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Anyone else getting higher CHT on #2?

JHartline

Well Known Member
Hopefully I haven't missed a previous thread on this...

I am consistently seeing CHT's around 15-20 degrees higher on the #2 cylinder during higher power settings. Also, both #1 and #2 run a bit higher than the others at most settings. Power setting around 50% and below result in more uniform temps but #2 is always the highest. On hot days the #2 CHT wants to get up around 385 during climbout.

I have checked baffling (including inter-cylinder), seals, etc and had done a couple of sessions with flashlight, mirror and RTV to get almost all the little gaps filled. My cowling is done per plans...nothing fancy there. Preflight and inflight mag checks indicate a healthy ignition system. I even checked to make sure my #2 CHT wasn't indicating +20 degrees at ambient temps. I'm curious if the temperature spread is a common thing among the 14's or if I have a elusive detail to pursue.

My plane has an IO-390, dual P-mags, and AFP FM-150 fuel injection system and I have about 35 hours on the plane. Again, I'm mainly curious if other operators are seeing something similar.
 
I have exactly the same thing at almost identical hours with identical equipment. I tried taking the small baffle plate off the front of number 2 and no change. I feel the gaps are well sealed.

I sure would like to bring down the number 2 cht. EGT on 2 is often a little lower than the others too.

All my EGT peak within 0.2 gph of each other so I think the injectors and fuel are okay so far as that goes.

I have a thunderbolt io390.

I was going to put another foam piece inboard of the first at the prop governor next time the top is off.
 
The fix is simple - bypass ducts on #2 and #3 to fix the zero fin depth issue.

LOTS of threads here on the subject.
 
Thanks!!

Doc - appreciate the confirmation.

Michael - found your circa 2012 thread. Some of the images have disappeared but there?s enough information to go on. Looks like the aft baffles on the 14 have similar bypasses built in for the rear cylinders. I?ll need to remove the cowling to investigate how to handle the front ones but it helps to know that others have successfully addressed this.
 
threads cira 2012?

I searched Michael's threads circa 2012 but could not find post prior to 4/2018. Curious about the #2 high temps fix.
 
I'm not sure how we would do that mod for #2 since our filter is right in front of it and the frame for the snorkel would keep any air from being directed as the example above shows. I see the problem: get air to the bottom of 2. Not sure how to do it still. I think we need an RV14 specific mod.
 
Cylinder temps

Perhaps you could give your engine a few more hours to settle in? My engine took a bit over 100 hours.

The Cylinder #2 spacer is incorporated into your baffles. See Figure 1: Left Forward Baffle Part # CB-00010 on page 47-09. Neither will you need to fix Cylinder #3 with a duct because Vans has already incorporated that into your baffles see Figure 1: Cylinder 3 Bridge on page 47-05 of the plans.

Again, I’m sorry I don’t have an answer for the OP original question. I just wanted others to understand the #2 and #3 baffle modifications were incorporated by Vans.

Before Post #2 my guess would have been to look at Cylinder #2 EGT, but that was addressed by JDA_BTR.

NOTE: The baffles are one of the many areas that Vans reduced the build time on the -14/-14A. They are among the best I’ve seen. The only modification I made was to shorten and bend the lower cylinder wraps to stop just short of the fin comb.

Below is pretty typical for my IO-390 with Vans baffles.

xf19ip.jpg
 
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Correct EFIS probe setting

Ensure that you have set the correct CHT probe type in the EFIS settings, K or J type will give a different output.

If you have J type but have set K type in the EFIS then the temperature will read very high when in reality it is normal.

It's worth confirming before carrying out any significant work.
 
I initially had higher temps on #1 and #2 - I balanced them by removing the front baffle on the left and cutting the one on the right down by 50%. There's only about 15-20 degree difference hottest to coolest now, and never a "hot" cylinder. Cruise CHT's are less than 340 all cylinders at cruise altitude (Florida, August).
 
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Thanks Marvin for the clarification. I've never seen RV-14 baffles and just assumed they were continuing with the same deficiency as legacy models. Good to see that they have addressed this.
 
I even checked to make sure my #2 CHT wasn't indicating +20 degrees at ambient temps. I'm curious if the temperature spread is a common thing among the 14's or if I have a elusive detail to pursue.

