Lets talk about diesels.

Discussion in 'Firewall Forward / Props / Fuel system' started by Terrh, Oct 17, 2019.

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  1. Oct 27, 2019 #61

    poormansairforce

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    One thing to bear in mind, and this does apply to airplanes, that in a heavy load situation oil weight/bearing clearances come into play since we need to move the oil through the bearing to remove heat created by the pressure/surface speed. The oil you use in your boat/airplane is probably going to be different than in your car.
     
  2. Oct 27, 2019 #62

    Dan Thomas

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    They often don't. Thermostats get clogged with sand and other debris like small seaweed.
     
  3. Oct 27, 2019 #63

    akwrencher

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    I have not seen an outboard motor built in the last 50 years that does not have a thermostat. Not saying people don't take them out on occasion, bbu the vast majority don't. Fuel economy goes to crap. This reminds me of when I was in my early 20s. Had a 4-53 Detroit in my first boat. Everyone "knew" that Jimmy's wouldn't warm up unless you ran them hard. Being the hard headed guy I am, I bought a new therm anyway. Surprise, it warmed up to therm temp at idle. Any engine will run "cold" when not under load......if you are talking egr's, which is what got mis interpreted into detroits running "cold". Any remotely modern engine will have a thermostat to control it's temp, if it's water cooled. Using the ocean for a radiator has no bearing on the temp of the engine. People removing thermostats in niche areas has no bearing on marine engine use or design in general. This is basic stuff, no mysteries. Boat engines wear out based on hours of use at percentage of power level and based on quality of engine design, installation, and maintenance, just like any other application.

    /Rant over/ :D
     
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  4. Oct 28, 2019 #64

    Rik-

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    Exactly how many outboards are used in automotive applications?
     
  5. Oct 28, 2019 #65

    akwrencher

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    None. That's not the point. Inboard outboard engines are the ones that came over from cars. They usually have heat exchangers as I noted above. Even if they don't they still have thermostats, which is what sets the operating temp, not the vastness of the ocean.
     
  6. Oct 28, 2019 #66

    Rik-

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    Your making my point aren’t you. Car motors are not the same as boat motor. Yes, same block configuration but totally different configuration and build. Everyone cries that an aircraft engine is different but you can just throw a car engine into a boat and be dumb, fat and happy.
     
  7. Oct 28, 2019 #67

    Voidhawk9

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    You'll find a heat exchanger in every car you drive as well. More often called a 'radiator' where I'm from.
     
  8. Oct 28, 2019 #68

    Rik-

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    You’ve figured it out, I can see a bright and prosperous future in the boat business for you.
     
  9. Oct 28, 2019 #69

    Dan Thomas

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    My old 283 was a straight-shaft inboard setup, driving the prop through a Borg-Warner Velvet-Drive hydraulic transmission. The cooling water came in through a small grated scoop in the bottom of the boat, and ran through 3/4" hose to the transmission oil cooler and from there to the positive-displacement marine water pump, divided into two lines and went through the exhaust manifold jackets before it was re-joined and went into the engine block at the former water-pump location through an adapter plate. Then it came out of the engine at the thermostat housing and divided again and went into the exhaust streams just aft of the manifolds and was blown out with the exhaust and kept the exhaust pipes relatively cool under the floorboards. No air cooling of exhaust in a boat like that.

    With all that preheating through the oil cooler and manifolds, the water wasn't stone-cold anymore when it went into the engine and the engine ran just fine at whatever power levels I demanded of it. The only problem I had was the one-mile-per-gallon fuel consumption at full throttle, redline RPM. Rochester four-barrel carb with huge secondaries. The engine-driven fuel pump could only pump about 99.9% of the required volume at full throttle and the engine would start to stumble after a minute or so. Didn't matter, since I couldn't afford full throttle for too long anyway.
     
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  10. Oct 28, 2019 #70

    Markproa

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    Agree with all of that and my point was that diesels are not the very heavy clunkers they used to be. My engine weighs 107kg with turbo and inter cooler included and produces 103hp which is not so different to an 0-200. Difference being it will sip about 10 litres per hour.
     
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  11. Oct 29, 2019 #71

    Rik-

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    Which engine are you using?
     
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  12. Oct 29, 2019 #72

    cheapracer

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    i think that's on the borderline, but an acceptable power to weight for a diesel, well done.

