Rich Posted May 17, 2015 Report Share Posted May 17, 2015 While going over the numbers for the 912ULS engine I noted the MP should be in the 18-28 HG range. Since new my engine operates between 12.8 and 14 HG. The engine runs fine but now I'm concerned that the wrong pressure sending unit was installed in the AC. Thoughts appreciated Link to comment Share on other sites More sharing options...
Tom Baker Posted May 17, 2015 Report Share Posted May 17, 2015 While going over the numbers for the 912ULS engine I noted the MP should be in the 18-28 HG range. Since new my engine operates between 12.8 and 14 HG. The engine runs fine but now I'm concerned that the wrong pressure sending unit was installed in the AC. Thoughts appreciated What does it read when the engine is not running? Link to comment Share on other sites More sharing options...
Roger Lee Posted May 17, 2015 Report Share Posted May 17, 2015 Possibly the sending unit or an air leak. Link to comment Share on other sites More sharing options...
Rich Posted May 17, 2015 Author Report Share Posted May 17, 2015 What does it read when the engine is not running? Tom, I have never looked after engine shutdown. Roger, Where would be a good place to start to look for a leak and could you tell me where the sending unit is located? Link to comment Share on other sites More sharing options...
FastEddieB Posted May 17, 2015 Report Share Posted May 17, 2015 For those who may not have picked up on it... ...without the engine running a MP gauge should roughly read atmospheric pressure. Which is not as simple as altimeter setting unless based at SL. Link to comment Share on other sites More sharing options...
Flying Bozo Posted May 17, 2015 Report Share Posted May 17, 2015 Sounds like the Inches of Mercury and the PSI got mixed up since there is a .49 conversion factor..HUH? 28 inches would convert to 13.72 PSI which is very close to the 14 in HG that you are showing. Link to comment Share on other sites More sharing options...
Tom Baker Posted May 17, 2015 Report Share Posted May 17, 2015 The MP line comes off the aluminum balance tube and will likely go through the firewall, at least that is how it is done on the CT. Anyway you can follow that rubber line to the sensor. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 17, 2015 Report Share Posted May 17, 2015 Maybe. Though I don't recall PSI creeping into the discussion. I don't recall ever seeing a MP gauge showing anything other than inches of mercury: Roughly what it would show at SL on a standard day. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted May 17, 2015 Report Share Posted May 17, 2015 Maybe. Though I don't recall PSI creeping into the discussion. I don't recall ever seeing a MP gauge showing anything other than inches of mercury: Roughly what it would show at SL on a standard day. The psi conversion might come into play by the coder of a flat panel display. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 17, 2015 Report Share Posted May 17, 2015 The psi conversion might come into play by the coder of a flat panel display. Sure. But for now, I think I'd advise that we all think in inches of mercury, since its still the norm for aviation. Link to comment Share on other sites More sharing options...
Ed Cesnalis Posted May 17, 2015 Report Share Posted May 17, 2015 Sure. But for now, I think I'd advise that we all think in inches of mercury, since its still the norm for aviation. The conversion factor seems correct. If unconverted data is being displayed there is no other way to solve this this so it will display inches of mercury than to think in both psi and inches of mercury and add the conversion prior to displaying the result. Link to comment Share on other sites More sharing options...
Rich Posted May 18, 2015 Author Report Share Posted May 18, 2015 If you look at the "48 Miles from Charlston" in my photo gallery, you'll see that the Tru Trak AP III is reading 13.5 HG at 5400+ RPM. Link to comment Share on other sites More sharing options...
BobJones Posted May 18, 2015 Report Share Posted May 18, 2015 When I was flying certified aircraft with a constant speed prop and manifold pressure guage, 23/23, 24/24, 25/25 were commonly used settings for manifold pressure and rpm with manifold pressure in inches of mercury. 13.5 seems really low unless there is something different about how or where it is measured. It does sound more like a psi measurement even though the guage says inches of mercury. IDK? Link to comment Share on other sites More sharing options...
