Van's Air Force
Don't miss anything! Register now for full access to the definitive RV support community.
Fuel injection or electronic ignition
- Thread starter flytoboat
- Start date
I am planning on starting with the EFII electronic ignition then adding the EFII electronic FI at a later time depending on how LOP ops and efficiency works out with just the electronic ignition. EI, IMO, is way more bang for the buck and easier to install, but the whole EFII system looks great. Hopefully we get a few more pireps on it in the next 6 months.
Kyle Boatright
Well Known Member
I've never played with FI, but my sense is that a carb to FI retrofit is a more involved process than switching from magnetos to (say) Pmag's. If my assumption is correct, I'd go with FI initially, then upgrade ignition systems down the road...
Toobuilder
Well Known Member
Electronic ignition is quickly becoming a "must have" because it benefits every aspect of the engine operating envelope from start, idle, cruise, and power. Fuel injection is nice, but really only outshines a carb in cruise efficiency or aerobatics. My vote: Ignition first, then look at injection.
Doug
Well Known Member
FI upgrade is going to be more expensive and a time consuming job.
Apart from the engine upgrade kit consider the fuel pump upgrades, both mechanical and electric, the cowling and FAB modification if you choose the Silverhawk system due to the extra length of the servo versus carb (approx 7/8") - I don't know the length of the AP servo so cannot comment. Other bits and pieces include the sniffle valve and throttle & mixture linkage modifications.
If you look carefully at the Lycoming Operators manual and compare the HP between the O and IO versions the carbureted engine give the same HP at about 1/2" less manifold pressure than the FI equivalent. This gives me some comfort in staying with the carb.
Apart from the engine upgrade kit consider the fuel pump upgrades, both mechanical and electric, the cowling and FAB modification if you choose the Silverhawk system due to the extra length of the servo versus carb (approx 7/8") - I don't know the length of the AP servo so cannot comment. Other bits and pieces include the sniffle valve and throttle & mixture linkage modifications.
If you look carefully at the Lycoming Operators manual and compare the HP between the O and IO versions the carbureted engine give the same HP at about 1/2" less manifold pressure than the FI equivalent. This gives me some comfort in staying with the carb.
turbosaaber
Well Known Member
FI
I would think about doing what would be more difficult to build now because when you start flying, taking the airplane down to do upgrades is like going to the dentist. I would do the fuel injection and wire the pmags so when you decide to upgrade your conventional magnetos you can just plug them and go fly quickly. Just a thought. I have both and I must say the PMAGs are incredible with outstanding service.
I would think about doing what would be more difficult to build now because when you start flying, taking the airplane down to do upgrades is like going to the dentist. I would do the fuel injection and wire the pmags so when you decide to upgrade your conventional magnetos you can just plug them and go fly quickly. Just a thought. I have both and I must say the PMAGs are incredible with outstanding service.
Assuming you are flying I agree with all the above - Electronic Ignition no question as it is much easier to install. P-mags are the most straight forward, but even if you go with Lightspeed (or another) it isn't that difficult.
Installing Fuel Injection will mean a new cowl scoop as the injector is longer than the carb (or other cowl surgery), probably a new fuel pressure gauge (or at least a transducer), new piping and a whole lot more. It is also more expensive by at least $1K.
Both will produce around the same benefit in fuel savings terms, but EI will give a small gain in top end performance, especially up high.
Pete
Installing Fuel Injection will mean a new cowl scoop as the injector is longer than the carb (or other cowl surgery), probably a new fuel pressure gauge (or at least a transducer), new piping and a whole lot more. It is also more expensive by at least $1K.
Both will produce around the same benefit in fuel savings terms, but EI will give a small gain in top end performance, especially up high.
Pete
RV10inOz
Well Known Member
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.
Sure we can get carb engines LOP, but best bang for buck will be an IO320. They are great engines made awesome by adding the I.
To operate at great efficiency requires the Fuel/Air ratios to be even. That can be achieved with injection, no Pmag can help that.
Sure we can get carb engines LOP, but best bang for buck will be an IO320. They are great engines made awesome by adding the I.
The question was about one or the other, not the relative cost and complexity of upgrade, which might be of future interest.
Electronic Ignition - both sides. Don't keep one mag; sets you up for more expensive life-cycle cost and maintenance than an EI and contributes nothing to efficiency.