A 20 F spread is pretty common fleetwide. Fly a 100 hours or so, then tinker with leveling CHTs if you wish. Won't hurt anything if you don't.

My plane has an IO-390, dual P-mags, and AFP FM-150 fuel injection system and I have about 35 hours on the plane. Again, I'm mainly curious if other operators are seeing something similar.

Confirm you have a jumper wire between terminals 2 and 3 on each p-mag. Even with the jumpers installed (i.e. running curve A), CHT will rise as much as 4 F for every degree of ignition advance when mixture is near best power, and ~2-3 F or so per degree of advance at peak and LOP.

Need to run it harder than 50% for break-in.
 
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Marvin,

Those CHT numbers are disgusting. I would never consider a 7-degree spread acceptable. :p That looks like a happy motor and I think you set a high bar to aim for. Was the modification you made intended to solve a specific issue or an effort to improve cooling flow overall? Did you have to modify the tension rods or make any other adjustments?

I don't have numbers for 11,000 but at 9,500 for a similar power setting mine looked like this:

PA - 9,500 DA - 10,960 OAT - +51F Percent power- 60%
20.0" / 2400 / 50 deg ROP / 167 KTAS / 8.8 GPH
CHT 1 - 341 CHT 2 - 359 CHT 3 - 330 CHT 4 - 317

Just one data point to show what temps I'm seeing. I don't have the EGT's but they were in the 1390-range I believe.

I'm not in a big hurry to do anything...just looking to get any true issues identified and handled before I wrap up phase-1. Thankfully they have been few. This CHT thing is one that can wait until I get some more time on the engine as you and others mentioned. I had not thought about that spacer (CB-00010) being Van's answer to the "washer" trick but that is what it appears to be.



Lots of great info on this today. Thanks you guys for your insights.
 
Thanks Dan. I'm running the A-curve and clocked at 4-deg after TDC right now. I feel like break-in is pretty much done but I'm still operating at least 60% as much as possible. Temps are stable and oil use has dropped.

I love it when the solution is to go fly more :D:D:D
 
James,

The modification was extremely minor as shown below. I simply did not like that it was on top of the comb because that is a leak. I mentioned it on VAF and DanH suggested I bend and move on (He should be a hand model his picture was better than mine:))

I would say your 20 degree spread is probably very normal at 35 hours. Give it 100 hours before doing much.

Before:
oJx.jpg

After:
oJz.jpg
 
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Thanks Dan. I'm running the A-curve and clocked at 4-deg after TDC right now. I feel like break-in is pretty much done but I'm still operating at least 60% as much as possible. Temps are stable and oil use has dropped.

I love it when the solution is to go fly more :D:D:D

Excellent. Yes, fly more and run it harder. Need combustion pressure to apply radial ring pressure.
 
Sorry if I'm kicking a dead horse... my angle valve IO360 in my 7 has the number 2 cht running 15-18 degrees above the others even after 550 hours ttsnew. Ran into a fella at OSH who after hearing my complaint said he's heard numerous guys address this same issue with drilling a couple small very calculated holes in the no. 2 cylinder head area to normalize the cht with the others. Is this "snake oil" advice or what? Engine is injected and I thought of modifying the No. 2 injector port slightly larger to allow for more fuel cooling. Trying not to buy Gami injectors just yet.
 
The problem in the 14 is that the ramp in front of cylinder 2 is on top of the fiberglass snorkel, with the baffle running down between the snorkel and the cylinder. So even if you did drill a hole down through the ramp, and into the baffle, it has to traverse the snorkel as well. And likely the area outside the baffle meaning you just make a worse air leak.

My arrow has a 3/4 inch tube that goes to the middle of cylinder 2 lower part to direct air straight there, so maybe if you really want some air the best way is to take off the baffle and snorkel, fit a piece of tube into a hole, and direct some air directly at the fins down there. Seems a chore.

I just can't come up with a clean way of getting more air to go through that slot between the snorkel and the cylinder. But maybe its not worth it for the time being. Lately my #1 is 10 higher than 3/4, and #2 is 15 higher than #1. All acceptable.
 
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