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Carb vs FI vs EFI Reflections on reliabilty

Larry DeCamp

Well Known Member
The shortcomings and blessings of carbs are well known:
Low pressure, easy start but poor distribution and floats sink.

? controlled leakage? Bendix style FI can be well balanced, use a mechanical pump but can be a hot start problem with more plumbing and hardware than a carb.

EFI offers ?car start? elegance with the requirement of two electric pumps due to high pressures and reasonable but required aux electrical plan.

Here is my point; I passed on EFI for my current project because Priority #1 was reliability for a 2 seat ship. Simplicity was also a priority because I want to fly, not develop and debug MAP,temp and O2 sensors !

BUT, after committing to ?a controlled leakage ? system, I have learned that the EFI software can be and is written to default to ?get me home safe? parameters in the event of sensor misbehavior. This has caused me to be more open to EFI as conservative flyer. I offer this for anyone wresting with the decision..Larry
 
It's interesting how people evaluate the reliability of electroincs vs. mechanical devices. This is often done on the basis of past experiences.

Well designed mechanical devices, when properly installed and maintained are generally pretty reliable. Modern electronics, ditto. It's the occasional anomaly that can throw a wrench into reliability.

For carbs, sinking floats, broken float arms, jet problems etc. For Bendix style injection, maybe split diaphragms, cracked line or a piece of debris in a nozzle. For EFI, maybe a broken wire, bad chip, sensor failure.

Mechanical devices do indeed fail and we've all had an experience with that in our lives or know someone else who has. Interestingly, people often feel just fine with one carb supplying fuel to an engine but are not ok with one ECU or a couple of EIs supplying fuel or spark delivery.

People 15 years ago didn't think too much about glass panels replacing their mechanical gyro instruments and steam gauges in GA aircraft, now almost nobody installs steam gauges. Electronics with a backup (also usually electronic these days) are fully accepted now.

So, in the EFI industry, we give the people what they want. If they worry about electronics failing, we have dual ECUs, dual sensor suites and dual fuel pumps along with backup power sources. That being said, we have sold over 1500 aviation ECUs and EFI kits which were employed in single setups and about 400 as dual setups, most of those, more recently. Over half a million flight hours shows that our stuff is extremely reliable.

As Larry pointed out, on our systems, most sensor failures (air temp, CHT, TPS, MAP) are not critical to maintaining engine power. In the case of the crank sensor, we've never seen an electronic failure of our Hall Effect sensors in 20 years and millions of hours collectively.

You should always fly what you are comfortable with. If that's a carb and mags, that's just fine but always be aware that in a single engined plane, there are plenty of critical single points of failure.

Cars haven't used points and carbs for 30 years now and coming from that industry before, I can say that EFI and EI resulted in the single most important leap in auto reliability ever. It reduced maintenance and repairs massively.

Finally, I always like to point out that one of our ECUs ran on the bench 24/7 for years, accumulating 145,000 hours without failure or any maintenance. I doubt if any carb, Bendix or mag can make that same claim. Just another point of reference.
 
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I fly commercially, and have had this discussion with several dozen out of the several thousand pilots I have flown next to. I have 6 civilian type ratings, and 4 military jets as well. I have had to memorize, and fly, other peoples system designs.

Airplanes have redundant systems because aviation grade electrical components are from the dark ages of the middle of the last century. Production light aircraft fell of a cliff 35 years ago, so they never improved. They are still in the dark ages.

50+ years ago, aviation grade was the gold standard. It still is in some regards (raw materials, fasteners, etc). But the auto world passed up aviation 30 years ago, and never looked back. Instead of redundancy, modern cars (and consumer electronics) went for "perfect". And they have nearly achieved it.

EFI and EI, properly done, bring a Lycoming into the 1990's, at least. Everything as "automotive" as possible.

Every modern car has 1 alternator, battery, single engine sensors, single ECU, single fuel pump. They just don't fail (except for Fiats). Towing companies make their money towing illegally parked cars.

