Horsepower debate (was DA40NG)

The ramblings of our community of aviators.

Moderators: Rick, Lance Murray

User avatar
waynemcc999
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Wayne
Aircraft: DA40
Registration: N211WP
Airport: KSBA

Posts: 316
Joined: Sun Jun 08, 2014 3:38 pm
Has thanked: 734 times
Been thanked: 156 times

Re: Horsepower debate (was DA40NG)

Post by waynemcc999 »

Antione,

Unfortunately I was still very much a newbie when I installed the ElectroAir/FineWirePlugs (early 2016)... and the nose wheel had not yet been corrected... so I don't have even a guestimate of the effect of those changes on performance.

I do know that with two mags and massive plugs I was not able to reliably get LOP. After installing ElectroAir/FineWirePlugs, and passing the GAMI test with stock injectors, I've been able to comfortably get LOP every time and at any altitude.

For me... bottom line: I'm pretty darn happy with 137 KTAS at 12,000' DA on 7.5 gph... and if/when I want, 145+ KTAS (vs. TAS Book of 126 KTAS) at 12,000' DA on 10 gph.

In summary, I don't have clean before/after ElectroAir/FineWirePlugs performance numbers... but my guess is that the ElectroAir (and perhaps also the PowerFlow Exhaust) is helping my TAS trend line decay much less with Density Altitude than would be expected from the stock engine (i.e. TAS Book). Per the thread topic, if DA40 Book is 180 hp, then it's not difficult for me to extrapolate that at reasonable cruise altitude (8000'+ DA) I am indeed getting more like what ~200 hp would give me at that DA.

Best regards,
Wayne

BTW: Antoine, thank you very much for sticking with this forum even after graduating to your super cool aircraft!!
Wayne McClelland
PPL/IR, 2008 Diamond Star DA40-XLS 40.922, KSBA
Photo logs of PilotsNPaws | Flying Doctors | Angel Flight | Cuba | Colombia
User avatar
Sandy
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Sanford
Aircraft: DA40
Registration: N159PS
Airport: KPDK

Posts: 243
Joined: Mon Apr 04, 2016 12:30 pm
Has thanked: 11 times
Been thanked: 46 times

Re: Horsepower debate (was DA40NG)

Post by Sandy »

There are multiple issues being discussed. The only one that I addressed was the horsepower of the Lycoming IO-360-M1A. To be clear, horsepower (Hp) is a function of engine RPM and Torque. When Torque is expressed in pound-feet, the formula is: Hp = (RPM x Torque)/5252.

Thus, Hp is directly related to engine RPM, whereby the Data Plate that is attached to the IO-360-M1A specifically states that it is rated at 160 Hp at 2400 RPM and 180 Hp at 2700 RPM. If you don't believe me, take off your cowling and look at the Data Plate on your own engine. It is what it is, and no exhaust system increases the output to 200 Hp. Further, as 2400 RPM is a more realistic high RPM for normal operations, the actual Hp being generated in actual operation is likely to be less than 160 Hp, in any event

This is further confirmed by the fact that the generation of power requires that fuel be used, with a relatively efficient gasoline engine consuming approximately 0.40 - 0.45 pounds of fuel per hour per Hp. Thus, at 135 Hp (75%), we are talking about approximately 54 - 61 pounds of fuel per hour, or about 9-10 gallons per hour of Avgas. The greater efficiency of diesel engines (approximately 0.34 pounds of fuel per hour per Hp), combined with the greater density of Jet-A (6.8 pounds/gal, as opposed to 6.01 pounds/gal for Avgas) explains why the 170 Hp Austro AE300 engine in the DA40 NG uses less fuel per hour, and it explains why the NG's maximum fuel load is 273 pounds vs the 240 pounds in a standard DA40 with 40 gallon tanks.

While I appreciate that various items external to the engine (exhaust system, propeller, etc.) influence performance, in the interest of remaining technically correct, I am merely suggesting that we address those issues independently of horsepower.

