Just for discussion, Mechanical fuel injection?

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Bill-Higdon

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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).
I found the CIS on VW & Volvoe easy to work on with a good pressure gauge and adapters. How ever I HATE the LJet on the 74 seires Volvos. I had one no one could fix after some "creative repairs" done to it just beofore it was given to a new exwife in a divorce
 

PMD

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I found the CIS on VW & Volvoe easy to work on with a good pressure gauge and adapters. How ever I HATE the LJet on the 74 seires Volvos. I had one no one could fix after some "creative repairs" done to it just beofore it was given to a new exwife in a divorce
As if just giving her the LJet wasn't revenge enough!
 

Dan Thomas

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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.
And that's fast disappearing. I haven't seen a new Prestolite starter for a Continental or Lyc for a long time. Overhaul costs are up. Continental has a version of their own for the large engines. Skytec and Lamar and B&C have been producing affordable permanent-magnet starters for quite a while now. They crank a lot better for less current, since there are no field coils to be energized. Their brushes and commutators last to engine TBO, then they're tossed out. The Prestolites needed regular brush inspections and, depending on types of service, occasional brush replacements.

Same goes for vacuum pumps. And if you buy a factory reman engine, it will come with new mags, since the manufacturer can buy them for less than it costs them to overhaul them. Carb or injection might be new, too. Aviation is slowly making its way through the same process everything else has already; it's just slower because the market is so small. When I was a kid there were radio and TV repair shops everywhere. There were appliance repair shops. Shoe repair shops. Watch and clock repair shops. Rising labor costs, accompanied by automation, opened a market for throwaway stuff. If you have an issue with your Garmin radio or MFD you pop it back to them via FedEx and you get back a unit with the same serial number on it, but it's an entirely new device. Not worth their time to try to repair microelectronics encapsulated in epoxy. A reasonable flat fee for the "repair" service. I think much of the up-front purchase cost funds that.
 

Dan Thomas

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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.
When I worked on that SMA, there was a lower temperature limit for operating it. We couldn't use it at the winter temps we could run the Lycomings and Continentals. I can't remember the specific temperature limit, but it seemed really unreasonable. Maybe the 15:1 compression ratio was insufficient. It was boosted, too.
The Nazis had a few diesel-powered airplanes in WW2. IIRC they had some issues at altitude. Boosting and compressing air works for compression ignition when there's enough latent heat in it, but when it's really cold? Jets don't have that problem, as the combustion is continuous.
 

PMD

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When I worked on that SMA, there was a lower temperature limit for operating it. We couldn't use it at the winter temps we could run the Lycomings and Continentals. I can't remember the specific temperature limit, but it seemed really unreasonable. Maybe the 15:1 compression ratio was insufficient. It was boosted, too.
The Nazis had a few diesel-powered airplanes in WW2. IIRC they had some issues at altitude. Boosting and compressing air works for compression ignition when there's enough latent heat in it, but when it's really cold? Jets don't have that problem, as the combustion is continuous.
The SMA engine's big problem was that it simply wouldn't start at low temperatures. There was an effort to STC a pair into Pa34 but you can imagine what the FAA would have said when the POH supplement mentioned that once you feathered one, it could only be re-started on a nice warm day. 15:1 is very low for a modern diesel, and the Junkers engines were 17:1. Yes, CR plays into that but the other HUGE player is injection pressure. You might have noticed how well a modern HPCR diesel pickup will light right off at -40, and the reason is the injection pressure is very high, thus fuel atomisation extremely fine and thus a very easy start. Continental has had a good run at the SMA 305 and their version CD-265 seems to have managed to be certifiable and startable at 15:1. Not sure what problems were encountered at altitude, but worth noting that the 205 engines had a service ceiling of 41,000' - far higher than anything that might have wanted to shoot them down, and the later 207 with turbocharger made its full 1,000 HP right up to 20,000 feet. One of the many, MANY advantages of diesels is they work far better at altitude then do gassers (SI) and are far, far more fuel efficient even at very high altitudes than jets.
 

TFF

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L jet never has given me trouble. Mine are on Alfa’s. Not much latitude for adjustments. The worst is the injection that used the distributor points VW and Mercedes. Now with better sensors like using Hall effect it works much better.
 

Hephaestus

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You might have noticed how well a modern HPCR diesel pickup will light right off at -40,
:oops: :popcorn: Um Bold statement :)

My work was at a oilsands site... Inside the Arctic circle...

We had a sweet spot for diesels in the late 90s-2010ish range (probably closer to 08). If the batteries and glowplugs were good. If the block and battery heaters were plugged in, you were good to -35ish.

It's been a definite decline since then... Diesels all get the webasto treatment now and it's still inadequate in many cases.
 

PMD

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:oops: :popcorn: Um Bold statement :)

My work was at a oilsands site... Inside the Arctic circle...

