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Fuel Injection conversion for beginners

HansR

Active Member
Hi.

I need your advice.
I would like to convert my carbureted O-360-A4A (converted to A1A) to fuel injection.

Now there is lots of information here at vaf, but I do not really understand what parts and what modifications I need to do. Please note I have no prior knowledge of FI.

Parts
What are the parts I need to buy, or is there complete kits with all? Really all parts I need, so I do not end up with one central part, but there is lots more to replace.

Modifications
What needs to be done to the engine?
Obviously I do not have any holes for injectors.

Makes
What makes of FI are good bang for the buck?
I have seen Avstar and Precision airflow. Are they good choices? Little installation work is a priority.

Thankful for help / HR
 
I just did this conversion last year.

Understand that theRe are 2 general types of injection systems. The most common is continuous flow, like the Precision or Airflow Performance systems, and a pulsed injection, like a car would have. The pulsed systems should be easier starting, and perhaps more economical on fuel, but otherwise both enable balancing the cylinder mixtures for the more aggressive leaning we like.

So continuous flow- you need a servo (the big thing where the throttle and mixture controls go, a flow divider, and injector lines, mechanical fuel pump, electrical fuel pump, fuel filter (if a suitable one is not already installed) and some flex lines as equipped to fit. Airflow Performance will sell you a complete kit for the upgrade. Also the mechanical fuel pump and electrical boost pump will need to be changed to ones that provide the 30PSI necessary for the injection system. The mechanical pump is a bolt on replacement, but the electrical pump will require some work to mount somewhere as it is entirely different package than the low pressure pumps for carb engines. A fuel filter will likely need to be added to filter fine particulates.

You will likely get involved in some rerouting and maybe replacement of the throttle and mixture cables. If you have a fuel flow sensor it may need to be relocated. Also, some flex lines will likely need to be made to run from the servo to the flow divider.

With regards to the injector holes, unless you have very old cylinders, they are likely there. They can be used as primer ports or for the injectors.

I got the Airlow Performance FM-150 which bolts in place of the carb. It Is smaller than the carb and does require a spacer block between the servo and the air box however to keep the air box lined up with the cowl.

As for the pulsed injection systems, I know little details except that they will require electrical power and generally some backup power source. This is a factor to consider if you want to keep the effort down.

Hope that helps. Airflow Performance has great support.
 
Hope that helps. Airflow Performance has great support.

Thanks Dan.

Now I understand much more. So the constant flow injection system seems the way to go, as I would not like to be dependent on the electrical system.
"Constant flow" - i assume it changes with throttle, but please confirm?

You mention the injector holes for primer - so you do not inject to the injector holes? Then I guess you inject in the servo(?) to all cylinders at once?


So I need
  1. Servo
  2. Servo spacer
  3. Fuel divider
  4. Injectors
  5. Mechanical fuel pump
  6. Electrical fuel pump

So if the injectors are not in each separate cylinder, what does the fuel divider do?

Do you know how much the complete conversion cost you?

What was the end result?
Besides the ability to run inverted, was the power increased?
Fuel consumption?
I also guess you got better heat distribution with less CHT spread?
Did the weight increase or decrease?

BR / HR
 
Thanks Dan.

Now I understand much more. So the constant flow injection system seems the way to go, as I would not like to be dependent on the electrical system.
"Constant flow" - i assume it changes with throttle, but please confirm?

You mention the injector holes for primer - so you do not inject to the injector holes? Then I guess you inject in the servo(?) to all cylinders at once?


So I need
  1. Servo
  2. Servo spacer
  3. Fuel divider
  4. Injectors
  5. Mechanical fuel pump
  6. Electrical fuel pump

So if the injectors are not in each separate cylinder, what does the fuel divider do?

Do you know how much the complete conversion cost you?

What was the end result?
Besides the ability to run inverted, was the power increased?
Fuel consumption?
I also guess you got better heat distribution with less CHT spread?
Did the weight increase or decrease?

