# Just for discussion, Mechanical fuel injection?

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#### Daleandee

##### Well-Known Member
In 40+ years of driving I've never had an EFI issue. Carbs? Let me tell you about the MG Midget....

Even my Suzuki Boulevard was FI. The 2005 was a carb and the 2006 was FI. Night and day compared to each other.
Please don't use MG carbs to talk about carb reliability or the lack thereof. That's kinda like using Lucas to tell why electrical systems are bad.

I use a carb and it's the same model the O-200 uses and they are quite reliable. Admittedly they have had teething problems (as every technology has at some point) but for the most part they work very well and have done so for years on training aircraft.

I currently own a 2007 Boulevard with F.I. It's the same engine that I had on my Intruder that had dual carbs. The fuel mileage is a bit higher on the F.I. engine but the performance and starting is about the same with either.

I won't fault anyone for using F.I. and someday the carbs on planes may very well disappear as they have on autos. I have experienced (in a friends aircraft) a rough engine when the fuel injection got wonky on it. Engine ran enough to get to the airport and make a precautionary landing but the old adage is true ... if it's man-made it can and will fail at some point.

#### proppastie

##### Well-Known Member
Log Member
I think if I had 40 years experience in automotive vs aircraft and older motorcycles I probably would have a different outlook on things. The only problems I ever had with a carburetor was cleaning passages in a motorcycle that had been sitting for maybe 4 years, and those little pumper carbs on chainsaws or my model aircraft engine,....now those I do not like. .....The two modern cars I have had with fuel injection have been trouble free as regards the FI and certainly I would welcome that technology in aircraft.....However not understanding the technology I personally would only install proven plug and play systems. It is great to see others with experience in this field posting their work.

#### PMD

##### Well-Known Member
Bosch CIS is somewhat like Bendix. Biggest difference is measuring air; CIS uses the flapper door where Bendix measures with impact air.
I my fading memory from VWAG days is correct: Bosch D (manifold pressure control analogue electronic) and Bosch K (CIS mass airflow mechanical) are based on Bendix patents - but developed much further by Robert Bosch. K Jetronic IMHO would make a nice system for an airplane, but lack of support these days would be a serious problem due to the aging nature of a/c fleets. When GM (Rochester mechanical injection on '57 and later SBC) introduced FI, it was also on Bendix licensed to GM and a small handful of Chrysler products came to market at same time with actual Bendix electronic injection (IIRC, ONLY time they ever sold into the production automobile injection business). ALL of this stuff is legacy from having the Kraut's do FI right in WWII aircraft and catch-up engineering on this side of the ocean during and post war. So thank DB-601/605 boffins for what we have today. Just odd that they had to license it back from Bendix to move forward! (IF I remember that correctly).

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#### Jay Kempf

##### Curmudgeon in Training (CIT)
Still running a now 41 year old CIS V8 (928). Still running great. Been blueprinted over the years but still very reliable on par with modern fuel injections systems. Seems I am always chasing some puzzle on the modern stuff. We have a Cayenne and and Audi as well both around 100k miles. Check engine lights always on for some nuisance reason: evap, coil, injector, igniter, O2 sensor, something...

#### PMD

##### Well-Known Member
Still running a now 41 year old CIS V8 (928). Still running great. Been blueprinted over the years but still very reliable on par with modern fuel injections systems. Seems I am always chasing some puzzle on the modern stuff. We have a Cayenne and and Audi as well both around 100k miles. Check engine lights always on for some nuisance reason: evap, coil, injector, igniter, O2 sensor, something...
Of course, I have been biting my tongue with my obvious bias, but when you mention electronic injection system problems I just have to say that is a result of burning the wrong fuel (be it in airplanes, boats, cars, trucks...). In millions of kms. I have never really had any problems worth mentioning with diesel engine injection systems - mechanical OR electronic. A rather wide range of problems with injection and ignition would simply not exist with a PROPERLY designed aircraft diesel (yes, SMA/Renault came close but auto conversions miss by a tonne - intentional pun poked at the pork).

