Back in the spring of 2007 about 03/26/2007 I had an idea that we might be able to weld a SS tube to the steel liner in the rotor housing. Prior to that we had a lot of trouble with the bonded in p-port tubes leaking cooling water into the combustion chamber. This resulted in a rather involved procedure for bonding in the tubes. I then asked this question on the newsletter. Has anybody tried, or can you try, tig welding SS to a chrome bumper? I figured the aluminum was not going to get that hot if we TIG welded the thin SS tube to the hard steel liner. Also one can skip weld. Weld four spots at 0 90 180 and 270 and let cool. Then weld the rest. We don't need to weld to the aluminum at all. JB Weld will handle the rest of it. I suspect that was better than heating the whole works and trying to solder or braze. This was just an experiment anyway. Not necessary for making p-ports.
I drove out to Sun & Fun that year and stopped at Mark Steitle's hangar in San Antonio Texas and he had actually tried it on a junk rotor housing. Here are some pictures of his fine welding job.
The question was; would there be any effect on the metallurgy of the liner due to the heating during the welding process that could adversely affect the apex seal sealing and or wear? I could not detect any by visual inspection. The apex seals cannot seal, or need to seal, in this area anyway as they are wide open on both sides as they pass over the intake port. That is why the differential pressure from chamber to chamber is zero in this area. Tig welding is a very localized heating process. Obviously the steel must be heated to melting temperature but a few hundreds of an inch away the aluminum is not melted. This process flies in the face of intuition. The metal has a worse time of it down by the peripheral exhaust ports where the heat can be 1800 F for thousands of hours.
I selected another junk rotor housing and bored another two inch hole. I then had my machinist friend Jim Poole cut away the aluminum back about 1/4 inch all the way around by hand. It was not easy and not very cosmetic. We did not have an NC mill and that is what it would take to do this job in a cosmetic manner.
Never the less I had a welder tig weld in a SS tube. I could see no improvement or advantage to cutting away the aluminum.
Now the time came to actually build a p-port engine and try it. I needed a p-port RX8 engine for testing so I bought one out of a junk yard that had been in a crash. It had a cracked front end housing in a non critical area but Larry Childs did a good job of welding that up. We bored the RX8 engine rotor housings and I had a welder weld in the SS p-port tubes. We did not removes any aluminum from around the holes as I deemed that unnecessary. John at Mazdatrix filled in the rest of the water jacket around the tubes with JB weld and Kyle reassembled the engine using as many of the original seals as possible as they were hardly worn.
We had some problems getting the JB Weld to seal the outer housings on the early P-port engines so we came up with a new, more reliable way of sealing the housings. The idea is to use a bolt on plate that can be sealed with red RTV good to 500 degrees F. The outer part of the housing is prepared to fit the plate with a die grinder. The plate is screwed to the rotor housing before the two inch hole is bored. Screw holes and screws not shown yet. The plate is available for purchase.
Here are some pictures of the p-port RX8 engine parts and the completed engine on the Mazdatrix dyno. (Another story.)
So far we have made many hard runs on the dyno with no problems and no water leaks.
Paul Lamar 11/21/2007