To Turbo or to not Turbo, that is my question?

[akmatov]

Eaglesoft has two versions of the Cirrus SR22, one with a turbo and one without.  Looking at real world data, ie off the inet if that is real world, the turbo version seems to give about a 4% greater speed, but has 14% less range.  Which leads to my question, what is the point of the turbo?  Surely, I'm missing something basic as I believe turbos sell better in the real world, I think.

[Todd Harrell]

Turbo gives you better performance at higher altitudes, which can also be a huge benefit at high altitude airports where density altitude is many times a huge factor. You can Google how a turbo works and get more info than you want on the subject. In overly simple terms a turbo has a separate turbine that compresses the intake air (much like a turbine in a turboprop). So, a turbo is useful if you want to fly higher or you operate out of high altitude airports.

[akmatov]

Thx, I understand how a turbo works, but given the specs I wasn't sure what the point was in my buying one as the main difference I  was seeing was shorter range.  So the basic difference is that it is useful if you are flying into a high altitude airport and you are willing to sacrifice range?

[thissmallfish]

Bear in mind performance values quoted for an aircraft are highly condition dependent. More head room also means there's a potential for grabbing more favourable winds, more payload etc.

[shipdriver]

Looking at the specs on Cirrus' and TCM's website, it looks like the turbo'd 22T has a lower compression ratio (typical for turbocharged engines to prevent detonation) as well as a little bit more weight which gives it a bit more anemic performance at low altitude (note the longer takeoff run required and lower climb rate for the turbo model) but in line with what Todd said, performance doesn't fall off with altitude like the naturally aspirated 550-N giving it a ceiling of 25,000 feet versus 17,500 feet. Also, the max cruise speed is 30 kts faster with the turbo version- a 16% increase which is a healthy increase for only 5 more hp and the same airframe. Note also that turbocharged engines are usually quieter (a useful trait on long flights!) than naturally aspirated engines because the turbo (or in the case of the SR22T, turbos) is in the exhaust path and in the case of these two engines, peak hp is developed 200 rpm lower for the turbo'd engine.

http://www.continentalmotors.aero/uploadedFiles/Content/xHome/Billboards/500series_032012.pdf

[akmatov]

And a lot has to do with what source we are using.  The 4% greater speed was based on a reported difference between 170 kts and 180 kts, probably should have been 5%. Do your sources report a greater range?

[shipdriver]

I got my numbers from the Cirrus and Continental websites. They have a range chart which shows a longer range for the non-turbo. It has a weight versus range chart for both aircraft. The main reason I believe is higher weight for the turbo model since the per pound range correction is identical for both: +1 lb weight = -1.7 nm range.

[akmatov]

OK, this is all good to know.  I got the normal CR22 and have been haunted that I got the wrong a/c.  Now, I'm reassured that I probably got the right one.  AFAIK at this time, the greater range is more useful for me.  If I start making a habit of flying into Tibet, I'll consider the turbo for it's better high alt performance.  You guys have really been helpful.