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Old 12-11-2019, 03:59 PM
mmcelrea mmcelrea is offline
Join Date: Dec 2008
Location: Northern Ireland
Posts: 16
Default fluctuating rpm / map

Hi.I have a new titan io370 with dual pmags, c/s prop and afp150 vertical induction fuel injection system. It runs fine apart from at 1150rpm when the rpm fluctuates between 1100-1200. Also when running at 2300rpm the map fluctuates by about 1". All other rpm settings seem stable in rpm and map. I'm guessing that at 2300 the governor is maintaining the rpm. Not sure if its a weird resonance or something else is going on. The engine is brand new and has around 4 hours flight time on the aircraft. Has anyone else experienced this issue and how did you solve it?
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Old 12-12-2019, 06:05 AM
mahlon_r mahlon_r is offline
Join Date: Jan 2005
Posts: 1,021

The governor will not maintain 2300 rpm un less you set it to 2300rpm. If it is set for take off RPM then it will not kick in until you reach that RPM. So it is unlikely that the rpm is being maintained by the governor at 2300rpm.
What type of indications are u seeing? Electronically generated or steam gauges generated? can you hear the rpm change at 1150 or do you just see it on the tach?
Merry Christmas,
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Last edited by mahlon_r : 12-12-2019 at 06:07 AM.
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Old 12-12-2019, 06:21 AM
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Plummit Plummit is offline
Join Date: Apr 2010
Location: Covid Country-SoCal
Posts: 1,079

Does the EGT rise when the MP wanders at idle? According to Vic, (great webinar Vic!) you may have an intake leak. Just a thought.

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Old 12-12-2019, 06:43 AM
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N941WR N941WR is offline
Join Date: Jan 2005
Location: SC
Posts: 12,887

Do you have restrictors in your manifold pressure lines?

If not, the P-mag timing could be bouncing around, causing the fluctuations.
Bill R.
RV-9 (Yes, it's a dragon tail)
O-360 w/ dual P-mags
Build the plane you want, not the plane others want you to build!
SC86 - Easley, SC
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Old 12-12-2019, 08:33 AM
mmcelrea mmcelrea is offline
Join Date: Dec 2008
Location: Northern Ireland
Posts: 16

There is a restrictor in the manifold pressure line, I believe as supplied by Vans so i dont know if its small enough. It only fluctuates at 11-1200rpm and you can hear it change. From the garmin pilot app I can see that as the rpm decreases the map increases.
During flight when we set the rpm to 2300 its stable but the map fluctuates.
I haven't noticed the egt following any pattern.
The instrumentation is all garmin g3x.
Is it possible that there is something resonating at those frequencies?
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Old 12-12-2019, 08:56 AM
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Raymo Raymo is offline
Join Date: Nov 2014
Location: Richmond Hill, GA (KLHW)
Posts: 2,177


Download the engine data and upload it to Savvy Analysis for review. Allow the data to be shared and post a link here.
RV-7A - Slider - N495KL - First flt 27 Jan 17
O-360-A4M w/ AFP FM-150 FI, Dual PMags, Vetterman Trombone Exh, SkyTech starter, BandC Alt (PP failed after 226 hrs)
Catto 3 blade NLE, FlightLines Interior, James cowl, plenum & intake, Anti-Splat -14 seat mod and nose gear support
All lines by TSFlightLines (aka Hoser)
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