"Another problem Toyo Kogyo experienced that had been seen at NSU was the formation of cracks in the rotor housing around the sparkplug holes. It was determined that they were a result of "thermal shock" or sudden thermal loads placed on the housing when it was taken from a relatively cool temperature and sharply accelerated to 7,000rpm in all gears on a road test. By developing a test bed procedure that could consistently reproduce these conditions, engineers could then do systematic studies on cooling system improvements and their effect at relieving thermal loads. Tests were showing that on cars driven hard immediately after startup, the temperature of the inner wall of the rotor housing reached 450*F within one minute of startup. This abuse consistently produced cracks in the housing around the sparkplug opening after 4000 cycles.
Improvements in the cooling system brought the maximum temperatures of the rotor housing trochodial wall to below 410*F. But the final improvement was the redesign of the housing itself. The bosses for the tension bolts which held the engine together were relieved from the inner wall of the housing, thereby relieving part of the mechanical restrictions on the part that gets the hottest. Repeated testing after this improvement produced no more cracks in the housing."
Phoenix7, I would love to read this early research. Even though it is non turbo in its scope.
So this was back in the 70s. They've made the improvements on the engine since then to further reduce this problem.
You lost an apex seal in the rear housing and I'm under the impression that the rear rotors tend to blow due to heat/preignition (cooling problems you're addressing) but it sounds like you may have also over-boosted and caused the sidehousing damage?
Actually my rear housing was a RE type which didn't have the latest 3rd gen cooling mod, which contributed to the failure I'm sure.
Are you monitoring exhaust temps?
Yes, front and rear.
Are you going to do the cooling mod and the pump at the same time of will you try the pump first and see if the damage occurs again?
Both
How did you lose the motor (under boost/load)?
Merging into 70mph traffic.
What are your mods?
RE 13B, ITO large street port, TO4S, HKS cast divided, 50/50 AI
Do you have close up pics of the sparkplug holes?
Yes, but they are not the best.
It's cool that you're documenting and finding things like this. Thanks.