The EFI's for airplanes actually have more redundancy than I would require. I would be happy with less. I don't know if they chose the redundancy, or it was demanded of them by users. But I won't complain about the redundancy, and will use one as designed.

Each of us is comfortable with some level of technology. For some it is carbs and magnetos. Frankly, they scare me. But, to each, his own.
 
Debating the reliability of "electronics" or mechanical devices" is pointless. The real questions are...

1. The reliability of each individual component, as installed.

2. The reliability of any required supporting system(s).

Every modern car has 1 alternator, battery, single engine sensors, single ECU, single fuel pump. They just don't fail...

The reliability of those specific components (as installed in road vehicles) has indeed reached a very high level...but there is a failure rate for each, and there always will be. Claiming they "just don't fail" is hyperbole, at best. And that failure rate can change in a different application, due to change in the local environment.

Consider the ordinary fuel injector, a remarkable electro-mechanical device. The installed environment is very different in a car (intake manifold, attached to a water cooled head held at 210F, and generally distant from exhaust components), in an SDS installation (top of an air cooled head), and the upcoming EFII installation (bottom of an air-cooled head, adjacent to a red hot exhaust header). Although all may have a low failure rate, should we believe the failure rate will be the same for all?

Even if you wish to believe the reliability of the individual component will be the same regardless of how installed, we must still consider supporting systems. That injector requires a machined screw-in mount for the aircraft head, an o-ring seal, a plastic electrical connector, wire crimps, pins and sockets, a signal wire, and a fuel supply hose or pipe.

I am not opposed to electronic fuel injection. Professionally, I love fuel injection. It's the best thing that ever happened to cars and trucks. But gang, let's quit the huge generalizations. The airworthiness of a particular airplane is a function of the application, fabrication, and condition of both individual components and support systems, here as installed by individual builders. The huge jump in road vehicle reliability is not just a matter of better components. It is a equally due to close attention to installation details, at the design level.
 
Dan brings up good points as usual.

The single most important part of Experimental EFI installations is probably wiring since there are multiple areas where a poor connection or strain relief could cause an open circuit. Dan rightly points out that auto OEMs can test and refine wiring installation and practices and then make every one the same on that model. We can't do that on varying, individual installations. The best we can do is insure that every crimp/ solder joint is excellent, proper strain relief is provided, wires are not routed near high temperature components without proper thermal protection and wires are protected from chafing.

Second area of concern (or perhaps first) is electrical system design- batteries, primary wiring, alternators, switching. I see a lot of incredibly complex schematics in this area being posted on VAF and I can't say I like many of these. Keep it simple, keep connections to a minimum and concentrate more on the most likely failure modes and scenarios rather than parts that might fail .001% of the time.

Third would be fuel systems. I'd urge people not to deviate from what we recommend for pumps, pump mounting, line size, fittings, line routing and filtration. Best reliability generally comes from following time-proven reliable practices.

We should not generalize overall system reliability, especially between brands with limited or no demonstrated track record.

With regards to injectors on air cooled engines, I haven't observed a noticeably higher failure rate on D-Jetronic or Motronic EFI equipped VW and Porsche engines despite the higher operating temperatures they're exposed to.

Highest temps in aircraft we see from instrumentation are after hot shutdown, not during operation where air is passing over the components and cooling fuel flow is high. Different mounting positions may see higher temperatures.

My first post assumed that people do a proper installation job on their EFI system as this is assumed (or hoped) on a carb, mag or Bendix installation as well. If you do a poor installation on any of these, it can bite you.
 
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Proper installation ?

So Ross, we have all read Bob Knuckles and some good references in VAF threads. Is there one source for reference regarding ?though shalt ? use these connectors, strain relief shrink tube length, solder /don?t solder etc. We all think we are OK, but probabably not ?optimized?. Maybe Dan would be kind enough to author a short course 😊
 
So Ross, we have all read Bob Knuckles and some good references in VAF threads. Is there one source for reference regarding “though shalt “ use these connectors, strain relief shrink tube length, solder /don’t solder etc. We all think we are OK, but probabably not “optimized”. Maybe Dan would be kind enough to author a short course ��

Solder is fine on most connections provided that strain relief and support extend well beyond the joint and don't allow large movements respectively. All our DB connections are soldered, individually heat shrunk (yes, each pin) or bridge siliconed and then supported from movement by the hood.

