By the way, I copied the wong photo into the report above. Here’s the correct one.
That was Lean of Peak I guess?
Yes, of course. I fly 99% LOP in cruise.
I calculated this to be 57 % power
Correct. 
so you could theoretically run your engine at any mixture setting.
Sure, but one can run LOP even at much higher power. The SR22TN is designed to be flown LOP at 85% power. ROP at 85% would toast the engine (unless going very LOP, which would then burn 30+ GPH…
Do you have GAMIjectors?
No. Most Cirrus don’t require GAMIs, as they have “tuned Continental injectors” from the factory. My “GAMI spread” is 0.2-0.3 GPH.
What is your leaning technique – I see that you are in “Lean Assist” mode, not in normalize mode.
I always use Lean Assist in cruise. Normalize is only used in climb.
Do you come from the rich side and run through the peak with the lean assist, or do you do a “big mixture pull” and then approach the peak from the lean side?
I never do the BMP, as that lacks precision for my taste and because passengers don’t like it. So I “come from the rich side” (which doesn’t hurt the engine at normal cruise power).
Did you close the throttle a bit?
Yes. When the tailwind is good, I adjust MP and RPM to get 11-12 GPH at ~40F LOP. Without tailwind, I use more like 12-13.5.
At 9000 ft DA on a recent flight in a NA SR22, I got this, which is further from peak EGT but with a higher fuel flow:
Yep, there are endless combinations how one can achieve a certain fuel flow.
I do the same. At the moment one of my EGT sensors is bad so i cannot use “lean assist” … I put it on 2600 rpm and pull the mixer to 13 GPH and it’s fine … my spread is similar to Bosco’s, maybe a tiny bit higher. But LOP works very well.
boscomantico wrote:
The SR22TN is designed to be flown LOP at 85% power.
As I have a “TN” I can confirm that. The other week there was a strong headwind of 50 kts at 8000 ft, higher it was even stronger, and pushing against it with 190 TAS @ 17.5 GPH worked well. That was 85% power. It is placarded as high power cruise (2500 RPM @ 17.5 GPH).
Stephan_Schwab wrote:
That was 85% power. It is placarded as high power cruise (2500 RPM @ 17.5 GPH).
Could you get to that power setting while maintaining the EGT of the hottest cylinder at least 75°F below peak? So you would stay outside of the “red fin” (supposing that the TN is like the NA in this regard):
What were your CHTs during the 85 % power cruise?
I am aware of the “red fin” but I’m using the lean assist function of the Avidyne R9 and the procedure per the POH. After level off I pull back the power lever to 2500 RPM. That gives me also 29.x" MP. Then I start the lean assist and pull back the mixture to somewhere between 17 and 18 GPH. There I can then adjust until it says “best economy”. On the flight I mentioned it did settle at 17.5 GPH and 85%.
The picture is from further ahead in the flight where the wind was already weaker. You can see the most important engine data on the MFD to the right of the map.
TIT = 1620
EGTs around 1545
CHTs around 356
MAP = 29.6
My RPM is 2450 due to a slight mismatch of power lever and governor. That equals “2500”.
On the SR22T-G5 that I did my IR on, the advice was to keep TIT below 1600°F, even though the green arc goes up to 1750°F. I don’t know about the TN though.
Absolute EGT doesn’t mean much; what you want to know is how far away you are from peak EGT. But Lean Assist gives you that value for the hottest cylinder (the one to peak last). That is what I would use to fine-tune the power setting. If you have 356 max CHT, this is what counts in the end and it is still safe.
Stephan_Schwab wrote:
My RPM is 2450 due to a slight mismatch of power lever and governor. That equals “2500”.
I don’t understand this. I think RPM is measured by the tach and not at the power lever? So what you see should be what you get, unless your tach is not correct. One technique that I recently learned about, but didn’t try yet, is to pull back the power lever to your desired RPM (say 2500) and then push it back up a little to fully open the throttle. RPM should remain where you set it, but you will fly with wide open throttle (WOT). This is due to the way the prop and throttle controls are linked.
Right. On my power lever there is a little quirk that needs a bit of adjustment during next annual. Hence the “2500”
Stephan_Schwab wrote:
TIT = 1620
EGTs around 1545
OT, but how can the TIT be higher than the EGTs?
Airborne_Again wrote:
OT, but how can the TIT be higher than the EGTs?
An EGT probe only sees hot gas every 2nd turn of the crankshaft, the TIT probe constantly gets hot gas from all 6 cylinders.
Achim,
Please allow me, difference of TIT / EGT might be better explained, by considering that EGT is a value of exhaust gas pulses per single cylinder and TIT is a value of several cylinder’s exhaust pulses.
Further, in context with the above posts, it may be worthwile to remind oneself:
EGT is not a constant temperature, but an averaged reading of one cylinder’s exhaust output.
Without any other changes, TIT and CHT readings are directly proportional to variation in RPM.
Without at least including other calibration references, both values are completely meaningless as an absolute value.
Considering Bosco’s trip report, how did we end up here?
Sorry about thread drift.
