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Rotax upgrade to fuel injection

backcountry

Well Known Member
Sometime back I heard there?s a company that supplies a fuel injection kit for existing Rotax carburetor engines. I?m not a fan of carburetors and especially dual ones - floats, balancing, dual controls, etc. it?s kinda like having two engine tied to the same crankshaft.
Has anyone modified the carburetor engine to fuel injection on the RV-12?
I?m cautious but interested if it?s ever proved to be successful.
 
Edge Performance offers an EFII system. It’s very similar to the current EFI/EFII systems that are currently being offered for our Lycoming based engines. After I’m finished building my current RV-7 project I’m planning on building a Rans S-7 backcountry/STOL airplane and it’ll definitely have an Edge Performance turbo/EFII. Like Tom said though, it’s more to it than than just changing to fuel injection....there’s also some plumbing involved which includes return lines. I’m not sure if the 12 has a header tank or not but if it does, it may simplify the plumbing a little bit.

https://www.edgeperformance.no

Mark
 
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We've been offering EFI systems for 912s for over 10 years and used to supply Edge with ECUs and other bits until they started to copy our parts without permission.

http://www.sdsefi.com/rotax.htm

You will need a return line to the tank and you'd have to check cowling clearance for the manifold and injectors. The manifold may interfere with other accessories We've done installations on several other airframes but never done an RV12 before. We would be interested in working with people who'd like to ditch the carbs. We have a couple of different manifold designs we could offer.
 
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We've worked with Ross on several things. Very nice products. But---as i said, there is more to it than removing the carbs and putting an injector rail in place.

Tom
 
If there's some reasonable interest in an EFI conversion for RV-12s we'd be willing to produce custom parts to make a standard installation easier for everyone- the same as we've done for Lycoming, Continental, Jabiru, Rotax and several popular auto conversions for many years.

I don't see any show stoppers putting EFI on a -12.

We'd want to find the best location for the fuel pumps, fuel pressure regulator, have a solution for the return line, throttle cable brackets and develop an intake manifold which clears everything we need to clear.
 
Excellent points Ross, which I was attempting to to across to Larry. Plumbing, wiring, ECU's, pumps, filters, etc all have to be planned and locations thought out. Similar to changing from a RV12 to a RV12IS---lots of differences!

Tom
 
Excellent points Ross, which I was attempting to to across to Larry. Plumbing, wiring, ECU's, pumps, filters, etc all have to be planned and locations thought out. Similar to changing from a RV12 to a RV12IS---lots of differences!

Tom

Yes and the best way to do all this is to standardize so it works the same for everyone and we can write better documentation for the install.
 
If there's some reasonable interest in an EFI conversion for RV-12s we'd be willing to produce custom parts to make a standard installation easier for everyone- the same as we've done for Lycoming, Continental, Jabiru, Rotax and several popular auto conversions for many years.

I don't see any show stoppers putting EFI on a -12.

We'd want to find the best location for the fuel pumps, fuel pressure regulator, have a solution for the return line, throttle cable brackets and develop an intake manifold which clears everything we need to clear.

What would an EFI system cost for 912ULS conversion? Might as well start there to gage interest...
 
For the parts minus the intake manifold, single pump, around $2740US for EFI only- no spark control. The intakes vary in price from $750-$1100, depending on the style. There's a lot of fab and TIG time there.
 
Looks like a lot of effort to upgrade an in service engine. What’s the justification!

The people who've made the switch usually mention that they are tired of synching 2 carbs, linkage issues, carb drip trays etc. and wanting something that avoids all this along with the other usual advantages of fuel injection- smoother running due to more equal mixture distribution, economy and power gains.

Rotax themselves finally saw the light and came out with the EFI iS version.

For sure the carbs make the engine run, but not as well as EFI.

Our high time Rotax customer does flight instruction and has over 2200 hours on the EFI over about 10 years. He's sold on it after running carbs for an equal amount of time before that and bought 3 more EFI systems for other aircraft including a twin engined one.

As usual, these choices come down to personal experience and wants. If you are happy with your carbs, you continue to use them usually. EFI probably won't interest you just as EI won't interest many people who are happy with mags on a Lycoming.
 
reliability, fuel efficiency, range/endurance.

