One hot cylinder

[lgez83df]

Hello everyone, I’m Mark Schwendeman and I have owned Long Ez 83DF since 1994.  It is still O-235 L2C powered but in 1999 I had it top overhauled (TT 1293 since FN) and put in the 9.7/1 pistons.  At this time I also installed EGT and CHT probes on #4 cylinder (previously only #3 had probes on it).  The EGT unit and probes are Electronics International the actual unit is an EAC-1.  At this time I learned I had a problem with #4 CHT.  Several things intervened including the aircraft spending 3 years at the EZ hanger getting tornado damage repaired (no Robert and Valerie aren’t that slow I took the repair it between jobs option to lower the cost).  Anyway she’s back flying now and I need help, #4 CHT is about 70 degrees F above everyone else.  I have checked for induction leaks and can’t find any.  I put in a ramp air outlet above #4—cost me 4 knots and only helped by 10 F.  I have swapped the probes with #2—no change.  I have even gone so far as to swap #1 and #4 cylinders because I was sure it was the cylinder—no change.  Fuel provided by an MA3 carb. Here’s the #’s:

At 8500 ft.  AOT 50 F  2790 RPM  22 inches manifold  146KIAS oil 181 F 64 psi and throttle cracked back to just at RPM drop (it helps enrich #4 and leans #1)
                                                                     :evil:
#4 430 F 1350 F   #4 435 F 1400 F   #4 448 F 1500 F (peak)
#3 360 F 1250 F   #3 365 F 1300 F    #3 389 F 1406 F
#2 370 F 1320 F   #2 370 F 1360 F   #2 385 F 1460 F
#1 370 F 1280 F   #1 373 F 1300 F   #1 387 F 1360 F

This problem gets worse as altitude increases, the temps climb on all cylinders by about 15 degrees at 12,500.  Climb temp on #4 runs about 440 F.
 
For my latest attempt I called Air Synergy Labs (www.Betterperformance.com) and had them build me an induction “Vortex Valve”.  These are very nice people, I sent them an intake gasket and they built me a test unit with mounting flange for FREE.  Results with this are mixed, I loose about 30 RPM static so there is some power loss, but the mixture distribution is better and temps are down to about 425 on #4 in the climb.  In addition I can now run WOT at altitude without #4 temp getting quite so high, although pulling the throttle back to just at RPM loss still enriches #4 and leans #1.  However, it won’t run smooth LOP which is what I was hoping for.  Here’s the #’s with the vortex valve:

At 8600 ft. AOT 53 F   2820 RPM  22inches manifold, 147 KIAS, oil 181 F 64 psi  WOT

#4 431 F 1350 F      #4 439 F 1400 F
#3 345 F 1204 F      #3 360 F 1252 F
#2 360 F 1292 F      #2 377 F 1367 F
#1 371 F 1248 F      #1 373 F 1305 F

Here’s how it looks with the vortex valve and throttle pulled back to RPM loss:

#4 431 F 1350 F      #4 440 F 1400 F
#3 349 F 1230 F      #3 362 F 1273 F
#2 370 F 1340 F      #2 379 F 1397 F
#1 379 F 1380 F      #1 375 F 1418 F
Lastly, here’s the #’s at 12,500 ft. WOT, 137 KIAS 2760 RPM OAT 40 F:

#4 456 F 1340
#3 369 F 1189
#2 386 F 1309
#1 381 F 1241

I forgot to mention I have a mag and a Jeff Rose electronic ignition (also a fine piece of equipment).  Anybody got any ideas?

[Drew]

Even your temps on the other cylinders are a little hot (updraft cooling add about 40ish for full rich and add about 70ish for leaned out)---however, this appears to be where most run their engines for updraft cooling (I had those numbers and lower in my downdraft longez).

But your #4 is way out of wack.  Cooling fins ok because you swapped cylinders which is leading me to believe that you have a "cooling leak" around that particular cylinder.

Usually, you can "steal" some cooling air from a cooler cylinder by closing some of the openings around the other cylinders and opening up a little more on the hot cylinder.  So I guess you don't have room for that.

Assuming there is not anything wrong with the inside of the engine (plugged oil galleries or something----can this happen??), I would next check to see how the baffling is sealing.  Put the plane in a dark area and put a light inside the cowl.  Look for the light leaks.  Try to do this with both cowls on---then one at a time.  Pay particular attention to things around the starter, alternator, etc.  If successful on that front, you will cool off the other three cylinders more----which will allow you to steal cooling air next.  If you cannot cool the other three off, there won't be anything to steal.

The plans way to do this in a cozy is to build a diverter ramp that will cool off the front 2 cylinders the most.  You test fly many times in cruise condition----and peel the ramp back an inch at a time until the cylinders balance.

Also, you did swap your cht probes----but check them with boiling water too.

You could ask Beagle to send you a copy of the article titled "Taming the Shrew" which goes into detail on different updraft cooling schemes along with good writeups on what worked well or not---along with good data (delta p).