CHT Blues!

Mv031161's picture


Removed the old reliable VM1000 ECM and installed the MGL Discovery Lite I-EFIS. Love the functionality and capabilities of the new system however Im chasing a ghost or a real problem. Done with all the usual mechanical troubleshooting.. I.e. compresion, boroscope, FF, Bafling, EGT, swaped probes, etc...using the k type probes and unit is set for them.   I never noticed any of cylinder so hot w the VM 1000 above 400!!! .. Now w the MGL im seing #2 rising to 460 @acro power and 430 during cruise!   I got Two questions and help request......anyone w an MGL system that have experience same? And regardless of what monitoring system you use; can you share with me your CHT reading @ high power (acro) and cruise? 


have just done exactly the same thing with the same unit. Turned out we had a cracked cylinder head. Mine was on cylinder 1, and CHT would do exactly the same thing as  you describe. My cylinder head temperatures at full power for aerobatic flight are approximately 160+ or -5°C. At cruise settings, 6000 feet plus, typically running rpm of 2500, 35 L per hour (I like to keep things cool) maximum CHT 160+ or -5° C. Approximately 150 kn indicated.

My biggest problem was an enormous amount of radio interference from the unit into the radio. It is taken as a long time to do the shielding and to get the radio back to something reasonable.



Did you replace the CHT

Did you replace the CHT probes as part of the MGL upgrade? I've been told that their accuracy degrades over time, and that folks are sometimes surprised with higher readings when they replace the old probes.

CHT probes

initially stayed with same CHT, EGT in the hope of only changing one parameter. The rise in cyl 1 triggered a swap of the wires from cyl 1 &3 then replacement of cyl 1 with new.

i have been paying rather more attention of late & at full power full rich 2700 /30" this week( 25-32 deg C, 1010mb)  I have 145-160 +\- 3 deg c across all cylinders & EGT 550-600 +\- 10 deg c

the temps remain very tightly grouped & in retrospect the readings that we thought were cooling or probe problems were accurately indicating a cracked head.

the other very noticeable thing is that the response rate of all parameters is very fast, in point the instantaneous oil pressure can be alarming. Doing repeated verticals with spins, tail slides & torque rolls can show wild fluctuations in oil pressure!! 

We are now bedded in nicely all working well. The secret with the radio noise is as much separation of ALL DC power lines & antenna cables from EFIS then Quad shield coax, plus Huge earths to everything.

try flying the GILS at 25/25 it's fun!!


Cht blues

Mv031161's picture

yes it was a programing issue. I have J probes not K probes. All good.  Drove me nuts! 

All K Probes have a yellow

Mv031161's picture

All K Probes have a yellow and Red wire, all J probes  are white and black unless you have GEM probes which are the  only ones using Red and white wires. I have Gem probes but is not mentioned anywhere unless you dig deep into your search.   I love the discovery I lite I efis...pretty cool gizmo