From Van's published numbers... 433 miles per tank (21.64mpg) vs 630 (31.5 mpg)... 45% more efficient is serious! Someone else can do the math.. but at some point, you make your money back...
 
As much as I would prefer FI over carbs... you'd have to reall, REALLY want it bad to sink that much into a conversion. I could see it if (for example) you had a damaged or run-out engine you were rebuilding.
 
RV12 upgrade to EFI

A good start would be to do an electrical system analysis. Work out what excess charge system capacity is available should be the first thing to check. I suspect with the std 912 Charge system it would be very border line, handling the additional load from the different fuel pump, ECU and injectors. (depending on what electrical accessories are already fitted to the aircraft.)

I have also briefly looked into EFI to help overcome fuel quality and vapour issues in a very hot environment and decided the heart ache and further reduction of payload capacity due to the extra weight of the additional charging system to increase the available capacity wasn't worth the cost and weight penalty.

Don't get me wrong, i'm not against the idea, just trying to operate within the operating and legal parameters with 2 people on board.

Out of interest what are the estimates for an EFI system electrical current requirements?
Would it be around 10 amps?
 
A good start would be to do an electrical system analysis. Work out what excess charge system capacity is available should be the first thing to check. I suspect with the std 912 Charge system it would be very border line, handling the additional load from the different fuel pump, ECU and injectors. (depending on what electrical accessories are already fitted to the aircraft.)

I have also briefly looked into EFI to help overcome fuel quality and vapour issues in a very hot environment and decided the heart ache and further reduction of payload capacity due to the extra weight of the additional charging system to increase the available capacity wasn't worth the cost and weight penalty.

Don't get me wrong, i'm not against the idea, just trying to operate within the operating and legal parameters with 2 people on board.

Out of interest what are the estimates for an EFI system electrical current requirements?
Would it be around 10 amps?

The stock 912 charging system outputs around 18 amps max. The EFI draws around 7.6 amps leaving about 8-10 amps for the rest of the plane. If we do fuel AND ignition, the current draw increases to the point where a higher capacity charging system is recommended for most aircraft.

I haven't done a weight analysis between carbs and EFI on the Rotax as there are many factors with fuel pump and intake manifold options but my rough estimate is about 12-13 pounds with a single pump and the lightweight manifold. You could remove the two carbs, perhaps the two cast intake manifolds and fuel pump.

It does look like the RV-12 is more cramped aft of the carbs than many other aircraft and the stock cooling ducts for the cylinders would preclude using our existing 4 into 1 intake manifold so a crossover type transverse plenum style or twin TBs would be required. Certainly some custom parts required.
 
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912 charging system VS. standard externally alternator

Couldn't that anemic 912 charging system be ditched and replaced with a standard external alternator? I wouldn't think that would be very difficult to do and would really bring the charging system up to speed which could then handle any device loads that you'd ever ask of it....including a full EFI/EFII setup. Modern external alternators are pretty compact and lightweight so I guess I?ve never really understood the purpose of that internal alternator on the 912?s.

Mark
 
Couldn't that anemic 912 charging system be ditched and replaced with a standard external alternator? I wouldn't think that would be very difficult to do and would really bring the charging system up to speed which could then handle any device loads that you'd ever ask of it....including a full EFI/EFII setup. Modern external alternators are pretty compact and lightweight so I guess I?ve never really understood the purpose of that internal alternator on the 912?s.

Mark

There are a few options for adding more amps to the 912 charging system already.
 
Guess I?ve never really understood the purpose of that internal alternator on the 912?s.

Mark

I suspect the designers were looking at...

  • No external drive
  • Minimal add'l weight
  • Simple addition to existing CD ignition coils
  • No moving parts
  • Reliability
 
I suspect the designers were looking at...

  • No external drive
  • Minimal add'l weight
  • Simple addition to existing CD ignition coils
  • No moving parts
  • Reliability

Probably true. Unfortunately they used a Ducati regulator, not well regarded as far as reliability goes.
 
There are a few options for adding more amps to the 912 charging system already.