For FF connections, most everything is crimped and strain relieved within the connector.

These practices have stood the test of time- literally millions of hours collectively in environments much more severe than what our airplanes see.

We have some limited info here: http://www.sdsefi.com/wiring.htm and hope to add some more photos/videos of other connections as time permits.

One thing I'm not too keen on is people using vinyl clad crimp connectors in aircraft. They don't offer great strain relief. I prefer non-insulated ones, solder or crimp and then slide a long piece of double wall, glue infused heat shrink over the joint. Time consuming and a PITA to do in many locations and cases but WAY better strain relief, corrosion protection and retention qualities. See the photos below:





Your EFI system totally depends on reliable ground and power connections.
 
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One thing I'm not too keen on is people using vinyl clad crimp connectors in aircraft. They don't offer great strain relief. I prefer non-insulated ones, solder or crimp and then slide a long piece of double wall, glue infused heat shrink over the joint. Time consuming and a PITA to do in many locations and cases but WAY better strain relief, corrosion protection and retention qualities. See the photos below:

Same here, bare terminals and adhesive heat shrink. It takes longer, but I never fool with that terminal again.
 
Well, there are crimp terminals, and then there are crimp terminals....

The crimp terminals we use as an OEM are sized appropriately for the wire, and the strain relief portion is metal. Used with the appropriate crimping tool, these are bulletproof.

This is a long way from the DIY kit you get at Pep Boys.
 
Well, there are crimp terminals, and then there are crimp terminals....

The crimp terminals we use as an OEM are sized appropriately for the wire, and the strain relief portion is metal. Used with the appropriate crimping tool, these are bulletproof.

This is a long way from the DIY kit you get at Pep Boys.

Agree 100%, this is the AMP crimper I use with PIDG terminals.
Boeing/Douglas approved, millions of flt hours have proved their reliability.

https://www.alliedelec.com/te-connectivity-59250/70089872/?mkwid=soJZfsyPI&pcrid=30980760979&gclid=EAIaIQobChMIrpWV-4Db2AIVgz2BCh1bVAovEAQYASABEgLKBPD_BwE

https://www.alliedelec.com/te-connectivity-59275/70089871/
 
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I bought one on Ebay for under $100 when building the RV. Also bought a new $30 crimper from B & C. The cheaper one was easier to use and made great crimps (except the for strain relief part but that's easily crimped with a second step). This became my go-to crimper.

Bevan
 
Larry;

Like I said, each of us has to be comfortable with what we built on a dark and stormy night. I won't try to tell anyone what that is for them, I can only answer it for myself.

In about 2 months I get my brand X QB kit (Bearhawk) delivered to my shop. It will be a very simple, day VFR airplane, with 1 EFIS, and an IPAD. If someone wanted to argue with me about complicating my electrical system for the little benefit of EFI over Bendix FI and dual Pmags, I would be hard pressed to come up with a rational explanation. Mech FI and dual Pmags would give me most of the benefits, and the airplane still works if the electrical system dies. I guess I could argue that reliable starting for me is as important as continuing to run for out and back into the backcountry.

But in reality, EFI is my comfort zone. I have a lot of experience with it in cars and motorcycles, and am completely confident in it if installed correctly. Why not just build my own and save $5000? I could, but SDS (and a couple of others) have a couple of nice features that I can see. And they have many dozens (probably hundreds) of unseen "lessons learned" from their installs in aircraft, and input from their very knowledgable customers. That extra money for that experience, for me, is priceless, as it is my little pink body riding in the airplane. I would rather pay them to learn from their lessons and mistakes, than repeat them myself.

I didn't mind spending the extra money for a QB kit. I choked a bit paying the price of a new Honda Accord for a rebuilt io-540. I will choke a bit more when I pay the price of a nice used Accord for a CS prop. Paying the extra for an EFI might be the easiest "extra" money I spend, because it makes me more comfortable flying with it.

