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Post by geobuff on Aug 11, 2017 0:38:18 GMT
OK guys, Diagnose the problem with my 912is: a) flying along at 5500 feet 2 days ago NOT in eco-mode b) reduce power a little so the 912is goes into eco-mode (lean of peak) c) over the next 60 seconds, the #4 cylinder EGT goes from 1600 degrees to 1800 degrees d) the Land-A light starts blinking e) I reduce power to idle and the EGT drops to 1400 degrees f) increase power to 5400 rpm, back into eco mode and EGT goes back up to 1800 degrees. g) press throttle to firewall and EGT drops to 1500 degrees Now if I could only write backwards so you have to use a mirror to find the solution: 1) on the 912is, EGT temps rise 100 degrees when going from full throttle to eco mode. Logically you would think it should be the opposite, but it is not. This is because eco-mode is 'lean of peak' which starves the cylinders of fuel relative to O2. Fire-wall throttle floods the cylinders with excess fuel, cooling them. 2) normally eco-mode generates 1600 degrees on cylinder #4. Now the EGT is rising to 1800 degrees, so something is further restricting fuel relative to O2. 3) each fuel injector (2 per cylinder) has 4 VERY TINY holes. If 1 of those tiny holes gets plugged, the cylinder is getting 1/8 less fuel (12%) but the O2 is the same 4) that is SUPER-lean, and the EGT will rise accordingly, in this case to 1800 degrees. Took the plane to Lockwood today. They hooked up the magic electronic computer box and it immediately said my left #4 cylinder fuel injector was partially plugged. Put in a new one and everything cool (no pun intended). In case you are wondering what a fuel injector looks like, attached a picture below. The long axis is 2.4 inches. If you look carefully you can see the 4 holes in the tip. The 'box' on the right side is for the electrical plug. The fuel line attached to the top.  PS, it cost $190. I expected it to cost more. |
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Post by jetcat3 on Aug 11, 2017 4:32:37 GMT
How cool! What an amazing little engine the 912 iS is. Thanks for sharing!
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Post by Glenn on Aug 11, 2017 12:46:15 GMT
Doesn't take much to plug up one of those holes. Since Lockwood replace the injector, I guess that means the injector can't be cleaned.
Glenn
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Post by geobuff on Aug 16, 2017 3:23:47 GMT
Another update on the Fuel Injectors. After getting #4 injectors replaced, a couple days later I noticed high EGT on the other 3 remaining cylinders. There were not extreme, but over the limit (1700 degrees in eco mode). At that point I realized the remaining injectors were dirty, not plugged. The question is why. All this injector problem started a couple weeks ago, so I assume I got a bad batch of gas.
I have been using MoGas 90 octane from a local Marathon station. Something was wrong with the last batch. Probably low octane for starters, as "recreational fuel" is unregulated. There is no assurance what the pump says is what you get. The automotive gas (regular and premium is regulated and if they say xx-octane, that is what you get.
So I changed my fuel from 'recreational fuel' to 'premium auto gas' (93 octane with ethanol), and put in a can of fuel injector cleaner. Over the next several hours of use, the EGT temps slowly dropped over 100 degrees as the injectors cleaned, pretty much into the normal range for the 912IS engine. Botton line here is I am done with ethnol-free recreational fuel and am now a premium auto gas convert. I know some of you are using the premium auto fuel and have been without problems. Of course, the gas is more fussy on the fuel injected engines compared to the carburetor engines, as I have found out.
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Post by jetcat3 on Aug 16, 2017 16:29:22 GMT
Geobuff, are you using 93E10 now? That's very interesting to hear. Glad it's running like a top with auto fuel!
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Post by geobuff on Aug 18, 2017 1:13:46 GMT
Yes, using 93E10. I will use 93E10 for now and not go back to 'recreational fuel', which was fowling my fuel injectors. .
I did an interesting test yesterday between 93E10 and 100LL. I put 93E10 in one tank and 100LL in the other tank. I had prefect smooth weather for testing yesterday. Flying full throttle on the 93E10 I was cruising at 121 kts, When I switched to 100LL, I would do 122 kts. It takes about 15 seconds to clear the lines when switching. I did the switch several times with the exact same results. From this I conclude that the Ethanol-laced 93E10 has a little less energy than 100LL, which is making exactly a 1kt difference in speed due to a very slightly reduced thrust.
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Post by mackattack on Aug 18, 2017 16:07:35 GMT
Really interesting test and outcome! Makes sense and also sufficient evidence that it doesn't really matter a whole lot in real world flying. Were you literally at WOT or top of the green?
