Two CHT, two EGT - which to monitor
Posted:
Sun Jan 27, 2019 12:34 pmby Bryan Cotton
All,
My AlphaMFD can monitor two of each using type Ks. Should I monitor the rear two cylinders?
Re: Two CHT, two EGT - which to monitor
Posted:
Sun Jan 27, 2019 2:23 pmby mike.smith
If I had to choose, that would be my choice, as they will typically run the hottest.
Re: Two CHT, two EGT - which to monitor
Posted:
Sun Jan 27, 2019 5:03 pmby lutorm
Yeah, I'd agree with Mike, certainly for CHT. Although it would be interesting to have a front and back EGT since that's where the big mixture difference is. If you only have EGTs for the back two, you have no idea how pig rich the fronts are running...
Re: Two CHT, two EGT - which to monitor
Posted:
Sun Jan 27, 2019 8:32 pmby Bryan Cotton
So I bought my exhaust used, and it had 4 EGTs before. How should I seal up the extra holes? I could weld them but it could be fun to move the probes around.
Re: Two CHT, two EGT - which to monitor
Posted:
Sun Jan 27, 2019 9:59 pmby woodmw
Could you install 4 probes and incorporate a switch to change between front and back?
Re: Two CHT, two EGT - which to monitor
Posted:
Mon Jan 28, 2019 1:33 amby wlarson861
my Jabiru exhaust had the egt holes drilled and then filled with stainless steel rivets. Looks like they intended the engine could be run with out EGT's if the owner wished.
Re: Two CHT, two EGT - which to monitor
Posted:
Mon Jan 28, 2019 11:11 amby builderflyer
Bryan,
The extra holes in my exhaust are filled with CP-42 rivets. No noticeable leakage and then easily drilled out if I want to move the probes around, just to see what the difference is in EGT.
Art,,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,,,Jabiru 3300 #261
Re: Two CHT, two EGT - which to monitor
Posted:
Sun Mar 10, 2019 8:52 pmby Bryan Cotton
woodmw wrote:Could you install 4 probes and incorporate a switch to change between front and back?
The one issue I see is that the switch is unlikely to be chromel-alumel. This could introduce errors. I suppose you could argue that going from chromel to copper and back should be a net zero voltage. Has anybody done this in practice?
Re: Two CHT, two EGT - which to monitor
Posted:
Mon Mar 11, 2019 5:44 pmby peter anson
The problem I see with only monitoring two cylinders is that it's impossible to know which cylinders are the hottest. The coolest running head on my Jab 3300 engine is the rearmost, coincidentally the one that is most often monitored on engines that only have one CHT gauge. In fact, I have a theory, totally unverified, that the reason some Jabiru engines in Australia have had valve failures is because they are monitoring CHT on the wrong head.
Why not just fit another gauge?
Peter
Re: Two CHT, two EGT - which to monitor
Posted:
Mon Mar 11, 2019 10:56 pmby Corby202
I would recommend monitoring all 4. Aircraft Spruce sell changeover switch's.
On my 2.2 Jab, on the ground the two rear cylinders (cht) are the hottest, this changes over during flight, not by much but it does change.