Cirrus Turbonormalizing

R

rajsingh

New Member
http://cirrusaircraft.com/turbo/learn/highaltitude.aspx

At this link they show the comparison between the normally aspirated SR22 and the SR22 Turbo. I do understand that the turbo helps maintain sea level pressure at higher altitudes, but this chart at Cirrus Aircraft website is showing, that at lower altitudes the normally aspirated SR22 has a higher speed. Can anyone explain that. I had been thinking that turbo is always better than the normally aspirated engine.
 
rajsingh said:
http://cirrusaircraft.com/turbo/learn/highaltitude.aspx

At this link they show the comparison between the normally aspirated SR22 and the SR22 Turbo. I do understand that the turbo helps maintain sea level pressure at higher altitudes, but this chart at Cirrus Aircraft website is showing, that at lower altitudes the normally aspirated SR22 has a higher speed. Can anyone explain that. I had been thinking that turbo is always better than the normally aspirated engine.
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Turbocharged: increases power output at sea level and at altitude.

Turbonormalized: no boost at sea level, but maintains sea-level power to higher altitude.

The SR-22 is actually turboCHARGED. It produces (IIRC) 32" Hg manifold pressure at sea level, vs. a max of about 29"-30" for a normally-aspirated aircraft. Why Cirrus likes to call it turbonormalized, I have no idea.
 
Roger said:
Turbocharged: increases power output at sea level and at altitude.

Turbonormalized: no boost at sea level, but maintains sea-level power to higher altitude.

The SR-22 is actually turboCHARGED. It produces (IIRC) 32" Hg manifold pressure at sea level, vs. a max of about 29"-30" for a normally-aspirated aircraft. Why Cirrus likes to call it turbonormalized, I have no idea.
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Maybe the manifold pressure is set to high, OR its a cold engine.

I fly the Turbos 22's and its not supposed to go that high except on the first takeoff of the day.

I do know people that will set them up to get 32" though.
 
Fly_Unity said:
Maybe the manifold pressure is set to high, OR its a cold engine.

I fly the Turbos 22's and its not supposed to go that high except on the first takeoff of the day.

I do know people that will set them up to get 32" though.
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Hrm. I could have sworn I read that in one of the articles about the SR-22 turbo when it first came out.
 
Well, we're splitting hairs over a few inches here. I'm aware Cirrus calls it turbonormalized, and given the fact that they barely make anything more than atmospheric pressure, I'd say it's a fairly accurate description.

Turbocharged aircraft (Navajos, 421s, warbirds) develop 40 to 50 inches to sometimes 60 inches (think warbirds) of manifold pressure.

The performance charts of the SR22 vs SR22 Turbo are different, because keep in mind, that even at a "low" altitude of say, 8000 feet, the SR22 would only be developing roughly 23 to 24 inches, while the Turbo could still develop 30 or 32 inches (if operated at 100% power).
 
32" is where the MP numbers turn red cause you are over max. Fly Unity is right, either the oil regulator is turned up too high, or the first cold flight of the day I will get overboost. After that I usually cant get much over 30" to show up.
 
And yes to the original question, the non-turbo is faster down low, has more useful load, and will out climb the turbo the first couple thousand feet. We have one out of the eight 22's that is a non-turbo, and the first time I flew it I could tell it was faster in the pattern.
 
wjmiller3 said:
And yes to the original question, the non-turbo is faster down low, has more useful load, and will out climb the turbo the first couple thousand feet. We have one out of the eight 22's that is a non-turbo, and the first time I flew it I could tell it was faster in the pattern.
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Is the non turbo faster because of the weight difference? I always flown the turbos.
 
Fly_Unity said:
Is the non turbo faster because of the weight difference? I always flown the turbos.
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Thats the only thing I can think of... Or maybe till the waste gate closes and actually starts making boost it is actually causing a restriction????:dunno:. If I remember right I think you get about 150lbs more useful load on the non-turbo. I am about in the same boat as you, I only have about a half dozen flights in our non-turbo. But it will get WAY in the yellow down low in level flight.
 
I'm just the opposite, bunch of time in straight -22s, but just a couple of hours in a turbo.