BR / HR

You need an injector for each cylinder. Modern cylinders have one hole pointed upward (preferred for injectors) and one hole pointed outward (usually for primers). Some old cylinders only had the outward facing holes. The flow divider not only separates the servo output into four lines, it also modifies the restriction to flow based upon fuel pressure. It is a required component.

When I converted, I saw a bit less than 1 GPH reduction at similar cruise power levels after balancing the injectors. I imagine this varies depending upon how poorly a given sump arrangement affects air/fuel distribution.

Larry
 
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When I installed my new IO-370, it was a change from a carb to FI. I had to do all of the airframe mods required to support fuel injection.

After researching various High Pressure Fuel Pump options, I decided to go with the Van's standard Fuel Injection set-up. Van's has a complete sub-kit that includes the pump bracket, dog house and center tunnel cover. You may be able to re-use your center tunnel cover - at least the part forward of the dog house. The kit will include a set of plans to show how everything is installed between the spar and the firewall.

I opted for the AFP injection system on the new engine, so I used their high pressure pump. The stock Van's pump mount is designed for the AFP pump.

I also bought the fuel line package from TS Flightlines for all the lines that go between the fuel valve and the firewall.

Another thing to consider is the Purge valve option that you can get from AFP. The system works fine without the purge valve but the purge valve has some benefits. It clears out all the fuel out of the lines which makes for a little easier hot re-start. It also prevents any fuel dripping into the air box after shut down.
 
Thanks Dan.

Now I understand much more. So the constant flow injection system seems the way to go, as I would not like to be dependent on the electrical system.
"Constant flow" - i assume it changes with throttle, but please confirm?


You mention the injector holes for primer - so you do not inject to the injector holes? Then I guess you inject in the servo(?) to all cylinders at once?


So I need
  1. Servo
  2. Servo spacer
  3. Fuel divider
  4. Injectors
  5. Mechanical fuel pump
  6. Electrical fuel pump

So if the injectors are not in each separate cylinder, what does the fuel divider do?

Do you know how much the complete conversion cost you?

What was the end result?
Besides the ability to run inverted, was the power increased?
Fuel consumption?
I also guess you got better heat distribution with less CHT spread?
Did the weight increase or decrease?

BR / HR
Constant flow means that fuel is metered to the injection nozzles constantly. The pressure to the nozzles is varied by the servo, which in turn increases or decreases the flow based on mass airflow of air through the Servo body. The injector nozzles screw into the cylinder heads on the top side of the cylinder, one nozzle (Injector) per cylinder.

I think the complete conversion was around $4K. I sold some of the parts removed and recovered a few $$.
 
Are my guesses correct?

  1. The fuel pump pumps with high pressure to the Servo
  2. The servo "pumps" gas proportional to air flow to the Flow Divider. The fuel is still liquid. The Servo also has the airflow valve to control MAP (throttle)
  3. The Divider ensures same fuel flow to all four cylinders
  4. The nozzles sprays the fuel into the cylinders.

Flow is unidirectional, no return line needed?

So, what I basically need, beside fuel lines and such are ?

  1. Electrical hp fuel pump
  2. Mechanical hp fuel pump
  3. Servo
  4. Divider
  5. Nozzles

The servo is mounted where the carb used to be?
 
Constant flow means that fuel is metered to the injection nozzles constantly. The pressure to the nozzles is varied by the servo, which in turn increases or decreases the flow based on mass airflow of air through the Servo body. The injector nozzles screw into the cylinder heads on the top side of the cylinder, one nozzle (Injector) per cylinder.

I think the complete conversion was around $4K. I sold some of the parts removed and recovered a few $$.

Thanks again. I was a little quick with my next post so I did not know you had answered.
 
In case it?s still fuzzy, you need to look at your engine to be sure you have the injection ports (extremely likely that you do). Near the plugs, you should see a threaded hole into the cylinder where the intake manifold attaches. These holes will be filled, either with a primer line, or a brass plug (usually with a square end for a wrench).
As part of the nozzle assemblies, there are small .028? flow-limiting apertures. You can buy these in slightly different sizes (0.0005? increments) to balance all the cylinders, so they will all reach peak egt at exactly the same mixture setting. This will allow you to smoothly operate lean of peak.
 
