Kit Aircraft Modifications

Hello Everyone,

I have been working on the cooling system over the last few weeks and we have made some solid progress. This is probably one of the most important check off items on the road to installing a liquid cooled engine in my RV-10.

Since I last posted we have had an engine test stand constructed and have the engine mounted in it. This is going to serve a couple of purposes. One is the ability to transport the engine to outside shops where work can be performed on it. This means that work can go on in my absence and as I am working 6 days a week right now in my day job it is a tremendous help in keeping the project moving along.

The first thing that needed to be looked at in the cooling system design was the failure analysis of the system as it was designed in the automobile. I did an engine to engine risk comparison looking at specific systems and more specifically sub-systems. In the cooling system as well as the electrical system the serpentine belt was a single point failure mode that needed to be addressed.

To address the failure mode of the single belt it was determined that a dual electric water pump system would be developed. This would be an either/or system where the secondary pump would be switched on if the primary pump failed. Failure of the pump could be gauged through current monitoring or temperature monitoring of the engine. The pump usage would also be alternated to make sure that the secondary would perform when called upon.

After much head scratching and conversation with GM engineers as well as the people from the aftermarket water pump manufacturer it was  determined that the dual electric pumps would be mounted to a manifold that has internal flapper valves to restrict recirculation of coolant when one pump is running.

This manifold has been built and we are now fabricating the mounting brackets for it. It will be mounted low on the firewall on the pilot’s side of the engine compartment.

In conjunction with this dual pump/manifold system we had a good long look at the old pump to make sure that we totally understood its functions before making the decision to remove it. The first thought was that we would remove it and replace it with fittings that attached directly to the engine block.

The more we dug into the pumps functions the more we found that it wasn’t so easily eliminated. The pump performs a number of functions. Temperature regulation via the thermostat,  coolant recirculation to help the engine get to temperature quickly and distribution of coolant to the cabin heat exchanger.

We would have had trouble maintaining these functions if we had removed the OEM water pump so we decided to modify the pump instead. We have removed the impeller and pulley from the water pump housing and by machining entrance and exit ports have converted the water pump into a coolant distribution manifold that retains the functions of the manifold portion of the pump while removiing the actual pumping of the coolant to a remote location where the twin pumps can be mounted.

All of this had to be researched and a plan put together before any effort was put toward fabrication of the actual cooling system components. Fabrication is the easy part! Luckily I have some top notch people working on this system for me and now that the majority of the engineering is out of the way I hope to have the engine back and available for the next chapter in this firewall forward development effort which is getting the dual custom engine management computer system designed, manufactured and tested.

I’ll talk to  you later.

Dave

Hi Everyone,

First off, I would like to hear back from all of those who are following this thread. Drop me a quick e-mail or leave a comment if you are enjoying this topic.

The engine is now being fitted to a spacial test frame that will eventually allow me to run the whole engine/gearbox/propeller system on my trailer. This is going to be very helpful in dialing in the engine and to catch any problems with the system before it is mounted in the plane.

It will also allow us to put a load on the engine during testing to see how the custom ECM set up performs. I should have the basics of the test frame done near the end of the week and I hope to have the whole set-up back to the ECM designer’s shop by the end of October.

Dave

Hi Everyone,

 Well, I managed to get the engine through customs and back home without any troubles. I have taken it to a friend’s shop where he has a forklift and could take it off of my trailer. He is also going to be the guy who builds my engine test stand.

Engine test stand you say! You betcha! I am going to be installing a newly developed dual Engine Control Module in my airplane and I am not going to be testing it in the air. We are going to put some hours on this system to ensure that all of the parameters are set correctly. As well, we are going to get the gearbox installed and put some load on the engine.

I am going to do this by designing the engine test stand to be mounted in my trailer such that the prop has sufficient ground clearance to be run with the engine. We will attach the test stand with bolts to the frame of the trailer and then hook the trailer to the van. I will also put in some stakes and tie the trailer down to them to keep it from hopping around.

I have decided to emulate the aircraft forward of the firewall as closely as possible so that the components used in the test stand will be able to be transferred directly to the aircraft. I purchased the steel for the engine mount yesterday and have begun the process of measuring the mount in my plane so that we can approximate it in the test stand.

I’ll give you more as I get it done and in the mean time I will keep on with the posts describing the work I have already completed.

Dave

Well I did it. I purchased the LS1 crate engine last Monday. I purchased a FAST intake and Nick Williams 92mm throttle body as well and had them shipped to Michigan where I am going to go in a couple days to pick it up. I saved a bundle by purchasing it in the states even though I have a GM discount. I got it for $900 less there. Amazing!!

Here at home I have started constructing an engine test cell. I am doing this because I have a couple of things I want hashed out before I install the engine in my airframe.

The ignition is the primary reason that I want to put some time on the engine in a test cell. We are planning to develope a dual ECM set-up and I want to get some hours on the system before installation in the airframe.