Yes, it sure does like to creep up there in speed down low. Flying an ILS at 190 kts is fuuuuunnnnn. Hey he said keep the speed up:D
 
I've always suspected the turbo was a little slower down low due to that big ol' paddle-bladed prop just not being as efficient at lower altitudes.

I've never had one up high, but ferried them down low and kinda thought they were sorta doggy below 7-8,000 compared to the normally aspirated/thin prop models.

But then again, I'm crap at aerodynamics so who knows what the real reason is.
 
OldTownPilot said:
I'm just the opposite, bunch of time in straight -22s, but just a couple of hours in a turbo.

Yes, it sure does like to creep up there in speed down low. Flying an ILS at 190 kts is fuuuuunnnnn. Hey he said keep the speed up:D
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Two of my favorite calls I have ever received on the radio were after I was told to keep max forward speed in the 22...... Uhhhh...Cirrus xxxCD I need you to slow down....uhhh you are showing a 50kt overtake on the Falcon you are following on final...:)) made me smile!! The other one was a Citation and it went about the same..
 
So while pondering this, I realized that the airplane with 32" MP that was "turbonormalized" was the one on the Mooney Acclaim.
 
turbo-normalized = sea level pressure to the flight levels, we still haven't found the ceiling for the twin turbos but the highest we've gone is FL250. A TN Cirrus producing over 32" for sustained flight should be checked, other than a density controller version, but there's only one and it's still being tested. The NA Cirrus will be faster down low because of the prop. In testing it's shown 2-4 knots of difference. The metal prop is also harder to slow down than the big composite prop. The point of the turbo is to cruise at 17K or FLs, because KTAS goes way up. The turbo only weighs 75 pounds, but normally there will also be oxygen installed, and a larger weight in the tail to offset the CG issues so that may be where your ~150lbs usefull load comes in.

The difference, in my opinion, between NA and TN, is fuel flow. I've flown NAs at 12K and burned 12.5GPH, and the trip between Duluth and Ada still only takes 4 hours-same as a TN flying at ANY altitude, but still burning 17.5GPH.
 
patthepilot said:
turbo-normalized = sea level pressure to the flight levels, we still haven't found the ceiling for the twin turbos but the highest we've gone is FL250. A TN Cirrus producing over 32" for sustained flight should be checked, other than a density controller version, but there's only one and it's still being tested. The NA Cirrus will be faster down low because of the prop. In testing it's shown 2-4 knots of difference. The metal prop is also harder to slow down than the big composite prop. The point of the turbo is to cruise at 17K or FLs, because KTAS goes way up. The turbo only weighs 75 pounds, but normally there will also be oxygen installed, and a larger weight in the tail to offset the CG issues so that may be where your ~150lbs usefull load comes in.

The difference, in my opinion, between NA and TN, is fuel flow. I've flown NAs at 12K and burned 12.5GPH, and the trip between Duluth and Ada still only takes 4 hours-same as a TN flying at ANY altitude, but still burning 17.5GPH.
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I have noticecd the difference in the turbo way below 17K.. Depending on the temp, I have got 200kts at 12k more than a couple times in our turbo's at 85%. Couldn't get anywhere close to that in our NA.

edit: and I am usually in the 16.5-17.0gph range.
 
wjmiller3 said:
I have noticecd the difference in the turbo way below 17K.. Depending on the temp, I have got 200kts at 12k more than a couple times in our turbo's at 85%. Couldn't get anywhere close to that in our NA.

edit: and I am usually in the 16.5-17.0gph range.
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You must have one of the few well built Cirrus'. A lot are out of whack and need to be adjusted from the factory. I've seen some Cirrus' that at full balls to the wall will do 160, and others that are closer to 180.
 
I hardly fly less then 15000 thousand feet in the Turbo (because I have to get over the mountains) but I true out around 190 kts and thats at 75% power, 15.6 Fuel Flow, Lean of Peak.

