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Fuel Injection or Carb?

Gordon Misch

Gordon Misch

MEMBER
Toledo, Wa (KTDO)
Well, once again soliciting wisdom - -

Together with a friend, I'm building an Experimental Amateur Built -12 knockoff, and the plan is to put it on amphibs. The question, re engine, is whether to go with the efficiency and intake icing resistance of Fuel Injection, or stick with a carb for reliable hot starting. The engine will probably be O-360 or something similar in that displacement range. Probably all electronic ignition, but possibly one magneto and one electronic.

We would very much appreciate thoughts and experiences from those of you with lots of time in each engine configuration, especially if on floats.

Thanks!
 
If you use EI? Hot starts aren’t a problem. FI is superior in every way. Modern FI doesn’t suffer from the rhetorical myths. The better question is mechanical FI or electronic.
 
Fuel injection with electronic ignition. Hot starts are no issue if done correctly. I like the idea of dual electronic ignition rather than one of each since they both will maintain the same spark timing over the entire power range. A magneto only sparks at one setting so when coupled with a variable spark the engine will not know what the spark timing is supposed to be.

Also electronic ignition makes for smooth starting, low idle and stopping which is particularly an improvement on the 0-360 which has a tendency to shake when starting and stopping. With electronic ignition you can shut down by pulling the mixture at idle rpms without any shake or after firing. This is very nice, particularly when on floats.

With fuel injection you may find an occasional need to run the fuel boost pump when at idle on hot days. This is a normal procedure.

The newer electronic fuel injection sounds intriguing, though is something I know little about.
 
Gordon Misch said:
The question, re engine, is whether to go with the efficiency and intake icing resistance of Fuel Injection, or stick with a carb for reliable hot starting.
Click to expand...

I never had any problem with hot starts with my YI0-360 (CubCrafters CC363i). Open throttle to normal start position, mixture idle cut off, crank, and mixture rich as soon as it fires which is always after one or two blades.

The only time this technique has failed was when I was not fast enough on the mixture control. Just do it again and immediate start.
 
Fuel Injection every time for me. I've never had a problem hot starting FI engines, which is limited to TCM IO-470's and Lycoming IO-360's. All of that was in Texas where hot starts can be pretty hot. Not having to worry about carb ice and being able to run lean of peak for a ~10% fuel savings is pretty nice.
 
To the dead battery-hand propping comment? If the battery being dead means not strong enough to
Spin the starter? It should have adequate power to run the electric fuel pump and more than enough for electronic ignition. But these days it’s easy to carry a jump pack and avoid having to prop start. My IO-390 with 10-1 and a carbon fiber prop would be no bargain to hand start. I keep a jump pack in the plane for backup power. I wouldn’t want a single point of failure, after all. :)
 
Fuel Injection every time.

Hot starts are never an issue - IF -you've learned "the process" - whatever the process may be for your particular installation. It will probably take some trial and error, but once learned you'll be good to go.
 
How does a traditional Bendix RSA-5 type FI do with non-ethanol gas? For a Super Cub type airplane that has always been my reservation with FI. Some places you just can't get 100LL.

The only other drawback I see to FI is initial cost. A carburetor is dirt simple and cheap. The FI is expensive by comparison and requires an expensive stand-by pump plus an engine driven pump even in a gravity feed situation.

I think I have $5k in my Airflow Performance FI system on the clipwing.
 
mvivion said:
Fuel Injection with a manual primer. Facilitates hand propping with dead battery.

MTV
Click to expand...

stewartb said:
To the dead battery-hand propping comment? If the battery being dead means not strong enough to
Spin the starter? It should have adequate power to run the electric fuel pump and more than enough for electronic ignition. But these days it’s easy to carry a jump pack and avoid having to prop start. My IO-390 with 10-1 and a carbon fiber prop would be no bargain to hand start. I keep a jump pack in the plane for backup power. I wouldn’t want a single point of failure, after all. :)
Click to expand...
I'm with Stewart on this. A light weight jump pack is well worth it's little bit of weight. Hand propping these engines, particularly when on floats is not something we old timers ought to be doing.
 
skywagon8a said:
I'm with Stewart on this. A light weight jump pack is well worth it's little bit of weight. Hand propping these engines, particularly when on floats is not something we old timers ought to be doing.
Click to expand...

Yep, and of course, that jump pack will always be fully charged……

MTV
 
I spent some time today reading about this system (the same as I linked above) https://www.flyefii.com/products/efii-systems/ It seems pretty robust. Redundant controllers and power supplies, fuel return to stay cool, and ability to prime via the injectors, which go in the primer ports.

I sure would like to hear from anybody who has used it.

Thanks-
 
Use individual breakers for the injectors. Coupled with their System 32 ignition you’ll have capability to run lean of peak beyond your dreams.
 
New technology is pretty incredible.

Today's solid state electronics continue to prove to be more reliable than our old gauges, why would it be different with fuel and spark systems?

That said, quite often parts availability is an issue up here. Being able to get a plane back in the air quick has always been a priority. Worth asking the question.

Jump packs are a better solution to hand probing, but even they have their issues. Plug it in as routine to keep it charged.
 