#### Jay Kempf

##### Curmudgeon in Training (CIT)
I have a pretty extensive shop and lots of experience repairing and maintaining old and new. Been playing with this stuff for decades. Support lots of Porsche, Audi and around the world and locally a bunch of Subaru people. I would say it isn't bad fuel in my experience that gets the modern high end stuff. It's over complication. But it is always something. Normal maintenance maybe but it adds up to a lot of time diagnosing codes that aren't the actual issue but a sort of finger print of a problem. Sometimes not. OTR stuff which is the origins of all diesel injection stuff is another league. Don't get me started on direct injection... The triumphant return of coked up intake valves... And tire pressure monitoring and over complicated Evap systems and errors, and and and and... Have laptops and tablets just for that stuff, plus Porsche specific stuff cause they can't play will with the rest of VAG... AAAAAACK! How many factory tools? AAAAACK! VVT ACK!!!!!! Glutton for punishment I guess. Still find the insides of a fuel distributor fascinating.

#### delta

##### Well-Known Member
Multiple carbs, tasty.
Yeah until you try to get one to pass smog in Vegas.

#### pfarber

##### Well-Known Member
HBA Supporter
I would suspect that aviation mechanical injection would still be miles ahead of automotive simply due to the annual condition inspections, mandatory ADs and overall higher level of maintenance required by law.

A car you drive it until it breaks. An airplane you take apart every so soften to look and see if something 'might' be wearing abnormally.

Even if I chose a DI motor, the miles/hours it would see and the annual maintenance might add some cost, but I don't question the reliability of DI. In an aircraft setting you simply would have more maintenance to monitor then correct coking issues. You can boroscore the valves in a few minutes, but it would take YEARS for any significant build up at the typical number of hours an AC sees in a year.

#### Dan Thomas

##### Well-Known Member
In my aviation maintenance experience I always encountered much more trouble with magnetos than I did with aircraft fuel injection, whether it was Continental's or Lycoming's (RSA). As long as the fuel screens in the strainer and servo are being cleaned properly, and the airplane doesn't sit for years, and the system has been properly calibrated, they work well. But what do I find in strainers and screens? Junk. Stuff that hasn't been apart in a long time. Stuff out of calibration because someone didn't know what they were doing. Cheap, shortcut maintenance, and then we wonder why the system is unhappy. That applies to magnetos, too. Hours and years matter. A lot.

EFI requires an electrical system that won't let you down. Over on the Pilots of America forums, a common story is another electrical failure, often at night. Loss of Com and lighting. Gets ugly. And why? Usually because the alternator brushes were worn out, even though the manufacturer demands 500-hour internal inspections of that stuff. An airplane's alternator is belt or gear driven at a ratio that brings it close to its designed redline when the engine is at redline, same as a car's, so that airplane's alternator is spinning WAY faster than the one in your car that almost never gets anywhere near its redline and lasts a long, long time. Or the alternator wiring is being vibrated and flexed until it breaks, and the cheap shortcut annual inspections don't see it and fix it before it fails. The master and starter contactors are 40 years old and corroded and burnt. Stuff just doesn't get looked after. So how reliable would EFI be in that case? Not.

I worked on an SMA in a 182. Diesel with FADEC, mechanical injection. There was an emergency lever to pull that mechanically locked the throttle to the injector pump control to bypass the FADEC if it failed. The throttle otherwise just talked to the computer. It was necessary for certification. And any EFI in a certified airplane is going to have to meet the same requirement. Lycoming somehow managed it with their ie2 engine. Not cheap.

#### TFF

##### Well-Known Member
The original Vette fuelie is really just a pressure carb. We would call a pressure carb a mechanical throttle body injection today. Bendix RSA is essentially the pressure carb with injectors going to individual cylinders instead of throttle body. My favorite is Chrysler story was they had an electronic fuel injection in the 50s. Driving prototypes. Vacuum tubes. Over the railroad tracks, the tubes would discharge and shut it all down. Not quite ready for prime time.

Most problems are not the designs, it’s cutting cost. Most are attempting having stuff subcontracted. I was at a trade show and there was Chinese sales people trying to drum up business. The pitch I heard was for some aluminum forgings and machined. They said we can make100 to your 3 now. What would we do with the extras? They said throw them away. If they were equal quality it would be one thing. They were hoping 3 would be good in that 100. They were life and death parts.

