ECI exp (AE) fuel injection with Van's F.I. (AFP) pump

4.2 Boost Pump(s)
The AE fuel injection system requires the use of at least one boost pump. AE strongly recommends using a boost pump that produces both a high and low pressure setting, or two boost pumps arranged so that one can produce at least 18 psi fuel pressure for emergencies, and another to produce 3-5 psi for take-off.

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flyvans.com said:

hi,



according to Don at AFP their pump can be throttled. They however don't have a voltage vs speed vs fuel pressure table, has anyone experimented/tested on that?

That's not quite true. What I said is that it may be possible to change the pressure by changing the speed of the motor, but we have never tried it, and you would have to have a DC motor speed controller not just a resistor to vary the speed. This can also be done with an solenoid valve and and additional pressure relief valve. But then again I don't know how accurate you have to hold the pressures to keep the ECI FI happy. It may be best to just suck it up and get the two speed boost pump ECI recommends.

Don

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Hi Bernhard,
We run off the engine driven pump in the cell, we have a very complex fuel delivery system where we can vary aux pump output in 1 psi increments.
The ECI fuel injection system is very similar to the systems used on TCM engines. Most certified aircraft using a TCM type system use one boost pump with a direct wire high setting and a resistor in the line for a low setting which will turn the aux pump rpm down thus lowering the fuel pressure. Cessna's use this style set up.
Thus the pilot can choose high setting for start priming and high power emergency use and use the low setting for idle and low power emergency use. Some wire the resistor into the system with a pressure switch bypass that automatically kick the pump form low to high when the pressure switch senses less the an intermediate fuel pressure output for the engine driven pump. Most of the pressure switch set ups are twins. Some use a limit switch based on throttle position to shuttle the pump to low. Cessna 210 use something like this. Most of the aircraft using these schemes use a Weldon style aux pump.
Maybe you could look at wiring diagrams for these aircraft at a local FBO. I am sure if you ask any mechanics about it they will know what you are talking about and will be able to help you.
If a resistor set up won't work with the AFP pump to throttle it, you could just wire in the pump you have for full out put and only use it for start or an engine emergency. When at high power, the engine will run fine but as you reduce power with that high unmetered pressure from the aux pump you will need to manually lean the engine to take some of the excess fuel away. And if you need to add more power, once leaned, you may have to richen it up a bit. so in essence you will control the fuel flow for the power setting you are running with the mixture control when the aux pump is on. Beech Debonaire's use this style set up.
Hope this helps,
Mahlon

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Bernie,

You have the correct fuel boost pump for the ECi fuel injection system. This fuel boost pump is not used during take off and landing, it is only used if the main engine driven pump fails or for priming during engine start.

If the pump is turned on during normal engine operation it will cause the engine to run excessively rich. If the engine driven pump fails during flight turning on the boost pump will provide fuel flow for about 95% power, and the need to lean the engine as necessary when reducing power to land. This system operates very much like the continental fuel injection system installed in a Cessna 210.

In all of the development and flight testing we have done for the F.I. system we did test a pump speed controller made by CJ Aviation, it made the option of low boost available. But we found that even at very low boost levels it made the system enrichen at low power levels and really was not necessary.

Bobby Looper A&P

Lead Tech. ECi Test Cell Operations

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• there must be something great about the c210's fuel system, will have to have a look at it ;-) anyone have a manual at hand?
• however, a key difference i see is that the cessnas have gravity feed systems while in the rv's, the fuel needs to climb from the wing tanks to the engine driven pump.
• a low pressure setting appears not required for operation and even a low pressure will make the engine run rich
• the afp pump will work just fine for the high boost requirements.

1. No additional pump, having high boost on "hot standby" using a fuel pressure switch.
2. Wiring the AFP pump for a dual speed setting
3. Adding a low pressure pump to the system

Bernie,

We recommend Van's pump only, with no fuel pressure switch, Low boost being an option for high altitude operations with auto fuel. With this type of mechanical fuel injection system there are three things that determine fuel flow at any time. #1 throttle position (regulates fuel based on proportionate air flow), #2 engine RPM (regulates fuel in proportion to engine speed), #3 mixture lever position (regulates fuel based on altitude). Since fuel flow is affected by RPM (low pressure at idle, high pressure at full throttle) any boost pump operation disrupts the normal fuel flow patterns and causes the system to run rich (a lot at idle, less at full power). The boost pump does not have output based on engine RPM that the engine driven pump has.

At one time Cessna had a pressure switch installed in it's fuel injected aircraft that would come on automatically if the engine driven pump failed. They no longer use this system because you could have a engine driven pump fail and not be aware that it occurred. If this happened and you attempted another take off and the boost pump overheated or failed the engine would quit. We do not recommend an automatic fuel pressure switch in our system.

We currently have the AFP pump installed in our RV-8 with a two position switch .High gives full boost pressure, Used for cold start priming, Engine driven pump failure, and Purging the system of vapor for hot starting. Low gives about 5psi. It's rarely used .Can be used to prevent vapor lock at high temps or high altitude with auto fuel.
Our aircraft and fuel systems have been extensively tested for over six years with many different types of engine configurations. This is a system that we know works and works well.

Bobby Looper

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• the Van's AFP pump by itself will do
• no automatic switching, at least not via fuel press switch

hi bobby,

thanks yet again for the helpful info.

i'm now basically convinced and ready to simply leave out any low
pressure
setting / pump if the following conditions do hold up:

let's say, full power takeoff, during that one experiences vapour lock.
now
engaging the high boost pump, will the engine just run way on the rich
side
but still produce power or is it now sooo too much rich that it might
stop
/ being flooded even at high power setting? not talking about smooth
running. of course this can be then manually corrected with mixture, but
i'm interested in the immediate short term condition.

the other situation, final approach, engine at more or less idle, one
experiences vapour lock. will engaging the high boost pump keep the
engine
running to allow for a go around? or, being at an idle setting with more
pronounced over-richness, flood the engine so it stops turning?

i'm sure you probably tested that, engaging high boost in either
situation?

kind regards,
bernie

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Bernie,

During full power take off conditions if the engine driven pump vapor locked, turning on high boost will bring the engine back to life but it will run rich enough for you to notice. There will not be a large reduction in power from the rich conditions; this richness is easily controlled with the mixture control. If you reduce power from full throttle while the boost pump is turned on it will become progressively richer as you close the throttle, again easily controlled with the mixture control.
One of the reasons we decided to use a system with a vapor return line is to prevent this exact scenario from happening in the first place. The idea is that if bubbles form at the inlet to the engine driven pump because of a reduction in pressure or high fuel temperature that the vapor separator in the pump will send vapor back to the tank preventing vapor cavitation of the pump.
In your second scenario vapor lock is not likely to be formed because the reduction in pressure at the inlet of the pump is much less at low power than it is at high power. Vapor can still form because of high fuel temperature or the fuel having a low vapor pressure (auto fuel).
Under these conditions the vapor return system is more than capable of returning the vapor formed to the tank.
If you were to turn on the boost pump under idle conditions the engine would run excessively rich unless you leaned aggressively. If you preformed a go around from idle conditions with the pump on the engine would accelerate a little slower than normal and be slightly rich as it reached full power.
We highly recommend a blast tube blowing cool air on the engine driven pump like certified aircraft use.

Bobby

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