Excellent! Now I think I am getting a good understanding.

Initially I was very confused, as my reference was car/outbourd EFI systems.

Any idea about the efficiency in aircraft FI vs EFI?

As you research this question do not neglect to compare the installation simplicity of the Bendix style mechanical FI system, with the EFI. Specifically, Normal Electrical system requirements, backup electrical system requirements, Fuel Return, etc.
 
I'm in the middle of this conversion now on my RV-7A O-360, using the Airflow Performance FM-150 kit for the 360, all new fuel lines from TSFlightlines, and Van's mounting kit for the electric fuel pump. I also decided to replace the Van's fuel valve with one from Andair, the fuel lines from the tanks to the valve (TSFlightlines), and the throttle & mixture cables with vernier-assist models from McFarlane.

The AFP FI kit is extremely comprehensive. Call Don at AFP & he will walk you through everything. There are very few if any decisions you need to make on this. Be sure to measure the total distance from the bottom of the sump to the top of the filtered air box so Don can determine the thickness of the spacer required to make up the difference. Otherwise, your FAB inlet will not align properly with the cowl opening.

You can download the AFP installation manual here: https://airflowperformance.com/wp-content/uploads/2018/12/API-Installation-Service-Manual-9003.pdf

Assuming your O-360 has the updraft sump, your kit will likely include the control cable bracket kit documented here: https://airflowperformance.com/wp-c...0-Updraft-Sump-Mixture-Throttle-Cable-Kit.pdf

I also suggest calling Tom at TSFlightlines. His advice has been invaluable on this project.

Finally, regarding mechanical vs. electronic FI: if I was building a plane, I'd build in SDS EFI from the start. That requires a very robust electrical system, and also fuel return lines to each tank & a fuel valve that switches both the supply & return lines. That was just too much for me to bite off in a retrofit installation. Not impossible, but it felt daunting for a non-builder like me.
 
As you research this question do not neglect to compare the installation simplicity of the Bendix style mechanical FI system, with the EFI. Specifically, Normal Electrical system requirements, backup electrical system requirements, Fuel Return, etc.

Right, I have no thoughts of going for the EFI, but is interested in the efficiency in the bendix style FI. Then a comparison with EFI is relevant.
 
I think I soon can sum up my information to take a decision upon:

In order of price
  1. Avstar
  2. Airflow performance
  3. Precision Airmotive

From what I have found on VAF, Airflow Performance seems to be the most preferred.

Finally, I need to know the maintanance cost for the three:

What is needed in terms of ordinary maintanance, and also scheduled overhaul?
Intervals and costs?
 
Spacer and other parts

Hi.


Modifications
What needs to be done to the engine?
Obviously I do not have any holes for injectors.



Thankful for help / HR

Hans, I'm also in the process of replacing an O-360-A4A with a clone injected engine. Assuming you are keeping your sump and vertical intake, one of the challenges you will face is the height difference between the carb and the injection servo. Since you will want to keep your airbox and intake in the same location, you may have to make a spacer. I decided to fabricate a part that included the top of the airbox cover and the spacer. See attached photo of the carb vs injection servo and the new part I'm fabricating to orient the intake in the same position to match the cowl.

Other parts of you will need would be a new high-pressure fuel pump and possibly a new pressure sensor speced to accommodate the higher pressure.

I'll post some more pictures as this progresses.

Brian

2-D24409-A-2-CF8-4-B3-D-9506-A9-B1-E9-E59-A1-F.jpg


E4725-F72-A245-4615-8-E6-D-8-D37-A57674-A4.jpg
 
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Hans, I'm also in the process of replacing an O-360-A4A to a clone injected engine.

I'll post some more pictures as this progresses.

Brian

Thx Brian. Do you have a drawing of the spacer? No problem for me to have it milled if I know to make it.

I have got a full list of parts suggested by Airflow Performance, maybe the spacer is included? Adds up to some money....

BR / HR
 
Thx Brian. Do you have a drawing of the spacer? No problem for me to have it milled if I know to make it.

I have got a full list of parts suggested by Airflow Performance, maybe the spacer is included? Adds up to some money....

