aaronk25 Posted March 30, 2013 Report Posted March 30, 2013 So I spent some time at GAMI this week with John Paul in Ada, OK and after a couple test flights and swapping nozzles we have all cylinders peaking within 0.0gph. My number 1 and 4 cylinder have always ran 30-50 degrees hotter than #2 an 3. #2 and 3 were the leanest and consequently the first to peak. #1 and #4 cht still are hotter at any power setting than #2 and #3 even after getting the injectors perfect. So if you look at the co-pilots front cylinder (#1) and the (#4) cylinder pilots rear there is something very interesting that John Paul noticed. #1 has a"L" bracket flange covering up 1/2 of the leading edge of the cylinder and head to keep the air going up and over the cylinder to supposedly help ramp air up and over the cylinder and head to help cool the cylinder directly behind it. However I believe these metal baffles are to restrictive and hinders the cooling to the #1 cylinder. With regards to the #4 cylinder the oil cooler pick up is right behind it and the cylinder has a wrapped piece of aluminum over it which probably dosent let much air get in around the back of the cylinder and head but certainly helps divert air back into the oil cooler. GAMI recommended shorting the #1 aluminumn vertical plate in front of the #1 and modifying the wrapped baffel on # 4 up into the airstream so it would scoop some air away from the oil cooler, as I have excess oil cooling but not enough # 4 cht cooling. I removed the vertical block plate in front of the #1 cylinder which the air flow now hits 1/2 of the exposed head and cylinder instead of just the top 1/4. I alsi bent up the #4 baffling and the result is #1 is the coolest and #4 temps are down significantly. My temps prior to this at peak egt cruise WOT at 6000 were #1 375 #2 330 #3 330 #4 375 after modification it's #1 320 #2 350 #3 330 #4 325. Oil temp is 175-180 remains unchanged. Might have to address in the hot summer months but I think I will still have enough oil cooler air flow to pass enough air over the cooler to keep temps under 190 in cruise. So I figure since the bird is a 77 and they didn't have multiprobe chts avail during design and testing they did the best they could with the tools at hand, but with newer more modern instruments has anyone worked with adjusting these? Also any idea why #2 which was a cooler running cylinder, and still is at 350 is now slightly warmer given its the pilots side front cylinder ahead of any changes? It's about 20 degrees warmer but still comfortably cool. Overall it's a hell of an improvement and before I couldn't run 50ROP (which I don't anyways) without blowing past my 380 personal limit and now I couldn't get above the 380 limit regardless where I put the mixture control. Thoughts?
jetdriven Posted March 30, 2013 Report Posted March 30, 2013 We did pretty much what you did. We shortened the #1 front baffle by 1/2" and then lifted up the #4 oil cooler ramp baffle and put a bolt in the side baffle to hold it 1/4" off the cylinder. you can also further tweak #3 by putting a silicone baffle strip spacer behind the rear baffle at the head, to get some air under it as well.
aaronk25 Posted March 30, 2013 Author Report Posted March 30, 2013 Interesting, you must have had higher #1 and 4 chts than the others. I wonder by moving the #4 baffle up more than 1/4" to 2" if it somehow took air off of the #2 cylinder. It's not alot warmer but maybe 10% warmer but its still comfortably cool.
kmyfm20s Posted April 22, 2013 Report Posted April 22, 2013 We did pretty much what you did. We shortened the #1 front baffle by 1/2" and then lifted up the #4 oil cooler ramp baffle and put a bolt in the side baffle to hold it 1/4" off the cylinder. you can also further tweak #3 by putting a silicone baffle strip spacer behind the rear baffle at the head, to get some air under it as well. Worked perfectly!
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