As discussed on the SJ Plenum page because of the air pressure at the throttle body entrance on the lower deck is greater than the upper deck where the injectors are causing some fuel to actually spray out of the injectors onto the cylinders. A number of us found slight blue markings on the cylinder fins from this phenomenon. To solve this the only solution was to equalize the pressure between the two locations. This is a common issue on turbo charged airplanes with the solution being what are known as Turbo Nozzles that go around each cylinder injector and are pressurized with the same ram air that flows into the throttle body to essentially equalize the pressures top & bottom. I opted to not purchase Turbo Rails that each feed a bank of three Turbo Nozzles as I felt a single manifold made for more even pressure distribution and reduced costs significantly. The system added weight & complexity to the upper deck however the positive effects were immediately noticeable and significant. The first time I tried LOP operations the engine ran EXTREMELY rough at 13.8 GPH. So rough that it felt like the engine was going to quit. After installing the turbo nozzles the very first time I was able to pull the mixture back to 10.8 GPH with just a slight stumble. This was before we attempted to balance the injector restrictors so at this stage I had a Peak Fuel Flow spread of about 1.6 Gallons (between first & last cylinder to peak). After two rounds of restrictor exchanges first changing them all form 0.028 to 0.026 and then swapping out two 0.026 restrictors to 0.0255 my fuel flow differential is between 0.4 and 0.6. Because of the location of my Fuel Flow Transducer I think it will be difficult getting accurate readings below 0.4 GPH spread. I plan to relocate the transducer during the first Conditional Inspection to improve the Fuel Flow accuracy.
The hole for our ½” feed line is between the #1 & 3 cylinders. This is a direct shot straight up from the air box to the manifold.
We tried to select a manifold that had the largest internal volume reasonably available. From the Manifold we ran equal length ¼” aluminum tubing to each Turbo Nozzle.
The 90 degree arm on the Turbo Nozzle is slightly smaller than the ¼” blue flex tubing but the hose clamps are able to take up the slight size difference. Had I to do it over again I would probably order the Turbo Nozzles with the straight arm attached at 45 degrees as I believe it would potentially place less pressure on that fitting.

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