Lots of opinions. Mostly I am on VAF to learn, which I have learned a lot. I have more questions than answers. But I have lots of Boeing, Airbus, and McD time. After all that time, I would prefer if Honda or Toyota made my airplane.
 
Larry;

Like I said, each of us has to be comfortable with what we built on a dark and stormy night. I won't try to tell anyone what that is for them, I can only answer it for myself.

In about 2 months I get my brand X QB kit (Bearhawk) delivered to my shop. It will be a very simple, day VFR airplane, with 1 EFIS, and an IPAD. If someone wanted to argue with me about complicating my electrical system for the little benefit of EFI over Bendix FI and dual Pmags, I would be hard pressed to come up with a rational explanation. Mech FI and dual Pmags would give me most of the benefits, and the airplane still works if the electrical system dies. I guess I could argue that reliable starting for me is as important as continuing to run for out and back into the backcountry.

But in reality, EFI is my comfort zone. I have a lot of experience with it in cars and motorcycles, and am completely confident in it if installed correctly. Why not just build my own and save $5000? I could, but SDS (and a couple of others) have a couple of nice features that I can see. And they have many dozens (probably hundreds) of unseen "lessons learned" from their installs in aircraft, and input from their very knowledgable customers. That extra money for that experience, for me, is priceless, as it is my little pink body riding in the airplane. I would rather pay them to learn from their lessons and mistakes, than repeat them myself.

I didn't mind spending the extra money for a QB kit. I choked a bit paying the price of a new Honda Accord for a rebuilt io-540. I will choke a bit more when I pay the price of a nice used Accord for a CS prop. Paying the extra for an EFI might be the easiest "extra" money I spend, because it makes me more comfortable flying with it.

Lots of opinions. Mostly I am on VAF to learn, which I have learned a lot. I have more questions than answers. But I have lots of Boeing, Airbus, and McD time. After all that time, I would prefer if Honda or Toyota made my airplane.

We agreed with this thought, after looking at some 60-70 years of history behind making it simple and reliable, We went with the same system that Conti has used for many years on the IO-470, 520 engines in many good long lived aircraft that bring you home every flight in all kinds of weather even if you don't save a little fuel over another system. I talked to AFS a month or so ago and was told that it was still being made and put out under the TITAN name. We also stay with two Slick mags for the same reason.
Just our two cents, Yours, R.E.A. III # 80888
 
Two points that have not been discussed are:

1. Our typical aircraft engine, air cooled (runs a lot hotter), boxer style and huge displacement engines running high power at relatively low rpm have a huge amount of vibration compared to a typical automotive engine. This is hard on fuel systems, ignition systems and electrical systems.

2. As my grandpa used to say, “When your car engine quits, there you is. When your airplane engine quits, where is you?!”

An after thought, but we have a Cessna 150 and a Cessna 152, each with around 14,000 hours running completely on carbs and mags. THis would equate to roughly 1.4-1.5 million miles each. Engine overhauls and component overhauls aside, that does say a whole lot of something for the old technology.
 
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No argument, or disrespect, for your choice, and comfort zone.

Fair winds, and following seas, to all.
 
You missed the price of the second one he posted for 26-20 gauge. $2939.73

All kidding aside, they are beautiful tools, yes, they can be bought used, and I'm absolutely sure they will make PIDG terminations which meet specification.

Walt, tell us about the insulation adjustment. Four positions; is it necessary to change the setting when switching from 18 to 22 ga?

I bought one on Ebay for under $100 when building the RV. Also bought a new $30 crimper from B & C. The cheaper one was easier to use and made great crimps (except the for strain relief part but that's easily crimped with a second step). This became my go-to crimper.

I assume this one?

http://www.bandc.aero/pidgstylecrimptool.aspx

Can you describe the issue with strain relief?
 
I'm going to play Devil's Advocate for a moment and suggest that one should not discount human error, either.


