DIY-EFI

[phenry]

Wes,
The mounts you found are just the sort of thing that could be employed. It is up to you what approach you take; I have seen several solutions that work fine.

Each solution has its own set of issues, the GPAS manifolds have bosses already moulded into them in about the right place, however they may not be big enough for the injector carriers you have identified and may need the bosses building up to take the threaded mount.

Some things to be considered:
• Holding the injector in place.
• Holding the fuel rail in place on the injector.
• Injector size. (see below).
• Injector wiring/plug clearance
• Fuel line connection to fuel rail.

When putting my system together choosing the correct injector was very tedious because we needed to select an injector that firstly delivered the right amount of fuel in its optimum operational range. We found the CHD 610 which is rated at 25 lb/hr best after trying a range of different sizes. This meant I had to make different fuel rails for each injector tested.

Keep in mind the penetration of the injector nozzle is a major consideration when choosing or building the mount.

One factor to be considered in my system was that I use Semi-sequential injection because the Aerovee does not have a distributor, there is no way of knowing which of the cylinders in each bank is going to fire next. Not a problem you have to deal with so you could go Full Sequential.

Next, which ever injector you choose the manifold / mount / fuel rail combination must be tailored to suit.

After a lot of experimenting I am currently building a new and "forever" final set of manifolds based on a pair of Aerovee manifolds I purchased from Facebook Maketplace. I will post some pictures as I (slowly) progress.

[sonex1374]

Hi Peter,

Good to hear from you again! I'm glad you're still refining and optimizing your EFI system! I've been slowly gathering the materials for a conversion myself, and hope to try it out eventually.

I bought these injectors based on another Sonex builder's experience, and they simplify the plumbing somewhat. The unit is actually two parts - the injector itself (the purple part) and the housing with the mounting boss, hose nipple and wiring plug.

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The injectors were purchased from ebay, and are replacement motorcycle injectors rated at 120 cc/min (a little high, but reportedly works OK for an 80 HP engine). https://www.ebay.com/itm/274442493663?ul_noapp=true

Hoses connect directly to the injector without the use of a fuel rail, but that means you can't create a continuous loop for the fuel flow (a bit of a tradeoff). Instead, you'll have a manifold that receives fuel from the pump and then splits to each of the 4 injectors, plus a return line to the fuel pressure regulator and back to the tank. SDS makes a nifty billet machined fuel manifold, and that's what I plan to use.

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http://www.sdsefi.com/sdsaero.htm

While you're at it, you might buy the fuel pump and pressure regulator from SDS as they are high quality units. Whether you buy the SDS computer, Microsquirt, or roll your own is up to you. I plan to keep the AeroInjector installed for use as the throttle body (mixture knob at idle-cutoff), plus plumbed for fuel as a manual backup to the EFI (mixture knob full-rich).

Jeff

[GordonTurner]

Not trying to inject any knowledge here, but a question related to Jeffs post. Instead of either hard fuel rails that would complicate install but allow circulation, or an octopus of small lines, one to each injector (half an octopus in this case), that don’t allow any circulation at the most critical sections, why not a loop of somewhat larger hose with a T at or near each injector? Maybe easier install combined with circulation for cooler fuel.

Gordon, not an efi engineer.

[kmacht]

It is great to see this discussion going on. I have been thinking about and planning an SDS conversion for my aerovee for quite a while now and finally have the money set aside to start the conversion.

Jeff - On the fuel injectors you posted, how does the fuel line attach? Is it just a push fit and hose clamps? If so, any concerns with leaks due to the 40PSI the fuel pumps will be pushing through the system?

What is everyone planning on or have used for fuel pumps? The dual walbro setup on the SDS site seems a bit overkill for the fuel volume the aerovee needs. It would be nice to find something that doesn't draw quite so much current as one of my concerns with the conversion is if the 20amp alternator can keep up (especially during a long taxi such as at airventure) or if I need consider running an external alternator off the back of the crank somehow.

