Adjusting Mixture

[Lance F]

The range they recommend for that is 1250-1350F.

I don't think they "recommend" that range rather they say you can expect the temperature to use to come out somewhere in that range. For me that turns out to be ~1275dF on cylinder #2. When I have a long climb to cruise altitude, I leave the engine monitor on #2 and just lean to maintain that 1275 as I climb.

 

[gismo]

I don't think they "recommend" that range rather they say you can expect the temperature to use to come out somewhere in that range. For me that turns out to be ~1275dF on cylinder #2. When I have a long climb to cruise altitude, I leave the engine monitor on #2 and just lean to maintain that 1275 as I climb.

Looking back I see my post wasn't very clear. The 1250-1350F recommendation is in regard to where the EGT should be on any big bore engine at full power, full rich mixture, sea level standard conditions. If the EGT is outside that range there's a good chance that the fuel flow at full rich is incorrect and should be checked. They also recommend setting the max fuel flow at the upper end of the manufacturer's specs or even a bit higher to make the cylinders last longer.

So I wasn't saying that you should set the mixture to 1250 or 1350 F when departing from a high DA airport, but rather that you should use whatever EGT you normally get at takeoff power and sea level standard conditions. And if the EGT is outside that range when taking off in sea level standard conditions get the engine's fuel system adjusted.

 

[Let'sgoflying!]

My Pictures! My Pictures!

I loved em'! (I didn't read all the other stuff!)
Looks like the forest is on fire but no smoke!

 

[taters]

Easy Way-Real simple.....pull out the mixture until the engine runs rough....then put it half-way back in from this point. DONE.




Other Way- Use EGT to find peak temp at Top of Decent., this will keep the engine from shock cooling..enrichen slightly on the way down if IF needed. Entering the pattern put mix back to Best Power which is generally 50-100 Rich of Peak..and leave it there

 

[flyingcheesehead]

Easy Way-Real simple.....pull out the mixture until the engine runs rough....then put it half-way back in from this point. DONE.

Every plane I've ever flown that had the instrumentation to know better, this technique would leave you WAY rich. I'd say that 1/4 back in, or maybe 1/3 at most, would be more accurate.

 

[sba55]

Every plane I've ever flown that had the instrumentation to know better, this technique would leave you WAY rich. I'd say that 1/4 back in, or maybe 1/3 at most, would be more accurate.

It really depends on the plane and engine, though.

If you put it 1/4 back in with my IO520, you'd be way rich and probably wasting about 5 gph. Without good instrumentation, I'd rather be safe than sorry, though. Most people fly too lean rather than too rich. Btw., even if shock cooling was a problem for our piston engines (which it's not), mixture settings wouldn't make enough of a difference to prevent it.

-Felix

 

[docmirror]

It really depends on the plane and engine, though.


Most people fly too lean rather than too rich. Btw.,

-Felix

Yes, the individual plane and engine can be quite different.

That second point has not been my experience. I've found that almost everyone adjusts too rich, mostly because they don't have the instrumentation to do it right. Or, they are deathly afraid of LOP ops.

 

[sba55]

Yes, the individual plane and engine can be quite different.

That second point has not been my experience. I've found that almost everyone adjusts too rich, mostly because they don't have the instrumentation to do it right. Or, they are deathly afraid of LOP ops.

Good points. I agree that people don't lean enough (especially on the ground!) - I guess my comment was due to people thinking that flying around at 50 dfROP is a good idea, thanks to Lyc/Cont.

-Felix

 

[taters]

Good points. I agree that people don't lean enough (especially on the ground!) - I guess my comment was due to people thinking that flying around at 50 dfROP is a good idea, thanks to Lyc/Cont.

-Felix

I almost never put a mixture to absolute full rich