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Post by Glenn on Aug 18, 2017 16:38:03 GMT
Yes, using 93E10. I will use 93E10 for now and not go back to 'recreational fuel', which was fowling my fuel injectors. . When I went thru the 9 series service class at Lockwood, Dean said that the correct fuel filter ( not paper) will allow some small particles to pass. This is by design. Some have tried using an incorrect paper filter but the paper fuel filter can become completely clogged which results in the engine stopping. So it does make sense that the fuel you used might have contained bit of garbage that passed thru the fuel filter and then lodged in the injectors. Probably a good thing you switched fuels. Glad to hear you had no inflight emergency. Glenn |
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Post by geobuff on Aug 19, 2017 0:24:01 GMT
Really interesting test and outcome! Makes sense and also sufficient evidence that it doesn't really matter a whole lot in real world flying. Were you literally at WOT or top of the green? Once I push the throttle 1/4 inch past LOP position, I enter high speed flight. Doesn't matter much if the throttle is 1/4 inch or 3 inches (WOT) past LOP throttle position. My WOT propeller speed is 5650 RPM |
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Post by geobuff on Aug 19, 2017 23:38:16 GMT
THE EGT SAGA CONTINUES: As I have been complaining for weeks, my EGT's are to high. Some of the problem was due to plugged fuel injectors, and changing fuel and using Fuel Injector cleaner got temps down at least 75 degrees. So EGT temps are currently acceptable BUT not as low as a year ago. My #4 EGT became erratic, so I decided to purchase a new EGT probe from Lockwood, for a mere $200. Not only did it fix my erratic nature of the readings BUT the temps dropped 100 degrees. Now, the temps did not drop at all BUT the probe is reading 100 degrees less. The bottom line here is the old probes are reading 100 degrees hotter than they actually are. In the picture below, note #4 EGT. In the left picture the #4 is reading 1619 degrees. After #4 replacement with a new probe, the temp is reading 1529 degrees. I will no longer worry about EGT temps because I now know the old probes are reading 100 degrees hotter than they actually are. If I wanted to spend another $600, I would just replace the remaining 3, but I can live with the facts. No worries.  |
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Post by jetcat3 on Aug 24, 2017 13:53:28 GMT
Very interesting Geobuff. Quick question for you iS owners, does the 912 iS struggle with hot starts? Or is the fuel pressure so great that it keeps the fuel from vaporizing?
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Post by Flocker on Aug 25, 2017 14:55:04 GMT
Very interesting Geobuff. Quick question for you iS owners, does the 912 iS struggle with hot starts? Or is the fuel pressure so great that it keeps the fuel from vaporizing? I've never had any hot start issues. |
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Post by geobuff on Aug 26, 2017 13:44:58 GMT
Never had a problem starting.
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Post by geobuff on Sept 24, 2017 17:44:35 GMT
THE EGT SAGA CONTINUES: As I have been complaining for weeks, my EGT's are to high. Some of the problem was due to plugged fuel injectors, and changing fuel and using Fuel Injector cleaner got temps down at least 75 degrees. So EGT temps are currently acceptable BUT not as low as a year ago. My #4 EGT became erratic, so I decided to purchase a new EGT probe from Lockwood, for a mere $200. Not only did it fix my erratic nature of the readings BUT the temps dropped 100 degrees. Now, the temps did not drop at all BUT the probe is reading 100 degrees less. The bottom line here is the old probes are reading 100 degrees hotter than they actually are. In the picture below, note #4 EGT. In the left picture the #4 is reading 1619 degrees. After #4 replacement with a new probe, the temp is reading 1529 degrees. I will no longer worry about EGT temps because I now know the old probes are reading 100 degrees hotter than they actually are. If I wanted to spend another $600, I would just replace the remaining 3, but I can live with the facts. No worries. I have replaced my second EGT sensor. When I replaces #4, the temp readings dropped 100 degrees, indicating the old probe was reading incorrectly. My #3 is also pushing the upper limit, at about 1650 degrees. I replaced that sensor yesterday, and the new reading is about 120 degrees cooler, registering 1530 degrees. Since I now know the sensors are reading 100 degrees hotter than they really are, theoretically I can just ignore them, except I get red lights flashing when the temps are reported too high. I have 500 hours on my Astore, so it seems the sensors are about 500 hour sensors and need to be replaced. Unfortunately they are $200 each, so that is an expensive swap. No, cleaning them does not help. Been there done that.... It seems the internal ceramic just starts to warp and create bad readings. I am not sure if the carbureted engines have EGT sensors, or this is just a 912_IS issue. Interestingly when I brought up the high temp issue a few months ago at both Tecnam and Lockwood, the only answers I got were "well, older engines just run hotter", which I now know is BS. I continue to be disillusioned by all the bad "expert" advise I get from the "professionals". My list of disillusionments is getting very long. So sad. Who can we trust. |
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Post by Flocker on Mar 20, 2019 23:34:17 GMT
They hooked up the magic electronic computer box and it immediately said my left #4 cylinder fuel injector was partially plugged. Put in a new one and everything cool (no pun intended). PS, it cost $190. I expected it to cost more. Took my plane to a service center today and had the same diagnosis. It all started with a flashing Lane B light after a descent into the airport. Conducted a BUDS download today and it turned out to be an injector issue. (Possible clogged) New injector on order. |
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PS, it cost $190. I expected it to cost more.
