Kurt Robertson Enterprises
Kurt Robertson Enterprises
Wankels' to Offenhausers'
Here is what happens in my rotary builds.
The most expensive part of our rebuild is a decent rebuild kit. Our total parts investment averages between $1000.00 and $1500 (1300-1700 RX8) depending on model, availability and year.
We install Atkins Rotary Engines (ARE) apex seals, ARE apex springs, ARE apex corner pieces, OEM turbo corner springs, ARE corner seals, OEM Oil seal set, ARE Oil seal Vitons, ARE water seal set, ARE side seal set and OEM side seal springs. The Atkins have put their names behind their products, along with 40 years of development and excellent service
Metallurgy and design of the apex seals manufactured by Atkins give our engines an excellent combination of exacting tolerances, durability, ductility, hardness, longer corner piece design, yet soft enough to quickly seat into the housings.
During the rebuilding process we press and red loctite new Mazda OEM three to eight window main bearings and deep grooved rotor bearings thru the entire rotating assembly. We raise the oil pressure internally, many builders call these things an upgrade- I call it rebuilt
Engines components undergo magnaflux, Zyglo and Dye penetrant on critical areas after our extensive visual and micrometer inspection and dimensioning. End play spacers are then chosen to give engines a overall clearance of .0020.
Rotor housings are checked for shrinkage, chrome flake and cracking before sent to sandblast. The inner chambers are sealed with a steel sandwich plate and spark plugs before the water jackets , exhaust port and exterior are blasted back to their original aluminum casting. Housings are then re inspected, water washed, sealed and prepared for final assembly.
Currently we are only reusing side plates found with acceptable stepping wear. We are in the process of pursuing a lapping machine which will enable us to bring back to life hundreds of side plates that were beyond tolerance, many of these plates have several hundred hours of porting on them and have been "moth balled" until now. We are excited about putting these housings back in service after lapping and have had dialogue with local heat treating facilities about re Nitrite processing.
The Atkins corner seals are no longer an upgrade for our rebuilds, they are standard equipment in every build. I have found that the durability and sealing qualities far surpass Mazda OEM seal configurations of all years
As far as porting if you can accurately run a die grinder you can port. Every engine ever built will get opened at one time or another and can be copied, or learned from. I have opened hundreds of engines, ones from every builder west of the mississippi since 1980 . Really a good way to determine port design is based on two basics, fuel economy restrictions and intended usage. A stock engine will get 17-24 mpg, a ported engine will get 10-31 mpg. Mazda produced many port designs to bolster fuel economyand it had detrimental effects on performance.
Often a ported rotary will simply be an attempt to copy a Turbo II or RX4 3B
A THOUSAND ENGINES have been ported by myself since 1980 and some vehicles had some very admirable times. During the 80s and 90s I wasn't the most technical, just accurate in operating a horizontal mill and die grinder.
Back in 1979, RX-7 only meant that there were six other models with six times as many rotaries running around Portland.
Stark & Norris machine shop in downtown Portland was surfacing side housings for wagons and four doors at an amazing rate and bridgeporting some of them for anyone who had $30 to spend on a side plate (120 dollars for a full set of bridgeported sides) could go bridge
Really porting of a rotary engine is not rocket science as some "marketeers " would like you to think and as far as "overporting" this is also misleading as Mazda "overported" their own configurations during the 60's and 70's with remarkable success.
Between myself, my other rebuilder and our consultant, we have accumulated over 90 years of building engines in the Northwest and produced over 4000 engines. I recently (2012) had an 1981 Tearported RX7 come in for a rebuild that I built an engine for in 1992- brought back a 20 year old memory!