Fuel Injection System Questions

I just got the latest RVator in the mail today and Van's discusses the situation with Precision Airmotive getting out of the carb business. While they leave open the possibility that there were be success with Precision selling off its carb business, the article also seems to imply that a lot of people who were planning on going carb might consider going with fuel injection now, particularly since apparently almost no one is currently selling any new carbed engines, including Lycoming. The article then addresses some of the fuel pump and cowling issues associated with making this change.

This makes me consider, more and more, switching from carb to f.i. while I still can (about ready to order engine from Aerosport and have note done much FWF). I'm sure that someone will step in to continue to make carbed engines viable, maybe even in the near future, but I'd like to know fully what my options are and what the ramifcations are in switching.

Thus, a couple more questions to help me learn more about fuel injection systems:

1. Do all fuel injection systems require a fuel return line? If so, where are these shown on any the drawings? Or are they? I haven't seen reference to this yet, but maybe that's just because I have a carb FWF package with its associated drawings.

2. Is the gascolator eliminated altogether? If so, why?

3. Assuming you have enough juice in your battery to run the f.i. fuel pump, but not enough to get the starter engaged, is it possible to hand prop a fuel injected engine?

4. Are all fuel injections systems entirely independent of the aircraft's electrical system once the engine is running? (e.g. will it run if alt/bat is lost in flight?)

Thanks for the help.

Steve,

Here are some answers:
1. No. Some systems do have continuous flow (return) systems, but I don't believe most used on RV's have that. Some have the Airflow Performance purge valve system, but that is another animal. I'm sure if you go to their site they will discuss that.
2. Many don't use gascolators with FI. The primary purpose of those is to separate water, which can hang up in a carb jet, killing the engine. FI systems will simply force the water through the system (provided it isn't in the form of ice).
3. Yes, but, probably not when the engine is hot. FI engines can take 10 to 12 blades to start when hot. Hand propping is not generally necessary, as one can either find a charger or car to give the battery a little charge.
4. Aircraft FI systems are nothing more than precision pressure regulators. For a given throttle, mixture and mass flow, they deliver a certain pressure of fuel. Various systems do this differently. This fuel is continuously sprayed through the injectors near the intake valves. No electricity is necessary. However, you would not have a backup fuel pump if you lost juice.

AlexPeterson said:

4. Aircraft FI systems are nothing more than precision pressure regulators. For a given throttle, mixture and mass flow, they deliver a certain pressure of fuel. Various systems do this differently. This fuel is continuously sprayed through the injectors near the intake valves. No electricity is necessary. However, you would not have a backup fuel pump if you lost juice.

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This assumes of course, that you are using a mechanical fuel pump for your main pressure source. If you decide to run wet pumps in the wing root, you are electrically dependent - but you are also immune to vapor lock, which seems to be the main argument against running 10% ethanol mogas.

Retrofitting alternate Fuel Injectors

Along these lines, if you have an existing FI engine with, say, Bendix injectors, but you wanted to install GAMI injectors or AFP injectors, can you do that? Or does AFP want to sell you a whole engine?

alpinelakespilot2000 said:

almost no one is currently selling any new carbed engines, including Lycoming.

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Lycoming, Superior and I believe ECI offer the 360 and Lycoming offers the 540 as carbureted engines (at least the parallel head engines) either through the kit engine program or through the OEM (Vans.) All of the vertical induction sump engines from kits start out as carbureted. From our shop a large percentage go with fuel injection though.

If you are currently running FI with a Bendix/Precision Airmotive system, you can install the Gamijectors or AFP's balanced nozzles aftermarket. We do it all of the time!

Good luck!

Airguy

airguy said:

This assumes of course, that you are using a mechanical fuel pump for your main pressure source. If you decide to run wet pumps in the wing root, you are electrically dependent - but you are also immune to vapor lock, which seems to be the main argument against running 10% ethanol mogas.

Click to expand...

Are you running wingroot pumps?...I thought I was the only one doing this so far.

I have 235 hours on wet pumps in the wingroots only system if you need to compare notes.

