Ryan,

Your statement above is not the case. If you believe marketing literature and want to run your engine at 85% power at temps that are sure to cause issues, then yes the TAT is 10kts faster. In reality, the delta between the TAT and T is more like 3-4kts at altitude (at similar TIT temps). See my post here from an experienced Cirrus pilot with TAT:

viewtopic.php?f=49&t=183680&start=45

My TSIO-550K in my G3T and in my G5T does not struggle to stay cool at any temps or weights. I've been flying SR22T's for 5 years and neither airplane ever saw above 380CHT in any phase of flight and my hottest cruise CHTs are 330-350. I climb at 130kts and typically see 360CHT as the hottest cylinder in the climb. I'm happy to share my engine data or Savvy historical data.

The couple tips I've learned in flying / maintaining these birds is to install GAMIs (even though it comes from the factory with 'balanced' injectors) and set the max fuel flow to 40-42gph which helps keep the engine nice and cool in the climb. Guys who may experience higher CHTs in the climb may have max FF set in the 35-38 gph range.

Dan,

Any data or suggestion that the 22T TAT-Tn version needs 42 gph in climb to keep cool? I know the A36 550 TN (slightly different motor/install) is usually cited as needing 36gph on climb to stay cool.

RAS

Hi Richard,

The TAT TN is different and turbo normalized and not turbo charged at the T is. The TAT TN runs at a lower MP and I believe a bit less fuel flow compared to the T on takeoff.

The T is recommended to have takeoff max FF of 40gph. Those who are much lower than that could see higher CHTs.

I can positively state that the TSIO550C in my Columbia 400 does not struggle or get hot at all on very hot days.

I routinely fly out of Henderson NV, with ground temps well over 100f at 2500' ground level. In the full power climb phase, my hottest cylinder might show 360, all the way up to the flight levels.

My FF is correctly set to just tickle the redline of 39.9gph at maximum RPM and MAP.

In cruise, I normally see in the 320-330 CHT's all around. Heck, I have trouble keeping the oil temperature high enough.

Don,

There are work around a just like in my A36TC. Same type of setup. Try running getting 255 hp out of that engine engine LOP on a hot day. It runs hot period. That is why Cirrus delayed a turbo installation for years.

YMMV.

What has not been stated is the reason for the extra FF. That SR22 engine is really a 350 hp engine. They just limit RPM to say the engine only puts out 315 hp. Hence the same FF requirements as a Navajo Chieftain engine on takeoff.

How do I know this? Look up the takeoff performance differences between a NA, TN, and T cirrus. If you can still find them.

The Columbia does not count. That extra airspeed makes a significant difference in cooling. It is a better aircraft in many ways, hence the thread.

Ryan, I guess I don't understand the perceived cooling issues. Here's one of the hottest days I could find on all of my flights from the last 12 months. This was on 7/8/2019 on a departure from Charlotte, NC (KCLT). According to weather archive information, the temp in Charlotte was 95deg on departure. According to the OAT in the engine log, the temp was reading 106F but I'm sure that's because the airplane was sitting for awhile on the hot tarmack.

Below is a snapshot of the engine log data. The hottest CHT on climb out momentarily reached 385 deg but it was just briefly. The hottest CHT during cruise varied from 350-355 deg. I simply have no issues at all keeping this bird cool.

I don't have any particular 'work around' on my bird, just GAMIs and a takeoff FF set for ~41gph. The recommended takeoff FF setting is 40gph, so I'm just slightly above that setting.

Don, let's see your fuel flow in that climb, I think that's Ryans point, you are pouring fuel on the coals to keep the CHT's manageable

That's a cooling issue

Here's mine on a hot august day, i'm running less fuel, and my CHT's are cooler

I'm definitely running more fuel flow. Like I said, you want to be doing about 40gph on takeoff / climb:

yeah, that's way too much for me, however, if I put low boost on and push red knob all the way in, it will hit 44GPH, so I'm setup to flow that if needed, but I've never had to, I target 1320TIT in the climb, what do you shoot for? what is your TIT in that full rich setting?

I can climb 31-34GPH at 1500fpm all the way up to 12k no problem, CHT around 355 or less most of the year, maybe 365 in peak summer, TAS about 156TAS in the climb

You have (by the book numbers) 40hp more than me, so what's going on?

Those are very good climb numbers and nice, low fuel flows Brian.

A typical climb for me is 130KIAS, 39-40gph (SOP is to climb with low boost pump on) and an average of 1,000 fpm up to 18K ft. Climb rate down low is generally 1,200 fpm. The highest CHT in climb is generally 360 deg.

TIT in the climb at full rich is in the 1350 range. I target TIT in cruise of 1570-1600 deg running at 75-80% power.

That's amazing, 1350 with 40gph? wow, I would see 1100F with that much fuel, in cruise I see 1520-1550 TIT when running LOP, around 17-17.5GPH, where is the fuel flow transducer mounted on your airframe? Is it before the mechanical pump or after?

What happens if you run 35gph in climb? It sounds like the Cirrus has overly small inlets for cooling, which should lead to less cooling drag and higher speed, but then your book numbers are 10-12kts slower than I'd expect to see for the HP

While the SR is similar to the Lancair / Columbia / TTx, they do have their differences. The biggest difference is in the frontal area / cabin cross section. Look at both aircraft straight on from the front and also sit in the front and rear of both aircraft when side by side. I share hangar space with a TTx and have flown both back to back. There’s a significant difference in cross section and cabin size that equates to better performance in the Lancair / TTx. It’s simple physics.

Some prefer the higher performance of the Lancair and others prefer the roomier cabin of the SR. You and I are fortunate that we have options and can choose what we prefer.

My comments aren’t centered around the airframe aerodynamics, but rather the engine and systems which should be very similar, being very far off in operation and performance

15% more fuel flow should yield more hp/performance, or one would think

You would think that, but no.

A major difference between the TAT TN engine and the TCM TC engine is the compression ratio. The TN is 8.5:1 compression, the TC is 7.5:1. There are potential advantages of a lower compression engine (future unleaded fuel compatibility high on that list) but it is less fuel efficient.

An 8.5:1 compression engine, if memory serves, makes 14.9hp/GPH of fuel flow. A 7.5:1 engine makes high 13's. I think 13.7. But the compression difference makes a significant difference in fuel flow for a given power output.

Don,

What is you MP during the climb? My TSIO520BE runs very similar temps as yours. I climb at 38MP 38GPH 2600rpm in my malibu. Never a cooling issue when run by the book. In fact it runs cooler than my NA V35B 520 with a BDS cooling kit. I never understood why people say this engine runs hot in my airframe. I do climb at 128ish which yields 1000fpm at medium weights.
Kevin