FI's prime benefit is super-critical LOP smoothness and some modification of CHTs if you bother tinkering with injectors. It's also ~$3K more than a carby. If you have that after buying EIs (I strongly recommend P-mags), then have LyCon port and flow Lycoming jugs for ~$1K. Vastly more bang/buck. FI comes in third.
John Siebold
Electronic Ignition - both sides. Don't keep one mag; sets you up for more expensive life-cycle cost and maintenance than an EI and contributes nothing to efficiency.
FI's prime benefit is super-critical LOP smoothness and some modification of CHTs if you bother tinkering with injectors. It's also ~$3K more than a carby. If you have that after buying EIs (I strongly recommend P-mags), then have LyCon port and flow Lycoming jugs for ~$1K. Vastly more bang/buck. FI comes in third.
John Siebold
Last edited:
Toobuilder
Well Known Member
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.
flytoboat
Well Known Member
Thanks for the great discussion here guys! I bought a flying RV6A in September and have already put almost 40 fun hours on her (mostly 200 mile cross countries). I do use the red knob and I'm trying to learn the leaning capabilities of my EIS 4000 (if anyone has any tips on that, please respond). I'll probably go with the pmags for now since that is a much simpler mod to make. I've got a few flying missions coming up this winter (Atlanta in February and West Palm Beach in early March) and don't want to take her out of service too long at a time.
RV10inOz
Well Known Member
John
That is bad advice hidden in there. You NEVER ever fiddle with fuel injectors to modify CHT's?..not ever! I can't make a big enough statement on that. You adjust the flow of injectors to do one thing and one thing only, and that is to get consistent F/A ratio's and having all cylinders peaking at the same time (fuel flow).
Once you have that accomplished it is all down to Baffles and exit air.
CHT is the result of heat IN - Heat Out. Get the F/A ratios sorted and the heat in is fairly similar, then worry about the heat out.
That is bad advice hidden in there. You NEVER ever fiddle with fuel injectors to modify CHT's?..not ever! I can't make a big enough statement on that. You adjust the flow of injectors to do one thing and one thing only, and that is to get consistent F/A ratio's and having all cylinders peaking at the same time (fuel flow).
Once you have that accomplished it is all down to Baffles and exit air.
CHT is the result of heat IN - Heat Out. Get the F/A ratios sorted and the heat in is fairly similar, then worry about the heat out.
RV10inOz
Well Known Member
Michael
1. The OP did not offer anyone any clues on the mission at all, so your point is not valid. If he said all I do is fly circuits (patterns) and that is it, I would say sure, the red knob is an off switch. I doubt that is his mission. Just a hunch.
2. 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. It is like saying I never touch my altimeter knob or never change my radio frequency because when I come home I am on the right CTAF. It just makes no sense and shows a lack of education and understanding and is in my opinion (and a few others
) a severe lack of airmanship. But I do not name the poor pilot, it is not his fault. He just has not been educated. Now some refuse the opportunity to learn too. So that is another case.
3. As for spending a lot of time in high efficiency cruise, that is rubbish. A typical scenic flight for friends family and tourists from my airfield, out over the bay and islands is done at say 2000', Take off and climb, 2 minutes later level out and a BMP. Straight to LOP. Stays there until I shut down at the hangar. That was high efficiency cruise. 80% power or there about, or less if I want to go slower, but it was suitably efficient for two reasons. We pay USD$7.66/USG for fuel and I like my CHTs cooler and heads, plugs and pistons cleaner. Why would I not want to do that? Hardly a slave to the red knob. I bet I touch it less than you do.
4. And how is the never touch a red knob pilot going to get far better bang for buck out of his EI ? Full rich fuel flows will be the same, mags or EI. They guy who flies LOP will get small gains in advanced timing.
1. The OP did not offer anyone any clues on the mission at all, so your point is not valid. If he said all I do is fly circuits (patterns) and that is it, I would say sure, the red knob is an off switch. I doubt that is his mission. Just a hunch.
2. 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. It is like saying I never touch my altimeter knob or never change my radio frequency because when I come home I am on the right CTAF. It just makes no sense and shows a lack of education and understanding and is in my opinion (and a few others
) a severe lack of airmanship. But I do not name the poor pilot, it is not his fault. He just has not been educated. Now some refuse the opportunity to learn too. So that is another case.3. As for spending a lot of time in high efficiency cruise, that is rubbish. A typical scenic flight for friends family and tourists from my airfield, out over the bay and islands is done at say 2000', Take off and climb, 2 minutes later level out and a BMP. Straight to LOP. Stays there until I shut down at the hangar. That was high efficiency cruise. 80% power or there about, or less if I want to go slower, but it was suitably efficient for two reasons. We pay USD$7.66/USG for fuel and I like my CHTs cooler and heads, plugs and pistons cleaner. Why would I not want to do that? Hardly a slave to the red knob. I bet I touch it less than you do.
