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Thread: Fuel Injection or Carb?

  1. #1
    Gordon Misch's Avatar
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    Fuel Injection or Carb?

    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!
    Gordon

    N4328M KTDO

  2. #2
    stewartb's Avatar
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    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.
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    skywagon8a's Avatar
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    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.
    N1PA
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    mvivion's Avatar
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    Fuel Injection with a manual primer. Facilitates hand propping with dead battery.

    MTV
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    frequent_flyer's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    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.
    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.
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  6. #6
    Narwhal's Avatar
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    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.
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    stewartb's Avatar
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    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.
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  8. #8

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    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.
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  9. #9
    Gordon Misch's Avatar
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    Thanks folks - please keep experiences coming; we're open to all points of view.

    Any thoughts re specific electronic fuel injection systems? Is there any experience with this system? https://www.flyefii.com/products/efii-systems/
    Last edited by Gordon Misch; 12-12-2021 at 03:34 PM.
    Gordon

    N4328M KTDO

  10. #10
    acroeric's Avatar
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    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.

  11. #11
    skywagon8a's Avatar
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    Quote Originally Posted by mvivion View Post
    Fuel Injection with a manual primer. Facilitates hand propping with dead battery.

    MTV
    Quote Originally Posted by stewartb View Post
    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.
    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.
    N1PA

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    mvivion's Avatar
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    Quote Originally Posted by skywagon8a View Post
    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.
    Yep, and of course, that jump pack will always be fully charged……

    MTV
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  13. #13
    Gordon Misch's Avatar
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    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-
    Gordon

    N4328M KTDO

  14. #14
    stewartb's Avatar
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    Use individual breakers for the injectors. Coupled with their System 32 ignition you’ll have capability to run lean of peak beyond your dreams.
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    aktango58's Avatar
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    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.
    I don't know where you've been me lad, but I see you won first Prize!
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    BC12D-4-85's Avatar
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    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
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    skywagon8a's Avatar
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    Quote Originally Posted by mvivion View Post
    Yep, and of course, that jump pack will always be fully charged……

    MTV
    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?
    N1PA

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    mvivion's Avatar
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    Quote Originally Posted by skywagon8a View Post
    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?
    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

  19. #19
    Bill Rusk's Avatar
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    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
    Very Blessed. "It's not an obsession, it's a passion"
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  20. #20
    stewartb's Avatar
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    What weight the fuel pumps add will easily be offset by the fuel you’ll save on every tank.

  21. #21
    stewartb's Avatar
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    Quote Originally Posted by mvivion View Post
    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
    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.

  22. #22
    skywagon8a's Avatar
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    Quote Originally Posted by mvivion View Post
    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
    Yes Mike, it is a very simple process. Push button. Click image for larger version. 

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    Look at 5 blue lights. Click image for larger version. 

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ID:	58715 Done!

    This jump pack hasn't needed charging for more than two years.
    N1PA
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  23. #23
    skywagon8a's Avatar
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    Quote Originally Posted by Bill Rusk View Post
    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
    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.
    N1PA

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    skywagon8a's Avatar
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    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.
    N1PA

  25. #25
    Crash, Jr.'s Avatar
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    Quote Originally Posted by Bill Rusk View Post
    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
    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.
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  26. #26
    stewartb's Avatar
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    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 by stewartb; 12-13-2021 at 11:47 AM.
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  27. #27
    hotrod180's Avatar
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    Quote Originally Posted by Crash, Jr. View Post
    .... all those Cessna guys with Cessna budgets ......
    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".
    Cessna Skywagon-- accept no substitute!
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  28. #28
    Gordon Misch's Avatar
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    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 - - -
    Gordon

    N4328M KTDO

  29. #29
    skywagon8a's Avatar
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    There are small dynamos available which can be dedicated to the engine's systems. Like this: https://bandc.com/product/alternator...ebuilt/#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.
    N1PA

  30. #30
    RVBottomly's Avatar
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    Quote Originally Posted by Gordon Misch View Post
    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 - - -
    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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  31. #31
    Gordon Misch's Avatar
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    Pete, yeah that's what I was thinking about. Vic, good point, ha!
    Gordon

    N4328M KTDO

  32. #32
    BC12D-4-85's Avatar
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    Modern road vehicles self diagnose. Mainly to maintain emission standards but also to record and display trouble codes when tasked. They can go into a limp mode with reduced power if something isn't right so the driver isn't left stranded.

