FI in a RV-320

A while ago I made comments about a project we were working on to install fuel injection on a RV using the smaller 320 cowl and not having to modify the cowl to make it fit. Well after mush work and a bunch of delays (not because of the project) we finally got it done. I don't have manuals for the air box mod yet but will when and if any kits are sold. So here you go:

PROJECT
The project was to fit a mechanical fuel injection system on a RV that had the smaller 320 cowl. This carbureted installation uses a MA4 carburetor which is 4.5? long. The RSA-5 fuel servo or FM-150 throttle body is 5.5? long, this would necessitate cutting off the existing snorkel and re-glassing the snorkel deeper to fit the longer throttle body with air box attached. The challenge here was to fit the fuel injection without modifying the original cowl.
AIRCRAFT
James Clark provided the subject aircraft an RV-6, N996PJ. The engine was a Titan 340 Stroker with a stock up draft sump and MA-4SPA carburetor. A stock Vetterman crossover exhaust system was on this installation. The engine had one P-Mag and one electronic ignition system. The engine was suffering from poor fuel distribution. Multiple carburetors had been tried with no success. According to the Titan dyno sheets the engine produced 178 HP on the Titan dynamometer. Data from the aircraft EFIS with the carburetor showed take off fuel flow full rich at 13.5 GPH at 2578 RPM and EGT/CHT cylinder 1 through 4 respectively 1240/399, 1244/377, 1385/393, 1350/368. With a cruise power setting of 2500 RPM and 25? MAP full rich fuel flow was 10.8 GPH, EGT/CHT 1219/355, 1248/351, 1325/384, 1332/363.
INSTALLATION
Using the new FM-150L (1 lb. lighter than a Precision Silver Hawk) fuel control an installation was done which included replacing the low pressure electric pump with a high pressure aux. pump and filter. Replacing the low pressure engine driven pump with the high pressure engine driven pump. (No return lines, duplex selector valves or purge return is required using the FM-150L). Removing the carb heat and primer system. Installing new throttle and mixture cable brackets but retaining the original throttle and mixture control cables. Re plumbing the fuel plumbing in the engine compartment using Teflon fire sleeved hoses. A Vans FAB-320 AP-1 was purchased to be used for the air filter box. The top plate was modified to fit the clamp plate for the FM-150L, and the filter was installed so that the top oval plate of the filter box held the filter against the floor of the fiberglass air box. The inlet ramp angle was adjusted to fit the inlet scoop on the cowl. A 3? rubber boot was fabricated to fit into the inlet scoop. Injector nozzles were installed in the tops of the cylinder head with the flow divider mounted off to the right side of the engine centerline. The flow meter transducer ?red cube? was mounted in the metered fuel line 3? from the flow divider inlet where the metered fuel hose came through the rear baffle.
Note: During the installation a different air box was used for initial flight tests. It was found that further development would be require to sort out this installation, therefore the Van?s box was used with modifications for the final design. It was found using the Van?s airbox design a standard Lycoming fuel curve provided the correct fuel air ratio to the engine, no compensation to the fuel curve was required because of air box air flow disturbances.

FI RV-320 the rest of the story

PERFORMANCE
The FM-150L was calibrated using the standard calibration for a Lycoming 180 HP engine. Injector nozzle sizes were the same for each cylinder. After initial run up and idle mixture adjustment a leak check was made before cowling the plane. Of interest was take off fuel flow. This based off of Lycoming charts, showed that the engine was making around 175 to 180 HP.
WOT Take Off 2700 RPM, Fuel Flow 15.1 GPH, 29.7? MAP (MAP before engine start 30.2?)

3500 Feet, 2400 RPM, 24? MAP
Full Rich Fuel Flow10.5 GPH, EGT/CHT #1 1214/343, #2 1261/335, #3 1217/343, #4 1238/336
All cylinders peaked at 7.7 GPH with EGT #1 1412, #2 1465, #3 1428, #4 1452
The fuel rich fuel air ratio .086 (AF 11.6). Peak EGT fuel air ratio .065 (AF 15.4)
GAMI spread <0.1 GPH. CHT spread 8 degrees F

3500 Feet, 2500 RPM, 22? MAP
All cylinders peaked at 7.2 GPH with EGT #1 1431, #2 1478, #3 1445, #4 1468
GAMI spread <0.1 GPH

8500 Feet, 2500 RPM, 22? MAP
All cylinders peaked 7.8 GPH with EGT #1 1412, #2 1457, #3 1418, #4 1452
GAMI spread <0.1 GPH
LOP operation engine smooth 6.5 GPH with EGT #1 1280, #2 1309, #3 1294, #4 1309
Running approximately 125 degrees LOP with smooth engine operation the fuel air ratio was approximately .055 (AF 18.2)

IN CONCLUSION
The design goal was met to install a fuel injection system in a stock RV 320 cowl without modification. Van?s standard air box design for a 320 engine proved adequate for providing inlet air to the fuel injection system. Acceptable engine performance was made using the stock up draft intake sump and standard Vans cowing for cooling the engine. Based on climb performance compared to a similar RV-6 with O-360 engine and constant speed prop the Titan 340 engine with Airflow Performance fuel injection made similar power. Fuel distribution was good using stock Airflow Performance injector nozzles used on a Lycoming 320 engine with GAMI spreads less than 0.1 GPH. Smooth LOP operation was run in excess of 100 LOP. This installation makes possible installation fuel injection on older RV-4?s and RV-6?s with Lycoming 320 engines using the smaller 320 cowl without modifying the cowl.


So if your interested in more details or some pictures of this installation please email me at [email protected]