The new fuel injected EA81 required a number of changes to the fuel and electrical systems of the CH701. The old engine had a carb and a pair of low pressure facet style pumps to deliver the fuel to the carb. The new engine requires a pair of high pressure fuel pumps, a pair of 10 mircon filters down stream of the pumps and a fuel return line to the header tank from the fuel rail pressure regulator.

I was advised to use the Walbro HP fuel pumps. These pumps are recommended for reliability and ability to pull fuel better than Bosch pumps. Fitting one gascolator, two fuel pumps, two filters and all the required fitting needed to facilitate maintenance of these items makes for a real head scratching installation. It took three four hour sessions out at the hanger to get it the way I wanted. I haven’t had to maintain it yet, so filter pulling will be the ultimate test.

The return fuel line uses a fire sleeved fuel hose, steel bulkhead fitting and 1/4″ steel tubing for the loop back to the header tank. This is a low pressure loop which dumps excess fuel back into the header tank as the fuel rail regulator does its thing to keep the rail at 36 psig.

I used a firesleeved stainless steel braided fuel line between the fuel pump system on the firewall and the fuel rail inlet. This was a surplus hose that came with my RV9A firewall forward kit.

I added a fuel pressure transducer on the fuel rail and a digital gauge in the instrument panel for monitoring fuel pressure. This transducer is ranged for a 0-100 psi and puts out a 4-20 ma signal which is displayed on a digital display.

The photo on the left shows the new intake manifold, throttle body and filter assembly. To the right of the air filter is the new swirl pot for the coolant system. This pot collects the hot water from the two head outlets and directs it to the cabin heater and eventually back into the water pump or when water temp reaches 180 deg.f the thermostat in the bottom of the swirl pot opens and send the hot coolant off to the belly mounted radiator. The copper sensing line on the pot will be removed and reworked prior to signing off the upgrade in the log book.

The CH701 which I have been flying since 1999 was long overdue for a fresh engine. The original subaru ea81 engine was starting to loose compression in two cylinders, the oil was coming out too dark when changed and oil pressure was way too low to ignore when flying. Last few flights in January, I found myself give the oil pressure guage more attention than I should. I grounded myself and starting looking for a fresh engine.

In May I found an engine at Ram Performance in South Carolina which had been “zero” timed by Ram’s owner Ron. It was not one of his latest rebuilds but rather one which had gone out to a customer, sat for a few years and then came back to Ram as part of a trade up to a newer package. Ron went thru the engine when it came back and was deemed to stil be zero time. The engine was backed up with a warranty, so I paid up and waited for its arrival.

The engine was pretty much as promised and was in almost fresh condition. Only problem noted was a broken bracket that holds the fuel rail to the head. Ram offered to replace it but I opted to make a new pair of brackets out of some 1/8″ 4130 plate and 1/2″ square tube. There were a number of nuts with nylon locking collars used in the Ram rebuild along with non-AN type bolts. As these types of locking nuts should not be used in an engine compartment, I replaced where necessary with AN hardware with steel locking nuts.

The new EA81 engine has a number of performance enhancements like fuel injection, electronic ignition, special grind cam, stainless steel valves and HD valve springs. This work provides an EA-81 which produces 115-118 hp on the RAM dyno. This engine delivered 118 hp when tested. The engine it is replacing was not likely making more than 90 hp so the increase of 28 hp should be quite notable.

The engine came with a Real World Solutions EC2 fuel and ignition controller. The controller is pretty basic and has no user interface. The EC2 controller has been popular with the Mazda rotary crowd and a number of Subaru conversions have used this ECU. When I started working on the engine, I discovered some poor electrical work had been done on the EC2 connections. A few wires pulled out of the LS1 spark coils with a slight tug and further digging into the wiring revealed a lot of really bad solder joints. My confidence in this part of the rebuild slid pretty low when I found these items. Rather than rewire the EC2 controller, I pulled the electrical components, 58 tooth flywheel and pickup assembly and put them in a cardboard box. Maybe I’ll find another project that can use this EC2 package but it was not going to be this one.

Fortunately I had a new SDS engine controler package sitting on the shelf which I could use for this upgrade. I had originally purchased the SDS package from Simple Digital Systems for a EJ25 engine I was going to install in my RV9A project. I ended up installing a new ECI IO360 engine and did not require the SDS package. So long story short, I installed new Hall Effect pickup in the rear lower pully and a made a few more modifications to the installation to accomodate inlet air temperature sensing and coolant water sensor. The SDS ECU package is high quality product and I have a lot more confidence flying with this system in place. I guess if you don’t have something to compare an EC2 package with you might not know what a difference there is.