ForcedAeroMotive: SuperCharged DA40

[Chris]

Interesting. If I'm reading the numbers right, then he is getting about 20kts IAS over what I normally get at 12,500', a nice boost. However, the nearly 70% increase in fuel flow at that speed is higher than I was hoping to see.

Also, the climb rate between 10k and 12k looks to be a around 200fpm at 110 KIAS with CHTs a little high (~400F) for my taste. Seems like he has plenty of power up there but had to keep the airspeed up using a shallower climb due to temps. Of course, I have no idea if this was a MTOW test or not, so it's hard to interpret the climb rate without that context.

I'm hoping Brock will give us an update with how things are going and whether or not they are going to continue tweaking the system. I'd love to see some more reports with a variety of power settings.

[Erik S.]

Wow -

Sorry to be the stick in the mud but I am a realist - I wouldn't have published these results. About 5 knots true faster than I get in the same conditions out here. Not a big deal.

My understanding was that the MAP was lower than expected. Much more improvements need to be made. They worked on it this past weekend and expect to re-try this week. Stay tuned.

Erik S.

[BRS]

Looks like Brock has broken 150 KTAS at FL120...
http://cirrusreports.com/flights/N8QQ/

Antoine you are a clever one. You were not supposed to find my posting for N8QQ which is my future N#. I guess I could have tried harder by making the data private. Well now that the cat is out of the bag I'll up date you.

We will all be excited to hear his report.

You guys are fun too peeking in on his pre report stats. I wouldn't be too worried yet if everthing is not in spec on first test flight. Seems they have some cooling to work on, and the higher than desirable fuel flow must simply be because he is using fuel as a cool agent which is expected to keep cool hotter than desirable CHTs. I be they sort that out.

He sure is running a fast prop rpm for cruise.

Erik, You are exactly right. This info was not for prime-time for the following reasons

<<<<<< IF YOU READ NOTHING ELSE, READ THIS PART: >>>>>>

The conditions of the first flight(s) were not accurate for performance numbers for the following reasons.
1. The flight was done on a very bumpy day and it was reported that staying on speed was rather tough.
2. There was no ram air to the intake and the intake air charge was hot. This is because an air filter was attached directly to the inlet of the supercharger in the lower (low-pressure & hot) section of the cowl.
3. The purpose of the flight was not for performance data but more for data gathering to aid in further development.
4. I was not flying, the plane was at a high rpm and full rich. Normally I would have been LOP and at a much lower rpm.
5. There is still some cowl work to be done which should affect the cooling.

>>>>>> IF YOU READ THE ABOVE YOU MAY NOW READ THE BELOW. <<<<<<
---------------------
The following is a quote of my notes to Rod based on the data of the first altitude flight. THIS DATA IS NOT READY FOR PRIME-TIME BUT IS PRESENTED SO AS TO SHARE WITH YOU ALL AN INTERIM STEP IN THE REFINING PROCESS.

From: Brock [mailto:brs...]
Sent: Friday, March 25, 2011 3:14 PM
To: rod...
Subject: Re: test flight 2

Rod,

I've uploaded the file you gave me to:
http://www.cirrusreports.com/flights/N8QQ/

I will be using the new N-number (N8QQ) from now on. BTW - phonetically that is "eight Quick Quackers" in honor of the Oregon ducks. That's the best I could come up with. [thnx to a fellow QQ]

Old data can be seen at:
http://www.cirrusreports.com/flights/N649DS/

Observations:

* Max CHT 420. - seems the pilot caught this and got it cooled down promptly. (desired 400 max short duration, 380 in cruise)
* Max PA 12,322 at 22.65" MAP (highest altitude that the AFM Performance chart shows 22.5" is at 4,500' so that's a gain of almost 8,000')
* Climb from PA 6,242 to 12,024 took 19 min (calculated ROC 304 fpm)
* Looks like the pilot might have been trying to maintain 110 IAS but was unable. I understand it was quite rough out.
* While level at PA 12,000 CHT leveled off at about 397.
* In the climb the RPM was 2660 and CHT above 395. But then RPM was changed to 2500 and CHT dropped to around 380.

