Before doing any hardware changes, I would certainly do another GAMI test see instructions: GAMI lean test
John Paul at Gami will get in touch after receiving the plots.
Do the leaning slowly and only going from rich to lean.
very relevant article by Joe Casey.
http://flycasey.com/intercoolers-on-a-piston-pa46/
I put Joe’s measurements in my spreadsheet. It shows intercooler efficiency to vary between 49 and 59%. Funny: I had modeled 40 to 70%…
In the PA46, intake air temps are 56 degrees C above ambient in the climb and about 48 above ambient in 70% cruise.
On a hot day, the temperature of “post intercooler” intake air will reach 85 degrees C in the initial climb – no wonder overheating is looming…
How do you counter that? Lots of fuel flow?
PA46 (and Extra400) operators should take a hard look and make their intercooler install as airtight as possible.
There are substantial gains to be made, especially in summer.
How do you counter that? Lots of fuel flow?
The main temperature control for CHTs is the yoke, i.e. use a shallower climb for cooler temps. I would reckon it is the same for intercooler efficiency.
Baffles also make a serious difference, full rich fuel flow during max TO power, climb power, magneto timing, etc.
Understood. There is a catch 22 issue though:
> Climbing at a shallower rate means it takes more time to get to altitude where the air is cooler. Staying longer in the critical area
> Full rich will shed some heat, but given the fact that the intake air is very hot, it is less dense. So the mixture will be overrich will cause a loss of power resulting in the same problem as above: we stay longer in the danger area.
After giving it a hard thought I believe that turbocharged engines in the PA46/ E400 category aircraft must be operated with an eye on Compressor Discharge Temp and Inlet Air Temp (as in the blog post by Joe Casey) During hot days, both power and climb rate must be restricted to a level that keeps the IAT at a reasonable level. This might very well mean slashing climb rate to half of its ISA value.
Another strategy may be to split the climb in 2 phases, with maybe a 5 minute plateau at FL100 to cool off the initial effort using economy cruise settings.
Getting “baffles” right means – in the case of the Extra 400, I dont know the PA46 well enough :
- get the intercooler seals 100% airtight
- make the intercooler itself operate at it max performance (we recently flushed the interior of mine to remove oil deposits)
- get the coolant radiator to operate at max efficiency (aerodynamics, airtightness) this helps CHTs and adds some margin
- make sure that the temps inside the cowling are Ok and homogeneous with no hot spots near induction air.
From my minimal measurements so far, lots of potential is untapped in all 4 areas above
Missed something?
Flyingfish wrote:
to get to altitude where the air is cooler.
But the air is also much less dense, so despite the lower temps, the lower density decreases the cooling efficiency.
Add to that the the turbo needs to work harder to produce full MP and cabin pressure and the net is usually WORSE up in the flight levels vs down around 12,000’
Michael wrote:
But the air is also much less dense, so despite the lower temps, the lower density decreases the cooling efficiency.
What Michael said.
The P210 will have more CHT issues the higher you climb. The cooler air in the Flight Levels doesn’t compensate for the loss in density.
I have found that a step climb is the best way to deal with this.
As you run out of options to cool the cylinders, just do an intermediate level off. After 15-30 minutes you have lost some weight and the temps are back to normal.
Step climb 2-3000’.
The ISA+++ days, at max gross are the hardest. I have had to do my first level off at 10.000. Normally I go all the way to FL150 without issues.
Both of you are absolutely correct: data shows that the problem gets worse as one climbs.
But the PA46 data shows that intercooler efficiency is not the weak link: it remains around the 60% mark. This is probably due to the high airspeed in cruise.
The cause seems to be lower air density making the turbocharger work harder.
Now the next question: how much turbocharger work (=heat) can be saved by carefully (re)designing the engine air intake?
At 200 knots ram air can be a serious factor in a well designed inlet, but compensating for turbulence, flow reversal in a bad inlet would be an even more important factor.
A quick back-of-the envelope calculation shows that a 350 HP engine operating at 20’000 ft and 75% power will consume 330 liters of air per second.
Are our inlets providing this without any “suction” by the turbo, and without wasting any dynamic pressure?
In the Extra, the air inlet is located deep in the boundary layer, the air box is primitive and the inlet mouth is very sensitive to yaw (the engine loses MP when flying uncoordinated). How good are the P210 and P46?
Since we are talking about intercoolers.
Most STC Intercooler modifications would come with a temp difference indicator in the cockpit (Delta temp Before-After). For each 15 degrees diff, you will have to reduce the power setting by 1"MP.
For those who have tried this, end up with a “Very sick puppy” that wont go anywhere.
After reading a lot of posts on the subject on different forums, it was clear that this limitation doesnt make any sense.
One of the engine Gurus has written this:
Interesting and unsurprising that an intercooled engine has to suck harder.
The intercoolers I have seen were of small cross section.