We had a sweet spot for diesels in the late 90s-2010ish range (probably closer to 08). If the batteries and glowplugs were good. If the block and battery heaters were plugged in, you were good to -35ish.

It's been a definite decline since then... Diesels all get the webasto treatment now and it's still inadequate in many cases.
I am in the bananna belt now, where it only gets to -40C but my last home was at my business where I was the coldest VW dealership on the planet (YTH, we also had AMC/Jeep). I still work up there and over near Yellowknife (warmer than YTH) on occasion, where we consider a January trip to Ft. Mac a break from REALLY cold winter conditions. I agree that oil sands have had diesel issues, but most of those were because of the dominance of Ford vehicles (who NEVER seem to get a diesel right or tell the truth). I was involved in solving 7.3 design screwups and watched the development of the severe service air cleaners (Donaldson) due 100% to the failure rate in oil sands market. Today, I have a lot of diesels around, and find that Cummins pickups and most VW/Audi diesels with decent batteries will go without ANY aux heat at -40 all of the time and the worst of them -30 (have NO block heater in wife's Q7 TDI and put battery maintainer on at -30C). Only have a couple of DMax around so can't comment on them overall. Not Weebastard...er...uh...WEBASTO but Eberspacher (ESPAR) heaters for me for standalone and 1 kW block heaters for plug-in support along with proper battery warming (silicone pads under batteries) and decent full synth oil take all of the risk and drama out of cold starts anywhere, any time. Having done this with both vehicles and aircraft in extremely cold conditions, all I can say is the newest diesels are almost as good as the best gassers IF you pay close attention to a number of maintenance things that are not that important for normal weather conditions - and that applies to both fuel engines. My experience is that while SOME people actually do this right, MOST miss some of the most important details and have no starts. Won't even suggest any such liberties with my older 4 cycle OR 2 cycle Mitsus and Detroits!!

Still, I very much agree that since '08 when DPF and SCR became dominant ways of dealing with emissions, things are not as good as they were. For our purposes: keep in mind aircraft have no such problems as those emission addons are not required. Also, give the diesel manufacturers a break by remembering how horrible gassers were in their earlier emission compliance days (diesel about 20 years behind in that cycle).
 
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Flyguyeddy

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For those of you who dont like the CIS-E units, you can “lobotomize” them and run a simple variable current module to adjust mixture. Then the Warm-up regulator is essentially removed from the system, as you dont need it with CIS-E and use a frequency valve or primer valve to prime the thing
 

Bill-Higdon

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For those of you who dont like the CIS-E units, you can “lobotomize” them and run a simple variable current module to adjust mixture. Then the Warm-up regulator is essentially removed from the system, as you dont need it with CIS-E and use a frequency valve or primer valve to prime the thing
Thought of that more than a few times
 

Bill-Higdon

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L jet never has given me trouble. Mine are on Alfa’s. Not much latitude for adjustments. The worst is the injection that used the distributor points VW and Mercedes. Now with better sensors like using Hall effect it works much better.
IF your talking about the one that came on the aircooled VW's they were a analog system complete with intermitent Ground Loops that would cause you to drink heavily, Take Odins name in vain & must have been designed by Joe Lucas
 

TFF

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My uncle had one on a VW and a friend had one on a early Mercedes 450SLC. My jag XJS is much better. Only problem with those are about a dozen sensors and rusty fuel tanks. My sons old Mercedes wagon CIS E would always blow this one **** relay killing the fuel pump circuit.
 

PMD

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IF your talking about the one that came on the aircooled VW's they were a analog system complete with intermitent Ground Loops that would cause you to drink heavily, Take Odins name in vain & must have been designed by Joe Lucas
The first D Jetronic stuff was also EXTREMELY sensitive to grounding and had a bunch of them. They also had a massive (but simple) computer that every dumbass "mechanic" would order a replacement for when he (there were no "shes" in VWC shops in those days) every time they couldn't properly diagnose a problem. We had to buy a big VW diagnositic "thing" that was essentially a fancy VOM and CRT oscilloscope that plugged into a dedicated plug (started somewhere around 1968 IIRC) under the back seat...LONG before OBD I came to be. It really didn't give a lot of information, but was the portent of things to come. The computer, though, was another thing. No data out for faults, just looking at everything else on the car to eliminate sensors/power/ground errors. The extra points in the distributor were not that big a deal, as you could easily meter them out to know they worked. I trained under a uber-great mechanic from RSA, and if we had a genuine computer failure, we would open the box and find the bad track or device for cars off of warranty, then go to Radio shack and buy a replacement resistor or capacitor (never had to replace a diode or transistor). Under warranty, if you returned a computer that was NOT actually bad, the dealer got it back and the warranty claim was denied.
 
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