What power setting do you use?

[Ragsf15e]

It will be important to clearly describe your engine for this, but it might be nice (and informative) to have a specific thread on power settings we all use and why.  Obviously there’s going to be a lot of differences based on the different TSIO-360 models and aftermarket intercoolers or wastegates.  I actually think there’s quite a wide variety of different ways we each look at this, even though my POH shows only 10 knots (and ~1.4gph) between 65% and 75% power which is noted as max recommended.

Ive been happily flying my 252 (SB engine) at 65% LOP for about 6 months, but I want to be aware of what else I might try and why? @shawnd mentioned that he only flies ROP just to keep his CHTs high enough in the winter. I hadn’t thought of that.  So last week I decided to try some settings out of the POH, except I’m not a fan of “peak TIT” , so I thought I’d add 1gph to them as a start to make sure I was really ROP.  I was cruising along at 15,500’, 65% LOP and decreased mp to 28, increased rpm to 2500 and mixture up to 13.7. Should be 75% except 1gph richer than peak.  Well my speed increased a little, but my CHTs started up and I gave up at 396f (and rising) on #3.  Maybe I needed more ff to be richer?  Dunno.  But it should have been at least as good as the POH setting of 12.7gph with the same rpm/mp, no?

So for now, here’s what I like with my MBcSB engine (220hp)… 2350rpm, 29.5mp, 10.4gph.  That gives me about 20f LOP.  It’s smooth, efficient, and book speed or slightly better than 65% “peak tit” in the poh.  I have also run 2350, 30.5, 11.2gph for 70%lop and it’s fine but only gains maybe 3 knots.  The 65% setting has my CHTs between 315-350f at 15,500’ and -2C OAT which seems good to me.

So what do others do?  If you run ROP, how far rich are you from the poh?  Why do you run rop?  Maybe it doesn’t run smooth LOP?  Anyone use the poh numbers (PO of mine used POH 70% numbers a lot).

[Z W]

TSIO-360-MB.

27-28" MP, 2500 RPM. Leaned to just under 1600 TIT, usually 12.5-13 GPH. Gives about 155 KTAS at 10,000, up to 175 KTAS at 17,500. CHTs vary greatly with density altitude and OAT, but range from 320's to 370's. I can maintain under 380 degree CHTs easily at all altitudes and temps by opening the cowl flaps which is my practice. I do have the infinitely adjustable electronic motor cowl flap.

ROP because my engine goes rough LOP. I've tried all kinds of power settings, still rough LOP. I do not have GAMI injectors.

Under 1600 TIT to take it a little easier on the turbo and exhaust, and because this setting is a nice balance of fuel flow, power, and all engine temps. Sometimes I can get 28" MP and stay under 1600, sometimes I have to walk it back to 27" MP. Peak TIT is somewhere near the 1650 redline at these power settings.

I've taken GAMI's online engine management seminar. I understand the "red box" and internal cylinder head pressures, and that what I do is not optimal for them. My take away is while that might be a good rule of thumb, the purpose of all of that is to keep your engine temperatures in proper operating ranges, which I do through a full engine monitor. I could run more efficient on fuel, but at the cost of either power (speed) or higher turbo and cylinder head temps. So I think this is a nice balance.

I've considered getting the GAMIs and trying to save another gallon or two per hour running LOP. My engine is getting to be higher time, and I unfortunately don't have a good local mechanic to work with on it, so I haven't done it. If I overhaul the engine I'd plan to start out with a fresh set of GAMIs.

[WilliamR]

With a 360-sb,

My LOP ops and temps are generally the same as OPs. 

ROP, at 28" and 2500 RPM (~75%) flying in the teens, at 13.7-13.8 gph, I see TIT low 1500's, ~100-120F ROP, and CHT just under 380 on the hottest (#5) with temps ISA +10 to 20C. My baffling is exceptionally tight.

Cowl flap fully closed. No GAMIs.

 

[Falcon Man]

Ragsf15e - your SB engine is 220 Hp. Do you think the power settings in the POH differ substantially from the stock 252 210 hp engine? The  max MP in the 231 stock engines were 40-42" as I recall. Max 36" required for 210 hp in the 252, so maybe we're comparing apples to oranges.

I like to cruise run my stock 252 MB1 210 hp engine at 65% HP @ 2200 rpm, 28-30 " MP and slightly lean of peak FF (~ 11.5-12.5 GPH). My game spread is 0.5 GPH, the CHT's run ~ 335-350F w/ cowl closed, ~ 1500-1550 F TIT.

What is the service ceiling on a 252 modified to an Encore. Stock 252 is 28K. I have never been above 23K.

Jeff

[Fly Boomer]

1 hour ago, Falcon Man said:

What is the service ceiling on a 252 modified to an Encore. Stock 252 is 28K. I have never been above 23K.

Sounds plenty high to me.  In the Backward Tales book (different thread) Coy says he was with a DER in an experimental 252 up to 31K.  Still climbing 500-600 FPM.

