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  #1  
Old 05-17-2023, 10:06 PM
Tankerpilot75's Avatar
Tankerpilot75 Tankerpilot75 is offline
 
Join Date: Jan 2015
Location: Oklahoma City, OK
Posts: 892
Default What a surprise!

I reinstalled my repaired PMag and did an engine ignition check and a CHT was low but itís EGT was normal and aligned with the other EGTs. Suspected a probe problem so swapped with #3.Nothing moved. I then put a heat gun to the #1 probe and guess what - #2 CHT climbed. Put the heat gun to #3 probe - #4 climbed. Checked #2 CHT and #1 climbed.

Decided to check the EGT probes a with the heat gun and they all climbed according to their correct cylinder position. I had just had my EIS worked on by GRT and they had replaced the motherboard to accommodate the change from slick magnetos to PMags. My old EIS didnít have the TacSen selection that newer EIS monitors have and electronic ignitionís require.

Suspecting an improper wiring somewhere I asked GRT to clarify how to read CHTs on the EIS, left to right/top to bottom OR relative to cylinder position on the engine (left CHTs on EIS screen for cylinders 2&4; right CHTs on EIS screens for cylinders 1&3). Jeff was kind enough to quickly respond and confirmed - read them left to right as shown below.

CHT1 CHT2
CHT3 CHT4
Same with EGTs.

But the CHTs on my EIS were in effect showing the information below.
CHT2 CHT1
CHT4 CHT3
and
EGT1 EGT2
EGT3 EGT4

EFIS data correctly corresponded to how the EIS was displaying the information therefore the ďwiring problemĒ had to be incorrectly wired CHT probes to the EIS. Not an mis-wired motherboard.

Hereís the really bad thing,Iíve never touched the engine monitor/probe wiring in the eight years that Iíve owned the aircraft. I once did replace an EGT probe but EGT probes were correctly wired.

The builder flew it for seven years in this condition. Iíve flown it for eight. Therefore this aircraft has flown 15 years with the CHTs probes incorrectly wired to the EIS monitor and no one suspected a thing. No wonder I occasionally had weird engine observations when I tried to analyze the occasional engine hiccups. CHTs were reporting on the wrong cylinders but EGTs were reporting on their correct cylinders.

How and why this occurred - who knows! But at least the issue is now corrected. Itís amazing what youíll find when you start really looking at things! RVs are definitely amateur built and maintained. Canít tell you how many A&Ps / A&P/IAs also have worked on this airplane but itís been quite a few. When things donít make sense thereís always a reason.
__________________
Jim Harris ATP, 2008 RV7A, 2nd owner, N523RM (2015) Superior XPIO-360 B1AA2, MT9 CS prop, Two PMags, Dual GRT Horizon EX with ARINC, EIS, Garmin 340, 335 w/WAAS gps, Dual 430s (non-WAAS), TruTrak 385 A/P with auto level & trim, Tosten 6 button Military Grips, Dynon D10A w/battery backup, 406 MHz ELT, Mountain High O2, CO2 monitor, Flyleds Works system, Custom Interior, TS Flightline hoses, ETX900 Battery, Bruce Cover

Retired - Living the dream - going broke!
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  #2  
Old 05-17-2023, 11:24 PM
PCHunt PCHunt is offline
 
Join Date: Feb 2007
Location: San Diego, CA
Posts: 1,892
Default

That's a great post. Could easily happen, and worth checking.

Thanks for your post!
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Pete Hunt, [San Diego] VAF #1069
RV-6, T-6G
ATP, CFII, A&P

2023 Donation+, Gladly Sent
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  #3  
Old 05-18-2023, 01:58 AM
rv8or rv8or is offline
 
Join Date: Oct 2007
Location: Norwich England
Posts: 242
Default Been there

5th owner.
Shorting link for non impulse mag missing.

Rob
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  #4  
Old 05-18-2023, 06:08 AM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 1,582
Default

TankerPilot, recently on a RV-9 I worked on, I discovered the same thing.. I de-pinned the connector and had to relocate every pin to get the CHTs and EGTs correct..

Tell me more about the PMAGs and the tach connection.. I too have an older EIS and am about to put on Pmags. I just assumed the tach function would pick up the correct signal..
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Tom
Las Vegas
RV-4 flyingÖ
RV-8 empenage finished 10-2020

Wings Started.. 11-2020
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  #5  
Old 05-18-2023, 06:48 AM
Tankerpilot75's Avatar
Tankerpilot75 Tankerpilot75 is offline
 
Join Date: Jan 2015
Location: Oklahoma City, OK
Posts: 892
Default

Quote:
Originally Posted by Taltruda View Post
TankerPilot, recently on a RV-9 I worked on, I discovered the same thing.. I de-pinned the connector and had to relocate every pin to get the CHTs and EGTs correct..

