Engine Overhaul: Test Running on the Truck

I will start by saying that test running this engine on the truck was no trivial exercise! Due to the SDS EFI installation, and the fact that the truck electrical system was 28 volts, it was a bit of a moutnain to climb. But i'm in this for education - so let the education begin! 

Hanging the Engine

The biggest issue with running on the truck was that the truck is setup for 6 / 8 cylinder large Lycomings (bed mount). We figured that we should be able to use the back side of the existing truck mount and with the juducious use of some thick angle, we managed to mount my engine mount to the truck. The mount was drilled to the angles, then the angles were drilled to the truck. 

The mount was then removed, and i attached the mount to the engine (once i figured out i had the wrong enging rubbers). 

We were then able to lift the engine / engine mount / steel angles and this bolted straight up to the truck. 

Electrical / SDS Considerations

To start with, i needed to basically replicate the 12V electrical system from the aeroplane, as well as replicate the fuel system, and find a place for the MAP sensors. 

I started with the electrical system and created a 'test box' which contained all the same components as the aeroplane, including the 'Engine Bus' fuse block, all the switches (and mixture control) and the SDS Controller. 

I also created a board containing the battery and starter contactors, a fuel system (including filters, pumps and regulator), as well as the MAP sensors. 

I was then able to find some locations on the truck were suitable for these components to be mounted. The main restriction was the length of the wiring looms from the engine test box. I used an old 12V mercedes battery to power the whole thing! 

Electrical / Fuel / MAP Sensor panel

ECU Test Box

I then needed to go through and plumb all the fuel lines, as well as run all the wiring / MAP hoses etc. It was a bit of a challenge to find some old -6 fuel hoses which were the right length - many were old hydraulic hoses from the maintenance shop, which i cleaned out meticulously before use. 

For the final install into the engine on the aircraft, these wires will be cut to a shorter length and neatened up. They will also need to be chafe protected with some spiwrap etc. 

The big CPC connector is the main harness for fuel injection, and the HALL sensors, You can also see the left hand coil wiring.

Coil wiring - i would like to support these a bit more, and chafe protect them.

TPS (Throttle Position) sensor and AT (Air Temp) sensors on the throttle body.

CHT (Cylinder Head Temp) Sensor

Fuel Hoses

Fuel Distribution Block on the baffles

I will need to remove this fitting and re-clock to better clear the engine mount.

Fitting a Test Prop

The ring gear is the very nice SDS billet aluminium ring gear, which came with the magnets already installed. We fitted it temporarily and checked the clearance of the SDS magnet mount. We ended up with a combination of thin washers which gave a 0.035" clearance (the tolerance was 0.025"-0.040"). 

The shop had a test club which we wanted to use to do the run - this was a CS prop which had been cut down, and modified with a big threaded bolt in the front to manually set the pitch. I was initially set quite coarse, with the idea that we would fine it off to get full RPM once running. 

Instrumentation / Control

We set up a bunch of instrumentation - the truck had a nice setup inside which gave us:

• Mechanical RPM (via a very old school Tach sender into the tach drive on the back of the engine). 
• Oil Temperature - from a sender at the usual location on the top of the accessory case
• CHT - via a set of 4 bayonet plufs into the normal location on the cylinders. 

Inside the truck we had CHT (on the screen), Oil Temp and RPM.

Mechanical TACH sender

For other sensors, which we could not get inside the truck, we set up externally mounted gauges:

• Oil Pressure - a big gauge plumbed into the normal location on the accessory case. 
• Manifold Pressure - via a line into the intake manifold port on the #1 cylinder
• Fuel Pressure - via a pickup off the SDS Fuel Pump manifold. 

Fuel Pressure

Oil Pressure

Manifold Pressure

Other than that, the SDS controller gave use a MAP readout (from the throttle body), as well as 

RPM (from the crank sensors). These both cross-checked perfectly with the truck numbers. 

The throttle was simply held with an ADEL clamp to the bottom of the sump and cable tied to the truck near the control box. 

Throttle Connection

Pre-Start Checks

Before starting the engine, we checked that we had 12V on the starter when the button was pushed, as well as 12V at each of the injectors and each of the coils. 

We checked that the HALL sensor flywheel magnets could be seen by BOTH the SDS ECU's:

PRI ECU seeing the Sync Magnet

SEC ECU seeing the main magnet. 

The dessicant plugs were removed and the top plugs installed. We torqued the plugs to 19 ft/lbs, then further torqued the adapters to 25 ft/lbs - you need 2 sockets to do this. 

We also heated up 6 quarts of oil using a very dangerous looking heater, then pressurised it using a modified garden sprayer bottle. A gallery plug was removed from each side of the case, and we pushed oil into the engine to fill up the oil galleries, as well as the filter and oil cooler. This allowed us to get oil pressure showing on the gauge within a few seconds of start - no long delays cranking waiting for oil pressure to come up. 

This thing was scary - the oil temp camp up very quickly, but it has caught fire when removed from the oil more than once! You need to turn it off and let it cool a bit before you remove it, unless you want flames!

Pushing the hot pressurised oil into the engine. We added 6 quarts in this way.

There were no excuses left!