I know there's other options for adding additional charging power to the Rotax but what about ditching that entire setup and just going with a single modern external alternator that we're all familiar with. I guess "adding stuff on" goes against the grain for me and my need for clean, concise, and consolidated systems. I really hate to "patchwork" things together. Also, regarding full ignition ?and? injection system, is there any reason to keep the stock Rotax ignition systems? Couldn?t the SDS ECU handle the both the ignition and injected side just like it does on the Lycoming based engines? I would think that it would be better to consolidate all engine operating parameters into one system instead of a hodgepodge of different components to control the ignition and injection. The bottom line is that if you loose one the othe one isn?t going to do you any good. I think having the Rotax setup exactly like we now have our Lycoming based engines with both electronic ignition and injection in one system is the way to go. I've never personally owned or operated a Rotax but I've heard that the ignition system is basically off of a Ducati motorcycle and that it can be troublesome and expensive to fix or replace if needed. So once again, I go back to the question of why not have one consolidated ignition and injection system?? Am I missing something?

Mark
 
I know there's other options for adding additional charging power to the Rotax but what about ditching that entire setup and just going with a single modern external alternator that we're all familiar with. I guess "adding stuff on" goes against the grain for me and my need for clean, concise, and consolidated systems. I really hate to "patchwork" things together. Also, regarding full ignition ?and? injection system, is there any reason to keep the stock Rotax ignition systems? Couldn?t the SDS ECU handle the both the ignition and injected side just like it does on the Lycoming based engines? I would think that it would be better to consolidate all engine operating parameters into one system instead of a hodgepodge of different components to control the ignition and injection. The bottom line is that if you loose one the othe one isn?t going to do you any good. I think having the Rotax setup exactly like we now have our Lycoming based engines with both electronic ignition and injection in one system is the way to go. I've never personally owned or operated a Rotax but I've heard that the ignition system is basically off of a Ducati motorcycle and that it can be troublesome and expensive to fix or replace if needed. So once again, I go back to the question of why not have one consolidated ignition and injection system?? Am I missing something?

Mark

Yes, if you can add some more amps to the charging system, we can do fuel and spark control and eliminate the carbs and factory Rotax ignition. This would give bigger economy gains than just the EFI side. There would probably be some weight gain there. Our coil packs weigh around 2 pounds each, not sure what the factory coils, pickups and ignitors weigh.

The Rotax stator ring weighs about 3 pounds. I suppose that could be removed and put towards an external alternator.
 
Ross, out of interest, what are the additional 912 charging systems you eluded to?

I'm sure Ross will chime in but I think he was referring to a standing external alternator like we were discussing....but there may be other options. If that anemic Rotax charging system could be eliminated and replaced with a standard external alternator, than there would be plenty enough juice to power a complete electronic ignition and and electronic fuel injection system...just exactly like we now have for our Lycoming based engines. This setup would not only allow you to remove the carburetors and the problems that go with them but also allow you to eliminate that Ducati ignition system that comes stock on the Rotax.

Mark
 
I run a B&C 26 amp alternator driven by the prop governor pad at the back of the gear box in my Rans S19. Works great, ultra reliable and well controlled voltage. I still have the Rotax charging system as a backup with a SH regulator but have never switched to it except at run up to verify its operation.
 
This position might limit the intake manifold design options unfortunately. Works fine with the carbs. Rotax does offer a belt driven option and it wasn't even too badly priced last time I looked.

On the RV-12, it looks like the easiest thing to do would be to stick with twin TBs and tap the MAP signal off the balance hose. Use a cross hex drive to activate both throttle plates simultaneously. We could retain the factory cast manifolds and weld injector bosses to those like we did with our earlier systems.
 
Ross,
Would utilizing twin Throttle Bodies lead to possible synchronization issues much like we have with carbs?
Alex
 
Ross,
Would utilizing twin Throttle Bodies lead to possible synchronization issues much like we have with carbs?
Alex

Not if it was designed properly with a stiff hex shaft driving both throttle plates with rigid, adjustable drive arms. Single cable activates the cross shaft. You'd still have to synch them but they would stay that way forever.