If you end up owning an unique technical modification then before you do consider the need to keep it functioning especially if it malfunctions. Often when there's no reply to a call for "help"

It's your's to maintain.

Gary
 
mvivion said:
Yep, and of course, that jump pack will always be fully charged……

MTV
Click to expand...
And if we can't remember to keep the jump pack fully charged, perhaps there are other things we can no longer remember? Perhaps then we should not still be flying?
 
skywagon8a said:
And if we can't remember to keep the jump pack fully charged, perhaps there are other things we can no longer remember? Perhaps then we should not still be flying?
Click to expand...

That may be true, but I’d bet that’d ground a lot of otherwise competent pilots. So, “Fully charged jump pack” is on your preflight checklist?

MTV
 
Guess I will be the one to go against the grain. Keep it as light and simple as possible. A carb is going to be lighter and less complex. Then fly the stuffings out of it.

Bill
 
mvivion said:
That may be true, but I’d bet that’d ground a lot of otherwise competent pilots. So, “Fully charged jump pack” is on your preflight checklist?

MTV
Click to expand...
If I charge my Jump Pack it holds a charge until I need it. 6-9 months hasn’t been a problem, even when sitting out in the cold all winter. Once I use it I recharge it, even though it’s probably still good for several more starts.
 
mvivion said:
That may be true, but I’d bet that’d ground a lot of otherwise competent pilots. So, “Fully charged jump pack” is on your preflight checklist?

MTV
Click to expand...
Yes Mike, it is a very simple process. Push button. 20211213_100232.jpg

Look at 5 blue lights. 20211213_100223.jpg Done!

This jump pack hasn't needed charging for more than two years.
 

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Bill Rusk said:
Guess I will be the one to go against the grain. Keep it as light and simple as possible. A carb is going to be lighter and less complex. Then fly the stuffings out of it.

Bill
Click to expand...
There is only one power setting when a carburetor will even approach the efficiency of fuel injection. The throttle must be fully wide open to get proper even downstream fuel mixture distribution. To get this setting you will be flying well above 5000 feet all the time as that is where the throttle will be wide open for cruise.
 
Gordon,
I realize you asked about fuel injection or carb. You should also consider a light weight constant speed prop, particularly since you are expecting a set of amphib floats. You will find when you are loaded to "max gross" ;-) on a hot windless day, you will be pleased when you can get maximum power from your engine. Then not sacrificing cruise speed because you had a fixed pitch prop.
 
Bill Rusk said:
Guess I will be the one to go against the grain. Keep it as light and simple as possible. A carb is going to be lighter and less complex. Then fly the stuffings out of it.

Bill
Click to expand...

Fully agree with you there. Now that cubs are the hot ticket all those Cessna guys with Cessna budgets are throwing constant speeds and fuel injection on them. Keep it simple and light.
 
Now that I think about it, my cold air induction sump probably saved more weight than the fuel pumps added!

Gordon, dual EI allows you to use automotive spark plugs and plug wires. Iridium plugs for under $10 each.
 
Last edited:
Crash said:
.... all those Cessna guys with Cessna budgets ......
Click to expand...

I'm a Cessna guy, but I don't think I have a "Cessna budget"--
at least the kind you're talking about.
Keeping it "simple & light" can apply to skywagons too.

BTW after seeing some of the posts on the current thread on Cub panels,
maybe you need to say "all those Cub guys with Cub budgets".
 
Thanks guys, I do appreciate all the thoughts. Overall the system seems really sweet, but the one thing that gives me significant pause about electronic fuel and spark is that electrical power is absolutely required to keep the motor running. Redundancies notwithstanding, that's an absolute that doesn't exist with carb and mags.

On the other hand, my car ALWAYS works. Never do a thing other than pour in gas and change oil.

I suppose a testable redundant essential buss including a small alternator could be a big mitigator, but there's the complexity and the realization that while most every back-country shop can probably lay hands on a usable mag quickly, this stuff is specialty. Decisions - - -
 
There are small dynamos available which can be dedicated to the engine's systems. Like this: https://bandc.com/product/alternator-8-amps-homebuilt/#review
Similar units for tractors are available for a lot less money. I used one to make a wind driven power source. Nothing to wear out. Works great.

As you noted, these systems for cars are very dependable these days. I can't think of having to do any maintenance on any ignition or fuel system in any of my cars for decades.
 
Gordon Misch said:
Thanks guys, I do appreciate all the thoughts. Overall the system seems really sweet, but the one thing that gives me significant pause about electronic fuel and spark is that electrical power is absolutely required to keep the motor running. Redundancies notwithstanding, that's an absolute that doesn't exist with carb and mags.

On the other hand, my car ALWAYS works. Never do a thing other than pour in gas and change oil.

I suppose a testable redundant essential buss including a small alternator could be a big mitigator, but there's the complexity and the realization that while most every back-country shop can probably lay hands on a usable mag quickly, this stuff is specialty. Decisions - - -
Click to expand...

Gordon, for some reason I get a big kick out of reading this post, and then looking at your horse-drawn avatar!
 
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