BR / HR

The spacer is not included in the kit. Call Don & tell him how tall your existing installation is from bottom of sump to top of FAB cover plate & he will quote you a phenolic spacer of the correct thickness. He has the CAD files of the fuel control, so the spacer is milled to the exact dimensions to mate with it.

You may also need a new FAB top plate. Mine had an extra cutout that was required to fit the bottom of the carberator, and it also had a large crack. I fabricated one from thicker aluminum using the old one as a template.
 
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Thx Brian. Do you have a drawing of the spacer? No problem for me to have it milled if I know to make it.

I have got a full list of parts suggested by Airflow Performance, maybe the spacer is included? Adds up to some money....

BR / HR

Hans,

I should be able to get you a drawing. What format do you want it in? My part is for a silverhawk airmotive servo. The spacer and the top of the FAB are now built into one part, but you will have to make sure your servo height is the same. Well, more importantly, the height differential to the old carb.

Go to my username and drop me an email with your address so I know where to send it.

Brian
 
The spacer is not included in the kit. Call Don & tell him how tall your existing installation is from bottom of sump to top of FAB cover plate & he will quote you a phenolic spacer of the correct thickness. He has the CAD files of the fuel control, so the spacer is milled to the exact dimensions to mate with it.

You may also need a new FAB top plate. Mine had an extra cutout that was required to fit the bottom of the carberator, and it also had a large crack. I fabricated one from thicker aluminum using the old one as a template.

When I called Vans and discussed this conversion with them, they suggested a support bracket on the top of the FAB since they are prone to cracking. That's why I opted to machine it all out of one piece of solid aluminum with the top cover portion of the FAB now being substantially thicker. The intake dimensions and bolt holes locations are the same for the carb and the injection servo. Be sure to safety wire the bolts holding the FAB cover to the carb/servo.
 
Throttle body injection?

Having flown for years with both FI and carbureted Lyco 360 engines, I am struggling to see the great benefit from converting an engine to FI. Unless you want to fly aerobatics I think the benefit is very limited. I do not get better engine performance or lower fuel flow with my injected IO360 B2F vs the O360 A3A, and the Injection system is only so I can go aerobatic. The carbureted one is in my Robin DR400 and the FI in the CAP10.

Going half way house I would consider a throttle body system as it is vey simple and easily installed and maintained in comparison to the rather archaic mechanical constant flow injection systems we still use in aircraft.

What are the pros and cons for going with a throttle body injector compared to FI? I would be interested in hearing any experience on the TBI. Had I not bought a rebuild project, then I would consider TBI.


EDIT

Ok, I read through the year long discussion on TBI, where several people threw in the towel after a long struggle. Engine failures are not an option for me either..
 
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Paperwork

I have about 300 hours on the RV 7 that I built. I hold the repairman certificate for this aircraft. I am converting my O-360 to AFP fuel injection.
My question is, what is needed to satisfy the feds after the conversion? Return to phase 1, re-do W&B, form 8130, or ?
I will be in touch with fsdo as needed, just don’t want to go forward blind.
Experiences?
Thanks, Jim
 
I have about 300 hours on the RV 7 that I built. I hold the repairman certificate for this aircraft. I am converting my O-360 to AFP fuel injection.
My question is, what is needed to satisfy the feds after the conversion? Return to phase 1, re-do W&B, form 8130, or ?
I will be in touch with fsdo as needed, just don’t want to go forward blind.
Experiences?
Thanks, Jim

I'm changing my engine from a certified O-360-A4A to a superior IO-360, and converting from a FP to a CS prop. I called a local DAR who is highly respected and he said the only thing that would require me to go back to phase 1 is the conversion to fuel injection and he would work with my on the that including the paperwok. I would have conjectured it would be the change in W&B and the prop. He said since I purchased the plane from a different part of the country, he would designate a new test area.

I have lots of respect for the knowledge and experience of many of the folks that participate on this site, but the advise I got from the DAR seems to conflict with some of the post I've read here. If there is some reference where this information is spelled out clearly, I would appreciate reading through it.

