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Porsche 911-930 Evaporator Blower Motor Comparison Test

Porsche 911-930 Kuehl Evaporator Motor

Here is a comparative test of the Porsche 911-930 Kuehl Evaporator Motor air velocities between the 2 styles, or configurations, of the Behr brand Porsche 911-930 Evaporator Box using the stock Bosch blower motor vs. the Kuehl Wirbelsturm (Hurricane) Evaporator Blower Motor.

First

We tested the 2 versions of the stock 911-930 Behr brand evaporator boxes. Their configurations can be best described as Pre 86 and Post 85.

A) The Pre 86 version was introduced around 1970 in 911’s and was used up through 1985. It was also used in the 930 or turbo up through 1985 as well. This box has a rather flat ½” high dimple on the top of the evaporator box. Inside the Bosch blower motor is mounted with its shaft upward and uses a metal blower wheel.

Porsche 911-930 Kuehl Evaporator Motor

B) The Post 85 version was introduced in 1986, for both 911 and 930 models. This box has has 2″ high hump on the top of the evaporator box. Inside the Bosch blower motor is mounted with its shaft downward and uses a plastic blower wheel.

Porsche 911-930 Kuehl Evaporator Motor

Second

We tested the Kuehl Wirbelsturm (Hurricane) Evaporator Blower motor installed in the Pre 86 box top using the metal blower wheel. Because of the shallow height of the Post 85 box version the Kuehl motor cannot fit in it, hence if you wish to upgrade your evaporator box to a high output unit you can do so by sourcing a used Pre 86 box top with its metal blower wheel and installing the Kuehl motor into it.

For our comparison tests we secured the bottom section of the evaporator box on a work bench; rubber vibration mounts were placed between box and the table top. In front of the evaporator box’s air outlet we positioned an anemometer at fixed position (height, distance and orientation) on a tripod. All of the evaporator blower motors were powered using a regulated power supply at a fixed voltage with an analog amp meter in line. The anemometer was set to take average air velocity readings in feet per minute every 10 seconds. After each unit was allowed to run for a minimum of 10 minutes we then recorded the our readings noted further below.

Porsche 911-930 Kuehl Evaporator Motor

Test Results

ModelFeet Per Minute (fpm) 
Pre 862,240
Post 852,600
Kuehl3,300

Porsche 911-930 Kuehl Evaporator Motor

Summary of Results

  1. The Post 85 Evaporator blower produced 360 fpm or 16% more velocity than the earlier Pre 86 model. Since both verisons of the Behr boxes we tested used the identical Bosch motor we will assume that the increase in velocity is likely related to the plastic blower motor wheel vs. older style metal blower wheel.
  2. The Kuehl blower motor produced 1160 fpm or 52% more velocity than the earlier Pre 86 model, and 700 fpm or 31% more velocity than the later Post 85 model.

Notes

  • If you wish to upgrade your 1970-1985 (Pre 86) Behr evaporator box’s air flow for greater velocity all you need is a Kuehl Wirbelsturm (Hurricane) Evaporator Blower Motor.
  • If you wish to upgrade your 1986-1989 (Post 85) Behr evaporator box’s air flow for greater velocity all you need is a 1970 through 1985 (Pre 86) Box top having inside the metal blower wheel and the motor platform, plus a new Kuehl blower motor.
  • You cannot adapt the 1986-1986 (Post 85) plastic blower wheel into a 1970-1985 (Pre 86) Behr box. And, you cannot adapt a a 1986-1986 (Post 85) plastic blower wheel onto a Kuehl blower motor.
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