There just isn't much room for a single transverse plenum with single throttle body unless we designed a rather intricate custom fabrication, casting, 5 axis CNC'd part or additive manufactured one. In these small quantities, any of those processes= lotsa $ and few would be willing to pay, me thinks. You'd have to move the coolant bottle and ignitors as well. Would look something like the factory iS manifold shape at least.

For charging system upgrades:

https://www.silent-hektik.de/UL_912_LiMa.htm

http://www.ultralightnews.ca/rotax912/912-externalAltKit.htm

https://www.cps-parts.com/catalog/rtxpages/912914externalalt.php
 
Fore and aft intake manifold.

Ross, What about designing an intake manifold/collective that runs fore and aft...similar to the Edge Performance setup? A single throttle body could be used with this type of intake and the individual intake runner lengths and angles could be adjusted to accommodate different airframes. You could also then ditch the stock cast manifolds. Edge may be a four letter word, but I?m just using their intake manifold design as and example and to give food for thought.

Mark
 
Ross, What about designing an intake manifold/collective that runs fore and aft...similar to the Edge Performance setup? A single throttle body could be used with this type of intake and the individual intake runner lengths and angles could be adjusted to accommodate different airframes. You could also then ditch the stock cast manifolds. Edge may be a four letter word, but I’m just using their intake manifold design as and example and to give food for thought.

Mark

There is no room for this type of manifold on the RV-12 installation without moving a lot of components already attached to the engine- coolant bottle, ignitors, hoses, cylinder air ducts etc. We offer a longitudinal one too but not suitable on an RV-12.

https://ixquick-proxy.com/do/spg/sh...ine_2.jpg&sp=3227af879683a1f19fb1abed6a5f1b69

https://ixquick-proxy.com/do/spg/sh...20143.JPG&sp=f525a6bad7ad99d2e637020aa08de5dc

These two photos give you some idea of all the stuff mounted in the middle of the engine.
 
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Ross,

Thanks for the charge upgrade options kinks.
The Flygas double alternator was another. @1.5 kg
www.flygas.info

Last time i enquired about the SH charge upgrade option, it was no longer available. Perhaps it's available again now?
Cheers,
 
Ross,

Thanks for the charge upgrade options kinks.
The Flygas double alternator was another. @1.5 kg
www.flygas.info

Last time i enquired about the SH charge upgrade option, it was no longer available. Perhaps it's available again now?
Cheers,

If not available, I wish they'd take down the page. I don't know. Someone told me about these a few years back and it seemed to work as advertised.
 
Ross,

A correction regarding the S/H F3030 - 500Watt charge system upgrade.

The system i made enquiries about January this year was the Silent Hektik V1410 525W rotor and stator

. The Silent Hektik V1410 option did not have the 2 ignition system charge coil windings to supply power to the ignition system, so it was not a direct replacement for the Ducatti 250Watt stator and rotor.
A battery powered ignition system was also required in conjunction with this option.

The current advert in the link you posted, is advertised as a 500 Watt direct replacement assembly for the ducatti 250 Watt system. (Joeri was good enough introduce me to google translate and pointed out K?rze wieder lieferbar = Available soon)
So, this is looking very much like an effective charge system upgrade with very the advantage of minimal weight and additional mechanical complications.
 
I contacted Silent Hektik for some more info. Underneath their answer.
Aero 2019 will be from 10-13th of April 2019.

Regards, Joeri

Guten Morgen
and thanks for the email.
We want to fabricate the first 100pcs alternators before
spring 2019 and show it at the AERO_2019.
warm regards
 
Ross,

Thanks for the charge upgrade options kinks.
The Flygas double alternator was another. @1.5 kg
www.flygas.info

Last time i enquired about the SH charge upgrade option, it was no longer available. Perhaps it's available again now?
Cheers,


The verbiage on that site is painful to read. Almost written in Chinglish.
 
New SDS EFI Parts for Rotax 912s

We've just finished most of the CNC'd parts for our all new 912 EFI kits. Engine test fitting should begin in July. These include new 40mm throttle bodies made specifically for this project.