Thoughts:

* Even though, in theory, max rpm will give max climb the limiting factor seems to be heat. The exhaust is tuned for 2450. Try climbing at that rpm. It might reduce the heat and make managing the climb better.
* MP is lower than I would have thought. I don't see much point flying again until the intake is finished. The lower side of the baffle not only lacks ram air but is lower pressure than the surrounding PA.
* What are you limiting the take-off MP to? Seems to have been 29.5" on takeoff. Is that going to be policy?

Look forward to seeing the numbers on a smooth day with the intake system finished.

BTW - What limitations did I get when the signed off the plane (after the 5 hours)?

-brs

Other comments:
The flight pilot mentioned that it flew much different from the DA40's at his FBO. Well that makes sense as he took off at 6000' with full rated power (29.5" MAP).
Rod said he hopes to finish the alternate air box and ram-air intake connections this week. More work on the cowl as well as do much more flying. Once the ram air is finished Rod expects the gain to be 4%-9% increase in MAP to get us up closer to 24" - 25" at 12,000'.
Cooling will be the biggest challenge, in my opinion. But Rod seems to have some tricks up his sleeves. So we will have to wait to see what happens.
I'm told the engine was rated at 180HP at 29.2" MAP. So the (nominal) max MAP which is pilot controlled will be set at 29".

[Antoine]

Antoine you are a clever one. You were not supposed to find my posting for N8QQ which is my future N#. I guess I could have tried harder by making the data private. Well now that the cat is out of the bag I'll up date you.

Hi Brock and all.

Firstly apologies to Brock for following the track... I must have misunderstood your info about posting on Cirrusreports. Also note that while you changed the N number, the serial was published, so I dont really deserve the Dr Watson medal

second, I fully support your analysis and findings. I am not surprised by the outcome. We have to keep in mind that for each horsepower of thrust, our engine throws out TWO horsepower of wasted energy which, unless perfectly harnessed, converts into an unpredictable mix of cooling drag and excess engine heat.

I have carefully examined the baffling in the stock DA40 cowling: the air intake side is more or less ok, but there is literally NO flow management once the air leaves the cylinder head area. furthermore, the inlet manifold is happily intermixed with the unshielded exhaust manifold.

this is probably one area where a great gain in efficiency can be obtained with the stock engine. With a supercharged solution that boosts power by a good 30% or more at altitude, proper cooling flow becomes critical.

In a nutshell: I believe that a redesign of the cooling circuit and lower cowling is very desirable for the stock engine and necessary in the context of the FAT project...

[BRS]

Someone posted on the other forum that he was disappointed with how small the cowl bump was on this project so I got a better picture. For you gear heads out there.

(whose plane is this anyway? Hope you don't mind me using your photo)

[BRS]

The photo below shows the finished installation. Notice how short all the ducting is. Amazing. At last measurement the total installed weight was about 18.5 lbs. Still hard to believe.

So when do I get to fly it? Well it is currently at Arapahoe Aviation for an annual (condition inspection). Once that is done then ForcedAreomotive will put another 3.5 hours on it, do some final paperwork then it will be "technically" ready for pickup.

I say technically, because we don't know what the 3.5 hours might reveal as needing more work. Will let you know.

BTW - anyone ever have their plane serviced by Arapahoe?

[Bret]

This looks like a Procharger or Paxton supercharger. Without a intercooler in the system you are going to have problems. We build blown racing engines for a living and I can tell you without alcohol your cylinder temps are going to be too high. Looks like the inlet air area is too small. How much boost is being developed with this setup? Remember it takes horse power to drive a supercharger. We have measured inlet air temps coming from the supercharger of 130 to 140 degrees F with 1.5 atmospheres boost with a ambient air temp of 75 degrees F. For every degree of inlet air temp increase you raise the cylinder temp by this amount. Compressing air will always raise the air temp of the outgoing charge. More fuel flow will be needed to cool the cylinder also. We solve all our problems of fuel with electronic fuel injection. When GA gets out of the stone age and uses electronic fuel injection aircraft engines will be much more efficient.

[Antoine]

We build blown racing engines for a living and I can tell you without alcohol your cylinder temps are going to be too high.