I also have this crazy idea to keep the aero-carb on the airplane as a backup in case I were to loose electrical power to the ECU somehow. The aerocarb would stay in place and you would just need shut off the ECU and open the mixture to the aerocarb in order to switch over. Has anyone thought about using the aerocarb as the throttle body? It would need a potentiometer attached to it somehow in order to also work as a throttle position sensor but other than the slide not being completely linear in the amount of air it lets in as it opens up I am not seeing why it wouldn't work. Thoughts?

Keith
#554

[lakespookie]

Keith something to consider the reason for the dual pumps is so that you have redundancy there is also the issue that if you run a single pump unless you build a bypass system a fuel pump failure can lead to fuel starvation. I would not run both pumps at the same time or continously except in an emergency

[phenry]

Keith,

Your idea about the dual fuel system is not crazy, that’s exactly how the system in my plane works. This has some major advantages, EFI redundancy can be reduced for example you do not need two pumps reducing current draw and cost. The pump I am using draws 2.5 amps and can deliver up to 45 Lt/Hr.

There is no need for a position sensor because the whole system works from inlet manifold pressure, throttle open, more air and ECU adds more fuel and visa versa.

Switching form EFI to normal operation in flight is no worse than a Sonex burp.

Reflecting on an early comment about not using Mega/Micro Squirts because they may be unreliable, if you can switch back to normally aspirated operation and believe me you can, why get hung up on a 1 in 100,000 chance of failure.

[phenry]

Jeff,

Great to hear from you again been a long time since the podcast. Yes, Chris and I are still at it, have the system running really well now and Chris has his 912 injected as well.

The injector setup you have picked is an excellent solution. What manifold are you intending use and how will the injectors be retained?

I have created the same type of fuel manifold you have shown. The fuel manifold and pump integrate together on a neat little rail that also holds the MAP sensor and propeller position sensor wiring.

[phenry]

Gordon,

While some setups have a full loop for the fuel lines, I understand this is mainly for cooling reasons (open to correction), We have found this to be unnecessary and have dead end lines, this reduces the complication and plumbing.

[Bryan Cotton]

I also have this crazy idea to keep the aero-carb on the airplane as a backup in case I were to loose electrical power to the ECU somehow.
Keith
#554

That is a great crazy idea! I like it.

[sonex1374]

What manifold are you intending use and how will the injectors be retained?

The injectors will be mounted into the standard AeroVee intake elbows (e.g. the red "intake logs"). Due to the depth of the injector the wall thickness of the elbow needs to be increased (the flat area above the intake ports on the head). Other builders have done this two ways - 1) weld a 3/8" thick aluminum plate to the outside of the elbow, or 2) attach a 3/8" thick plate to the elbow using bolts that screw into holes tapped in the elbow. The welding required the red anodizing be removed first (using spray oven cleaner to "eat" the anodizing off), and the drill-and-tap method requires adding tapped holes and then using permanent red loctite to attach the plate. The reinforcing plate also has the tapped holes for the injector hold-down bolts to retain the injector itself.

The whole thing can easily be made by first machining the reinforcing plate to the correct outside dimensions, adding the 4 tapped holes (2 for the injectors, 2 to attach to the intake elbow), then the plate can be positioned onto the intake elbow and the hole locations transferred directly from the plate. You could almost make this a bolt-on kit this way (installer would need to drill the elbow for the injector holes and the plate attach screws though).

I agree that the dual walbro pump that SDS uses is probably overkill. I think one good quality pump is sufficient with a manual AeroCarb backup. This type of EFI gets it's redundancy not electronically but with the manual fuel delivery option. Simple, light and electrically-efficient.

I also think that dead-end lines to the injector are probably OK. The lines are under pressure (40 psi), and that should help keep them liquid and not vaporizing. Running good quality injector hose, proper injector clamps, and insulated with fire sleeve should take care of the rest.

Give my best to Chris!

Jeff