High CHTs on engine break in

[Nick]

Originally Posted by DanH

Is "really rich" based on an F/A meter, or a relationship to peak EGT? Can you offer some numbers?

EFii ignition has two available timing maps. You would have specified a compression ratio when ordering. What CR do you have?

Clark has not installed the F/A meter yet, so all numbers are coming from EGT and FF. EGT @ 2000 MSL / 17 GPH are 1050ish, highest CHT #3 at 415. if you bring the FF back to 13GPH and the EGT up to 1350 the CHT will get stable around 430.

Timing is 25deg WOT, CR: Clark will have to chime in here, but I believe it is standard 8.5:1

My concern is so much the CHT's we are seeing, more the large split between 1/3 and 2/4. I don't believe the break-in has happened yet. The temps we saw today are only marginally better than we had on First Flight. I think another few hours will make a world of difference.

[DanH]

Originally Posted by Nick

Clark has not installed the F/A meter yet, so all numbers are coming from EGT and FF. EGT @ 2000 MSL / 17 GPH are 1050ish, highest CHT #3 at 415.

Got it. Yep, that's rich, sho'nuf. Have you done a GAMI spread?

Timing is 25deg WOT, CR: Clark will have to chime in here, but I believe it is standard 8.5:1

Ok, good. That makes max advance 30 with reduced MP, which is sensible, and you can dial that back later if all else fails. For now, you may wish to experiment by pulling the hose off the MP sensor, which should lock in fixed 25 degree timing, no advance. Don't forget to plug the hose.

BTW, timing is a function of magnet installation in the flywheel. It's fair to assume no problem, but a quick running check with a timing light is SOP with similar systems. Stuff happens.

My concern is so much the CHT's we are seeing, more the large split between 1/3 and 2/4.

Please quantify the split. We're not seen all four.

BTW, what sort of cowl does Clark have?

[carrollcw]

Standard vans cowl.

Chts on 1/3 are 30-40 deg hotter than 2/4.

Thanks

[turbo]

taping the leading edge between the top and bottom cowl pieces helped drop my chts about 7 degrees.

[DanH]

Originally Posted by carrollcw

Standard vans cowl. Chts on 1/3 are 30-40 deg hotter than 2/4.

That's not horrible. Twist the little knob and do a GAMI spread. If all cylinders peak within 0.2 GPH, you're pretty much left with the usual cooling air leakage and flow management issues.

Let's assume you did a great job of sealing around the inlets. With two hot cylinders on the short inlet side, my guess would be that you've located the glue-in upper ramp too far aft (left, below). Remember, the inlet air must expand and slow to convert dynamic pressure to increased static pressure. A pinch does the opposite.

[carrollcw]

Update - I removed both dams which resulted in lower/balanced chts in all cylinders. Now I am working on balancing my EGTs!