The first thing most people do when upgrading their car is to remove the Air Pump and throw on some under drive pulleys. The problem with this is now the contact patch on the water pump pulley is greatly reduced and most find that they can turn it with their fingers even with the belt tightened above stock tension. What most people then do is over tighten the belt to stop the slipping.
The rotary engine uses hydrodynamic journal bearings to support the eccentric shaft. The way it works is by flowing oil under pressure between the bearing surface and the shaft and basically “floating” the shaft through the fluid dynamic effect. Increasing the lateral load to one side on the shaft reduces how well the journal bearing can do its job of “floating” the shaft and results is metal on metal contact and accelerated wear. Over tightening the belt creates just this type of lateral load.
Pictured below is just one example of excessive bearing wear caused by running under drive pulleys without the air pump and over tightening the belt to compensate. The first picture is of the front bearing on two motors with a similar history. Both ran Mobil 1 10w30 most of their life and were autocrossed. The 99,800 mile motor stayed in stock form until it met its end due to a water jacket o-ring failure. The 66,000 mile motor had the air pump removed and under drive pulleys install around 53,000 miles. It also met its end to a water jacket o-ring failure.
The front stationary gears are in their correct orientation so what you are looking at is the top of the bearing as it sits in the motor. The copper color area is the wear.
The next image is of the rear stationary gear bearing. The picture is upside down to the way it installs in the motor so you are looking at the bottom of the bearing surface.
Close up of rear bearing wear:
As you can see the bearing wear is exceptionally worse on the 66,000 mile motor and the wear pattern on the bearing clearly shows the extra load applied by the lack of an air pump or idler in its place is the cause.
The only solution is to keep the air pump or replace it with an idler pulley. Currently there are three companies that have a solution available now or in the near future. They are:
Pineapple Racing: $179.00 + shipping
Requires removing two bolts out of the water pump housing to install.
Tweakit Racing: $142.00 shipped
Bolts to Air Pump stock mounting points
Garfinkle Motor Works: Will be released soon. Price to be determined, but estimated below $200
Bolts to Air Pump stock mounting points
