Edit: 1998 M20J
I recently completed a "Top" overhaul. During the break-in, it became apparent that my injector setup was no longer valid. We swapped out an injector on the #4 cylinder that solved the biggest problem we were seeing with the #4 cylinder which was it was running too rich. Now with this swapped out injector, it is still running too rich but not quite as bad. It's still hard to manage though because if I try to run LOP, by the time #4 gets to 10 degree LOP, the other three cylinders have started flaming out.
I did a GAMI lean test and sent the data to GAMI. It turns out they want to change out three of the injectors so they sent me three new ones.
Before we install them, I wanted to ask a question here about CHT. The #4 CHT is hard to manage. (never was before) I normally target a maximum of 380 for CHT. Currently, as I start to lean out the mixture, the EGT for #4 peaks first and the CHT easily will overshoot 380 if I don't hurry up and get to the lean side.
I'm not currently flying this way though because like I said, the other 3 cylinders start to get rough at this point. I am staying on the rich side and the #4 CHT is hard to manage there too. If I lean the engine such that the EGTs rise above 1300, #4 CHT goes over 380. So, I have to keep it pretty rich, burning about 13.5 GPH @ 7500 to to not exceed 380 on #4 CHT.
Everything lean of this, gets me into the problem of the #4 CHT or if I keep leaning such that #4 CHT comes back down, the other three cylinders are just running too rough
So, here is my question. Do you think the injector swap out will fix this? Is there something else we should be looking for? I noticed that barely cracking open the cowl flaps has a huge effect on the CHTs. I can do this and lean further. However, I don't really want to fly around like that. I can hear it. And, it might take a knot off. I'm not sure about that.
I have looked at the baffling and it looks good. Flashlight test and all. There is nothing about the baffling material that leads me to believe it's kinked or anything.
I never had to work hard to manage temps before and I'd like to get back to not having to do it now. I'm definitely going to swap out the injectors as prescribed by GAMI. Just thought I'd check in here to see if there were any other thoughts on it. I've been told that sometimes a cylinder runs hotter due to differences in airflow. Maybe that's it.
Also, maybe once I swap the injectors, and get get all the cylinders peaking at the same time, it'll be easier.
Here is a pic of my engine monitor with me ROP. Notice I am already pushing the 380 and barely have EGTs 1300+.
Here is another pic with me trying to get LOP. Notice that by the time #4 gets to 10 degrees LOP, the other EGTs especially #3 are already much cooler. (60-70 degrees LOP for #3)
I really want to have the option to fly LOP but it's not really even an option right now. Currently, I'm about ~50 into the Top overhaul and oil consumption is very stable at about 1 qt every 8-10 hours.