Flying Bozo Posted May 18, 2015 Report Share Posted May 18, 2015 I think your sender is putting out PSI to an inches HG display. If you are really doing 13.5 in HG you are idling. Link to comment Share on other sites More sharing options...
Rich Posted May 18, 2015 Author Report Share Posted May 18, 2015 Thanks for all the input. I'll be calling TruTrak this morning and see if they supplied the wrong sending unit. Link to comment Share on other sites More sharing options...
Tom Baker Posted May 18, 2015 Report Share Posted May 18, 2015 You never did say what it is with the engine off. If it is up near 30 then it is not the sender, but a leak in the line, I did notice you said new engine, but I wouldn't expect that the MP sensor would be changed at an engine change, unless it was specifically requested to be changed. Link to comment Share on other sites More sharing options...
Rich Posted May 18, 2015 Author Report Share Posted May 18, 2015 Hi Tom, I did mention that I never looked at it with the engine shut down. I'm not close to the airport so I'll need to wait for the next trip. The engine is the engine supplied with the aircraft when new (2012). Approx 190 TT. I just spoke to Zack at Tru Trak and he's researching as I write this post. I'll post the findings, probably later on today. I just got the call and they want to know what it's saying with the engine off as you suggested. It'll have to wait until I get out there. Link to comment Share on other sites More sharing options...
BobJones Posted May 18, 2015 Report Share Posted May 18, 2015 I'll bet it reads close to 14.7. Link to comment Share on other sites More sharing options...
Rich Posted May 25, 2015 Author Report Share Posted May 25, 2015 Bob, Close but a little low. I went out to fly today and noting the manifold pressure with the engine off it read 15.5. Baro pressure at the field was 30.07 At 3K feet the manifold press on the Tru Trak unit read 12.5 @ 4750 RPM. I need to relay this info to Tru Trak on Tuesday. Link to comment Share on other sites More sharing options...
FastEddieB Posted May 25, 2015 Report Share Posted May 25, 2015 Just a reminder that barometric pressure and altimeter setting are two different things. At Denver, you can have an altimeter setting of 30.00 in/hg and barometric pressure of about 25". I assume field elevations in PA are usually less than 5,000', but at anything other than SL the difference still has to be considered. Link to comment Share on other sites More sharing options...
Roger Lee Posted May 25, 2015 Report Share Posted May 25, 2015 I flew yesterday at 4200' with an altimeter setting of 30.07. The MAP was 23". MAP really isn't very useful with a 912UL or ULS with a fixed pitch or ground adjustable prop. Link to comment Share on other sites More sharing options...
Roger Lee Posted May 25, 2015 Report Share Posted May 25, 2015 It just a display that the D120 Dynon has. If you used the D120 Dynon with the Rotax 914 turbo and or an in flight adjustable prop then it would be helpful. Link to comment Share on other sites More sharing options...
Rich Posted May 25, 2015 Author Report Share Posted May 25, 2015 Thanks for all the replies. I'm just an "A" personality when it comes to my airplane. Even though I know all is well with the engine, I want the readouts to be correct. May be it's a simple fix. I'll know on Tuesday and post what Tru Trak has for a remedy. Thanks again. Link to comment Share on other sites More sharing options...
Rich Posted May 26, 2015 Author Report Share Posted May 26, 2015 A call this AM to Tru Trak. The EDM must be removed and sent in to the shop as there isn't a remote sending unit. The sensor for the MP is located within the EDM. I'll be waiting until the snow flies again to remove and ship the unit. Link to comment Share on other sites More sharing options...
TrutrakTech Posted July 1, 2015 Report Share Posted July 1, 2015 I apparently need to venture out of the Autopilot sub-forum. The sensor is on the engine data module board itself, no remote sensor. It sends a signal over to the screen. Units and arithmetic on the signal are done in the software of the screen. I doubt it's a software issue, otherwise we'd see this all over the place. I do suspect this is a sensor problem. There could be damage to the sensor's diaphragm. We'll check it out when we get it! Link to comment Share on other sites More sharing options...
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