On the other thread of hangar queen airplanes. It’s not the designs are bad. Sitting for 20 years with water in the tanks will pinhole the aluminum and rot out carbs. Not to mention if stuff like the floats are good. Mags tend to die because the plastic becomes brittle. Time and heat. Even a museum race car, you would not dig it out after 30 years of sitting and try and run 200 mph.

#### rv7charlie

##### Well-Known Member
I would suspect that aviation mechanical injection would still be miles ahead of automotive simply due to the annual condition inspections, mandatory ADs and overall higher level of maintenance required by law.

A car you drive it until it breaks. An airplane you take apart every so soften to look and see if something 'might' be wearing abnormally.
[snipped]
Your suspicion would be inaccurate. Ask those of us who have owned/flown/driven both. Bendix style injection can be 'better' (note the quotes) than an a/c carb, depending on your goals. But it never was, and never will be, anything close to modern automotive electronic injection, in any way except *possibly* the fact that it doesn't need electricity to operate.

'A car you drive it until it breaks. ' And, for all practical purposes, it never breaks. Yes, you can read about problems, but if you could get failure/miles or hours (years) of operation, the failure/problem rate would be incredibly small, compared to a/c mechanical injection.

'An airplane you take apart every so soften to look and see if something 'might' be wearing abnormally.' And you *need* to do that, because it's such a finicky, failure prone system. Multiple screens/filters scattered through it; injectors that are clog-prone and suck unfiltered cowl air into the intake with the fuel. In operation, it's highly dependent on the operator. While auto injection 'just works', the pilot must manipulate starting mixture with the boost pump, with different techniques for cold starts vs hot starts. The overall health of the engine is also highly dependent on the pilot's skill in managing the injection system, unlike a car.

Now, I do prefer Bendix style injection over a carb; my current RV6 is injected. With some work, cylinder to cylinder mixtures can be balanced for more efficient operation, but that's not the norm in an off-the shelf system. A car is much more likely to be close to perfect from new, and will likely remain that way for 10s of thousands of miles due to government regs on efficiency and pollution. You get no help from the FAA on those issues.

And that 'take apart every so often' thing can be, and often is, a huge negative, since if it wasn't broke before it was 'maintained', it may well be after.

FWIW,

Charlie

#### PMD

##### Well-Known Member
I would say it isn't bad fuel in my experience that gets the modern high end stuff. It's over complication.
I think you missed by (admittadly obique) slam at gasoline. It is not bad fuel (although, sometimes it IS) it is WRONG fuel. Gasoline is really a stupid fuel for an airplane (or a car, or a truck, or ESPECIALLY for a boat)

#### BJC

##### Well-Known Member
HBA Supporter
Gasoline is really a stupid fuel for an airplane
I think that you are conflating theory with current technology reality.

BJC

#### Jay Kempf

##### Curmudgeon in Training (CIT)
Gasoline is a by product. A solvent. I get it. When you get that light weight diesel designed and fly off 2000 hours I'll pay attention...:_)

#### PMD

##### Well-Known Member
Gasoline is a by product. A solvent. I get it. When you get that light weight diesel designed and fly off 2000 hours I'll pay attention...:_)
It is being worked on (there is a fair bit of accumulated running time). It isn't me, but being bound by ND agreements for one, and knowing the very public progress of two others, all I can say is hang in there, the future of really good aviation engines is just around the corner. I hate to take away from the work done by Frank Thielert, Christian Dies, SMA, Continental and now EPS, but all of those engines have one thing in common: they are WAY too heavy. Another is that their costs are still out of line (take a look at the FANTASTIC Soloy conversion of the 182 and sadly I have to ask "who is going to spend a quarter mil on top of the airplane to put that in their their hangar???"

#### TFF

##### Well-Known Member
The company that pulls it off wins. At least for the rest of the world. In the US, it will be a wash. A lot depends on where the crude comes from that it would be diesel, kerosene, gasoline in percentage of refined. US crude has more gas and than diesel. It’s why diesel costs more here. Multi fuel being able to handle kerosene and diesel wins everywhere else. Most Jet prices are subsidized by airline fuel usage. More demand from GA will make someone figure out how to make money on it.

