252/Encore vs. Rocket

[Shadrach]

Quote: donshapansky

I didn't show those figures I said the lowest in the previous post was 15.0 gph and as high as 16.0 gph on a cool day. I never see over 72 - 73% power on the EDM 930 and the trip a couiple days ago at 15.0 gph was 64 - 65% on the EDM 930.

[aviatoreb]

Quote: Shadrach

Hi Don,

I am sorry to revive an old post - but I was rereading all those posts regarding Rocket engine ops and this one by you really caught my eye.

I am confused by one thing that you are saying here.  Isn't it LOP that power is simply proportional to fuel flow, and for 7.5:1 compression ratio as is the TSIO520NB, that the constant of proportionality is 12.7hp/gph.  So 15.0*12.7=190=>190/305*100=62.45% of max power.  Why is your edm showing different values for different days at the same gph if this proportionality concept is correct, ranging from 64-73%?  For example LOP shouldn't 73% be 17.5gph?  What am I missing?

You see in my rocket, I have a EDM-700 which has all the instrumentation readings to allow me to find nice LOP settings but it will not directly tell me my hp - so I have been using that 12.7 multiplier factor to infer my HP.

Thanks,

Erik

[donshapansky]

The true advantage of LOP operations is the ability to increase MAP and get back the lost speed that would be the case of NA (normally aspirated engines). In my case a ROP setting I used was was 29" @ 2450 rpm would net around 73% power and 22 gph to keep the hottest cylinder around 385 - 390 F.

LOP, the numbers you see are dictated by air density to keep all cylinders 50 LOP or greater will vary on a given day between 16.0 down to 15.0 gph, with rpm at 2450 and boost at 32.5 MAP the power will show 70 - 73%% on the EDM with very little loss of speed.

That is the real advantage of LOP operations, cooler, cleaner engine on less fuel with little performance loss.

[aviatoreb]

Quote: donshapansky

The true advantage of LOP operations is the ability to increase MAP and get back the lost speed that would be the case of NA (normally aspirated engines). In my case a ROP setting I used was was 29" @ 2450 rpm would net around 73% power and 22 gph to keep the hottest cylinder around 385 - 390 F.

LOP, the numbers you see are dictated by air density to keep all cylinders 50 LOP or greater will vary on a given day between 16.0 down to 15.0 gph, with rpm at 2450 and boost at 32.5 MAP the power will show 70 - 73%% on the EDM with very little loss of speed.

That is the real advantage of LOP operations, cooler, cleaner engine on less fuel with little performance loss.

[aviatoreb]

Quote: donshapansky

The true advantage of LOP operations is the ability to increase MAP and get back the lost speed that would be the case of NA (normally aspirated engines). In my case a ROP setting I used was was 29" @ 2450 rpm would net around 73% power and 22 gph to keep the hottest cylinder around 385 - 390 F.

LOP, the numbers you see are dictated by air density to keep all cylinders 50 LOP or greater will vary on a given day between 16.0 down to 15.0 gph, with rpm at 2450 and boost at 32.5 MAP the power will show 70 - 73%% on the EDM with very little loss of speed.

That is the real advantage of LOP operations, cooler, cleaner engine on less fuel with little performance loss.

[donshapansky]

I can't give you a hard and fast set of numbers due to the variables of air density, every flight I do the same procedure, set the EDM up for LOP operations and start leaning to peak EGT. The No. 5 cylinder always is first to peak but the peak can vary from 1580 - 1610 F, then the graph flips and I continue to lean until No 2 cylinder which is last to peak is showing somewhere in the range of 30 - 40 LOP then let it settle for a couple of minutes, close the cowl flaps down and then tweak to 50 LOP and the fuel ends up somewhere between 15.0 - 16.2 GPH. I do use 32.5 - 33.5 "MAP depending on if I'm in a hurry I definitely see 73% at the higher MAP setting and a couple more knots indicated. When I say no loss in speed I may off by a couple but not more than 2 - 4 ktias.  I have heard many pilots who don't really understand the procedure say that they don't see any advantage to LOP they say just reduce the MAP until the fuel flow matches the LOP flow and the ROP alternative is the same. That is not true when you observe the above procedure in operation, the challenge is to get the engine to run smoothly LOP and not shake and vibrate to point of being annoying.