Sandy
User avatar
Thomas
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Thomas
Aircraft: DA40
Registration: D-ENMA 40.337
Airport: LSZC BUOCHS SWITZERLAND

Posts: 202
Joined: Tue Oct 19, 2010 6:20 pm
Has thanked: 64 times
Been thanked: 42 times

Re: Horsepower debate (was DA40NG)

Post by Thomas »

Sandy`s vote is interesting, my question is … what is the role of the prop, performance means speed and T/O acceleration depending on the mass of air which the prop is moving. So more/less HP means different prop pitch at the same rpm.. If the governor regulates 2700 at T/O its 2700 with 180HP or 200HP – but with 200, you move more Air mass. Or am I wrong in my thinking
Thomas Bienz DA40-180 40.337 D-ENMA
Home Airport LSZC Buochs Switzerland
User avatar
TimS
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Timothy
Aircraft: OTHER
Registration: N1446C
Airport: 6B6 Stowe MA

Posts: 424
Joined: Thu Dec 02, 2010 1:10 am
Has thanked: 53 times
Been thanked: 61 times

Re: Horsepower debate (was DA40NG)

Post by TimS »

Sandy,

If the Powerflow exhausts increase torque approximately 44 lbs/ft at 2400 then there is an increase of 20 HP.
Further if you run LOP, and know the compression of the engine you can get a pretty accurate estimate:
For 8.5/1 compression ratio multiply fuel flow times 14.7 to determine HP.
For 7.5/1 engines use 13.7 times fuel.

Note: I have no information on the Powerflow system or the DA-40 specifics.

Tim
User avatar
TimS
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Timothy
Aircraft: OTHER
Registration: N1446C
Airport: 6B6 Stowe MA

Posts: 424
Joined: Thu Dec 02, 2010 1:10 am
Has thanked: 53 times
Been thanked: 61 times

Re: Horsepower debate (was DA40NG)

Post by TimS »

Thomas wrote:Sandy`s vote is interesting, my question is … what is the role of the prop, performance means speed and T/O acceleration depending on the mass of air which the prop is moving. So more/less HP means different prop pitch at the same rpm.. If the governor regulates 2700 at T/O its 2700 with 180HP or 200HP – but with 200, you move more Air mass. Or am I wrong in my thinking
If the RPM is the same, but HP increases then you are either moving more air or losing additional power to drag.
To determine how much you lose to drag and how much you gain in air movement needs a lot more knowledge than me to figure out!

Also, be aware, propellers are airfoils and the airfoil is optimized to meet three variables:
1. Specific RPM
2. Relative wind velocity
3. Horsepower applied to the prop.

A constant speed prop goes a bit further and usually accepts a slightly lower peak performance at the target to provide a better performance across a larger range of relative wind and power settings.

Tim
User avatar
blsewardjr
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Bernie
Aircraft: DA40
Registration: N377DS
Airport: KCHO

Posts: 330
Joined: Tue Jul 26, 2011 11:19 pm
Has thanked: 63 times
Been thanked: 69 times

Re: Horsepower debate (was DA40NG)

Post by blsewardjr »

I think Antoine is correct about what the PowerFlow does in terms of adding power. Basically, the OEM exhaust system REDUCES the actual horsepower from the RATED value (180hp at 2700) to something lower. The PowerFlow exhaust helps restore most of that power. Here's how PowerFlow explains it for a 160hp engine
In order to prove what our system can do, and hopefully combat some skepticism, we installed a Power Flow Tuned Exhaust on one of their test stands, and compared the dyno numbers to the same engine with the OEM Cessna exhaust. The engine used was a Lycoming O-320 A1A, rated at 160hp.dyno rig

Here is what we found:
Peak Horsepower Developed:
PFS Tuned Exhaust:157.1hp
OEM Cessna exhaust:133.3hp
Bernie Seward, IR, AGI
2003 DA40 N377DS
KCHO Charlottesville, VA
Antoine
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Antoine
Aircraft: OTHER
Registration: N121AG
Airport: LSGG

Posts: 2038
Joined: Fri Oct 15, 2010 11:00 pm
Has thanked: 87 times
Been thanked: 210 times

Re: Horsepower debate (was DA40NG)

Post by Antoine »

Sandy wrote:It is what it is, and no exhaust system increases the output to 200 Hp. Sandy
We have different opinions here: if you bolt a turbo to this engine you can obviously coax it to make 250 or more HP regardless of what the plate says.
Similarly, if you use a resonant exhaust system you can make the engine breathe better (more air in the cylinders) and make more horsepower than what it would without the improved exhaust. Here is an explanation from a car tuning web site

When correctly designed, the modified exhaust can be tuned to resonate and the pressure vibrations in the tuned exhaust can be timed to have a low pressure wave arrive at an exhaust valve as it opens, pulling the gasses out.