I would suggest you work with your local DAR.

Brian
 
I have about 300 hours on the RV 7 that I built. I hold the repairman certificate for this aircraft. I am converting my O-360 to AFP fuel injection.
My question is, what is needed to satisfy the feds after the conversion? Return to phase 1, re-do W&B, form 8130, or ?
I will be in touch with fsdo as needed, just don’t want to go forward blind.
Experiences?
Thanks, Jim
I was required to go back to phase 1 for 5 hrs when I did this conversion a year ago.
 
Brian and Dan, thanks for the info.
My DAR is no longer available as he has moved out of the area.
I will call my FSDO next week to discuss.
I anticipate a return to phase 1, which is fine, no big deal...
Thanks, Jim
 
Brian and Dan, thanks for the info.
My DAR is no longer available as he has moved out of the area.
I will call my FSDO next week to discuss.
I anticipate a return to phase 1, which is fine, no big deal...
Thanks, Jim

I called the FSDO when I did the conversion and they said no Phase I necessary. They said only things that change W&B or flight characteristics. The 2 pound difference with the change was not enough to warrant more than a change to the paperwork.

Larry
 
Having flown for years with both FI and carbureted Lyco 360 engines, I am struggling to see the great benefit from converting an engine to FI. Unless you want to fly aerobatics I think the benefit is very limited.

Yup. It's for aerobatics
 
I called the FSDO when I did the conversion and they said no Phase I necessary. They said only things that change W&B or flight characteristics. The 2 pound difference with the change was not enough to warrant more than a change to the paperwork.

Larry

I find the inconsistency frustrating. Perhaps we should expect nothing more from a government agency. I've heard it mentioned here on VAF that the W&B and flight characteristics are determining factors, but unless there are established and document thresholds, it would seem very subjective.

Brian
 
Yup. It's for aerobatics

Having flown for years with both FI and carbureted Lyco 360 engines, I am struggling to see the great benefit from converting an engine to FI. Unless you want to fly aerobatics I think the benefit is very limited. I do not get better engine performance or lower fuel flow with my injected IO360 B2F vs the O360 A3A, and the Injection system is only so I can go aerobatic. The carbureted one is in my Robin DR400 and the FI in the CAP10.

Going half way house I would consider a throttle body system as it is vey simple and easily installed and maintained in comparison to the rather archaic mechanical constant flow injection systems we still use in aircraft.

What are the pros and cons for going with a throttle body injector compared to FI? I would be interested in hearing any experience on the TBI. Had I not bought a rebuild project, then I would consider TBI.


EDIT

Ok, I read through the year long discussion on TBI, where several people threw in the towel after a long struggle. Engine failures are not an option for me either..

Efficiency is my motivation. A carburetor is simple and it works, but it's the shot gun method of feeding fuel to the engine. You can feed each cylinder with more precision using injectors. They both have their pros and cons though.

Brian
 
Efficiency is my motivation. A carburetor is simple and it works, but it's the shot gun method of feeding fuel to the engine. You can feed each cylinder with more precision using injectors. They both have their pros and cons though.

Brian

Brian, what kind of increased efficiancy can be experter?
Lower fuel consumtion?
More power?
Closer egt's?
 
Efficiency.

My experience is that a carburetor and standard fuel injection system gives the same fuel consumption for the same power on identical engines.

While the carburetor is a simple device, the mechanical fuel injection system is not much better, as it injects fuel in a continuous stream. There is no sequencing of the injection, and there is no differentiation between cylinders based on knock or EGT. This can of course be improved by optimising the individual injectors, and requires some EGT analysis before buying a custom set of injectors from GAMI. I have not gone that far as I fly aerobatics and can’t lean aggressively for that reason.

I just wish Ellison would do some effort to do business again, as their TBI still seems to get good reviews. Just a shame about the customer support..
 
My experience is that a carburetor and standard fuel injection system gives the same fuel consumption for the same power on identical engines.

Agree, but with a caveat...same power on same fuel consumption if mixture distribution to individual cylinders is reasonably equal.

