Thinking about electric puller fans on a radiator, there's a choice of a single 16" fan or twin 11" fans arranged diagonally. The single 16" fan has about 5% more swept area if you don't consider the hub, and is rated at 25% more CFM. The single 16" fan is the better choice on that basis but twin 11" fans are interesting because one can be closer to the coolant inlet and the other closer to the coolant outlet. Are twin 11" fans somehow more efficient despite the disadvantage on paper?

Thanks,
Sixto
87 300D

How about this, Sixto:

If both fan designs have the same failure rate then 2 fans will be less likely to leave you stranded.

But 2 fans are twice as noisy.

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1985 380SE Blue/Blue - 230,000 miles
2012 Subaru Forester 5-speed
2005 Toyota Sienna
2004 Chrysler Sebring convertible
1999 Toyota Tacoma

The 16 will outperform the 11s with a shroud. No E fan is considered a primary fan without a shroud.

My W124 2.5T has a normal primary fan, but there are two smaller aux fans up front. The aux fans have a shroud too. All the older ones have a single large fan. The A/C cools great in that car. The CDI only has an electric fan, it is as large in diameter as the normal mechanical fans, but it is thinner. It does have a shroud as well.

Not sure what this all means... just giving you some data points.

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John Robbins
'05 E320 CDI - 240k
'87 300TD - 318k