4. And how is the never touch a red knob pilot going to get far better bang for buck out of his EI ? Full rich fuel flows will be the same, mags or EI. They guy who flies LOP will get small gains in advanced timing.
RV10inOz
Well Known Member
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.
Can I recommend to you attending the March APS Seminar in Ada OK. Email John Deakin and book in, tell hime I said to get you started on the online course as part of the deal. A VAF freebie for ya from me!
And it is not my money I am giving away, so it is even better 
Andy Hill
Well Known Member
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
Andy's right;
Full power at SEA LEVEL. Full (available) power at altitude would benefit from EI, as the manifold pressure reduces and the spark advances. This is noticable at the altitudes used for speed testing and cross country trips.
As for EI or FI, I'm for combined units like SDS, which use Electronic automotive fuel injection and Ignition.
I have Electronic Ignition & Injection on my RV-8.
My Thorp T-18 has a carb with a single P-mag and one Bendix mag. I added the P-mag. Well worth the extra cost over a mag overhaul, and although it didn't install it'self, it did go together in about a day.
The cheapest way to get both is the full EFII or SDS conversion, done all at once.
I have the Tracy Crook EC-2 system of injection & ignition, which is probably no longer available, although it's still serviced. The automotive injection with approx 40 psi fuel pressure to the injectors, and continuous return of unused fuel to the tank virtually eliminates vapor lock & carb ice. Also, fuel mixture & timing can be altered in flight with the interface unit.
So many choices...
Full power at SEA LEVEL. Full (available) power at altitude would benefit from EI, as the manifold pressure reduces and the spark advances. This is noticable at the altitudes used for speed testing and cross country trips.
As for EI or FI, I'm for combined units like SDS, which use Electronic automotive fuel injection and Ignition.
I have Electronic Ignition & Injection on my RV-8.
My Thorp T-18 has a carb with a single P-mag and one Bendix mag. I added the P-mag. Well worth the extra cost over a mag overhaul, and although it didn't install it'self, it did go together in about a day.
The cheapest way to get both is the full EFII or SDS conversion, done all at once.
I have the Tracy Crook EC-2 system of injection & ignition, which is probably no longer available, although it's still serviced. The automotive injection with approx 40 psi fuel pressure to the injectors, and continuous return of unused fuel to the tank virtually eliminates vapor lock & carb ice. Also, fuel mixture & timing can be altered in flight with the interface unit.
So many choices...
Last edited:
Kevin Horton
Well Known Member
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
Well Known Member
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.
Basically the lean find mode works, however it delivers a sub optimal result, therefore it does not work when compared to doing it the manual brain method.
So the first issue being lag in the probe which delivers numbers to the screen and depending on how the sampling is done it can be clumsy. The biggest problem is the way people use them.
The majority of people use the lean find from the rich side, slowly leaning away until they get to lets say 25dF LOP. If they immediately return back to peak they find they ended up further LOP than they thought. so there is some hysteresis going on, and that is not helpful, but when added to the next bit I explain it compounds.
So lets say we have set 25dF LOP and settle into the cruise, and our boredom leads to curiosity, and we think, lets just find peak from the lean side. Assume Peak was 1420 and we set 1395, well we richen up slowly until the first one peaks (should be the last one from the rich side) and we sail right past 1420 and end up at maybe (for the story sake) 1450-1455.
OK so back to 25dF LOP and now at 1430 EGT on that cylinder. Things are smoother, the plane picks up a knot or two, or five.
How could that be? Simple answer is the cooler cylinder (a lot cooler than slowly being run through the 30-150dF ROP range) is now more volumetrically efficient and is now capable of flowing more fuel. Most of the effect is from the CHT drop off and a small amount from the probe and the algorithms.
As for the finer details, Walter Atkinson did a lot of research and development for the Auracle guys and hence we know a bit more about this than was known many years ago.