[DA]To wit, how many good airplanes have been put in the dirt because the pilot mismanaged some aspect of that "simple" mechanical system? One of the two C150s I trained in met its end a month after my checkride (in that airplane) because the student and instructor forgot the carb heat. How many other "loss of power" accidents over the past decades could we attribute to lack of carb heat or an improper mixture setting?

And beyond that, how many good engines have been doomed to early overhauls, how many millions of gallons of gas have been wasted, because the crude mixture adjustment was set incorrectly?

Debating the reliability of "electronics" or mechanical devices" is pointless. The real questions are...

1. The reliability of each individual component, as installed.

2. The reliability of any required supporting system(s).

I'd argue that one of the "supporting systems" in any engine installation is the biological controller.

Or to look at it another way, we all exhort each other to "keep it simple". But what is "simple"? Is it... simple to fabricate? Simple to assemble? Simple to understand? Or is it simple to use? A slide rule is incredibly simple, from a mechanical standpoint. But a $10 scientific calculator from Wally world, while incredibly complex, is dead-simple to use by comparison. [/DA]



Anyway, there's no good way to really analyze one vs. the other, especially given sample sizes and all the variables present (in system design, component selection, and workmanship) in experimental installations. I'd even go so far as to say that this plus piloting habits are going to be far more influential on "reliability" than the overall approach to fuel and spark delivery.

In the end, 98% of us are going to choose the approach that fits our pre-existing biases and experience, and then rationalize it to everyone else ;)

(Disclaimer: I'm planning for an SDS EFI install, because reasons)
 
Is there any data to provide a vector on all this?

I?ve looked at the various options for electronic engine management. I would appreciate anyone who has data that can shed light on this simple comparison:
- Engine #1; Precision or AFP fuel injection and dual pMags. The fuel injectors have been balanced.
- Engine #2; Any electronic engine fuel and ignition management system.

Assume both engines are identical except for the above. Is there any data that shows:
- Either engine will produce more take off power?
- Either engine will be have a higher efficiency LOP cruise performance (fuel flow for same TAS)?

Everything I?ve read tells me that either set up, if properly operated, will have close to identical performance. If that is the case, then any reason to choose one over the other falls down the list of builder priorities (cost, must have the latest shiny bobble, etc.).

I?d like to hear if my analysis is wrong - and if so why.

Carl
 
...Assume both engines are identical except for the above. Is there any data that shows:
- Either engine will produce more take off power?
- Either engine will be have a higher efficiency LOP cruise performance (fuel flow for same TAS)?

Everything I’ve read tells me that either set up, if properly operated, will have close to identical performance...

First, think about Magnetos vs Pmags. Magnetos, by virtue of a locked down timing will be a compromise at virtually any flight condition but one. It will be too advanced for takeoff, and too retarded for LOP. The Pmag, is a vastly superior ignition in that it adjusts to open this envelope up significantly.

That said, the Pmag has a pretty restricted curve that has been well documented on this and other sites, so if you are going to compare the Pmag to "any" other product, and that product has a completely adjustable program, then yes, there is performance to be had. The SDS products for example will allow a significant retard for takeoff power (even more so than the "too advanced" magneto's) as well as proper RPM/MP curves for best power up and away, AND additional advance setting when high and LOP. The envelope is simply bigger on the SDS products, and that shows up as "better" performance.

Edit to add the following observations about the fuel side.

Mechanical injection, even when balanced does fall on its face at really low fuel flows. I'm sure anyone who flies traditional FI LOP has seen this. This is a function of the nozzle itself being a regulation element of the system. If you pinch down the nozzle size to provide stable, balanced flow at low flow, then at takeoff power you would need something like 900 PSI to deliver enough fuel. EFI, on the other hand provides regulation by opening and closing a pintle within the injector. The rail pressure is always high, so the spray is atomized regardless of fuel flow. the only difference is how long the injector is open. So instead of the dribble you get with mechanical injection, you always get a nice pattern. Will this translate to more power on a test stand? I doubt it, but it most certainly will improve LOP and idle performance. I hope to be collecting data as soon as the Rocket gets in the air. Will let you know what's truth and whats hype.
 
