Kim

Ok so today I bought a racecar, nice car and so on but that not what this thread is about.



With it came an extra disassembled 13BPP motor, salvageable except from one rotorhousing which had a nice crack in it.

Im interested in what could have caused that crack and any info on those housings as they look MFR



Bad housing

http://www.wankelkim.net/rx7/fb/pp13b%20(2).JPG



Good housing

http://www.wankelkim.net/rx7/fb/pp13b%20(7).JPG



check the car out

http://www.wankelkim.net/rx7/fb



Thanks in advance



Kim K. Nielsen

DJ Rotor

My vote is for detonation.

theflatlander

was the sparkplug over tightened?

BLUE TII

My guess is a thermal stress crack.



You get boiling at the hottest part of the waterjacket and then NEAR ZERO heat from that hot spot is transfered to the coolant as the air on the metal surface from the boiling does not transfer heat well. The localized hot spot gets hotter at a much faster rate than it can dissipate the heat to the surrounding metal and you get a thermal crack.



Underdrive waterpump is good to stop cavitation, 6-rib belt conversion is good to stop waterpump pulley from slipping, Evans NPG+ coolant is good since it has a higher boiling point to help stop the localized hot spot and you can run it zero presssure which sure is nice if you have an epoxied P-port or water seal intrusive bridgeport as a small leak will not shoot pressurized coolant into the engine.

j9fd3s

ive seen that around the trailing plug holes on the turbo cars, they need to be beaten a LOT to do it though.

Lynn E. Hanover

It looks to me like local overheating, and the engine was run for some time in that condition. 12A Pports often do this around the trailing plug hole, but not to the extent I see here.



Detonation would take out the apex seals and gouge the hell out of the housing, but not crack it. Auminum looses strength fast as temperature goes up. There was no coolant on the back side of this failure.



Use distilled water. Use a 22-24 pound pressure cap, and add a test port and a gage to be sure it holds 22-24 pounds. Don't slow the pump down. Use a restrictor to prevent cavitation.

If you cannot hold 180 degrees during a race, add more radiator. Same for oil temps. Nothing over 180. The oil temp controls rotor face temps, and hot rotors cost HP, and in a turbo engine lead to detonation.



Jet for 1575 WOT EGTs. No more problems.



No overheating problems since 1980. (that was a chunk of the track going through the radiator).



Lynn E. Hanover

j9fd3s

lol we thought about building a car for a buddy and since it would have been in the back (ahem driver) we were just gonna fill the thing with useless guages, like cabin pressure, battery temp etc etc, and one of them was radiator pressure! its not a bad idea though, we've noticed that the normal sized stant caps are totally inconsitent, about 1 in 5 hold the rated pressure out of the box....



what happens if you lower the oil temps a little further?

Kim

I read somewhere else that its possible to rechrome the housings.

Is there any chance at all that this housing could be repaired and rechromed?

HeffSpooled

Sure they can be recoated, but that one has a structural integrity problem. I doubt it can be fixed.



http://www.jhbperformance.com/products/rotorhousing.php

Kim

I was afraid of that



Guess it time to find some guineapig housings to try my own PP skills