Full of nerves, we took the truck outside and gave it a go!

Finally, here was the first start. We realised after that it took a few blades to get going, as the ECU was resetting with the initial voltage drop casued by the starter. 

There was a for bit of smoke etc out of the breather, which was to be expected until the rings seat

Post first run - what did we learn... 

The first run went well. She started and ran great. The goal was to get the engine up to operating temperature, then slowly increase the RPM in small increments to see how the engine performed. For instance, we ran it at 1000rpm for a minute, then 1200 for about 2-3 mins, then 1800 for 2-3 and did a mag check, then 1500 RPM etc. 

We learned:

• At full throttle we were only able to get 2400 RPM - we need to fine off the prop for the next run. 
• The oil pressure was a little low - we need to change the oil pressure spring to a stronger one. 
• The CHT's were getting very hot very fast. We terminated the run when the #4 got up to 230C (440F). 

#3 and #4 were getting too hot so we termnated the run.

Oil temp was not too bad - so the oil cooler seems to be working ok. 

We also removed and cut open the filter, which looked remarkably clean:

Some tiny shards of something metallic, and some molykote.

Trying to reduce the CHT's 

We needed to address the CHT issue, which was somewhat expected. To try and lower these numbers, i had a go at building a shroud of sorts - not my finest work, but i only spent an hour on it. 

Second Engine Run

The next day, we replaced the oil pressure spring, and fined off the prop a little then went out for the second engine run.

Replacement oil pressure spring (stronger). 

We found that the shroud had lowered the CHT's by about 15c, but this was still not enough. We also found that we achieved the required 2700 rpm, but we were not at the correct MAP values - the prop was now too fine, and had to be coarsened.

Final Run - full power!

Since the shroud was kind of working, but not working great, i did a bit of a modification to it to raise it up a bit and try and increase the air capture area. Please don't look too closely at my work! 

Nerves!!!

We also coarsened off the prop a little, then we headed out to the middle of the airfield for the final run! It was pretty cool getting escorted across the runways into the middle of the airfield, and dropped into the grass with an engine that you built on a truck!

The Final Run

Now the engine was settled in and setup well, the aim of the final run was a progressive increase in power up to full power over a period of time. It was to test the engine achieves the numbers we expect, but also start our way toward bedding in the rings. 

We would pause a for 5 mins at each of 1000/1200/1500 RPM then longer periods of 10 mins at higher RPM's. This would be pending both CHT and Oil Temp restrictions. 

The new shroud was holding on - just!

The last run went well, however the CHT's were still a problem. We got to 2000 RPM and had planned to stay there for 10 mins, however a combinatin of high CHT's and the fact that 2 of the shroud rivets had given way, made us terminate early. 

We increased the engine up to full power and it achieved 2700 RPM and 29" of MAP - so we are satified that the engine is running well, but we didn't want to push the temperatures any further. 

Post Run / Inhibiting

After the final run, we drained all the oil and pulled off the filter and cut it open. It was noticably blacker, but it was nice and clean. 

Possibly some case paint?

A couple more little shards

A little copper shard - probably a rocker bushing

This oil gets drained as we don't want combustion products sitting in the engine for long periods.

The engine won't be installed on my aircrat for a while, so we decided to inhibit with VpCI-326 as recommended by Lycoming in SL 180. This involved adding 7 quarts of fresh oil to a container, then adding 1:10 of the inhibiting chemical (it stunk!). We saved 1 Litre of this mixtre to fog the cylinders, then added the rest to the engine. The engine was started for the last time, then brought up to temp (75C Oil Temp), then shut down. 

7 litres of oil...

..with 700ml of VpCI-326

I ran the engine for about 10 mins, with progressing RPM's up to 1700. The oil got up to about 75C, but i didn't want to run it for any longer. 

The CHT's were sitting ok, but the engine oil would not get any hotter unless a went up to a higher RPM (this as at 1700 already) - so i called this good. 

Once the inhibiting was done, we let the engine cool down and fogged each of the cylinders through the top spark plug hole. Dessicant plugs were added (using new dessicant). 

Pulling it all apart to take it home

The engine was removed from the truck, and all the intake and baffling was removed. Top plugs were removed and replaced with dessicant plugs. I added some dessicant bags into the intake space and will make an airtight cover for the throttle body hole in the sump. I also have a dessicant dryer i have made up which will be installed once the engine gets home. 

Filling up the dessicant plugs

The prop flange is marked so we know which orientation it needs to stay in!

Intake removed so it would not be damaged in shipping.

All the baffles were actually removed to allow me to strap it down to a pallet for taking home. 

Fixing an Oil Leak

The only small issue we found was an oil leak from the base of the left hand igntion coil cover plate. We thought at the time that since these would not be removed again, we would apply Loctite 515 to them. However i don't think this had enough clamping force to cure this sealant (it cures via pressure). So both coils were removed, and cleaned up, then re-installed with new gaskets and this time using Hylomar sealant. Fingers crossed this sorts out the leak. 

What a journey! 

This has been one of the most challenging, expensive, stressful, nerve wracking, funnest and most rewarding parts of this aircaft project to far. I recommend it to anyone who can find an engine shop open to it! 

Here's a little recap!