Frank

Couple follow up questions

Couple follow up questions

1. Do f.i. systems require the use of the high pressure boost pump in the same way that low pressure facet pumps are used for carbed engines (e.g. boost pump on for take-off and landing and generally turned off in cruise) or does the high pressure boost pump need to be on all the time?

2. Does fuel injection make unnecessary a primer used for cold weather starting?

Thanks as always, for the education.

The high pressure boost pump is used for priming and there is no need for a priming system on a fuel injected engine and aircraft with a high pressure boost pump installed. The boost pump is also used back up type operation in case the engine driven pump fails. Good practice to have it on for take off and landings or any time you think vapor might be an issue.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."

Scott Chastain said:

This is a real point of interest for me, since my first engine start is coming up in a few months. I have an Aerosport IO-360 with the Silver Hawk Ex installed. Having read many threads on the benefits of running LOP, I plan on doing so once the engine is broken in. However, since my injectors aren't balanced, I'd like to know:

1. Are builders running LOP prior to having Gami or AFP balance their injectors?

2. Do Gami or AFP require specific data from unbalanced injectors before sending them in?

3. Do Gami or AFP allow a core deduction for injectors that are sent in, or does a person have to pay for brand new injectors lock stock and barrel?

Thanks!

Click to expand...

1. It's possible. I have nozzle tuned some engines that didn't need any tuning. Some were from BPE, one was a 320 from Mattituck. These engines had our fuel injection system and nozzles to begin with.

2. I can't speak for GAMI, but we need the data run before we can determine what needs changing. Contact us by email to get data forms and instructions.

3. Again I can't speak for GAMI. If you have the new style Bendix/Precision nozzle all that is changed is the restrictor (the insert that slides in the nozzle body). If you have the old style nozzle (all pressed together) then you will have to buy a new set of Airflow nozzles ($38.50 each), or new Precision nozzles. The special size restrictors for tuning are $25.00 each. These parts are not returnable.

We offer the nozzle tuning service at our shop for $300.00. This includes all restrictors. It usually takes a half a day to dial the engine in.

Don

Scott Chastain said:

1. Are builders running LOP prior to having Gami or AFP balance their injectors?

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I am. I have 42 hours on my Mattituck TMX-IO360, vertical induction, Precision Silver Hawk injection.

My injectors are very well balanced right out of the box -- 0.0 to 0.3 gph spread at peak depending on the day. I can get 75-100 degrees LOP before any roughness is detectable.

Sure saves a lot of gas, too. Here's a data point for you. Running at 20"/2300 RPM at 7500 MSL: 150 ROP is 9.3 gph, and 75 LOP is 6.4 gph. TAS difference is only a couple of knots.

Search the forums for "LOP" -- there is tons of information about this.

-Geoff

Carbs

Seems like it is almost heretical to mention the humble and simple Ellison Throttle Body Injector! Light, simple, low fuel pressure, leans better than a standard carb, and hand starts easily if required. Also aerobatic.

frankh said:

Are you running wingroot pumps?...I thought I was the only one doing this so far.

I have 235 hours on wet pumps in the wingroots only system if you need to compare notes.

Frank

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Haven't got that far yet (ordering the tail feathers this week - woo hoo!) but yes, I'll be running dual wet pumps in the wing.

fuel injection w/auto fuel

I really want to be able to run auto fuel with my planned FI engine. Recently I found this in the silverhawk fuel injection warranty:

... The use of Non-Aviation grade fuel Voids all Warranties.

So my question is are any of you running auto fuel with the silverhawk FI?

On the one hand, I'd say "Don't run Silverhawk, then"...

And on the other hand, I'd say Pox on the warranty - if you wanted it all guaranteed and 100% safe then you'd be flying a Cessna. Build and fly what you want.

tsneidin said:

I really want to be able to run auto fuel with my planned FI engine. Recently I found this in the silverhawk fuel injection warranty:

... The use of Non-Aviation grade fuel Voids all Warranties.

So my question is are any of you running auto fuel with the silverhawk FI?

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Interesting. My Superior IO-360 came with updraft Silverhawk FI and Superior expressly rates the engine as being suitable for mogas. And it has a warranty.

How?

How are they going to know what fuel you use