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I'm going to play Devil's Advocate for a moment and suggest that one should not discount human error, either.


[DA]To wit, how many good airplanes have been put in the dirt because the pilot mismanaged some aspect of that "simple" mechanical system? One of the two C150s I trained in met its end a month after my checkride (in that airplane) because the student and instructor forgot the carb heat. How many other "loss of power" accidents over the past decades could we attribute to lack of carb heat or an improper mixture setting?

And beyond that, how many good engines have been doomed to early overhauls, how many millions of gallons of gas have been wasted, because the crude mixture adjustment was set incorrectly?

One of the main reasons people tell us they want EFI instead of a carb is the carb ice issue. Mechanical FI also gets rid of that concern of course.

Certainly human factors account for more problems than the injection hardware does, both from an installation and operational standpoint.
 
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I’ve looked at the various options for electronic engine management. I would appreciate anyone who has data that can shed light on this simple comparison:
- Engine #1; Precision or AFP fuel injection and dual pMags. The fuel injectors have been balanced.
- Engine #2; Any electronic engine fuel and ignition management system.

Assume both engines are identical except for the above. Is there any data that shows:
- Either engine will produce more take off power?
- Either engine will be have a higher efficiency LOP cruise performance (fuel flow for same TAS)?

A lot depends on how you fly and what mods are done to the engine. If you're low, ROP, there is little difference between Bendix setups and EFI. I haven't seen more than a 3.5% difference in power between Bendix and EFI setups on a decently balanced engine (airflow wise).

If you fly high, LOP and especially at low power settings, like Dave Anders often does to catch the big tail winds, the EFI is clearly better. Bendix type FI can't meter accurately at low fuel flows. Dave dumped his AFP setup because it didn't meet his needs under these conditions where the EFI was still easily balanced below 4 gph. How many people fly like this? I really don't know. http://www.vansairforce.com/community/showthread.php?p=1110419 Page 7, post #64

We've seen some sizable airflow imbalances with various induction and cylinder setups. The EFI allows you get equal AFRs in each cylinder at ANY power setting. Tailoring nozzles on Bendix types only gets it close within a narrower cruise range and that can work well enough for many people as we've seen. No screwing around changing out nozzles with EFI, it's all done from the cockpit in a few seconds.

"Canned" ignition curves are not optimal for higher CR engines or when running LOP as Michael points out.

EFI cures all the hot start and funny idle issues with mechanical FI.

I think it all comes down to preference as has been suggested. Those tired of carb heat/ ice and Bendix hot start/ idle issues will probably consider EFI. Those who don't care so much about this and who don't trust an electrically dependent engine, will probably stay with the legacy hardware.

No one solution is best or right for everyone. Luckily we have a number of choices in the area of fuel and spark delivery.
 
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A lot depends on how you fly and what mods are done to the engine. If you're low, ROP, there is little difference between Bendix setups and EFI. I haven't seen more than a 3.5% difference in power between Bendix and EFI setups on a decently balanced engine (airflow wise).

If you fly high, LOP and especially at low power settings, like Dave Anders often does to catch the big tail winds, the EFI is clearly better. Bendix type FI can't meter accurately at low fuel flows. Dave dumped his AFP setup because it didn't meet his needs under these conditions where the EFI was still easily balanced below 4 gph. How many people fly like this? I really don't know. SNIP

Yep - familiar with such outlier special cases as well as the advertising logic - but again I?m looking for actual data, not theory or opinion.

So to my orginal question, and assuming operation like 99% of us fly, is there any measurable performace difference between these two engines?

Side notes - there have been several ?you will have hot start problems? offered. I have a lot of hours behind an IO-360 and dual pMags and not once have I ever had a hot start problem - or for that matter any start problem. This same engine runs smooth LOP well below any practical fuel flow - so my personal data on mechanical fuel injection running at low fuel flow does not support the previous comments. No - never operated down at 4gph, but a lot of time at 7gph which for most people is a reasonable speed vs fuel flow operation spot for high efficiently LOP cruise.

Carl
 
...So to my orginal question, and assuming operation like 99% of us fly, is there any measurable performace difference between these two engines...?

