Fuel injected for sure.
To operate at great efficiency requires the Fuel/Air ratios to be even. That can be achieved with injection, no Pmag can help that...
FI's prime benefit is super-critical LOP smoothness and some modification of CHTs if you bother tinkering with injectors.
Depends on the mission profile of the OP, David. Remember, there are plenty of pilots who don't touch the red knob in flight at all. And unless you are really going to spend a lot of time in high efficiency cruise vice the more "typical" sport flying, ignition is going to give you better bang for the buck. Remember, not everyone is a slave to the red knob... Some only use it to shut down the engine.
I do use the red knob and I'm trying to learn the leaning capabilities of my EIS 4000
I would not add EI in the hope of any extra HP... At full power / ISA is where the Mags are optimally timed - EI will just be the same. So your sole benefit at Max Power is effectively an improved spark.Electronic ignition. Adds a few extra hp
Don, I am as big a promoter of an EMS as anyone can be, but the lean find functions on all EMS are flawed and not as good as doing the "brain work" in your head.
The lean find function can be handy while doing GAMI Lean tests, but after that it is not an effient or accurate function.
David - I'm interested to learn what flaws you have found in the lean function of the EIS-4000. Once the pilot has selected Lean Mode, it watches all EGTs, looking for the highest value. Once the EGT is reducing from a peak, it shows how many degrees each cylinder is below peak EGT. Have you found this doesn't work as described, or do you do some additional "brain work"? If so, I'd love to learn what it is.
Me too, as I use the lean function on my D180 from time to time.
RV10inOz; said:...As for plenty of pilots who don't touch the red knob? Well I would like to meet them, unless they are flying circuits all day I have a great struggle in seeing the logic...
RV-6A with 0-320 E2D. If you only had the money for one or the other, which would you choose (and why)? Fuel injection or P-mags? Looking for the most bang for the buck.
Thanks for your thoughts.
Bill, what timing did you use on your O290?
Thanks for the long, useful explanation David. I've definitely noticed the lag, and the increase in peak EGT after some time in cruise. I've generally done a slow mixture pull to peak EGT, then set around 30 deg F LOP. After 10 minutes or so I enrichen to redefine the peak EGTs, then set 50 deg F LOP.Kevin, the flaws I see are in two areas, the methodology of use, and the maths used with probes that have a small amount of lag.
I started off using 50dF LOP, as I wanted to really sure to be clear of the danger zone. I generally cruise at 8000 to 10000 ft, at 2450 rpm and full throttle. 50dF LOP usually gives me between 160 and 165 kt TAS, burning between 8.0 and 8.2 US kph. I?m happy with that.Kevin, you might like to adopt the John Deakin method of being a lazy pilot He readily admits it.
Level out?do nothing while the plane accelerates, do a BMP, do nothing, then when the CHT's have rolled off a bit, sneak up from the lean side.
It is far less work, can't hurt anything, and is better all round.
You will not use the Lean find again, or not the same way.
Last of all?..why set 50dF LOP? Do you always fly at a fuel flow of 75-80% power?
The reason I ask is why the fixation on 50dF LOP. It is not uncommon, but it is a flawed thought. We know why that is and it does not make sense.
I would not add EI in the hope of any extra HP... At full power / ISA is where the Mags are optimally timed - EI will just be the same. So your sole benefit at Max Power is effectively an improved spark.
The whole point of EI is that as you move away from full power / rich mixture, the Mag stays timed for full power, whereas EI adjusts to the new optimum timing.
As I understand it anyway
I think you illustrate a common dilemma - it is fine for the engine boffins to tell us where best SFC / efficiency is in HP terms, but if that results in more HP then the airframe just wastes the benefit.I started off using 50dF LOP, as I wanted to really sure to be clear of the danger zone. I generally cruise at 8000 to 10000 ft, at 2450 rpm and full throttle. 50dF LOP usually gives me between 160 and 165 kt TAS, burning between 8.0 and 8.2 US kph. I?m happy with that.
Knowing what I know now, I could run richer, go a bit faster, but burn more fuel. Given current fuel prices, I?m happy to slow down a bit if it saves me a bunch of money on fuel. The data I have on SFC vs fuel flow from Lycoming, combined with my flight test data suggests that the best SFC is somewhere between 30dF LOP and 50dF LOP, so I generally run in that range.
Kevin, at those altitudes, the better BSFC should be around 10-20dF LOP. So if you want the engine at its best efficiency, run at the higher fuel flow, set up 10-20dF LOP and then if you want to slow down a bit to enjoy less aero drag, use the RPM (i.e 2200 or 2100) and or reduce MP and slow down that way.
Keeping the F/A ratio about the same is the idea.
This will yield the best overall efficiency.
Of course there is this argument?" I did not buy/build a fast aeroplane to go slow!"
... then if you want to slow down a bit to enjoy less aero drag, use the RPM (i.e 2200 or 2100) and or reduce MP and slow down that way.
Keeping the F/A ratio about the same is the idea.
This will yield the best overall efficiency.
David,
Are you saying that once you have established a F/A ratio at any throttle setting (MAP) on the standard Lycoming FI system, changing the throttle position does not affect the ratio at all?
Thanks.
Johan
REDUCE MANIFOLD PRESSURE?!?!?!
But this violates the whole premise of WOTLOPSOP!!!
That would be correct except that is not what happens. In other words in a perfect world a set F/A ratio would remain constant but the FCU's as much as they are pretty good they are not perfectly linear, and lets face it, we are talking about measuring in inches here when miles is more appropriate.