[donshapansky]

I can't give you a hard and fast set of numbers due to the variables of air density, every flight I do the same procedure, set the EDM up for LOP operations and start leaning to peak EGT. The No. 5 cylinder always is first to peak but the peak can vary from 1580 - 1610 F, then the graph flips and I continue to lean until No 2 cylinder which is last to peak is showing somewhere in the range of 30 - 40 LOP then let it settle for a couple of minutes, close the cowl flaps down and then tweak to 50 LOP and the fuel ends up somewhere between 15.0 - 16.2 GPH. I do use 32.5 - 33.5 "MAP depending on if I'm in a hurry I definitely see 73% at the higher MAP setting and a couple more knots indicated. When I say no loss in speed I may off by a couple but not more than 2 - 4 ktias.  I have heard many pilots who don't really understand the procedure say that they don't see any advantage to LOP they say just reduce the MAP until the fuel flow matches the LOP flow and the ROP alternative is the same. That is not true when you observe the above procedure in operation, the challenge is to get the engine to run smoothly LOP and not shake and vibrate to point of being annoying.

[aviatoreb]

Quote: donshapansky

.. The No. 5 cylinder always is first to peak but the peak can vary from 1580 - 1610 F...

[aviatoreb]

Quote: donshapansky

 I have heard many pilots who don't really understand the procedure say that they don't see any advantage to LOP

[donshapansky]

The reference during peak EGT is to the hottest cylinder in my case always No. 5. The TIT never gets to 1650 F and ends up at 1550 F to 1570 F, which is very safe. All the cylinders cool down to hottest usually No. 2 at 350 - 365 F and the rest all close but lower. GAMI leaned most agressively on the No. 5 injector as it was the hottest and it worked well, it is now in line with it's neighbors and it is interesting to see how some days you could paint the lines in a level line then some days No.2 will be hottest with the rest just slightly cooler, it appears to be linked to OAT to some degree, which is probably a density issue. 

[donshapansky]

I should clarify that altitude has little effect on the numbers I use, the pictures I posted recently I was at 4,500 ', that is unually low I usually am at 8 - 11K and even at 15 - 17 K I go through the same steps and the numbers are virtually identical in terms of the engine parameters. As far as the EDM telling the truth my K factor is very close to actual fuel burn and the Constant HP adjustment was done as per the instructions in the manual. On take off I see 98 - 99% power showing with actual boost at 37.8 " and I get 2675 RPM, with my max fuel flow has been tweaked several time to get rich enough at the prevailing formula by the gurus at 1 gal per 1 inch of MAP, that really cooled the engine down. I can leave Midland, TX at 100+ F and never see over 350 - 360 F in the climb all the way to altitude. What has to be watched is a cold day departure it will for 44 gph and make the engine burble, just pull the mixture back to 37 gph and watch the thing climb at 1900 '/min and 130 kts! or 155 kts @ 1000 '/min.  

[BrianNC]

Quote: donshapansky

I should clarify that altitude has little effect on the numbers I use, the pictures I posted recently I was at 4,500 ', that is unually low I usually am at 8 - 11K and even at 15 - 17 K I go through the same steps and the numbers are virtually identical in terms of the engine parameters. As far as the EDM telling the truth my K factor is very close to actual fuel burn and the Constant HP adjustment was done as per the instructions in the manual. On take off I see 98 - 99% power showing with actual boost at 37.8 " and I get 2675 RPM, with my max fuel flow has been tweaked several time to get rich enough at the prevailing formula by the gurus at 1 gal per 1 inch of MAP, that really cooled the engine down. I can leave Midland, TX at 100+ F and never see over 350 - 360 F in the climb all the way to altitude. What has to be watched is a cold day departure it will for 44 gph and make the engine burble, just pull the mixture back to 37 gph and watch the thing climb at 1900 '/min and 130 kts! or 155 kts @ 1000 '/min.  

[donshapansky]

I don't recall that particular flight but from many other flights of the same altitude it would have been 210 - 213 ktas.

[donshapansky]

I don't remember that particular flight but it would have been 210 - 213 ktas.