#### proppastie

##### Well-Known Member
Log Member
the future of really good aviation engines is just around the corner.
lycoming has that new engine, I image it is kind of pricey,......with the low volume high engineering,tooling and certification costs, I would guess that new engine(s) you have been working on will not be cheap..

#### pfarber

##### Well-Known Member
HBA Supporter
Your suspicion would be inaccurate. Ask those of us who have owned/flown/driven both. Bendix style injection can be 'better' (note the quotes) than an a/c carb, depending on your goals. But it never was, and never will be, anything close to modern automotive electronic injection, in any way except *possibly* the fact that it doesn't need electricity to operate.

'A car you drive it until it breaks. ' And, for all practical purposes, it never breaks. Yes, you can read about problems, but if you could get failure/miles or hours (years) of operation, the failure/problem rate would be incredibly small, compared to a/c mechanical injection.

'An airplane you take apart every so soften to look and see if something 'might' be wearing abnormally.' And you *need* to do that, because it's such a finicky, failure prone system. Multiple screens/filters scattered through it; injectors that are clog-prone and suck unfiltered cowl air into the intake with the fuel. In operation, it's highly dependent on the operator. While auto injection 'just works', the pilot must manipulate starting mixture with the boost pump, with different techniques for cold starts vs hot starts. The overall health of the engine is also highly dependent on the pilot's skill in managing the injection system, unlike a car.

Now, I do prefer Bendix style injection over a carb; my current RV6 is injected. With some work, cylinder to cylinder mixtures can be balanced for more efficient operation, but that's not the norm in an off-the shelf system. A car is much more likely to be close to perfect from new, and will likely remain that way for 10s of thousands of miles due to government regs on efficiency and pollution. You get no help from the FAA on those issues.

And that 'take apart every so often' thing can be, and often is, a huge negative, since if it wasn't broke before it was 'maintained', it may well be after.

FWIW,

Charlie
You mixed mechanical AC with EFI in autos. I was comparing AC mechanical to auto mechanical. Most of the previous posts were about poor auto mechanical injection. If you read the entire thread you'll see the previous 6,8? posts were about auto mechanical injection. You kinda jumped in the middle of the conversation and went off on a tangent.

I have 99.9% faith in auto EFI (my first post).

And I agree with most of what you said, but there is a caveat. An automotive part is pretty much run to failure. You really don't rebuild anything so they can be made more reliabily so they work up until the point they don't. An aviation part is pretty much a core that is rebuilt at a fixed interval. Sure you could get a car starter rebuilt, but now a days its not worth it. Buy a new one. An AC starter is so expensive new that rebuilding is usually the economical way to do it. You can buy new, but I would think that most people would rebuild for a significantly lesser amount than new.

#### PMD

##### Well-Known Member
The company that pulls it off wins. At least for the rest of the world. In the US, it will be a wash. A lot depends on where the crude comes from that it would be diesel, kerosene, gasoline in percentage of refined. US crude has more gas and than diesel. It’s why diesel costs more here. Multi fuel being able to handle kerosene and diesel wins everywhere else. Most Jet prices are subsidized by airline fuel usage. More demand from GA will make someone figure out how to make money on it.
The straight run distillation assay values only matter if you have a topping plant or refinery with a very low Nelson Index. Modern refineries are much more complex and can balance product output to market demands by cracking, reforming and other reflux circuits. A replacement for LL100 could indeed make the US market a wash, but the difference in costs of making one very small volume, very specific product vs. the HUGE volume of diesel and jet fuel that pours out of refineries all over the world every day is quite significant.

#### PMD

##### Well-Known Member
lycoming has that new engine, I image it is kind of pricey,......with the low volume high engineering,tooling and certification costs, I would guess that new engine(s) you have been working on will not be cheap..
Using modern tech in a certified aviation engine is long, long overdue. IMHO, until we dump the army of ambulance chasers and insurance companies that suck the industry dry, it will be a dead end due to cost. Then, there is the fuel itself: gasoline engines don't work very well under high boost at high altitude, diesels take all of that in stride. All we need is a diesel that is light enough and cost effective (and Continental comes closest right now with their 265HP version of the SMA 305 - a great replacement for an O-540). Then there is the energy density, fuel safety, fuel cost, fuel availability and inherent fuel efficiency differences that all weigh heavily towards compression ignition of heavy distillate fuel.

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