Tell me more about the PMAGs and the tach connection.. I too have an older EIS and am about to put on Pmags. I just assumed the tach function would pick up the correct signal..
Your fix is exactly what I had to do except I only de-pinned CHTs, labeled the wires and re-arranged. This was extremely difficult because of the limited space I had to work in - not enough service wiring.

There are several EIS setting changes required when you upgrade to electronic ignition systems. PMags rpm signal strength is weaker than a traditional magneto (particularly at lower rpm’s) and the GRT EIS manual mentions that electronic ignitions may need to increase the Tach sensitivity signal by removing a resistor and changing the TachSen setting from low (L) to high (H) - section 7.7 in EIS manual. You also need to change your TachP/R setting from 1 to 2 pulses per revolution.

In my case the PMag rpm signal would drop to zero when engine rpm’s fell below 1,000 rpm. Older EIS monitors lack a TachP/R2 setting (only have TachP/R1), and lack both TachSen1 and TachSen2 settings. Therefore to get rpm readings below 1,000 rpm, required in my case, either GRT to “adjust” the sensitivity of my EIS or an upgraded motherboard. I elected to upgrade the motherboard - $450! Of course I later discovered I would also have to re-calibrate my Aux3 and Aux4 L/R fuel tank configuration settings because of the new motherboard. Law of unintended consequences. Major pain in the rear!

I then had an infant mortality issue with the left PMag (bearing too tight) which became very difficult to diagnose and explain correctly to PMag tech support because of this CHT probe misalignment with EGT probes correctly installed. Thankfully EMag Ignition said to just send the PMag to them and they would look at it. Their turnaround was quick.

After re-reading this post I realized I failed to mention the real hero in this saga, my friend Dan Burdette. He has an RV9A with one PMag and knows more about engines and ignition systems than I will ever know. He assisted me with this troubleshooting and was actually the first to identify the CHT misalignment.
__________________
Jim Harris ATP, 2008 RV7A, 2nd owner, N523RM (2015) Superior XPIO-360 B1AA2, MT9 CS prop, Two PMags, Dual GRT Horizon EX with ARINC, EIS, Garmin 340, 335 w/WAAS gps, Dual 430s (non-WAAS), TruTrak 385 A/P with auto level & trim, Tosten 6 button Military Grips, Dynon D10A w/battery backup, 406 MHz ELT, Mountain High O2, CO2 monitor, Flyleds Works system, Custom Interior, TS Flightline hoses, ETX900 Battery, Bruce Cover

Retired - Living the dream - going broke!

Last edited by Tankerpilot75 : 05-18-2023 at 07:24 AM. Reason: Give credit where credit is due.
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  #6  
Old 05-18-2023, 07:22 AM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 2,639
Default

Quote:
Originally Posted by Tankerpilot75 View Post
I reinstalled my repaired PMag and did an engine ignition check and a CHT was low but itís EGT was normal and aligned with the other EGTs. Suspected a probe problem so swapped with #3.Nothing moved. I then put a heat gun to the #1 probe and guess what - #2 CHT climbed. Put the heat gun to #3 probe - #4 climbed. Checked #2 CHT and #1 climbed.

Decided to check the EGT probes a with the heat gun and they all climbed according to their correct cylinder position. I had just had my EIS worked on by GRT and they had replaced the motherboard to accommodate the change from slick magnetos to PMags. My old EIS didnít have the TacSen selection that newer EIS monitors have and electronic ignitionís require.

Suspecting an improper wiring somewhere I asked GRT to clarify how to read CHTs on the EIS, left to right/top to bottom OR relative to cylinder position on the engine (left CHTs on EIS screen for cylinders 2&4; right CHTs on EIS screens for cylinders 1&3). Jeff was kind enough to quickly respond and confirmed - read them left to right as shown below.

CHT1 CHT2
CHT3 CHT4
Same with EGTs.

But the CHTs on my EIS were in effect showing the information below.
CHT2 CHT1
CHT4 CHT3
and
EGT1 EGT2
EGT3 EGT4

EFIS data correctly corresponded to how the EIS was displaying the information therefore the ďwiring problemĒ had to be incorrectly wired CHT probes to the EIS. Not an mis-wired motherboard.

Hereís the really bad thing,Iíve never touched the engine monitor/probe wiring in the eight years that Iíve owned the aircraft. I once did replace an EGT probe but EGT probes were correctly wired.

The builder flew it for seven years in this condition. Iíve flown it for eight. Therefore this aircraft has flown 15 years with the CHTs probes incorrectly wired to the EIS monitor and no one suspected a thing. No wonder I occasionally had weird engine observations when I tried to analyze the occasional engine hiccups. CHTs were reporting on the wrong cylinders but EGTs were reporting on their correct cylinders.

