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SDS / EFII Comparison?

breister

Well Known Member
I'm confused, perhaps because I'm looking for big differences that aren't there. I've read through both sites (SDS and EFII) and the posts I could find here. It looks like both companies are about to introduce new generation systems which replace both ignition and fuel delivery.

My mission: Cross country and local leisure flying, IFR, no racing.
My objectives: Replace my carburetor and magnetos with a modern integrated system with the expectation of easier starting, better reliability, better power and economy

Can anyone help me with a layman's breakout of differences between the two?

  • First off, are these systems overkill for my objective, and if so what would be the cheaper / less sophisticated integrated solution?
  • Is there a significant difference in system price / installation effort required?
  • Do both systems automatically tune to lean of peak?
  • Are both fully redundant systems suitable for IFR? If so, do both / either require a dual bus battery backup?
  • Anything else a prospective buyer should consider?

Thanks all!
 
EFII

I can't give you a comparison as I have the EFII system and have no experience with SDS.

I went with EFII because a hangar neighbor had one installed in his RV-4 and was quite happy with it - he does aerobatics and has had excellent performance with his system.

Requiring redundancy for IFR work, I have the "legacy" two ECU system installed. Immediately after installation and ground programming, I realized a great improvement in performance of the plane and a reduced fuel usage at altitude.
There are NO hot start issues as there is always cool gas being pushed to the injectors. Thus, starting in the summer is very quick. Winter requires a couple of pumps on the throttle to squirt a bit of fuel into the intake tubes and she fires up right nicely.
I set my idle down to 700 (hot engine) and she runs beautifully.
The legacy system trims all injectors to the same flow - which (on my plane) does not result in equal EGT and best power setting. YES, the system does permit running Lean of Peak (LOP). IF you program the system to run LOP, then that's where it will be when you put the throttle/prop controls at that power setting. OR you can adjust the mixture potentiometer to get the setting you desire.
Both systems do require backup power source(s) as they are fully electron dependent. I went with two batteries and only one alternator (I don't have enough room behind the engine to put one of the B&C units).

I'm eagerly awaiting the new system to start tweaking the settings for each injector to get those EGTs to balance out. Hopefully resulting in an even better fuel savings.

Robert Paisley provides outstanding customer support. Often I would get a response to an email inquiry within minutes of my clicking "send." Can't get any better than that!
 
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Thanks Mel, that's exactly what I was looking for.

Since the fuel system uses a loop invalidating traditional fuel flow sensors, does the system provide a "real" fuel flow output for modern EFIS units to track used / remaining fuel?


I can't give you a comparison as I have the EFII system and have no experience with SDS.

I went with EFII because a hangar neighbor had one installed in his RV-4 and was quite happy with it - he does aerobatics and has had excellent performance with his system.

Requiring redundancy for IFR work, I have the "legacy" two ECU system installed. Immediately after installation and ground programming, I realized a great improvement in performance of the plane and a reduced fuel usage at altitude.
There are NO hot start issues as there is always cool gas being pushed to the injectors. Thus, starting in the summer is very quick. Winter requires a couple of pumps on the throttle to squirt a bit of fuel into the intake tubes and she fires up right nicely.
I set my idle down to 700 (hot engine) and she runs beautifully.
The legacy system trims all injectors to the same flow - which (on my plane) does not result in equal EGT and best power setting. YES, the system does permit running Lean of Peak (LOP). IF you program the system to run LOP, then that's where it will be when you put the throttle/prop controls at that power setting. OR you can adjust the mixture potentiometer to get the setting you desire.
Both systems do require backup power source(s) as they are fully electron dependent. I went with two batteries and only one alternator (I don't have enough room behind the engine to put one of the B&C units).

I'm eagerly awaiting the new system to start tweaking the settings for each injector to get those EGTs to balance out. Hopefully resulting in an even better fuel savings.

Robert Paisley provides outstanding customer support. Often I would get a response to an email inquiry within minutes of my clicking "send." Can't get any better than that!
 
WRT the fuel flow, SDS came out with a fuel flow output thats integrated into the ECU a few years ago. That function was not offered on the SDS based EFII systems.

The individual fuel trim function likewise was developed by SDS several years ago and was also not offered to the EFII customers.

And once again, the LOP function has been around a while for SDS users, but once again, EFII stuck with a dumbed down SDS ECU.

Likewise, the individual port mount injectors were an SDS innovation, now several years old, while EFII continued to claim the "superior" performance of the backwards facing, induction tube mounted injectors.

SDS has always offered complete adjustability and tuning of their systems, while EFII has touted that their installations are plug and play - with the settings "tuned by the factory" for your engine.

EFII has now copied all of the SDS innovations and tunability and wrapped it in a ECU with a new color. Yes, the 32 bit box offers some theoretical advantages and certainly growth potential, but thats just hardware... Obviously SDS has a new box in the wings too. The difference is that the SDS box will fly with 25+ years of programming experience behind it and hundreds of thousands of hours operating time.
 
