Mixture settings? Backfiring and burping on T/O

[conom06d]

So i'll start off that i'm still learning this plane but I'd like to see if anyone on here has any pointers for me as to leaning the mixture prior to takeoff. I know you are to leave it full rich below 3k feet, however, my engine tends to run really rich when its full in. I dont know why nor does my mechanic. He told me to lean it out like you would above 3K and see how that helps. It does cut back a bit but I am afraid of overheating the motor on climbout. I would say the mixture is out about 1"-1.5" and is still backfiring a bit...

 

My questions are:

Can it backfire due to a "too lean" scenario or just when it's too rich and flooding? Also, do you have any leaning techniques for those of you with those phiniky carburated O-360 motors? Also, is there anything i should change for the carb since it is now warm out? the plane flew perfect in the cold wx but not the heat is making her burp a bit...

[N6843N]

Without being there it is hard to understand what is going on from your discription. There are two models of the MA-4-5 carburator, one is calabrated richer than the other, that came on our planes. The first thing to do is determine which one you have from the data plate on your carb. The data plate can be veiwed from the right side, side, cowling when removed. I would not lean my engine for takeoff below 3K feet as matter of fact I rarely used to lean for takeoff from an airport I used to visit that had a field elevation of 6K feet. My advice to you would be to have your plane checked  by Top Gun in Stockton or Lasar in Lakeport. They understand everthing Mooney.

[Lood]

If you don't have one already, you should really get at least one EGT gauge - or first prize: A JPI EDM 700. An EGT takes all the guess work out of leaning and will prevent you from running either too lean or too rich. I used to lean out on the ground - even at 3000', untill the engine started running a bit rough and then pushed the mixture in about 1". During climbout, I always keep a sharp eye on the CHT's and never let it go higher than 380 deg. Or if you have a single EGT, keep it at around 1200 deg during climbout but still keep an eye on the CHT. I had a serious backfire problem that was only solved once they did a complete rebuild of the exhaust muffler on my F. Many experts told me to do a thorough check for leaks on the intake side i.e. worn seals, gaskets, etc as well as on the exhaust side. Apparently these can also cause backfiring. Under normal circumstances, full rich and full power at 3000' shouldn't cause backfiring.

[georgeb]

I don't know how it is for you left coasters, but here in West Texas where the density altitudes regularly reach 7k and above, you learn about leaning on the ground from day one (litterally, I learned it from the moment I started my first 360 in my trainer). You learn it or you're going to have to constantly be cleaning your plugs. The technique I use (as do most of the pilots in my region) is to lean from the moment you start up (once engine is running smooth of course) by backing off the richness until you reach peak rpm and then give it a couple or four twists (about a 1/4 " for me because I have a quadrant) and leave it there for a few minutes while you do other pre-flight stuff occationally reapeating the process until ready for runup. During runup, we pretty much do the same thing always keeping the mixture just rich of peak rpm. At takoff some richen it a bit (I do), some leave it alone, but rarely (if ever) do I takeoff full rich. Once you're at full throttle immediatly after starting your rollout for takeoff, you can toy with richening a bit more and you'll immediately feel the surge in power if you were too lean. CHT's are fine as are egt's as long as you're not climbing too steep. I find that this technique keeps my plugs healthy and my engine happy.  Don't know if this will work for you down at sea level, but if you don't constantly lean at high densities and high temperatures (as we have here in ELP), you're in for a rough time (pun intended) . You might try this in your area. The few times I've flown to the left coast, I've still used this technique and I can honestly say that I've never had to use full rich. Keep in mind that while I use this technique in my fuel injected 360, the same applies for every other plane that I've flown and that I am familiar with. As I stated before, we ALL learn that from the get go here in the southwest.

Good Luck and happy flying.

George

9488V

 

[conom06d]

Thanks for the responses guys. Yeah I think the seals and everything are good unless they went out on that flight cuz I literally just had it in the shop being checked thuroughly but anything is possible. My plan at the moment is to go and see if my mechanic will go for a trip around the pattern with me and recreate the problem.Ill try to find what carb i have tho and if all else fails, I'll be making a trip down to stockton haha

 

@georgeb: Yeah nearly all my time has been flown at high altitude mountain area and those are the procedures im used to as well. That is the method i am used to practicing however at sealevel at 90 degrees Im more worried about cooling the motor than anything else so i like to keep it a little richer.

[Kwixdraw]

Might not sound logical but haven't some of us had such problems from a bad baffle in the muffler? Might be worth a look. I'm led to believe that it has something to do with the exhaust outlet being blocked so the engine doesn't breathe correctly.

[Stefanovm]

I am a central Texas E owner, too. I found out real quick that if I do not do as georeb states runup will be 200 rpm drop. Follow his instructions, 50 rpm. Also on climb out and a hot day, I always lean as the power will increase just as noted. Today out of KFHU (Sierra Vista, AZ) at 5:30 am with a density altitude of 6K+ meant lean for sure. After stop at E11 (Andrews Co, TX), same procedure with a DA of 5K+. I do not have to be as aggressive on the ground at home, 07TS (Cross Country Estates, Georgetown,TX), but fail to lean at least some and 200 rpm drop will be the result. I tend to lean for smoothness on climb.  Mine does not really backfire, but run rough at full rich on the ground, absolutely.

My CHTs, two different gauges and cylinders went to about 375 on takeoff out of KFHU. The rest of the flight was was at the bottom of the green, looks like about 300, as that is what it was on the large CHT gauge that I have. The other is Mooney OE in the dash.

The EGT peaks at 1400 and I run 1350 most of the time. It is on the back cylinder on the pilot's side, but appears to have at one time been on the front one. I do not really trust the EGT because the mixture control does not do much to ever change the EGT like it does on other A/C I have flown.

[conom06d]

Thanks for those inputs. I will continue to play with the mixture settings. I think the exhaust baffles could be looked at too. I flew it again today after a long ground runup and series of mag checks. The mag drops of the right mags were consistently 150 rpms but still ran smooth. The drops of the left mags were between 150-200 but seemed to run a little rough but ive had that before and worked on with the mechanics. I let her warm up for about 15 minutes with checks and all before taking off and it didn't backfire once. I had the mixture in just about full rich, slightly leaned,  and the OAT was 10* cooler today. Im really leaning towards it being a "pilot error" leaning problem haha. I'll do another flight sometime this week when its warmer to see how that effects it again and see what i can do with the mixture and maybe that mag fluctuation