Radiator shroud question

I was reading on another forum and this quote was posted in a sticky.

I don't see how this is true. Are they talking about when the fan is on? Because if that's what they mean, I see what they are saying... but if they are saying that is true with the radiator fans off, I'm not sure how that's possible.

Fans must be installed with a shroud that completely covers the back of the surface of the radiator. Otherwise, at low speeds, the only air movement through the radiator will be the surface area of the fans. Depending on the type of fan, you can lose 40-60% efficiency of your cooling system.

I think they mean with the fans on... if the shroud isn't tight, the fans have no effect on the area not directly in front of them.

Yup, I've solved lots of overheating problems by installing a factory shroud and clutch fan after someone "upgraded" to an electric fan and ditched the shroud.

A cookie sheet makes a dandy budget shroud.

Shawn

odd.. my fiats and my saab do not have shrouds around their cooling fans. The Fiat has a single (small) cooling fan that just hangs behind the radiator and the Saab has a pair of cooling fans that more of less cover most of the radiator.

Neither has had problems with overheating

Spitfires have no true shrouds and I suspect are the main culprit with thier chronic overheating.

mad_machine wrote: odd.. my fiats and my saab do not have shrouds around their cooling fans. The Fiat has a single (small) cooling fan that just hangs behind the radiator and the Saab has a pair of cooling fans that more of less cover most of the radiator. Neither has had problems with overheating

Less displacement, more radiator.

It's usually V8's that I've sen problems with. I don't think my wife's corolla would overheat if I tried.

Shawn

spitfirebill wrote: Spitfires have no true shrouds and I suspect are the main culprit with thier chronic overheating.

The late ones with electric fans do.

Personally, I think most of the overheating problems they have these days is due to neglected and therefore crudded up radiators. I've fixed quite a few of them with nothing but a radiator swap.

They were not known for overheating back in their days, back when the radiators were relatively new. It's only now, many years later, that they've picked up the reputation for overheating. Owners are very resistant to replacing a radiator that looks good, no matter how clearly the overheating symptoms point to a radiator problem.

foxtrapper wrote:

spitfirebill wrote: Spitfires have no true shrouds and I suspect are the main culprit with thier chronic overheating.

The late ones with electric fans do.

That's only a shroud around the blades (at least on mine) . Better than nothing, but not much.

And you may be right on replacing the radiator. The engine in my 64 was redone and any crud cleaned out. I took the radiator to a shop to have it boiled out, but it still runs hot in the summer in stop and go traffic. I'm not sure the radiator shop did much other than take my money.

Fans are needed at high speed too - most people think that if you're driving at 80 mph, you have an 80 mph breeze through the radiator. Not even close! Heck, even NASCAR cars run fans.

We did some cooling testing on our dyno a while back, developing a new fan setup. The shroud/no shroud testing is pretty telling.

http://www.flyinmiata.com/tech/fans.php

Radiator Shroud Flaps, anyone?

As seen on VW Corrados, E39 M5 AC fan shrouds and Flyin' Miata fan shrouds!