The Lean Find method is fine for doing GAMI Lean Tests. But for real world operations once you know the richest cylinder number, use it, do a BMP, let things cool off, and then sneak up from the cool side to find peak on that one cylinder alone using the raw data. then back off 10/20/25/40/60/80 dF LOP.
The reason some people have complained and moaned about speed loss LOP was they never knew what they were doing for a start, and they were actually WAY leaner than they should have been. People running 50+dF LOP when 10-20 was optimal were 5-6 knots slower and some more.
The electronics just does not seem to cope with the smaller amounts of accuracy needed when you are arguing over 10dF, and add to the error there the larger amount of the cylinder temps due to the application of a LF method means a sub optimal result.
While I am on the bandwagon the fixation everyone has about %power is almost as useless. Near enough is good enough. 63 or 67%, call it 65. 82 is near enough to 80. And many of the EMS out there are not good at doing either ROP or LOP?.and perhaps both! Some are so bad that if you pull the mixture to ICO??I would call that NIL Power, yet they still display amazing numbers!
Hope that helps.
Basically the lean find mode works, however it delivers a sub optimal result, therefore it does not work when compared to doing it the manual brain method.
So the first issue being lag in the probe which delivers numbers to the screen and depending on how the sampling is done it can be clumsy. The biggest problem is the way people use them.
The majority of people use the lean find from the rich side, slowly leaning away until they get to lets say 25dF LOP. If they immediately return back to peak they find they ended up further LOP than they thought. so there is some hysteresis going on, and that is not helpful, but when added to the next bit I explain it compounds.
So lets say we have set 25dF LOP and settle into the cruise, and our boredom leads to curiosity, and we think, lets just find peak from the lean side. Assume Peak was 1420 and we set 1395, well we richen up slowly until the first one peaks (should be the last one from the rich side) and we sail right past 1420 and end up at maybe (for the story sake) 1450-1455.
OK so back to 25dF LOP and now at 1430 EGT on that cylinder. Things are smoother, the plane picks up a knot or two, or five.
How could that be? Simple answer is the cooler cylinder (a lot cooler than slowly being run through the 30-150dF ROP range) is now more volumetrically efficient and is now capable of flowing more fuel. Most of the effect is from the CHT drop off and a small amount from the probe and the algorithms.
As for the finer details, Walter Atkinson did a lot of research and development for the Auracle guys and hence we know a bit more about this than was known many years ago.
The Lean Find method is fine for doing GAMI Lean Tests. But for real world operations once you know the richest cylinder number, use it, do a BMP, let things cool off, and then sneak up from the cool side to find peak on that one cylinder alone using the raw data. then back off 10/20/25/40/60/80 dF LOP.
The reason some people have complained and moaned about speed loss LOP was they never knew what they were doing for a start, and they were actually WAY leaner than they should have been. People running 50+dF LOP when 10-20 was optimal were 5-6 knots slower and some more.
The electronics just does not seem to cope with the smaller amounts of accuracy needed when you are arguing over 10dF, and add to the error there the larger amount of the cylinder temps due to the application of a LF method means a sub optimal result.
While I am on the bandwagon the fixation everyone has about %power is almost as useless. Near enough is good enough. 63 or 67%, call it 65. 82 is near enough to 80. And many of the EMS out there are not good at doing either ROP or LOP?.and perhaps both! Some are so bad that if you pull the mixture to ICO??I would call that NIL Power, yet they still display amazing numbers!
Hope that helps.
Toobuilder
Well Known Member
RV10inOz; said:
No, there is no logic, and I am not advocating the practice. I give the red knob a good workout on every flight, just as you do. However, this forum is filled with statements like "...I don't lean below 5,000 feet...", so I know there are plenty of pilots who use it as an on/off control. There are also plenty of pilots who think the rudder pedals are for steering on the ground only... You can't fix them all.
So until you are able to "convert" every pilot to active and proper engine management, there will still be a bunch of people who fly like they were trained- engine fat and let the mechanic deal with the plugs when they foul. These are the type that FI will NOT benefit for the most part. But EI WILL provide better starting, smoother running, better resistance to fouling, and cheaper plugs when they do fail.
My point is, EVERY pilot gets a benefit from EI, while it is primarily the "active engine manager" type of pilot which will derive benefit from injection. And if you already are an active engine manager, then the type of flying you do will decide which system (FI or EI) will give you the quicker payback. It simply becomes a math exercise at that point.
Last edited:
N941WR
Legacy Member
Back to the OP's question...
