Duramax diesel

Discussion in 'Chevy' started by Starman, Oct 26, 2009.

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  1. Jan 19, 2010 #41

    pepsi71ocean

    pepsi71ocean

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    Other answers in blue.


    I should also mention that rpm's don't necessary negate to HP with a diesel. You can run 3,000 rpm's and produce very little Horsepower.

    But as long as your not loading the diesel you also will not get any heat production or horsepower gain, simply because unlike a gas motor if you raise the rpm's up your mostly free wheeling off the motors ability to self ignite.

    For example, in the winter i can High idle my truck at 1,200RPM's all day long and not see the engine coolant warm up for anything, But switching to 3 cylinder High idle will put a load on the motor about 17% to be exact, that means the engine will warm up. With EB on and 3 cylinder high idle i can load up to 30% on the motor.

    Conversely, on 6 cylinder high idle, with 0-1% load i'll burn about 1 gallon an hour. but on 3 cylinder high idle i'll burn 2-2.5GPH, and with my Exhaust break on with 3 cylinder high idle a whopping 4.5GPH.

    This is all at 1,200RPM's, but as you can see the gallon usage went up considerably, as i increased the load on the motor.


    diesels are a different animal from gassers.
     
    Last edited: Jan 19, 2010
  2. Jan 19, 2010 #42

    Starman

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    Thank you for the explanation, Pepsi, that sounds more like it. I misread your earlier posts in a couple of ways and thought that the 1200 - 1350lb weight was what you were saying was for the Duramaxes, but I see it's for the Cummins.

    So they don't look so bad after all, the fuel consumption, while it will understandably be worse while under boost, must still be better than a gas engine putting out the same power. The remaining concern would be the fact that running it at 3000rpm for extended periods will wear it out fast due to oiling problems. I want to start with an engine that will take no internal work (until I win the lottery) so maybe the Duramaxes fall short in that regard, however, even wearing out 'faster' might still provide decades of flying before it needs a rebuild.

    It looks like the Cummins engine is just way too heavy and low on power to be useful in an airplane.

    You may be interested in knowing, since you like the Chrysler products, that when I was working at Chrysler running test engines that I worked with their carburetor expert and I was telling him that I thought the hemi design was unesthetic because it had that awkward valve arrangement with one rocker arm being 'backwards'. In answer he told me that they had gotten a hemi to spin at 11,000rpm. That was just in case GM ever developed anything to beat the hemis that were winning all the drag races, but GM never did.
     
  3. Jan 19, 2010 #43

    pepsi71ocean

    pepsi71ocean

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    You can get most diesel to get their rpm's up by increasign their valve spring weight, well atleast on a Cummins.

    I spend a few years as a mechanic, and ended up spending alot of time under my hood of my 5.9L and a few other of my friends trucks.

    2 F450's and 1 GMC 3500.



    Diesels are very reliable motors, and are also very complicated to learn and run, it doesn't take long to blow one up either.
     
  4. Jan 21, 2010 #44

    Starman

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    That's a lot of good info, thanks! I should explain more of what I had in mind. When I said I didn't want to rebuild the engine I meant the first engine. I want to throw a stock engine in there so I can go flying without having to wait to work on an engine first. Then later, after I start flying, I'll get another engine and take my time building it the way I want and then switch the engines. There should be no problem with a stock, slightly used engine hanging in there for several tens to a hundred hours hours of flying time.

    It is for a pusher design, and so the prop diameter needs to ba as small as possible, which means the engine needs to be running at or near redline to make best use of the smaller diameter. The original plan was to use a gas V8 and run it a little less than 4000rpm and use an approximately 60" diameter prop, direct drive. The redline for the duramaxes is 3200rpm, I think, and so how many hours do you think one would last at that spped without enlarging the oil runs? Do you think if the oiling problems were fixed that it would run a long time at redline?

    Even on a gas engine I wouldn't use a reduction gear because I don't make stuff that will break or need fixing, nor do a want to run a V8 at much more than 3500 for very long. Also, 'nothing' weighs and costs much less than a reduction gear.
     