    For an aircraft with lots of tech I'd want an instrument display that monitors and alerts the pilot to out of range data. It's available.

    Gary
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  33. #33
    stewartb's Avatar
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    EFII's ignition has redundant CDI boxes. Their Bus Manager provides a smart backup power manager when you add a second battery. Not a big weight penalty with EarthX. The Bus Manager can even monitor fuel pressure and activate the electric pump if pressure falls off. Pretty cool tech. I have no disappointment in my API fuel injection or Pmags but if I was specifying an engine today I'd be tempted go with EFI and solid state EI. The fuel efficiency potential is incredible.

    https://www.flyefii.com/products/bus-manager/
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  34. #34
    Gordon Misch's Avatar
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    Good points. Yes, the system does provide for component status monitoring.
    Gordon

    N4328M KTDO

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    aktango58's Avatar
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    Lots of issues with industrial Diesel engines. Ask Mark out in Platinum about his issues with generators for the town.

    Commercial fishermen are all going back to pre-electronic engines to get away from break downs. Lots of guys missing openings due to a sensor putting an engine in limp mode, then it taking days to get to port for them to spend an hour and change a $50 sensor... and the loss of fishing is in the tens of thousands of dollars.

    I don't think there is a right or wrong answer. Most of the considerations I would have is again keeping it maintained. Who can help, how long to get parts? Living in the lower 48 or Anchorage one probably has a much easier time than I do in my region of Alaska.
    I don't know where you've been me lad, but I see you won first Prize!

  36. #36
    stewartb's Avatar
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    Electronic ignition on diesel engines? Who knew?

  37. #37
    cubdriver2's Avatar
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    Quote Originally Posted by aktango58 View Post
    Lots of issues with industrial Diesel engines. Ask Mark out in Platinum about his issues with generators for the town.

    Commercial fishermen are all going back to pre-electronic engines to get away from break downs. Lots of guys missing openings due to a sensor putting an engine in limp mode, then it taking days to get to port for them to spend an hour and change a $50 sensor... and the loss of fishing is in the tens of thousands of dollars.

    I don't think there is a right or wrong answer. Most of the considerations I would have is again keeping it maintained. Who can help, how long to get parts? Living in the lower 48 or Anchorage one probably has a much easier time than I do in my region of Alaska.
    Farmers around here are having the same problems. Prices on 20+ year old 🚜 has more then doubled.
    Progress.

    Glenn
    "Optimism is going after Moby Dick in a rowboat and taking the tartar sauce with you!"
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  38. #38
    Crash, Jr.'s Avatar
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    For those with fuel injection (specifically electronic injection): who was able to just bolt it on and go? Who had to mess around with it to get it to work right or had issues right after install?
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  39. #39
    aktango58's Avatar
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    Quote Originally Posted by stewartb View Post
    Electronic ignition on diesel engines? Who knew?
    That's funny!

    For those that are not motor savvy, the 'new' thing for economy over the last decade or two has been dropping ignition in cylinders when not needed. Some autos actually will idle on half the cylinders to save fuel, (electronics shut off fuel and spark to the cylinders).

    Then newer diesels shut down the fuel to the cylinders to save fuel. Of course, when something is not 'perfect', the engine goes direct to limp, as in very little power allowed so you can 'get home', often at 2-3 knots.

    I don't know about you guys, but I pretty much ignore the check engine lights in my rigs. Always sensors getting carbon on it, or something stupid. Read the code and it is always a bad wire.

    I fight hydraulic leaks in the old loader, so pick your problems you want to solve.
    I don't know where you've been me lad, but I see you won first Prize!

  40. #40
    BC12D-4-85's Avatar
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    A long time ago in the Age of Steam there was a Beaver that had a yellow light that said "Push to Test". I'd do that for fun just to see what would happen. Might have been low fuel line pressure but don't recall. Now with these new electronic enhancements I expect there'd be even more gizmos and light show displays to play with.

    Gary

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