[Fix]

For -SB I have the following settings:

ROP
65% Key 50 25" 2500 12.5g/h
75% Key 53 28" 2500 14,5h/h

At 15000 Feet (FL 150) with 65% ROP, 12.6g/h
TIT ~1500, CHT 345-367F

[Ragsf15e]

5 hours ago, WilliamR said:

With a 360-sb,

My LOP ops and temps are generally the same as OPs. 

ROP, at 28" and 2500 RPM (~75%) flying in the teens, at 13.7-13.8 gph, I see TIT low 1500's, ~100-120F ROP, and CHT just under 380 on the hottest (#5) with temps ISA +10 to 20C. My baffling is exceptionally tight.

Cowl flap fully closed. No GAMIs.

 

Thanks.  Mine didn’t like that 75% setting with the cowl flaps closed but maybe my baffling isn’t perfect?  It’s happy LOP for sure.

[Ragsf15e]

3 hours ago, Falcon Man said:

Ragsf15e - your SB engine is 220 Hp. Do you think the power settings in the POH differ substantially from the stock 252 210 hp engine? The  max MP in the 231 stock engines were 40-42" as I recall. Max 36" required for 210 hp in the 252, so maybe we're comparing apples to oranges.

I like to cruise run my stock 252 MB1 210 hp engine at 65% HP @ 2200 rpm, 28-30 " MP and slightly lean of peak FF (~ 11.5-12.5 GPH). My game spread is 0.5 GPH, the CHT's run ~ 335-350F w/ cowl closed, ~ 1500-1550 F TIT.

What is the service ceiling on a 252 modified to an Encore. Stock 252 is 28K. I have never been above 23K.

Jeff

My 252 is modified to an Encore, so the poh was updated to new power settings that should match the 220hp.

[Falcon Man]

I knew your airplane was modified. I was curious to know if the added 10 HP changed the settings much compared to a stock 252. Is 36" your max MP to achieve the 220 hp?

[wombat]

Engine: TSIO520NB  (Rocket STC)

ROP only so far, it tends to miss once every 10 to 30 seconds if I run LOP.   Just need to spend some time investigating which cylinder is overly lean and adjusting it.

I run at one of the following:

31" MP, 2,300 RPM @ 18.5 GPH  (72%)

32" MP, 2,400 RPM @ 19.8 GPH. (76%)

33" MP, 2,400 RPM @ 21 GPH (78%)  (Very rare)

If I'm in a hurry or there are headwinds, I use the higher power settings. Otherwise the lower ones.

[Ragsf15e]

2 hours ago, Falcon Man said:

I knew your airplane was modified. I was curious to know if the added 10 HP changed the settings much compared to a stock 252. Is 36" your max MP to achieve the 220 hp?

No, 39”/2600rpm is max.  Id guess the cruise settings are slightly higher hp to be 65% of 220hp rather than 210hp, but I doubt it’s much different.

[Ragsf15e]

1 hour ago, wombat said:

Engine: TSIO520NB  (Rocket STC)

ROP only so far, it tends to miss once every 10 to 30 seconds if I run LOP.   Just need to spend some time investigating which cylinder is overly lean and adjusting it.

I run at one of the following:

31" MP, 2,300 RPM @ 18.5 GPH  (72%)

32" MP, 2,400 RPM @ 19.8 GPH. (76%)

33" MP, 2,400 RPM @ 21 GPH (78%)  (Very rare)

If I'm in a hurry or there are headwinds, I use the higher power settings. Otherwise the lower ones.

Wow! That thing is thirsty! But I bet it screams!

[Z W]

Just musing out loud here...

You have a TSIO-360-MB (or GB or LB). You're flying it in cruise at 75% power of your 210 rated HP. Say 28"/2500RPM/13.5 GPH, just for a rough example. At 75% power, no matter how you get there, you're putting out 157.5 horsepower.

You take that same engine and reconfigure it to a TSIO-360-SB. The engine internals, to include crankshaft, pistons, connecting rods, and compression ratios, have not changed. But now your takeoff power settings are 39" and 2600 RPM which generates 220 HP.

You take off again, and set your engine the same to 28"/2500RPM/13.5 GPH, putting out 157.5 horsepower. You are now at 72% power, with the engine performing exactly the same as before the conversion. Are you taking it any easier on your engine than before?

All that to say - why do we focus on % of horsepower for cruise power settings? Wouldn't it be better to choose settings that produce ideal temperatures for CHT, EGT, and TIT? How are you even "taking it easy" on the engine by running it at reduced horsepower?

% power isn't even a very good rule of thumb. I didn't do the math to verify what I posted above is 75%, I think it's actually a little less, but it requires a mathematical formula to know, it depends on whether you're ROP or LOP, and the number your engine monitor displays for it can even be wrong. Rules of thumb are supposed to be quick and easy and this is not.

What the guys at GAMI say always sticks with me: "It's not how hard you run the engine - It's how you run the engine hard."