912s are normally-aspirated, 914s are turbo.
As far as burning more fuel, what's the kit maker have to say about that? How do you know it's not normal for his kit? Ask other owners of the kit...
Try swapping the injectors and see if the problem moves. However, since you say only one cylinder has the issue, it tends to rule out fuel issues. You DID check the other spark plugs and they look fine, right?
Trash the fuel injection and put the carb back on. Why would you even consider adding more complexity to an aircraft for such a nominal increase in fuel economy?
Aeromoto wrote: Trash the fuel injection and put the carb back on. Why would you even consider adding more complexity to an aircraft for such a nominal increase in fuel economy?
Av gas in France is crazy expensive. 15% fuel burn decrease would be helpful. Regular car gas was $8-9/gallon in 2011.
Kenny_McCormic wrote: Missed the new computer, if that's the case I'd be tempted to say the EFI is fine, potential wiring issues aside. I dont think it would work at all with the injector hooked up backwards or I'd suggest that. From whats been provided, I do think the EFI conversion might be coincidental to the actual problem. How is ignition controlled on one of these? Id assume any HV leak would show up on the radio as noise, so if its ignition related it would have to be on the low tension side or a bad plug.
What is a HV leak? Did you mean HG? Apparently the ignition is completely separate from the fuel injection kit and hasn't changed. From what I understand there is something on the crank that is picked up from some magneto that tells the injectors when to fire.
kb58 wrote: 912s are normally-aspirated, 914s are turbo. As far as burning more fuel, what's the kit maker have to say about that? How do you know it's not normal for his kit? Ask other owners of the kit... Try swapping the injectors and see if the problem moves. However, since you say only one cylinder has the issue, it tends to rule out fuel issues. You DID check the other spark plugs and they look fine, right?
Kit maker is also trying to figure this out as the kit was supposed to save him 15%, not burn 15% more. We've already replaced both injectors on that bank with new ones. The other spark plugs look fine, cylinder 1 is black and I think wet.
Fueled by Caffeine wrote:Aeromoto wrote: Trash the fuel injection and put the carb back on. Why would you even consider adding more complexity to an aircraft for such a nominal increase in fuel economy?Av gas in France is crazy expensive. 15% fuel burn decrease would be helpful. Regular car gas was $8-9/gallon in 2011.
He runs car gas but yeah, it's pricey.
IF we simplified the problem and we know that cyl temps for #1 are way lower and the plug is too dark/wet. Would we think:
So it was supposed to burn 15% less but burns 15% more so that's actually a 30% benefit he's missing out on as it stands now. That's significant!
Enyar said: IF we simplified the problem and we know that cyl temps for #1 are way lower and the plug is too dark/wet. Would we think: Too much gas, normal spark Normal gas, poor spark
I doubt it's the spark. They have dual ignition systems to prevent problems, and didn't you say you tried to run it on both systems with no difference? It would be very unlikely (although not impossible), that both ignition system would give problem to the same cylinder at the same time.
Does the injection manufacturer have a website. I am curious to know find out more about it, because the lack of an O2 sensor anywhere in the system, makes me dubious about the setup.
HV-High voltage.
You can't run an O2 sensor with leaded fuel for long, a lot of avgas is still leaded to some extent.
Enyar wrote: He runs car gas but yeah, it's pricey. IF we simplified the problem and we know that cyl temps for #1 are way lower and the plug is too dark/wet. Would we think: 1. Too much gas, normal spark 2. Normal gas, poor spark
I'd be guessing (1) simply because of the increased fuel consumption.
If I were in your shoes I'd try to hook up a scope to the injector for cyl #1 to see if there is any noise that might hold the injector open longer. If you've already swapped injectors around and all that jazz, my gut feeling says it's an electrical problem. Or both ECUs have the same problem, which seems a little odd to me.
Kenny_McCormic wrote: HV-High voltage. You can't run an O2 sensor with leaded fuel for long, a lot of avgas is still leaded to some extent.
Enyar mentioned that his uncle is using regular car gas, which is unleaded in Europe. So at least sticking a wideband up the exhaust should be possible without messing it up.
Actually, if he has access to a gas analyzer that might be a good idea to find out if it's running rich.
BoxheadTim wrote:Kenny_McCormic wrote: HV-High voltage. You can't run an O2 sensor with leaded fuel for long, a lot of avgas is still leaded to some extent.Enyar mentioned that his uncle is using regular car gas, which is unleaded in Europe. So at least sticking a wideband up the exhaust should be possible without messing it up. Actually, if he has access to a gas analyzer that might be a good idea to find out if it's running rich.
Remember, aircraft, something breaks people die. An O2 sensor that MIGHT be exposed to leaded fuel is a liability.
In reply to Kenny_McCormic:
I know, I wasn't suggesting to leave the sensor on there or hook it up to the ECU. However I'd try to use the sensor or a "proper" exhaust gas analyzer as a diagnostic aid to figure out what's going wrong.
I think its safe to say we know its running rich. Does it have a manifold vacuum gauge? That will rule out a lot of valve train problems.
Kenny_McCormic wrote:BoxheadTim wrote:Remember, aircraft, something breaks people die. An O2 sensor that MIGHT be exposed to leaded fuel is a liability.Kenny_McCormic wrote: HV-High voltage. You can't run an O2 sensor with leaded fuel for long, a lot of avgas is still leaded to some extent.Enyar mentioned that his uncle is using regular car gas, which is unleaded in Europe. So at least sticking a wideband up the exhaust should be possible without messing it up. Actually, if he has access to a gas analyzer that might be a good idea to find out if it's running rich.
The Rotax 912/914 was designed to run on mogas. While it is possible to run it on avgas. it is not recommended. Also, an O2 is not necessary to keep the engine running (simply run it on a pre-determined map, like this setup), but it is the most precise way of knowing how the gas is being burned in the engine.
In reply to fanfoy:
Thanks for clearing that up, I don't know light aircraft engines, just engines. I do find it odd that that the kit maker thought they could somehow add open loop fuel injection and tune it closer to the ragged edge for efficiency, without having problems.
That's OK, Rotax introduced an injection system for the 912 last year and they share your opinion, because they didn't use an O2 sensor. They use EGT to correct for fuel. That's understandable when you need to sell to the hyper-conservative civil aviation people. A lot of those people still run dynamos and points ignition, because you really can't trust that new tech like alternators 
and they will want to run avgas in their airplane even if the engine manufacturers tells them to run mogas.
But for an after-market injection system, I would have assumed that they would have used the much more reliable and precise O2 sensor.
What if you take the injector from the bad cylinder and put it on a different cylinder - does the problem follow the injector? It could be leaky - or the wrong part, one that flows significantly more.
In reply to MadScientistMatt:
If I read Enyar's first post correctly, they've already replaced the fuel rail and the injectors on the affected cylinder pair, without any apparent changes.
BoxheadTim wrote: In reply to MadScientistMatt: If I read Enyar's first post correctly, they've already replaced the fuel rail and the injectors on the affected cylinder pair, without any apparent changes.
Missed that, sorry. I'd look for issues with the intake, exhaust, or valvetrain resulting in less air making it to the #1 cylinder, in that case.
You'll need to log in to post.