This will be a twin throttle body setup to best fit the maximum number of airframes out there. A single cable will activate the throttle arms to get rid of the factory Y cable. A rigid link with rod ends will keep the throttle plates permanently in synch.



All mating surfaces are O-ring sealed.



Injector adapters sandwich between the factory intake manifolds and heads. The floppy rubber carb isolators are ditched as are the carbs, drip trays, choke cables etc.

Injectors are mounted inline for maximum cowling clearance. We use some of the same fuel hardware bits as our Lycoming kits where appropriate to save on costs and part numbers stocked.

New stainless hardware will be supplied with the kit.

As usual with our kits, we try to minimize weight with careful design of the components.
 
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Will also be interesting to see what the hourly fuel consumption is with this new Fi rig. Wondering what type of fuel pump and fuel pressures are needed with these fuel injectors?
 
Will also be interesting to see what the hourly fuel consumption is with this new Fi rig. Wondering what type of fuel pump and fuel pressures are needed with these fuel injectors?

I?m sure Ross will chime in, but I?ll bet worst case scenario fuel burn will be the same as the carbureted version...but more than likely better. I?m sure the duel Walbro fuel pumps will be used along with the Borla fuel pressure regulator which will maintain 45-50 psi on the fuel rail. More than likely it?ll basically be the same setup as what?s offered for the EFI Lycoming installation.
 
Will also be interesting to see what the hourly fuel consumption is with this new Fi rig. Wondering what type of fuel pump and fuel pressures are needed with these fuel injectors?

While we haven't tested this new setup yet, our earlier Rotax EFI systems have shown a 4-18% reduction in fuel burn. The wide range there is dependent on leaning strategies, altitude and whether you have EFI only or EFI plus our EI. Many Rotax systems we supplied in the past still retained the factory fixed ignition timing which is a compromise just as on a Lycoming.

With the newer EM-5s, we also have the capability to individually trim fuel to each cylinder in flight for zero GAMI spread. This should eke out 1-2 more percent in savings.

We use a smaller version of the electric Walbro pumps we supply on Lycoming systems. Can use twin pumps if desired. Fuel pressure is generally set around 40 psi.

Price wise, I haven't received all the machining bills yet but we are hoping to keep the new kit price in line with the older kits using the fabricated intake manifold which chewed up a lot of hours making, fitting and welding.

You can see some of the other parts and older systems here: http://www.sdsefi.com/rotax.htm
 
More than enough pressure to prevent any vapor lock with winter grade MoGas with 10% ethanol in late spring or summer heat at higher elevation airports, when motor is hot, after a burger run?
 
More than enough pressure to prevent any vapor lock with winter grade MoGas with 10% ethanol in late spring or summer heat at higher elevation airports, when motor is hot, after a burger run?

Yep. That?s one of the beauties of electronic fuel injection.
 
Final Parts

I finally received the last of the prototype parts today for our Rotax EFI system. These were throttle linkage parts to rid folks of the hated OEM Y cables.

The new linkage will use a proper single ACS aircraft throttle cable.

Once the TBs are synched, they will stay that way forever.

Testing on the engine will begin as soon as I can mesh schedules with owner of the test aircraft, possibly next week.

Excited to see how everything works and get this in production if everything goes well.
 
Me too. We already have a couple tweaks we want to do on production parts to make installation easier.

The setup will go off to one of our partners in the US next week for fitment and running on the test stand.
 
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SDS Update

Test running of the new Rotax system was delayed twice by scheduling conflicts with our two beta testers and finally winter set in here early which forced us to send the prototype bits down to our partner in the southern US a couple months late. That's been the story of this development project- delay after delay.

Finally some happy news-the test engine is finally running on the test stand with the new setup as of last weekend.

Should have some more data to crunch by next week.

Have already modified a couple of part designs for production and there may be more based on feedback from the test program.

Lining up some CNC mill time for mid January in hopes that production parts can start being made then.
 
Update

Running of the system continues in the southern US. Had some issues with fuel delivery on the test rig which delayed things a bit but that's fixed now and things are back on track.

Ignition system will now be changed over to SDS to evaluate the full setup this month.
 
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