    It is of course still around 20% away from what can be done with petrol in weight or HP, all a balancing act of what your expectations are.
     
  13. Oct 29, 2019 #73

    PMD

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    Not exactly mainstream, but over in the world of road racing, a class called "D/SR" was once the race car equivalent of the aircraft homebuilt movement. Outboard engines were very popular "way back when" and very successful. That class today is far more like the kit plane biz and is dominated by litre bike 4 cycle engines (that conveniently contain a nice close ratio dog box).
     
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  14. Nov 15, 2019 #74

    PMD

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    OH...I should have mentioned: an entire line of diesel outboards (OXE in Italy) are based on a GM car engine (2.0 diesel at 125, 150, 175 and 200 HP) and are about to release a 250 and 300HP line of outboards based on the 3.0 litre BMTrouble-you diesel. So, I guess you could say those "outboards" are indeed used in automotive applications. COX claims that their 4.something litre 300HP V8 is designed in house, but from what I have learned about their lack of transparency, I strongly suspect it is a modified automotive design as well.

    Over in the spark ignition world (who cares?????) 7 marines 600HP outboards use a barely modified GM LSx engine
     
  15. Nov 17, 2019 #75

    SouthySuper

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    The current research in heavy fuel rotary engines for aviation is quite impressive. I’m currently working on a firewall kit for a 13b, mine is petrol not diesel. A few months back I was at a private airshow and meet. I’ll find the chap’s name in a bit, but the coolest thing I’ve seen in a while was a 20b 3 rotor converted to run diesel with spark assist. I think they were using synthetic oil for lubrication and the greasy diesel was enough for the apex seals. I did not get more than a few questions in because the translator had the trots. It was an impressive kit. German fellow thought up the whole idea.
     
  16. Nov 18, 2019 #76

    Markproa

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    Peugeot DV6, the plane is a Gazaile 2 though still building.
     
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  17. Nov 18, 2019 #77

    cheapracer

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    Yeah, that PSA/Ford diesel, that gets good write ups for reliability ect. (car mags), appears to be used in a few light planes in Europe, seems to be an exception to the rule when it comes to power and weight for a diesel.

    Hope it works out for you.
     
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  18. Nov 19, 2019 #78

    Rik-

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    Good, looking forward to seeing how it performs
     
  19. Nov 19, 2019 #79

    PMD

    PMD

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    Sorry to be weeks/months behind on this thread. Have been on emergency callouts and travelling for last several weeks, so very little chance to post.

    To begin with, as has already been posted, the GM 5.7 was NOT just diesel heads on a gasser block. Yes, it shared the architecture (dimensions, such as bore centers, bolt patterns, etc. to use existing production tooling) with the Olds 350, but nothing else. I should point out, though, that the most successful diesel engine in history BY FAR (VW 4 cyl) WAS very much a gasser block with few differences and diesel head stuck on top. ALL of these '70s/'80s engines were a dead end sidetrip into pre-chambers and indirect injection that resulted in fairly good efficiency, but not much power. Going back to direct injection (allowed by better materials to deal with the extreme fuel pressures at the injector nozzle) solved all of that big time, and common rail solved the last restriction on power (i.e. timing accuracy due to air in fuel at lower pressures).

    Your point about SMA, though, is spot on. It is EXTEMELY difficult to go from clean sheet of paper to aerodiesel. I THINK (read hope in capital letters!!!) EPS has this sorted out on their design, and suspect Continental has had a pretty good run at it with the 305 redux. The water cooling points are also quite well taken. One of the really big issues with the SMA design was that it was totally unsuitable for a multi engine installation since you didn't have a hope in hell of restarting it if you had a shut down at normal medium altitude and/or winter temps. BUT: modern common rail engines simply don't have that restriction - or easily get around it with a tiny bit of glow plug time. I have started our old VE pump VW TDI at -42C without any preheat, and our common rail V6 TDI around the same range with ease (don't LIKE doing that, but sometimes you gotta do what you gotta do).

    As a certifiable diesel freak, I can tell you that pretty much ALL of the normal limitations of aviation diesels (weight particularly) are easily addressed by building a common rail opposed piston engine (i.e. variations of modernized Jumo 205)
     
    Last edited: Nov 19, 2019
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  20. Nov 19, 2019 #80

    Rik-

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    You’ve gotta admit it was a real POS.
     

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