Flew to Casper today and had our mechanic put on the covers on engine designed from Cirrus to keep engine temps up during flight. In a matter of minutes in cruise CHT's went up to 400 and climbing and I had to run full rich mixture (20GPH) just to keep it around 390 (encouraged to stay below 380). Took the covers off and CHT's wouldn't get above 310 and could barely stay in the green (240 F) during final descent. It was negative 20 C

Any suggestions? besides doing a power on descent all the way to the ground? (hard to do with some of these Wyoming approaches where you need to drop thousands of feet within a couple miles) I wish Cirrus had some sort of Cowl flap or spoilers.
 
Fly_Unity said:
I hardly fly less then 15000 thousand feet in the Turbo (because I have to get over the mountains) but I true out around 190 kts and thats at 75% power, 15.6 Fuel Flow, Lean of Peak.

Flew to Casper today and had our mechanic put on the covers on engine designed from Cirrus to keep engine temps up during flight. In a matter of minutes in cruise CHT's went up to 400 and climbing and I had to run full rich mixture (20GPH) just to keep it around 390 (encouraged to stay below 380). Took the covers off and CHT's wouldn't get above 310 and could barely stay in the green (240 F) during final descent. It was negative 20 C

Any suggestions? besides doing a power on descent all the way to the ground? (hard to do with some of these Wyoming approaches where you need to drop thousands of feet within a couple miles) I wish Cirrus had some sort of Cowl flap or spoilers.
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You are in a turbo correct? If cruise CHT's were comming up past 380 you need to LEAN to bring then down, not enrichen. If you enrichen and bring the fuel flow up you are increasing CHT's. Running cruise at that much fuel flow is a no-no, WAY to much heat. I would suggest instead of leaning based on peak, just set 2500, pull flow back to 16.5-17.0 gallons and see what the CHT's read, if they are hot after a few minutes come back to 16.0 see what that gets you. I know this is going to give about 85%, which is what we always fly, and I have never had a problem staying below 380, but I have never flown with the covers on either.
 
wjmiller3 said:
You are in a turbo correct? If cruise CHT's were comming up past 380 you need to LEAN to bring then down, not enrichen. If you enrichen and bring the fuel flow up you are increasing CHT's. Running cruise at that much fuel flow is a no-no, WAY to much heat. I would suggest instead of leaning based on peak, just set 2500, pull flow back to 16.5-17.0 gallons and see what the CHT's read, if they are hot after a few minutes come back to 16.0 see what that gets you. I know this is going to give about 85%, which is what we always fly, and I have never had a problem staying below 380, but I have never flown with the covers on either.
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as far as I know when your ROP, giving more fuel will decrease temps. Only when your on the backside of the Peak curve will the temps decrease when you lean. Today at 17 gph temps ran at at 400, when I slowly went to 16 gph temps did nothing but rise, so I went to 20 gph and got an instant drop down to 390, as I started to slowly pull it back from 20, the CHT's started to increase again. I tried the "blueline" LOP (the Garmin perspectives LOP recommended fuel flow) and no cooling there. Another note is that the hot cylinders were # 1 and 2 (the back ones) The rest of the 4 cylinders were only around 340.

Im not impressed with these covers, they do not provide even heat, when I took them off, every cylinder was within 30 degrees. Just talked with our Cirrus Service Center and he said NOT to use them unless they are enlarged. sigh... I will just go without them and try doing more of a power descent. Cirrus has a -20C temp limit? thats what it was at today.
 
20GPH should be ROP, and peak being around 18.5 or 19. So leaning from 20 would only bring you higher CHTs. If you're at the base for LOP ops, 17.5, then lean, you'll already be on the lean side of peak. Have you run a GAMI lean test? I'd highly suggest doing one, and maybe you'll find injectors out of tune or maybe not even set up right. I can baby step you through everything, but honestly-in your descent where you say you're worried about staying in the green of 240 for your CHTs, it won't hurt the engine much cooler there. Also, as you say, keep the power up, or don't descend as quickly, start your descent farther out, or if you were running at 15.6 GPH, which is REAL lean, enrichen to 17.5 or slightly above, which is putting you closer to peak, but thus keeping CHTs hotter. The whole thing about "shock cooling" is a little silly, but I'll save that for a later time.
 
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