EFII Fuel Flow

EFII does have fuel flow sensing to feed to an EFIS. The installer will need to tune the settings of the EFIS to gain accurate readings from the system. Re-reading your question, I believe you are speaking of the Open Loop vs Closed Loop Air Fuel Ratio feedback that is current in automobiles. On the EFII system, it is in Open Loop (IIRC), which means the AFR sensor is not feeding data to the ECU to adjust the Air Fuel Mixture in a "live" mode. As I understand the reasoning, that is because of differences in Aviation Fuel compared to unleaded Automotive fuels. EFII or SDS personnel can jump in and speak to that.

With the Air Fuel Ratio input to my AFS-5600T EFIS, I connected it to the "Coolant Temperature" input (at Rob Hickman's recommendation). I asked Rob it that field could be given an "renaming" option so we could re-title it to AFR or such, and he said that would be in a future software update (to date that hasn't happened as it is a low-level request). Configuring the field to read the AFR, I removed any decimal point and read 137 as meaning 13.7 AFR.

So, using the mixture potentiometer, you adjust the mixture to achieve the performance desired at a given power setting (ROP / LOP). Program the ECU for that power setting. From that point forward, the system will run at that setting when you fly with those power settings. But, with that mixture potentiometer, you have the option to fine-tune the mixture +/- 50% at any point in time.

Manifold Pressure readings (constant speed prop) are connected just as you would for non EFII/SDS systems.

In reality, the installation of these systems is not difficult, but the results are very satisfying.
 
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Thanks to everyone who responded, I should have closed this out sooner.

I started down this path thinking technology had advanced in the past few years to truly automated / integrated systems. However after both public and private discussions with both users and vendors I came to the conclusion that a) these aren't truly automated, and required at a minimum some period of tinkering to truly determine optimum results across all altitudes, temperatures, power settings, etc.; and b) they aren't truly integrated (i.e. the fuel injection does not truly interact with ignition timing, etc.).

I have no doubt all of these are fine systems; but for my mission (mostly weekend trips) I really couldn't justify $10k or more including installation and tuning costs (I wasn't planning on installing it myself) to get this going in an airplane I only spent $30k on (yes I got a great deal), when at best I might see a few percent better fuel mileage than other cheaper options.

So, at the end of the day I decided to go with replacing one mag with a single popular electronic ignition (as I did in my previous planes) and just keep the carb for now. Using the difference in price I can upgrade to a C/S prop and still have change left over.
 
I wouldn't recommend doing anyone's EFI if you're not confident in your own ability to do the mod & tuning, but if you're willing to learn systems, you don't need to spend $10K to get the job done.

http://megasquirt.info/

(Just the most obvious option.)

Charlie
 
I used a Microsquirt on a single cylinder motorcycle successfully. about 8 years ago. Other than somebody who has done wiring for a living, I have probably done more 12v wiring than 99.9% of the population. I would definitely not recommend someone "learn" about fuel injection by cobbing one together on an airplane. Even if I did it, I would consider it only slightly above a "high school science project".

I can scratch build my own EFI system for the airplane I am building, but I would not even consider it as an option. The systems offered on the homebuilt market have a couple of decades of "lessons learned" built into them. Their price, to me, is bargain. A bendix style mechanical FI and 2 pmags costs more than the SDS full system. A new carburetor and 2 new mags costs a bunch as well.

A rebuilt carb and 2 rebuilt mags costs quite a bit less. But you get to rebuild the mags at 500 hours. Every 500 hours. And you will probably rebuild the carb at least once between TBO's. They cost more over time as well than SDS.

EFI on an airplane may not be for everyone yet. You do have to be comfortable wiring something up in a hot/cold/vibrating environment, and have the wiring survive. Or know somebody who can. But properly installed, it is the best, and cheapest option over time.

I know several will argue with me about the cheapest, but when you include fuel savings running LOP (bendix style can do this also), automotive spark plugs vs aircraft (p-mags can use them too), and the fact that the EFI has no moving parts to wear out or that need to be rebuilt (OK a new electric FP every 1000 hours if you like), the EFI pays for itself very quickly. The mechanical Bendix FI and duel EI is a close second. A lot of pilots might be more comfortable with it. I am more comfortable with EFI. But not one I designed myself when my butt is riding in it.
 
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WRT the fuel flow, SDS came out with a fuel flow output thats integrated into the ECU a few years ago. That function was not offered on the SDS based EFII systems.

The individual fuel trim function likewise was developed by SDS several years ago and was also not offered to the EFII customers.

And once again, the LOP function has been around a while for SDS users, but once again, EFII stuck with a dumbed down SDS ECU.

