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Fuel Injection Options

David Z

Well Known Member
I'm planning on fuel injection, either an IO-360, IO-370 or IO-375. When building the tanks, I did not add a port for a return line. The fuel selector I have does not have the fuel return function either.

I'd like to avoid a return system if possible. Fuel return lines means doubling the fuel lines, being more weight, double the chance of leaks, double the complexity, more time to build. Seems like increasing a bunch of things I don't want.

The various sources I look at, they all talk about fuel return systems being required or not required for most fuel injected engines. I'm also at a stage that's fairly easy to change. Exchange the fuel selector and add fuel return fittings to the tanks, not that difficult.

What's the real answer. I know there's AFP, Precision, Silverhawk, Bendix and I'm sure other options as well. Which options require a fuel return system? What options come on the standard IO-360-M1B from Van's? What about Titan's IO-370 and Aerosport Power's IO-375?
 
David---there are 2 categorys for injections we use. Mechanical, and electronic.

Electronic is an automotive based full flow system, with full returns to the appropriate tank, with the extra assorted plumbing. Yes, a duplex style selector valve would be required. SDS, EFii and maybe a few others are examples.

Mechanical is a mass airflow/proportional system. No returns necessary as the engine uses all the fuel. Plumbing is simplified, and a single chamber selector valve is used.AFP, Avstar, Bendix, Precision are a few examples of mechanical systems.

The engines as supplied to Vans use mechanical injections, unless you have a special order arrangement with Lycoming. Aerosport and Titan will use whateve system you want. There are advantages to both styles, as well as some things to look for. Decide on your mission, or building options, and do your research.
Tom
 
I'm planning on fuel injection, either an IO-360, IO-370 or IO-375. When building the tanks, I did not add a port for a return line. The fuel selector I have does not have the fuel return function either.

I'd like to avoid a return system if possible. Fuel return lines means doubling the fuel lines, being more weight, double the chance of leaks, double the complexity, more time to build. Seems like increasing a bunch of things I don't want.

...
All this is true, but I would not limit your FI choice based solely on this, as adding the return line is a one-time investment, and you'll be spending a lot of time after with your choice of FI.
 
David---there are 2 categorys for injections we use. Mechanical, and electronic.

Excellent description.

Minor addition; David may have noted a return line for a purge valve installation with older Airflow Performance constant flow mechanical systems. Earlier AFP systems used a drum-type mixture valve, which works great but has a higher leak rate in idle cutoff as compared to a disc-type mixture valve. With a drum mixture valve, the purge valve ensured a clean shutdown.

The drum valve is still available, but it seems AFP has been steadily switching all their models to a disc valve metering assembly. Low leak rate, no purge valve needed.

Here's the fun part. A purge valve can be installed with any constant flow system, with an eye toward circulating cool fuel to flush the system prior to start. The return line does not need to run all the way back to a tank, just to a tee on one of the tank feed lines prior to the selector valve. To flush, select the other tank. A duplex selector valve is not required.
 
HI Dan---yep-----I was mainly talking about more current systems. Certainly a purge return can be adapted to any mechanical system.

Tom
 
David, I have an aerosport power IO-375 with Silverhawk and a return line is not needed.
 
...any constant flow system,...
Regrading mechanical fuel injection systems, a constant flow system is the style found on Continental FI systems, correct?

The other common system is a mass-airflow system, commonly known as the Bendix RSA series fuel injection, correct?

George
 
Regrading mechanical fuel injection systems, a constant flow system is the style found on Continental FI systems, correct?

The other common system is a mass-airflow system, commonly known as the Bendix RSA series fuel injection, correct?

They are both constant flow systems, with different approaches to metering. Fundamentally, Continental metering is based on RPM, while a Bendix-style (meaning Bendix, Airflow Performance, Precision, and Avstar) meters based on deltaP.

The SDS and EFII automotive-style injections are speed-density systems. Metering based on a mass airflow sensor is currently not available in a dedicated aircraft system.

Technically, when speaking of a purge valve, I should exclude Continental.
 
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