Ignoring the "99%" hyperbole, the answer is yes. There is a measurable difference between an advance setting optimized for LOP and one for ROP. I have demonstrated a 3 knot TAS difference between my optimized advance number for a typical 8500 cruise when ROP and when LOP. This is repeatable and documented well on this forum. A Pmag set to be optimized for LOP will be too advanced for ROP, while a Pmag set for ROP will not have enough advance for LOP. Period. Dot.


As to your FF point, 7GPH is right around the area where my IO-360 experience shows them to start falling off a cliff. This is good for a reasonable LOP cruise at 9500 feet, and I don't think that's an "outlier" case. Out west, that's barely above MEA in some areas, so higher is better. That means leaner. Its a major PITA to have the EGT's split as the Bendix system falls apart because you are trying for better altitude. I think it is a performance benefit to have solid fuel metering at any altitude I wish to fly.
 
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Side notes - there have been several “you will have hot start problems” offered. I have a lot of hours behind an IO-360 and dual pMags and not once have I ever had a hot start problem - or for that matter any start problem.

You obviously don't run MOGAS. Go try it about once.

As to your FF point, 7GPH is right around the area where my IO-360 experience shows them to start falling off a cliff. This is good for a reasonable LOP cruise at 9500 feet, and I don't think that's an "outlier" case. Out west, that's barely above MEA in some areas, so higher is better. That means leaner. Its a major PITA to have the EGT's split as the Bendix system falls apart because you are trying for better altitude. I think it is a performance benefit to have solid fuel metering at any altitude I wish to fly.

I see better than that on mine, IO360 with Bendix injection. I routinely cruise at 16,500 and 17,500 WOTLOP and my "cliff" seems to start at about 5.8 gph. I also have .024 orifices and a 4-pound divider spring if that makes any difference, and I suspect it may.
 
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I see better than that on mine, IO360 with Bendix injection. I routinely cruise at 16,500 and 17,500 WOTLOP and my "cliff" seems to start at about 5.8 gph. I also have .024 orifices and a 4-pound divider spring if that makes any difference, and I suspect it may.

It would make a difference.
 
Yep - familiar with such outlier special cases as well as the advertising logic - but again I’m looking for actual data, not theory or opinion.

So to my orginal question, and assuming operation like 99% of us fly, is there any measurable performace difference between these two engines?

Side notes - there have been several “you will have hot start problems” offered. I have a lot of hours behind an IO-360 and dual pMags and not once have I ever had a hot start problem - or for that matter any start problem. This same engine runs smooth LOP well below any practical fuel flow - so my personal data on mechanical fuel injection running at low fuel flow does not support the previous comments. No - never operated down at 4gph, but a lot of time at 7gph which for most people is a reasonable speed vs fuel flow operation spot for high efficiently LOP cruise.

Carl

Unfortunately I can't provide dyno data due to NDAs with some of our partners.

I'm not sure how 99% of people fly but if you frequently fly between 12,500 and 18,000 feet on O2, you'll see some small benefits in power and fuel economy with EFI. I can only offer the numbers that Rusty Crawford and Dave Anders have provided. These two frequently fly high and long legs and pile on lots of hours.

Lots of folks are tired of the Bendix hot start "grind". One of the top 3 reasons they want to buy EFI from us. If you don't have that problem, EFI won't be of any aid there.

It sounds like you're happy with your setup. In that case, if I were you, I'd have a hard time parting with a bunch of $ for minimal benefits.

Some people are plain uncomfortable with EIs and EFI and they never phone us. Today, I quoted 2 people.
One had timed out mags and a tired carb. He didn't want to deal with carb heat any more. He wasn't looking for uber efficiency, just solid, reliable running. Since he was going to have to spend a bunch to fix up the legacy parts, he's seriously considering EFI/EI. I'd say a good 60% fit in this category. The other guy was most interested in a bit more power and the best economy possible LOP. He likes the individual cylinder trim and the adjustable timing, LOP switch.

Other's just want to turn the key, hot or cold and go. They want it to run more like their car.