I am not affirmative that it is 200 HP, because it may be that the original engine installation and exhaust system waste power so the baseline is actually lower.
But it is probably 20 HP more than whatever the baseline is. So, yes, I believe that you can increase power by means of a resonant exhaust
Sandy wrote: This is further confirmed by the fact that the generation of power requires that fuel be used, with a relatively efficient gasoline engine consuming approximately 0.40 - 0.45 pounds of fuel per hour per Hp. Thus, at 135 Hp (75%), we are talking about approximately 54 - 61 pounds of fuel per hour, or about 9-10 gallons per hour of Avgas.
According to this https://www.lycoming.com/sites/default/ ... 297-36.pdf the specific fuel consumption of the IO-360 M1A is more like .66 lb/hp.hour
At 75% power (135 HP) this engine should use 11 GPH.
My XLS used about .3 to .5 GPH less and I am attributing this to increased efficiency from the resonant exhaust.

You are right about this: We will only make full rated power at the full power RPM because power is RPM x torque. So unless we are revving it to 2700 RPM, we will have less power available.

My comfort zone used to be 2400 to 2500 RPM and wide open throttle, leaned to 9.5 or so GPH. I think this is a great place to run the IO-360 M1A:
When I sold my XLS, compressions, measured by Diamond Egelsbach as part of the pre-buy inspection were "as new" and the cylinders and valves were clean.
So I definitely believe that this engine was happy and I was delighted by the "182 eater" performance which was my original point by the way :)

Wayne: thank you too. I am still here because I thoroughly enjoy our discussions. You guys are a wonderful bunch of people to spend time with.
User avatar
TimS
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Timothy
Aircraft: OTHER
Registration: N1446C
Airport: 6B6 Stowe MA

Posts: 424
Joined: Thu Dec 02, 2010 1:10 am
Has thanked: 53 times
Been thanked: 61 times

Re: Horsepower debate (was DA40NG)

Post by TimS »

Lycoming still uses ROP, normally about 200 degrees ROP.
This is not exactly an efficient use of fuel.

When I was getting new engines for both the Cirrus (cracked case issue) and the Aerostar (cam shaft spalling) both Lycoming and Continental said the HP rating for the engine is in the installed configuration and run as specified in the manual. Now the HP is not "exact", it is within a specified tolerance. The tolerance was much tighter on the bottom end, but did allow for some slop on the higher end. Basically, if the engine was supposed to be 180HP, the FAA wants the companies to guarantee 180HP when new. The end result, the actual HP is usually slightly more.

Tim
User avatar
Chris
5 Diamonds Member
5 Diamonds Member
FIRST NAME: Chris
Aircraft: DA42NG
Registration: N449TS
Airport: KHIO

Posts: 624
Joined: Sat Jun 19, 2010 3:34 am
Has thanked: 388 times
Been thanked: 178 times

Re: Horsepower debate (was DA40NG)

Post by Chris »

Where's Greg (gwroclaw) when we need him? :)
Antoine wrote: According to this link the specific fuel consumption of the IO-360 M1A is more like .66 lb/hp.hour
I'm confused by the math here. As you noted, the manual states 11GPH at 135HP, so wouldn't that be 66 lbs / 135 HP = 0.48 lb/hp-hr? Anyway, I think it's reasonable to use fuel flow to estimate actual HP given near-standard conditions, so it would just be a matter of measuring fuel flows at max power for birds with and without the PF to get an accurate read of the difference (and an estimate of the actual HP for each).
Chris
N449TS / DA42-NG / 42.AC049
KHIO
User avatar
TimS
4 Diamonds Member
4 Diamonds Member
FIRST NAME: Timothy
Aircraft: OTHER
Registration: N1446C
Airport: 6B6 Stowe MA

Posts: 424
Joined: Thu Dec 02, 2010 1:10 am
Has thanked: 53 times
Been thanked: 61 times

Re: Horsepower debate (was DA40NG)

Post by TimS »

Chris wrote:Where's Greg (gwroclaw) when we need him? :)
I'm confused by the math here. As you noted, the manual states 11GPH at 135HP, so wouldn't that be 66 lbs / 135 HP = 0.48 lb/hp-hr? Anyway, I think it's reasonable to use fuel flow to estimate actual HP given near-standard conditions, so it would just be a matter of measuring fuel flows at max power for birds with and without the PF to get an accurate read of the difference (and an estimate of the actual HP for each).
Fuel flow determines power when LOP.
Air flow determines power when ROP.
Also, make sure both planes are running approximately the same degrees LOP.

Tim
Post Reply