How and why this occurred - who knows! But at least the issue is now corrected. Itís amazing what youíll find when you start really looking at things! RVs are definitely amateur built and maintained. Canít tell you how many A&Ps / A&P/IAs also have worked on this airplane but itís been quite a few. When things donít make sense thereís always a reason.
According to my EIS install manual, you can wire them any way you want, in fact they mention wiring it the way yours is because the cylinder positions correspond with what youíre seeing from the cockpit: CHT 2 & 4 on the left - 1 & 3 on the right. Mine is wired with 1 & 2 on the to and 3 & 4 on the bottom - I think - at least thatís the way I thought I was doing it. Iíll check the next time I have my cowl off. I would actually prefer to have it displayed the way yours is.
__________________
SH
RV6/2001 built 2000/sold 2005
RV8 Fastback/2008 built/sold 2015
RV4/bought 2016/sold/2017
RV8/2018 built/Sold(sadly)
RV4/bought 2019/sold2021
RV6/August 2022 build - Flying
Cincinnati, OH/KHAO
DEC2022
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  #7  
Old 05-18-2023, 01:05 PM
Tankerpilot75's Avatar
Tankerpilot75 Tankerpilot75 is offline
 
Join Date: Jan 2015
Location: Oklahoma City, OK
Posts: 892
Default

Quote:
Originally Posted by Scott Hersha View Post
According to my EIS install manual, you can wire them any way you want, in fact they mention wiring it the way yours is because the cylinder positions correspond with what you’re seeing from the cockpit: CHT 2 & 4 on the left - 1 & 3 on the right. Mine is wired with 1 & 2 on the to and 3 & 4 on the bottom - I think - at least that’s the way I thought I was doing it. I’ll check the next time I have my cowl off. I would actually prefer to have it displayed the way yours is.
If you have a GRT EFIS then your engine CHT readings using the other wiring (my previous CHT wiring) would display cylinder #2 as cylinder #1, #3 as #4, etc. The GRT EFIS cannot be configured to read them right to left. If it could I would have just changed EFIS configuration settings.

Jeff Defow, at GRT, indicated several requests have been made to have EFIS configuration changes to accommodate this orientation but GRT has elected to continue with the left to right approach. If you don’t have a GRT EFIS then the other wiring approach will work just fine.
__________________
Jim Harris ATP, 2008 RV7A, 2nd owner, N523RM (2015) Superior XPIO-360 B1AA2, MT9 CS prop, Two PMags, Dual GRT Horizon EX with ARINC, EIS, Garmin 340, 335 w/WAAS gps, Dual 430s (non-WAAS), TruTrak 385 A/P with auto level & trim, Tosten 6 button Military Grips, Dynon D10A w/battery backup, 406 MHz ELT, Mountain High O2, CO2 monitor, Flyleds Works system, Custom Interior, TS Flightline hoses, ETX900 Battery, Bruce Cover

Retired - Living the dream - going broke!

Last edited by Tankerpilot75 : 05-18-2023 at 01:18 PM.
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  #8  
Old 05-18-2023, 07:34 PM
Scott Hersha Scott Hersha is offline
 
Join Date: Jan 2005
Location: Cincinnati, OH
Posts: 2,639
Default

Quote:
Originally Posted by Tankerpilot75 View Post
If you have a GRT EFIS then your engine CHT readings using the other wiring (my previous CHT wiring) would display cylinder #2 as cylinder #1, #3 as #4, etc. The GRT EFIS cannot be configured to read them right to left. If it could I would have just changed EFIS configuration settings.

Jeff Defow, at GRT, indicated several requests have been made to have EFIS configuration changes to accommodate this orientation but GRT has elected to continue with the left to right approach. If you donít have a GRT EFIS then the other wiring approach will work just fine.
Yep, I didnít think of that - good call. Iíve wired mine as the manual suggests, so my EFIS will match, not that I considered that when I wired it and set it up. Looks like I limped into it. My first EIS (20+ years ago) was stand alone - no EFIS.
__________________
SH
RV6/2001 built 2000/sold 2005
RV8 Fastback/2008 built/sold 2015
RV4/bought 2016/sold/2017
RV8/2018 built/Sold(sadly)
RV4/bought 2019/sold2021
RV6/August 2022 build - Flying
Cincinnati, OH/KHAO
DEC2022
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  #9  
Old 05-19-2023, 01:15 PM
BoydBirchler BoydBirchler is offline
 
Join Date: Jul 2020
Location: Indianapolis
Posts: 241
Default

Very common on dual mags, is to find the left switch position is actually checking the right and the right switch position is checking the left...Easy to do, if you forget the switch is making on the mag you are not checking.
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