Lowish CHTs, highish oil temps io-390 exp30 (210hp) or is this normal?

[aadamson]

Recent flight. 11,500, cruise for 3 hrs at 174-176 tas.

Oil temp 185-196
CHTs 340-308 (#4 being significantly lower than the other three)

Normal and call it good or is there something that can be done to raise that #4 cylinder. I think that is the rear pilot side cylinder. Note, this is the stock 4 inch duct to the oil cooler and a 14 (non A)

 

[transientair]

Normal for me—your CHTs were even a little higher than mine normally are.

 

[bjdecker]

Looks like every other angle valve (IO-360-A,C, IO-390-A,C,) stuffed into the Van's stock cowling... #4 CHT runs low.

I had blamed that on the location of the oil cooler inlet (#4 on my -7), but since you're seeing it on the -14 with the Oil Cooler inlet above #3, methinks it's something else.

Maybe it's because the length of the cowl inlet diffuser is longer on the left side...

 

[aadamson]

Not sure I want to tackle this, but I wonder if moving to the 5 inch duct in the #3 side would allow more air thru the duct and less thru the fins of #4, raising the temp in 4 and lowering the oil temps. Anyone running the 5 inch change and seeing the CHTs balance any better?

 

[dmattmul]

Recent flight. 11,500, cruise for 3 hrs at 174-176 tas.

Oil temp 185-196
CHTs 340-308 (#4 being significantly lower than the other three)

Normal and call it good or is there something that can be done to raise that #4 cylinder. I think that is the rear pilot side cylinder. Note, this is the stock 4 inch duct to the oil cooler and a 14 (non A)

View attachment 92955

Savoy reports mine at 190-195 F oil temp in cruise is right at the 50 % median for over 100 390’s they monitor. 4 in duct to oil cooler. Mine OT improved slightly with SCEET tubing.

 

[Dugaru]

Recent flight. 11,500, cruise for 3 hrs at 174-176 tas.

Oil temp 185-196
CHTs 340-308 (#4 being significantly lower than the other three)

Normal and call it good or is there something that can be done to raise that #4 cylinder. I think that is the rear pilot side cylinder. Note, this is the stock 4 inch duct to the oil cooler and a 14 (non A)

View attachment 92955

Seems relentlessly normal to me. 176KTAS must be nice!!

 

[asw20c]

Yeah, I would tend to agree with the others that this sounds fairly normal based on my own experience. You didn't mention if you were running lean of peak. Assuming you were, perhaps a few other ideas that could be contributing to one cylinder running cooler than the others; either an induction leak (although you didn't say what your EGT's were) or slight variations in your fuel injectors. One fairly simple way to see if it is indeed the fuel injector is to swap it with another cylinder and see if the low CHT follows.

 

[aadamson]

EGTs for the same flight. Don't think it's an induction leak.

 

[lr172]

Has it always been like this or is this new?

 

[aadamson]

Pretty much since first flight. It's only got 25hrs on it so it's just getting broken in ...

 

[Reflex]

Alan,

I have 75 tach time on mine. Your temps (and your concerns) are almost exactly what I'm seeing. My #4 CHT is much lower than the other three (290 -295 in cruse) and I'm seeing about 330 on #2 at cruise. I finally got to see 200 degrees on my oil temp on a steep long climb out when OAT was above 90 degrees.

Max temp CHT I've seen on any cylinder is 386
Max oil temp I've see is 208 and I see 195 right now in cruise.

Interestingly, my EGT on #4 is much hotter than the other 3 and has been so since the first flight.

Fred

 

[bwagner]

Typical temps on my RV14's IO390exp installation during a recent slow cruise on a warm morning. CHTs were surprisingly mild from day one while oil temps started out ~225F and still top 200 on hot day climb outs

 

[Raymo]

Might timing be a little less advance than spec?

 

[georgemohr]

Normal, in our experience. Open up the bottom cowl for better oil temps.

 

[aadamson]

Its a TD and the tunnel is already open, e.g. nothing there

 

[georgemohr]

Yeah, ours has the open tunnel as well, it does have a tunnel flap you can close (so probably a little more restrictive?). Still the additional exit air was very impactful.

 

[aadamson]

I bet this is why vans suggests the louvers kit that they offer. My hesitation is opening up the lower cowling in any way, will also allow for more cht cooling. Which is why I'm now wondering about the 5 inch duct to oil cooler. I need to go find that thread on the entrance duct from the scat to the oil cooler that someone designed

 

[giorgioca]

I think you are referring to this;

Modifications: Bigger oil cooler for IO-390-EXP119, try #1 (failed in flight).

A blog about building a Van's Aircraft RV-14A, RV-14 and RV14.

rv-14a.blogspot.com

 

[Desert Rat]

I went through the same process and asked the same questions. Especially since I was seeing oil temps in the 210-225 range early on. A couple of the guys who responded above were kind enough to respond to me as well and they were right.

The 390 is going to have cooler CHT and hotter oil temp than the 360 that most folks learned to fly behind because it carries a lot of the heat away in the oil.

If it were me, I'd leave well enough alone and keep flying it for now. Lycoming says that 390 may take as much as 50 hours to fully break in so those temps (which aren't bad already) may continue to change a little more while the engine tries to find it's happy place.

For comparison, here's a screenshot of how mine was behaving at about 25 hours. It has the stock size air dams in front of 1&2 and takes oil cooler air off of a 4" duct behind #4. This was running 75% power, 175 KTAS and 12.5 GPH rich of peak.