Since you have a flying plane and are trying to figure out which mod best for you, you are going to get a bunch of different answers based on personal experience. That and the typical human reaction of, "Buy what I did because it helps justify my purchase and decision making."
With that in mind, here is my experience with both the 135 HP O-290-D2 I used to fly behind and the 180 HP O-360 I currently fly behind.
Both engines had/have P-mags and fixed pitch Catto props. Besides the engine, I also switched out to a Sam James short holy cowl with the engine change. Both engines used the Vetterman crossover exhaust.
With the O-290 I did not run LOP. I tired it and could not get the engine to run smoothly. My performance was typically 165 MPH / 140 Kts at 7 GPH running ROP.
The ECi O-360 with tapered cylinders seems to breath much easier and my typical cruise setting is 60 to 65% power at 150 to 155 Kts (172 to 178 MPH) while burning 7.0 to 7.2 GPH.
My CHT's at those power settings range from 295 TO 315*F. I don't have the EGT's because the few screen shots I have only list the degrees below peak, not the absolute numbers, and I don't have a data dump off my SkyView, just photographs.
Based on my experience with the O-290, I was not a fan of running LOP with a carb because the engine just felt rough, so I never did it. With the O-360 and the dual P-mags, I have no issues running smoothly as much as 50*F LOP with some cylinders running even leaner.
Thus, I have the simplicity of a carb and the efficiency of injection.
Would I like to change out my carb? Sure, but it will be difficult to justify the expense based on fuel savings simply because I'm already there.
Your experience with your Lycoming O-320 may be different than what I see with my ECi O-360. (ECi mentioned that the tapered cylinders I have flow better than the straight cylinders because the straight cylinders must conform to the Lycoming cylinder type certificate, or whatever the proper term is.)
Since you have a flying plane and are trying to figure out which mod best for you, you are going to get a bunch of different answers based on personal experience. That and the typical human reaction of, "Buy what I did because it helps justify my purchase and decision making."
With that in mind, here is my experience with both the 135 HP O-290-D2 I used to fly behind and the 180 HP O-360 I currently fly behind.
Both engines had/have P-mags and fixed pitch Catto props. Besides the engine, I also switched out to a Sam James short holy cowl with the engine change. Both engines used the Vetterman crossover exhaust.
With the O-290 I did not run LOP. I tired it and could not get the engine to run smoothly. My performance was typically 165 MPH / 140 Kts at 7 GPH running ROP.
The ECi O-360 with tapered cylinders seems to breath much easier and my typical cruise setting is 60 to 65% power at 150 to 155 Kts (172 to 178 MPH) while burning 7.0 to 7.2 GPH.
My CHT's at those power settings range from 295 TO 315*F. I don't have the EGT's because the few screen shots I have only list the degrees below peak, not the absolute numbers, and I don't have a data dump off my SkyView, just photographs.
Based on my experience with the O-290, I was not a fan of running LOP with a carb because the engine just felt rough, so I never did it. With the O-360 and the dual P-mags, I have no issues running smoothly as much as 50*F LOP with some cylinders running even leaner.
Thus, I have the simplicity of a carb and the efficiency of injection.
Would I like to change out my carb? Sure, but it will be difficult to justify the expense based on fuel savings simply because I'm already there.
Your experience with your Lycoming O-320 may be different than what I see with my ECi O-360. (ECi mentioned that the tapered cylinders I have flow better than the straight cylinders because the straight cylinders must conform to the Lycoming cylinder type certificate, or whatever the proper term is.)
N941WR
Legacy Member
I used the standard "A" Configuration with the P-mags, 26 to 34* BTC. I know the recommended timing for the -D2 is 18* BTC, per Lycoming to reduce the possibility of "...detonation under certain atmospheric and altitude conditions."
Note, the 18*BTC is for the -D2 variant of this engine only. Lycoming also recommends the use of high octane (91/98) fuel to help reduce the possibility of detonation in these "high compression" BTW, "high compression" was 7.5:1.
My engine was actually an O-290-D2B, which had 7.0:1 compression and the recommended timing was 25*BTC. It also came configured for an adjustable pitch prop, not a CS prop. I converted it to FP when I changed the accessory case.
Kevin Horton
Well Known Member
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.
rzbill
Well Known Member
Interesting about the commented scale of the lag and EGT offset.
It supports why I see a pretty big power dropoff "feel" at more that -20F LOP using peak determined from ROP side.
