M

meyer228

Active Member
Just did an EFIS/EMS upgrade and discovered my CHT's were a little hot (417F - #3). My previous EMS would only monitor one cylinder at a time so I usually monitored #3 and it would occasionally go above 200C on climb out. So checking and considering the usual suspects. Full rich , intake leaks, timing, baffles, exit opening, air dam...

Mixture is full rich but my timing was +3.5 on the left mag...

Does any one know or have a guess regarding the effects of timing on CHT?

We've set both mags to 25. Going to go fly it Friday and report back.

RV6a, CS, o320-D1A w/ported heads
 
Last edited:
meyer228 said:
Mixture is full rich but my timing was +3.5 on the left mag...

Does any one know or have a guess regarding the effects of timing on CHT?

We've set both mags to 25.
Click to expand...

+ 3.5 above the 25, for a total of 28.5?

Too much advance will raise CHT, too little will raise EGT. Has to do with where the fuel/air charge is doing its burning.
 
Mike S said:
+ 3.5 above the 25, for a total of 28.5?

Too much advance will raise CHT, too little will raise EGT. Has to do with where the fuel/air charge is doing its burning.
Click to expand...

28.5

Yes, I understand that. Just wondering if anyone has had experience in how much it would raise the CHT's.
 
I dialed mine back about 3 degrees and got about 30 degrees drop.

Bob burns
Rv-4 n82rb
 
I found a Mag with a +6 degree advance. Dialing it back to suggested timing dropped by CHT's at least 30 degrees F.
 
Besides CHT temperatures, what advantage or disadvantage will dropping the timing a few degrees do with an electronic (dual Pmags in my case) ignition?

:cool:
 
GalinHdz said:
Besides CHT temperatures, what advantage or disadvantage will dropping the timing a few degrees do with an electronic (dual Pmags in my case) ignition?

:cool:
Click to expand...

There's a really good thread (Mike S. posted earlier in this post) that has a bunch of information on timing.

I just found mine to be advanced and out of sync. And I had been experiencing slightly higher CHT's.
 
CHT update...

Sure enough. CHT's down about 20 degrees.

I also put a small strip of foil tape along the bottom of the number one cylinder for a later flight and that balanced the temperature differential between 1 and 3 and brought the temp down another 20.

Now I think I make that permanent and replace the foil with sheet metal.
 
Had this exact issue last year.

At the annual, we decided to have a concerted look at high CHT's. Over 400 when stunting.

Retimed the P Mags, modified the deflector plate on the #1 cylinder, swapped aero plugs for NGK Iridium plugs, tidied up the sealing around the baffles.

Wow - CHT's dropped 50f. Problem was we don't know which fix did or contributed to what.

:eek:
 
Hi Michael, I enjoyed meeting you and Grant when you guys RV delivered a gps to 68CA.

Enjoy your new panel and low cht's......

Warren
 
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