That's not a given with a lot of carbed engines under all conditions, easily seen by looking a GAMI spreads. Some cylinders too rich, some too lean, and the combined power output will be down a little.

Injected engines are often more powerful at full throttle due to higher volumetric efficiency. The pressure drop due to a venturi is called "carb loss" for a reason. Higher mass flow does mean they will burn more fuel.
 
My experience is that a carburetor and standard fuel injection system gives the same fuel consumption for the same power on identical engines.

While the carburetor is a simple device, the mechanical fuel injection system is not much better, as it injects fuel in a continuous stream. There is no sequencing of the injection, and there is no differentiation between cylinders based on knock or EGT. This can of course be improved by optimising the individual injectors, and requires some EGT analysis before buying a custom set of injectors from GAMI. I have not gone that far as I fly aerobatics and can’t lean aggressively for that reason.

I just wish Ellison would do some effort to do business again, as their TBI still seems to get good reviews. Just a shame about the customer support..

Sorry - disagree.

If you always run 100+ degrees rich of peak (as you seem to do), carb vs fuel injection makes little difference for engine operation - other than you are dumping excess fuel into the engine and not getting useful power out of it. Now consider you still have the carb icing issue. For that reason alone I will never fly behind a carb. I have personal knowledge of one RV builder doing an off field landing as a result of carb icing.

Now overlay how many of us fly. I’m LOP 95% of the time, 7.5-8.5 gph above 9K’ which yields very good cross country range. A few carb people are lucky enough to run their engines like this, but many are not as the cylinder fuel mix spread is too great.

WRT buying GAMI injectors - not required or desired. For ~$26 each you get replacement injector nozzles from AirFlow Performace (fits standard systems as well). Usually three data runs and the GAMI spread is less than 0.1 gph.

Carl
 
Sorry - disagree.

If you always run 100+ degrees rich of peak (as you seem to do), carb vs fuel injection makes little difference for engine operation - other than you are dumping excess fuel into the engine and not getting useful power out of it. Now consider you still have the carb icing issue. For that reason alone I will never fly behind a carb. I have personal knowledge of one RV builder doing an off field landing as a result of carb icing.

Now overlay how many of us fly. I’m LOP 95% of the time, 7.5-8.5 gph above 9K’ which yields very good cross country range. A few carb people are lucky enough to run their engines like this, but many are not as the cylinder fuel mix spread is too great.

WRT buying GAMI injectors - not required or desired. For ~$26 each you get replacement injector nozzles from AirFlow Performace (fits standard systems as well). Usually three data runs and the GAMI spread is less than 0.1 gph.

Carl


Hello Carl,

I am regularly flying 4 to 5 hour legs between the UK and Denmark. I lean aggressively whether I fly behind a carburetor or injection system, which returns the same fuel flow for either engine for me. But I have not optimised the injectors for minimal GAMI spread, so that will be the reason for that. I agree that FI can give better economy, but it does requires the injectors to be optimists to be able to take advantage of that.

And I will look at the AirFlow injectors instead of the GAMI; thanks for that tip!

I have no problem with carb icing, as long as the Carb Heat is used as per the normal procedure. Carbs can ice up, (I know that for a fact) and you need an effective carb heat system for that, which was not a strong side of the original Vans design. The design did not raise the temperature enough to melt the ice When it had first built up. A couple of pilots here have learned that the hard way, and an improved carb system is now required by the local EAA chapter to cope with Scandinavian weather conditions. So icing is really a problem that can be solved with minor modifications of the Carb Heat system and not a fault of the carburetor per say.
 
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Brian, what kind of increased efficiancy can be experter?
Lower fuel consumtion?
More power?
Closer egt's?

Yes to all of that, Hans. I'll have to let you know when I get there. It stands to reason that a well balanced injection system will distribute fuel with greater precision with more consistent EGTs, but unless you spend the time to balance them there may not be much gain. For this reason, I've never really understood the benefit of throttle body injection systems. I'm having a new engine built from scratch and had the option to use injection. My engine builder has considerable experience and advocated for injection, so I decided to go in down that path. I don't think I would swap out a carb for an injection system on a perfectly good running engine unless I was really board.
 
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