I have been running at peak (again determined from ROP side) or barely into LOP because the fuel flows and engine power were in a sweet spot and agreed with the Lyc charts for economy.
From the commentary, it appears I am further LOP than I think.... which is OK by me. It is the spot where all the stars align, no matter what the EGT says. I'll play with LOP measurement from the lean side some day.
It supports why I see a pretty big power dropoff "feel" at more that -20F LOP using peak determined from ROP side.
I have been running at peak (again determined from ROP side) or barely into LOP because the fuel flows and engine power were in a sweet spot and agreed with the Lyc charts for economy.
From the commentary, it appears I am further LOP than I think.... which is OK by me. It is the spot where all the stars align, no matter what the EGT says. I'll play with LOP measurement from the lean side some day.
RV10inOz
Well Known Member
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.
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.
Kevin Horton
Well Known Member
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
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.
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.
You'll want both eventually but...
By way of background info I have dual P Mags and Airflow Perf fi. I recently sold my Skybolt which had fi and Bendix mags.
I?d install the fi but would immediately start saving for the P Mags. I don?t believe there is a strong rationale to favor one project over the other since both are vastly superior to their predecessors.
By way of background info I have dual P Mags and Airflow Perf fi. I recently sold my Skybolt which had fi and Bendix mags.
I?d install the fi but would immediately start saving for the P Mags. I don?t believe there is a strong rationale to favor one project over the other since both are vastly superior to their predecessors.
Dean Pichon
Well Known Member
I have dual P-Mags and Performance Airflow fuel injection in my -4. I am completely satisfied with both and would not want to have to pick one over the other. For this year's annual, I removed the FI system for the first time since installation (12 years) and returned it to Don at AP for overhaul. It was working fine, but he recommended servicing the unit every 10-12 years. In a few days, he returned it to me. For me, never having to worry about carb heat was worth the initial investment. Similarly, I pulled both mags, at Brad's recommendation (5 yrs in service) and returned them for inspection. They, too, came back after a couple of days with a clean bill of health. Hot or cold, it starts right up and runs great.
Good luck,
Good luck,
RV10inOz
Well Known Member
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!"
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!"
G3i Ignition
Well Known Member
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
Absolutely correct,
Example, If you set your P-EI or other at the base timing @ 25 BTDC degrees as suggested/ manual and your @ 500ft MSL. At 100 % power your timing will be at 25 degrees BTDC. Without any changes and you climb to 7000ft MSL and go to 100% power the timing will still be at 25 degrees BTDC. The timing curve is based on ambient static pressure. When operating @ lower manifold pressure than that, the timing curve is advanced. What I have seen in testing is a variance of 3? - 5? below ambient before timing advance takes place. Folks that stop by at my both, I had a timing simulator that showed the timing map for different manifold pressures based off ambient static inches of pressure.
Andy Hill
Well Known Member
Hi Kevin
From your figures, I would suggest try reducing RPM a bit to say 2350? This will reduce HP / Fuel Flow. You can now target the best SFC via optimum LOP whilst gaining back some of the HP lost. With WOT you will also get a more square operation (and over square at lower altitudes) which I believe is more efficient?
Depending on your engine/prop this theory holds good until you start running into RPM restrictions - either as laid down, or just by feel.
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.
From your figures, I would suggest try reducing RPM a bit to say 2350? This will reduce HP / Fuel Flow. You can now target the best SFC via optimum LOP whilst gaining back some of the HP lost. With WOT you will also get a more square operation (and over square at lower altitudes) which I believe is more efficient?
Depending on your engine/prop this theory holds good until you start running into RPM restrictions - either as laid down, or just by feel.
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!"
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
skylor
Well Known Member
Huh?
REDUCE MANIFOLD PRESSURE?!?!?!
But this violates the whole premise of WOTLOPSOP!!!
REDUCE MANIFOLD PRESSURE?!?!?!
But this violates the whole premise of WOTLOPSOP!!!
Last edited:
Toobuilder
Well Known Member
Which brings us back to the electronic ignition. It allows the red knob to act as a throttle. Leave the black knob all the way to the stop and pull back to 150 LOP if you want to go slow. Of course, keeping heat in the engine will become a big problem as your CHT will plummet.
10-20 LOP data
10inoz
I agree that with fixed timing 10-20 lop at 10k will wring the most crankshaft energy out of a unit fuel burned. I suspect though that with advanced timing, as with EI, the optimal point is a bit leaner. I have yet to find data though. Maybe Tom has some dyno pulls he has not shared?
