Antoine wrote:Speed increases approximately with the cubic root of power increases as we know.
So a 11% increase in power (to 200 HP) really buys us 4-5 knots.
I am not a maths-genius myself but if the numbers given were right and assuming a top speed of 2700rpms at standard atm, the equation would probably look like this
{sqrt(200/180)*150}-150=8.1138 kts increase, not 4-5 kts.
If you use the cube root as Antoine indicated instead of the square root, you only get an improvement of about 5 knots.
What i was trying to get to is that increasing engine power without turbonormalizing is not very efficient.
we need lots of horsepower which come at the cost of increased fuel burn, increased weight and therefore work against higher speed.
If we can clean up the airframe, we could get a few more knots for no extra fuel burn of weight. And if we want much faster cruise... Its altitude and turbo I guess.
Chris wrote:If you use the cube root as Antoine indicated instead of the square root, you only get an improvement of about 5 knots.
{cbrt(200/180)*150}-150=5.36 kts increase
This makes sense, at least regarding the formula. Thanks, Chris! Unfortunately now I don't know anymore from where Powerflow gets its 8 kts because this requires an increase of nearly 17% of power. Quite a lot for an exhaust system.
Antoine wrote:What i was trying to get to is that increasing engine power without turbonormalizing is not very efficient.
See the more we think as a group the more we face reality:
I would say Powerflow's claimed 8 knots are comprised of 5 real knots and 3 of wishful thinking ...
Adding a turbo is going to add at least 80 lbs to the empty weight. Now that is going to really hurt.
My plane has a useful load of 825 lbs, less 300 of fuel, that's 525 for payload.
So with the turbo we're down to a payload of 445 lbs with full fuel.
Maybe I could remove the rear seats to save some weight
Antoine wrote:I would say Powerflow's claimed 8 knots are comprised of 5 real knots and 3 of wishful thinking ...
I'm sure you're right.
Antoine wrote:Adding a turbo is going to add at least 80 lbs to the empty weight.
The ForcedAeroMotive supercharger that Brock is adding to his DA40 is supposed to only add 35-40 pounds. Getting rid of the 18 pounds of ballast in the nose for some of us would give a net loss of only 22 pounds, which I'd be willing to trade for improved performance up high.
But we'll have to wait to get a final pirep from Brock as to whether the supercharger hits the the claimed performance and weight targets.
Antoine wrote:
So for Benelux, maybe you're better off with a normally aspirated engine
We in Switzerland, would definitely go turbo...
Hello Antoine,
I know Belgium's top is at least 2500 ft , so I have a good chance to get clear off the ground with a normally aspirated Lycoming
But, I don't plan to hang around the low lands all my life, so a turbonormalized IO-360 would really tempt me. I should participate to a flying rally over the Alps with "Le Cercle de Wallonie" next 13 to 15 may.
Before buying the DA 40, I was inquiring the MCR 4S 914 (ROTAX 914 TURBO).
For the same price, we preferred a sturdier, normally aspirated recent IFR certified G1000 DA 40 :-D .
Antoine wrote:
So for Benelux, maybe you're better off with a normally aspirated engine
We in Switzerland, would definitely go turbo...
Hello Antoine,
I know Belgium's top is at least 2500 ft , so I have a good chance to get clear off the ground with a normally aspirated Lycoming
But, I don't plan to hang around the low lands all my life, so a turbonormalized IO-360 would really tempt me. I should participate to a flying rally over the Alps with "Le Cercle de Wallonie" next 13 to 15 may.
Before buying the DA 40, I was inquiring the MCR 4S 914 (ROTAX 914 TURBO).
For the same price, we preferred a sturdier, normally aspirated recent IFR certified G1000 DA 40 :-D .
Hi Jean
Well if the Alps include the swiss Alps please let me know if you intend to stop . It would be a pleasure to meet you!
And it is really funny you also considered the MCR4S. I did as well, same decision, same reasons!
But i flew it for a few hours and really loved it! Thats how I realized the value of "lightness"...
Chris wrote:
The ForcedAeroMotive supercharger that Brock is adding to his DA40 is supposed to only add 35-40 pounds. Getting rid of the 18 pounds of ballast in the nose for some of us would give a net loss of only 22 pounds, which I'd be willing to trade for improved performance up high.
But we'll have to wait to get a final pirep from Brock as to whether the supercharger hits the the claimed performance and weight targets.
What kind of performance gains can I expect with the supercharger?
For cruise we expect to see an increase of 10-15 KIAS over what your airframe did prior to the supercharger installation. Owners report 8-21, depending on the conditions. The full potential of the supercharger should be realized from 12000' to mid teens. For example, our test Cirrus was fastest at 8000' in a cruise setting prior to the supercharger. After the FAT system was installed we saw the full 15+ knot increase at 12,000'. In addition to increased cruise speeds expect to see an increase in climb over what your airframe was capable of prior to the supercharger being installed. A supercharged Cessna 182 will climb approximately 500 FPM faster at all altitudes above 5000'. A FAT power Cirrus SR22 will climb from sea level to 12000' faster then any other Cirrus, over a minute faster then a turbo.
15 kts@12k ft isn't as much as others promise. But 500 fpm above 5000' is nice.
I am a powerflow convert. I have a 2003 Steam guage. I see 150+ -sometimes 152 on a nice cold day usually if I am in cruise at 8k-10k. I cruise 2300-2400 WOT at those altitudes. I forget the manifold reading.
I have PF, the hartzel metal top prop to match the PF, gami's and finewires. The later two do make a difference too. And they save fuel since I can lean more a- plus I can run LOP at those same altitudes on ~8gph and loose maybe 10kt. I never try LOP lower than 7 or 8k since I never seem to be able to set it up to keep all the temps where I want them, even though it is sufficiently smooth.
I believe that some Diamond has flown 158 - mine does not even have wheel pants and I am hitting 150. Do I have a super DA40? I don't think so, each of the items, PF, hartzel, finewire and gamis added increments I observed. Or maybe I do have super DA40.