The cooling system is the second reason. I am going to go with a dual electric water pump set-up that will require some engine test time to determine whether a thermostat is required. As well, we need to determine how effective the electric fan will be on the cooling when the engine is operating at various loads and speeds.

All of this is better tested on the ground under controlled conditions rather than in the air. I am determined to improve upon the set-up that Bud Warren is using at Geared Drives. I have decided not to go with the OEM computer, water pump and Bud’s cooling system. All of this will require some validation and I am going to do this the right way.

Dave

I have been spending a lot of time lately thinking through the cooling system and specifically the water pump. On a liquid cooled engine the water pump is a single point of failure. A pump failure means that you are coming down and sooner than you would like.

The other thing that needs to be considered when choosing an automotive engine for an aircraft is that a pulley driven water pump is optimized for a very specific RPM range and that is usually around 1000-2200 RPM. This is where the automotive engine spends most of its operational life.

You want a liquid cooled aircraft engine to flow as much coolant as possible at its cruise RPM and for the LS1 married to a Geared Drives psru that turns out to be about 3300 RPM. This is much higher than the optimized speed of the OEM water pump. If you turn that pump faster you end up simply wasting horsepower and not getting an equivalent increase in coolant flow.

There are a couple of ways around this problem. The first has been used in racing circles for years and that is to under drive the pump by changing its pulley size. This works well when running at cruise speed but unfortunately means reduced flow at idle. This doesn’t bode well for the long taxi on 104 deg. F afternoons in Texas.

The second is to install an electric motor driven water pump in lieu of  the OEM water pump. Meziere makes a  number of bolt on replacement pumps that have an idler pulley built in to maintain your existing belt geometry.

The electric pump accomplishes a couple of things that are positive for automotive engines in aircraft. First, it eliminates the need to physically drive the coolant pump using a belt. This will net you 15-20 horsepower at the propeller. Second is the smoothing out of coolant flow over the entire range of engine RPM. This means that you are getting optimum cooling flow when you are taxiing down to the end of the 12,000 foot runway as well as when you are throttle to the firewall.

There have been numerous instances of automotive engines over temping on the ground while taxiing and I have to wonder whether this inefficiency of the coolant pump at idle RPMs is a contributing factor.

The last bit I am going to talk about today is in regard to redundancy and failure modes as mentioned earlier. I am going to be installing dual electric coolant pumps in my RV-10. The main pump will be mounted to the engine in place of the stock unit. The aftermarket unit from Meziere duplicates all of the hose connections of the stock unit and maintains the belt path and operation. The secondary unit will be run in series with the main unit and will be mounted onto the radiator where the bottom rad hose bung would normally be located.

This will eliminate a major failure mode in the installation of a GM LS1 engine in my RV-10 and give me the peace of mind that I need for the  future flights into IMC that I plan to make after getting my instrument rating.

 Have a great time building and modifying!

Dave

Greetings,

Here in Canada we have to install a gascolator in our aircraft to establish a low point for fuel on the engine side of the firewall. I decided to install one of the Van’s Aircraft designed Gascolators as it wasn’t expensive.

It was challenging to find a place low on the firewall of my RV-10 because of the design of the  engine mount. The mount I am using for my LS1 installation as well as Vans original design have a tube that runs the perimeter of the lower firewall. This meant that I had to devise some sort of standoff that would allow me to mount the unit and at the same time have the drain clear the mount tubing.

What I did was take a chunk of aluminum the same size as the base of the gascolator and deep enough to allow the drain valve extension to clear the mount. I then drilled the block to accept a threaded brass extension which was then threaded into the gascolator. The threaded brass extension was then fed through a hole in the firewall and the gascolator was bolted through the firewall as well.

On the inside of the firewall I threaded an aluminum 90 deg AN fitting on to the brass extension and clocked it to be parallel to an angle brace that runs diagonally across the firewall. I secured rigid flared tubing to this brace and ran it between the output of the high pressure Walbro pumps and the 90 degree fitting on the firewall.

I now have a low point for fuel in the engine compartment and have the drain valves for both the gascolator and the header tank side by side so they can be easily checked for water contamination during the pre-flight inspection.

Thanks for taking this in. I would appreciate your comments on this blog. Please feel free to drop me a line or two.

Dave

Hi Everyone,

The fuel in my RV-10 is located in three tanks. Left and right wing tanks of 30 gal. each and an auxiliary tank located in the baggage compartment.

As mentioned earlier I have installed a header tank on the cockpit side of the firewall. This header tank needs to be full of fuel all of the time as it supplies the high pressure Walbro fuel pumos that charge the fuel rails on the engine.

I have installed two Facett fuel pumps in the bottom of the center tunnel on a bracket that has them angled up from horizontal 45 degrees. This is necessary to make sure that bubbles in the fuel do not congregate in or around the pumps. This also helps stave off vaopr lock if the fuel gets too warm. I shouldn’t have too much trouble with this as I am returning unused fuel back to the tank supplying the system.