Lots of different reasons why people choose EFI-or don't.
 
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Sensor calibration ?

I started this so I will drift the thread a little. All the expert input so far is sincerely appreciated, that was my goal to bring that forth.

One of my big questions when reading about fine tuning ( splitting hairs) in performance is sensor and instrument calibration.From industrial experience, garbage in = garbage out ! I question that certain conditions or performance criteria are claimed when sensor/instrument calibration is completely unknown. I would be reluctant to work hard optimizing a performance objective and know nothing about calibration. Yes relative improvement can be encouraging. If any experts care to comment, we might all benefit 😊
 
I think when it all boils down, what's most important is probably TAS vs. FF since we spend the majority of time in cruise. A four way GPS run combined with one hour set up in cruise conditions on one tank and then refilling that tank on the ground seems like it would have the required accuracy to determine performance to a pretty fine degree.

We have a wideband AFR combined with multiple EGT probes to determine/ crosscheck AFR. We have ignition timing read out in 1 degree increments, MAP in roughly .5 inch increments, RPM at whatever resolution is offered by the EFIS, FF to .1 GPH. Anything more that that is likely outside experimental error margins.

Seems like you have all the tools to make a change and observe the results. You could cross check calibration with known reliable sources if that was a worry.

Dave Anders also uses his Savvy Analysis/ EFIS info and SDS EFI data logging to compare minute data points post flight. Another good tool in the box for those trying to find best efficiency.
 
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If a person is only wanting to hop in his plane and go at 2000' AGL to a meal and never actually wants their planes best performance then there is no reason to change anything. However if you are one of those that want the best you can do or if your old parts are timing out, then appling the next, more modern, and better technology only makes sense. If you want accurate data, then be certain you are using an electronic panel and downloading it to Savy Analysis and couple that with the SDS data logging you can't generally get better than that for our planes. That will provide hours of ability to accurately compare things.
As for the SDS I'm still extremely happy I decided to go that way. It allows you to sent the parameters as you would like them and then just leave it alone and the engine will perform that way without even looking at. Or, you can require even more from the SDS to fit your mission. I personally like that all cylinders are tuneable in any condition I fly.
Just an additional note that I haven't seen. My ehaust is now always white, which is an indication that it's never running overly rich. The other observation is that my oil doesn't turn black between oil changes from over washing the cylinder walls with excess fuel, and it seems to get better oil mileage. That may be nothing, but it see it.
Cheers
 
...Yes relative improvement can be encouraging. If any experts care to comment, we might all benefit 😊

Nothing wrong with relative improvement as a final product if you can isolate changes that drive that improvement. The best example of this is adjusting timing on the fly and observing the change in airspeed. Since my only goal is to determine the most power for a given configuration, then peak speed is my only concern. I don't really care if my TAS is off by a few knots one way or the other - just as long as I can identify a peak that directly corresponds to an ignition setting.
 
Some time back Mahlon mentioned (I can't recall if it was on this forum or in person) that when they dynoned engines the carburetor versions always put out more HP. (That was a comparison to aviation components, not something like Ross has put together, which is bound to provide max power all throughout the power band.)

The deal is, where do you want your power and how do you fly. When I was doing the car racing thing, I could buy headers for my car that were either four into one or Tri-Y two-in-to-one design. The 4-1 would dyno at max power but the 2-1's would produce more middle band power and have a wider power band. I bought the 2-1's and guys who would drag race would buy the 4-1.

This comes back to what is your mission and desires. Some people want bragging rights on max power and minimum fuel burn. Others just want systems that are bone simple and well known. Bush pilots seem to gravitate towards carbs because they can fix them in the bush. Electronic components can be fixed in the field but usually after a visit from a brown delivery van.

Since an RV is unlikely to land in a place where you life is in jeopardy, if you can't get out (Unless your name is Vlad), we can take some "risk" with our systems.
 
I haven't seen an SDS EFI equipped Lycoming put out less power than a carb or Bendix FI yet, assuming the fuel system is properly hooked up and the timing is set correctly.
 
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