as it "should" be its coolest when running down the road or the waterpump (high volume?) is pumping water too fast that it doesn't cool properly at highway speeds

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thats a myth

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so a fan pulls more air than natural airflow at 55 mph....I think NOT

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Not THAT part! This Part:
"or the waterpump (high volume?) is pumping water too fast that it doesn't cool properly at highway speeds

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Not THAT part! This Part:
"or the waterpump (high volume?) is pumping water too fast that it doesn't cool properly at highway speeds

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Some people still believe that you can "pump water so fast through the radiator it doesn't have time to cool". That is just flat wrong.

However - it IS possible to spin the water pump too fast, (such as using a non-a/c pump with an a/c pulley) which can result in cavitation at highway speeds. So it's actually pumping less water than normal despite the higher RPM, which could result in a cooling problem...

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so clutch fans are useless also....

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A quick fix would be to cut some holes in flat areas of the shroud. Cover them with flaps of rubber or hinged plastic hanging from the back of the shroud above the hole.
At low speed the fans will draw the flaps closed.
At high speed the air trapped behind the shroud will escape through the shroud.

I had the same problem when I was running the Maxima fans on the hot rod. Adding the flaps helped cool it down on the highway and did not change the low speed cooling.

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Some later model cars have these holes and flaps from the factory.

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God am I glad all my old O.E.M. stuff works like it did when new and that old bird won't go over 190* under any circumstances.!!

You want restriction here is my grille.

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which direction are your fans blowing?

if they are blowing forward wouldn't this block any outside air from passing through the rad?

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I may be nuts, but dont most fans pull air? Dont think Ive ever seen a fan push air?

Im sure somebody uses a pusher?

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My Becool 1000hp rated radiator/dual fan module has no shroud (this was a surprise to me when I purchased it) whereas the lower rated Becool modules do have a shroud. So obviously the effect of a fan shroud is more complicated than what most of us seem to believe, which is that a shrouded fan cools better than an unshrouded one.

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