Looks like the inlet air area is too small.

How much boost is being developed with this setup? Remember it takes horse power to drive a supercharger. We have measured inlet air temps coming from the supercharger of 130 to 140 degrees F with 1.5 atmospheres boost with a ambient air temp of 75 degrees F. For every degree of inlet air temp increase you raise the cylinder temp by this amount. Compressing air will always raise the air temp of the outgoing charge. More fuel flow will be needed to cool the cylinder also. We solve all our problems of fuel with electronic fuel injection. When GA gets out of the stone age and uses electronic fuel injection aircraft engines will be much more efficient.

Maybe you can suggest a way to get aircraft engines out of the stone age?

And while I am all for EFI, allow me to disagree about EFI making aircraft engines "much more efficient". The reality is: EFI can only improve efficiency marginally, because there is not much room for improvement during cruise - that is 90% of the flight, if the (mechanically injected) engine is properly leaned, something that has become very easy with the advent of engine monitors.

And while you are right on the matter of the increased temperature of the air charge, consider two things:
- Aircraft engines operate at less than 1 atmosphere to start with, with cool or even very cold air at altitude.
- The guidance is to not exceed sea level pressure (29.2 in I read in a previous post) after the blower so this is only a normalizing system. This is not a car racing engine here!

So, yes, it is probably desirable to have an intercooler, but it is not as bad as you seem to believe and it may even be that the temperature of the inlet charge is not high enough for the intercooler to function properly.

And finally, yes a supercharger will use horsepower, but the alternatives are a larger displacement engine or a turbocharger, both of which add significant weight, which in turn uses... horsepower to stay in the air.

So we know there is no free lunch, but Rod's solution is IMO a very clever compromise... for people who fly regularly in mountaineous areas, the additional fuel burn buys much needed improved take-off performance as well as more safety margin when flying high AND close to the rocks.

I also wonder why you think the inlet area is too small?

[Bret]

As far as EFI it can constantly monitor air fuel ratio make minute changes that a pilot can't during taxi, cruise, landing etc. Density of air is everything to a internal combustion engine and it does not matter what the engine is in. Density of air changes with temperature and pressure. The post said the developers were having problems with heat. Any time the cylinder pressure of a engine is raised so is the heat. Heat is what makes the power. All normally aspirated engines run manifold pressure just below 0 psi . When positive pressure devices such as supercharger, turbo etc are used positive psi can be achieved. As altitude increases oxygen decreases, so a engine needs more air flow to maintain AFR and have the proper oxygen level to make power. Again I say this. Decrease inlet air temperature and you will decrease EGT and have a more dense air charge (more 02). As far as inlet size, again, it takes horsepower to compress air. you want the lowest pressure in the inlet side of the supercharger so the larger the better as long as the inlet has more gain for the engine and doesn't create more drag than help make horsepower. I think the developers are doing a good thing. Racing engines are some of the most efficient engines running. And by that I mean horsepower to fuel used. When we can make 2.4 horsepower per cubic inch and these engines can run all day long that is efficient use. For every atmosphere you increase in cylinder pressure you double horsepower. A IO-360 needs ((RPMXCubic Inch)/3456)) 281 cubic inch of air flow at max rpm at 100% . We have done test engines for red bull air craft with electronic fuel injection and positive pressures. I can tell you this, any pilot would love to have the results we came up with.

[BRS]

You guys seem to know way more about this than I do. However before you tell me it's not going to work, setting your self up so that you can later tell me "I told you so" why not wait another week (or so) and I'll have numbers that will say if it works or not. Hey, it might not. I knew that going into this project. But, "nothing ventured nothing gained".

On the other hand FAT has STC's for Cirrus', several Cessnas, and some piper models (I believe). They seem to work and I'm not taking FAT's word for it but have read what owners have had to say.

Whether it works or not depends upon if the objectives have been met. I suspect that some of us may have different objectives than others. This is not meant to operate like a turbo normalized aircraft. So if that is your objective, it will not be met.

If the supercharger does not add utility then I'll have a very one of a kind DA40. And some good memories achieving it. Time will tell, we are almost there.