I have run the two pumps in paralell in the same fashion as the high pressure Walbo pumps. I am building an IFR capable aircraft with all of the necessary redundancies of which dual fuel supply and pressure pumps are a part.

I used aluminum tubing with AN flared fittings throughout the installation and made sure that all of the lines were supported and isolated from other items in the center tunnel. I took great pains to make sure that the fuel lines were routed away from heat sources such as the cabin heat exchanger.

Each of the Facet pumps will have its own power supply from independant sources so that an electrical system failure won’t put me out of business.

Here is a picture of the tunnel with the pumos in the center bottom.

Dave

With a liquid cooled engine now in the works I had to start thinking about how to modify the cabin heating system. The RV-10 has installed tee shaped ducting in the center tunnel that is connected to the heat muffs on the exhaust pipes in the original configuration. I wanted to maintain the same outlets so I had to fashion a heat exchanger and plenum that would allow me to connect 2″ SCAT tubing towards the forward endo of the tunnel as well as aft.

I found a MOCAL heat exchanger that along with banjo fittings would fit into the tunnel while laying on its side. From there I made up a stand that Would allow me to anchor it to the floor as well as have it at the proper height for the SCAT tube runs. They run quite high in the tunnel.

I had to make the whole thing removable as it is the last piece of the puzzle to be placed inside the tunnel and I need to be able to get at everything else in there during annual inspections and for maintenance.

The heat exchanger is connected to 90 deg. bulkhead fittings on the firewall (3/4″) with braided teflon hoses and I have insulated the lines as best as I can to keep the heat down in the tunnel. I am going to be making a bypass valve on the firewall side that will allow me to vary the amount of fluid that is going through the exchanger.

On top of the heat exchanger is a 4″ SPAL fan that I have pulling air through the fan into the plenum. This fan is of high quality and it seems to move the air quite well through to the two distribution tees in the front and back footwells.

I haven’t decided whether I am going to vary the speed of the fan with a thremostat or whether it will simply turn on and off. I still have some thinking to do on that.

Dave

The LS1 requires a fuel rail pressure of about 60 psi and as such needs to be supplied by an aftermarket Walbro Fuel pump. With most low wing aircraft there are two pumps to supply the engine with fuel. There is the engine driven pump and an auxiliary pump that is used during take-off and landing.

To maintain this redundancy and because the LS1 doesn’t have an engine driven pump, I have installed dual Walbro high pressure pumps to supply the fuel to the fuel rail. These pumps are gravity fed from a long cylindrical header tank mounted above them. This ensures that the pumps are wetted in all but the most extreme of flight attitudes.

I have plumbed them in paralell and have wired them to two separate power supplies. I will have the primary pump running all the time and the secondary will be switched on by my Vertical Power system based on flight mode. I have wondered whether or not I will change the designation of primary and secondary at each annual inspection so that any one pump isn’t overused.

I mounted the two pumps on brackets that I mounted to the co-pilot side of the centre tunnel. Each pump is secured to the bracket by two stainless steed worm gear clamps. They each have a check valve so that they can operate in parallel independently.

The fuel is routed from the tee just past the pumps up out of the centre tunnel and forward to the firewall where it is secured to the stiffener rib running diagonally down and outward where it turns 90 degrees through the firewall and into the back of the gascoaltor.

Tomorrow I will explain the dual low pressure pumps.

Dave

Hi Everyone,

The fuel system is the first area that I had to address because it is very different from the one employed for the Lycoming. The LS1 requires that pressurized fuel be supplied to the injectors via a fuel rail. This is a looped system with more supply capacity than will be used by the engine. The unused fuel is depressurized at the termination of the fuel rail by a fuel regulator. It then returns to the supply tank. This differs from the lycoming set-up in that there are no return lines required.

So to begin with we are adding complexity to the fuel supply system. There are quite a few more lines involved in the LS1 set-up that have to be bent and flared to get the fuel to the engine and back.

Header Tank

On a component basis I am going to start with the header tank. I installed a quart sized header tank on the cabin side of the firewall on the pilot’s side. This tank serves a couple of functions that are very important.

The first function is to keep the high pressure pumps always wetted. Automotive style high pressure fuel pumps do NOT like to be run dry. This would be a very real possibility should you mount them in the wing tanks.

The second function is to act as a collector and distributor of two streams of low pressure fuel. the low pressure pumps feed fuel to this tank and the pressure regulator returns depressurized fuel back to this tank. This keeps the fuel cool. Allows for any bubbles in the fuel to move away from the high pressure pump intake ports and provides a path for the fuel to be returned to the supply tank.

The photo above shows a large portion of my fuel system including the header tank, supply lines, return lines, twin high pressure supply pumps, and fuel transducer.

Next post I will describe the high pressure pumps and how I have installed them.

Dave