Likewise, the individual port mount injectors were an SDS innovation, now several years old, while EFII continued to claim the "superior" performance of the backwards facing, induction tube mounted injectors.

SDS has always offered complete adjustability and tuning of their systems, while EFII has touted that their installations are plug and play - with the settings "tuned by the factory" for your engine.

EFII has now copied all of the SDS innovations and tunability and wrapped it in a ECU with a new color. Yes, the 32 bit box offers some theoretical advantages and certainly growth potential, but thats just hardware... Obviously SDS has a new box in the wings too. The difference is that the SDS box will fly with 25+ years of programming experience behind it and hundreds of thousands of hours operating time.

this subject has been explored at length here and in other areas.
And on the subject of "new"... The "NEW" SDS thingy will also be untested and therefore require some "beta". Both companies are pushing new boundaries with one, a year ahead of the other in R&D.
As Robert has always said, if you have any questions feel free to email or call them directly. I know he, himself is very rarely on here as they are just too busy building and selling systems.
I myself don't even check in here much more because... well,... flying, work, and flying FOR work!! the best of both worlds.

To set the record straight, SDS started copying the EFII system in 2015.
SDS never had much penetration into the experimental market - only a few customer designed installations. EFII made the first full, safe kit for Lycoming engines in 2007 and has more than 400 installations to date. The weakest part of the EFII kit was always the 1990s technology SDS ECU that was included.

Now that EFII is introducing the new System32 control electronics, the weak part of their kit is gone - thank god!

The new parts are state of the art and very impressive. Robert Paisley has been designing engine electronics since the 1980s. I'm sure a lot of people will be upgrading as quickly as they can to System32.

I myself will be upgrading, but only because I want the latest and greatest. Ultimately it won't change how my plane flies or how the engine runs. I'll just have to decide do I want to take a full weekend or so from flying to do any work... (honestly, once you start flying, the LAST thing you ever want to do is more work)
 
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I have been aware of SDS's existent for well over a decade because of my involvement with another industry (automotive engine conversions). They have been selling EFI for a long time, successfully. I don't think they have changed their website in that decade. LOL.

I have absolutely nothing against EFII or its owner. I am sure I could be just as happy with his system as SDS's. The two companies' systems have vastly more in common with each other than they have differences. Everything but the ECU's are off the shelf automotive parts, with some custom mounting.

The big difference I see is that it looks like EFII chose a more cookie cutter approach, and they do more of the installation for you. More of the wiring and connectors are pre-made, which might be a great idea if the buy is not VERY comfortable soldering and crimping wires. The downside, if you consider it a downside, is by putting extra connectors at the firewall, you create more potential failure points in the wiring. Extra connectors, professionally done, might be more reliable than fewer connectors done by someone without a lot of wiring experience. Look at your wiring ability, and make your choice.

I chose the "cookie cutter" approach with my engine conversions, but it was an easy choice as the install vehicles were always the same. With homebuilt aircraft it is a lot different. Firewall forward they might be pretty similarly laid out, but that is about it.

Like I said I don't have a great preference for either. I have a few things I would rather see on both systems, mostly from a wiring standpoint. But I would start out using either system, bone stock, as they both work.

I have emailed Ross at SDS extensively, and have found him extremely knowledgeable and helpful. I would guess the owner of EFII is similar, based on what I read. I will be buying a system in the next month or 3, and I will be buying SDS.

But I would not disparage EFII for their different product philosophy either.
 
The weakest part of the EFII kit was always the 1990s technology SDS ECU that was included.

Could you be more specific? Are saying the re-badged SDS ECU's sold by EFII were unreliable, or merely lacked features introduced later?

BTW, that 540 you're flying was certificated on October 31, 1957.
 
...The weakest part of the EFII kit was always the 1990s technology SDS ECU that was included....

It's a well known fact that no good technology came out of the 90's, as long as you ignore the deployment of the internet, cell phones and fiber optics and a bunch of fruity computer stuff that I can't remember😀.

Everyday, I design electronics that use integrated circuits developed since the 70's. They seem to work OK.

Nowadays, hardware is pretty reliable as long as conservative engineering practices are followed. The ongoing problem is software quality, largely due to the layers of abstraction (3rd party tools, libraries, developers). Try and calculate the MTBF of software-driven systems, and you'll see what I mean.

So don't be surprised when the 90's lawyer calls (on his cellphone) or emails (using the internet) seeking compensation for false and defamatory statements!

Cheers
 
17 years with SDS and could not be happier

I bought my first EFI system from SDS shortly before 2000. I bought my second one about a year ago.

I could not be happier. The system provides excellent versatility in both EFI programming as well as ignition.

Ross has been there answering all my questions for 17+ years. I have no experience with EFI.

If you are looking a very versatile, affordable EFI+Ig system that has a proven track record and great personalized service. I would recommend SDS.

Charlie
Longview, Wash.
 
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