10inoz
I agree that with fixed timing 10-20 lop at 10k will wring the most crankshaft energy out of a unit fuel burned. I suspect though that with advanced timing, as with EI, the optimal point is a bit leaner. I have yet to find data though. Maybe Tom has some dyno pulls he has not shared?
RV10inOz
Well Known Member
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.
RV10inOz
Well Known Member
REDUCE MANIFOLD PRESSURE?!?!?!
But this violates the whole premise of WOTLOPSOP!!!
Yes shame on me?.off to the naughty corner for even thinking such a thing!
As pointed out above, use RPM and mixture, but when that is not enough, you have to use the throttle!
If you want to fly that slow, by a Cessna 172
Don at Airflow
Well Known Member
Really? Let's look at some facts.
David,
I have to disagree with you on this comment. As a designer of these products you kind of have to look at the application. Granted we?re not in a laboratory environment here but looking at the change in fuel air ratio with the engine at 55% power and above, with changes in airflow of 20%, the fuel air ratio changes 0.2% to 0.5%. Seriously, you think in operation the engine sees a 0.2% change in fuel air ratio??
I can?t say what our competitors accuracy in fuel air ratio is but I believe from the air box flow testing, dyno testing and field service we have had in the 2000 plus units we built, the accuracy in holding the fuel air ratio correct is close enough for the application we?re in.
Don
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.
David,
I have to disagree with you on this comment. As a designer of these products you kind of have to look at the application. Granted we?re not in a laboratory environment here but looking at the change in fuel air ratio with the engine at 55% power and above, with changes in airflow of 20%, the fuel air ratio changes 0.2% to 0.5%. Seriously, you think in operation the engine sees a 0.2% change in fuel air ratio??
I can?t say what our competitors accuracy in fuel air ratio is but I believe from the air box flow testing, dyno testing and field service we have had in the 2000 plus units we built, the accuracy in holding the fuel air ratio correct is close enough for the application we?re in.
Don
Part Throttle + Carb Heat
Operating with Carb Air Heat, or partial carb air heat can increase fuel atomization.
A small reduction in throttle setting will disrupt the airflow after the fuel has entered the airstream, without a great reduction in airflow volume. But the turbulence can change the fuel distribution to the cylinders.
Some combination of the two can even out the notoriously uneven Lycoming exhaust temps, run the engine more smoothly, and allow more leaning.
My T-18 with O-290, Marvel MA-4 and one P-mag responds to carb heat and part throttle particularly well above 6000 ft. I establish the cruise altitude and speed, then apply some carb heat and observe the EGT's change. The difference between EGTs is reduced. The engine 'might' run a little smoother, I then lean a bit more, and/or reduce the throttle. Slowly trying different combinations until I'm satisfied. It works well for a steady cruise configuration, but I resume standard operation approaching the destination when maneuvering and throttle changes are anticipated.
This plane will never receive the big investments in FI or Avionics, simply because I got it to help me get ready for my RV-8. So I'm happy to learn to use it the best I can for the way it is. I went with the Pmag when one mag failed. I've done other cost effective improvements when repairs are indicated, but the RV-8 gets 'the good stuff'.
Operating with Carb Air Heat, or partial carb air heat can increase fuel atomization.
A small reduction in throttle setting will disrupt the airflow after the fuel has entered the airstream, without a great reduction in airflow volume. But the turbulence can change the fuel distribution to the cylinders.
Some combination of the two can even out the notoriously uneven Lycoming exhaust temps, run the engine more smoothly, and allow more leaning.
My T-18 with O-290, Marvel MA-4 and one P-mag responds to carb heat and part throttle particularly well above 6000 ft. I establish the cruise altitude and speed, then apply some carb heat and observe the EGT's change. The difference between EGTs is reduced. The engine 'might' run a little smoother, I then lean a bit more, and/or reduce the throttle. Slowly trying different combinations until I'm satisfied. It works well for a steady cruise configuration, but I resume standard operation approaching the destination when maneuvering and throttle changes are anticipated.
This plane will never receive the big investments in FI or Avionics, simply because I got it to help me get ready for my RV-8. So I'm happy to learn to use it the best I can for the way it is. I went with the Pmag when one mag failed. I've done other cost effective improvements when repairs are indicated, but the RV-8 gets 'the good stuff'.
