Hangar Flying => Hangar Flying => Topic started by: lgez83df on January 02, 2006, 08:06:27 PM
Title: One hot cylinder
Post by: lgez83df on January 02, 2006, 08:06:27 PM
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?
Title: One hot cylinder
Post by: Drew on January 03, 2006, 05:55:59 PM
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).