  5. Jan 21, 2010 #45

    pepsi71ocean

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    The primary issue with running close to reline (for extended periods of time) is that without proper modification expect to see abnormal cylinder temps, overheated wrist pins, and pistons, or possible damage to the rings, any of which can cause that motor to throw rods, and seize up.

    Plus lets say you can get the motor to run at 3,200 non stop, the engines cylinder temps will rise until you melt or burn the injectors/pistons/ rings which can cause a runny injector which will then cause a piston to melt down and the you will blow holes through your pistons, scorch the walls and rings, drop valves eti.

    now im not saying this will happen but it CAN happen.

    Having worked on 3rd Gen Cummins with the HPCR's i know this can be an issue, ive scene it and often time the Dealerships confuse this with "dusting", which is a seperate issue all together. Its caused by abnormal temperatures no by dust particles slipping past the airfilter.
     
  6. Jan 21, 2010 #46

    Starman

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    Aren't you the one who had the threads about building direct drive V8, V10, V12s? I'll comment on other parts later but must get to work.
     
  7. Jan 22, 2010 #47

    pepsi71ocean

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    correct, i was replacing rpm for displacement.

    Developing 500 block Horsepower at say 3,300RPm's is quite different then the automotive engine that develops that same 500 HP at says 5,500rpm's.

    but yes ask away.:)
     
  8. Jan 22, 2010 #48

    wsimpso1

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    I can tell you a couple engines not to use. International engines as applied to Ford (Power Stroke) had numerous problems. We used to blow them up with regularity on transmission tests, and it read like a race program with too much rpm too. Bent crank, cam drive gear, low pressure oil pump, high pressure oil pump, head gaskets, anything gasketed to the block... My vibration plots showed a resonance that intercepted firing order near redline, which means that redline was set too high. International was making the horsepower number by letting it rev into some engine resonance, probably crank. Ugh. Perhaps their other customers (who used a lower redline) were wiser in accepting lower hp numbers...

    Can not speak for the other diesels... I can tell you that much of the complexity can be moved aside in an airplane application, but you would have to treat a diesel the same way you would treat a gas engine, and build your engine starting at the speed shop, as airplane engines do not operate like cars.

    These engines are all inherently common rail with EFI. Everything about them is built that way, so it might be a long task refitting them for mechanical fuel injection, and then you might give up quite a bit of power too.

    Redundency is important for aircraft use - Fuel pumps, filters, controllers, batteries and power busses would each exist in pairs.

    Think on the case of the fixed pitch prop: That prop will let the engine make 100% torque at one speed. Drop the speed, and torque that the prop can transmit will drop with the square of speed. So at 50% rpm, the most torque the prop can transfer (and thus the engine can make) is 25%, and at 50% speed, the power is 12.5%... In most airplanes, that is power level will not support level flight at any airspeed - you are descending. In a fixed pitch application, all of that hardware to get boost up at low rpm and giving you a flat torque curve from 1200 to 3300 rpm is simply not usable.

    For a constant speed prop, it does get more capable at lower rpm. Even if your engine can output 90-100% torque from 50% to 100% rpm and your prop can apply it as thrust, that means that you can cruise at 45% power. And everything that is added to the engine to get big torque below 50% rpm is still wasted unless you like flying at max loiter speed.

    So, toss the EGR hardware (not needed for aircraft use and there is a bunch of it on these guys), toss the powersteering pump and the AC compressor, toss the sensors that the speed shop guys would toss and the aftermarket controller doesn't need, and replace the induction manifolds and variable turbocharger set up with a straight conventional single or pair sized for your preferred operating speed range, airflow and boost, and duct the air you are compressiong to intercoolers that are placed in properly shaped ducts somewhere else in the airplane. Oh, since they will be properly fed with air at higher speed, they can probably be lighter and more compact airplane hardware too. While you are at it, I would bet that there are other go fast goodies that will take weight out of the engine without compromising reliability.

    In the end, I bet that you could simplify that complex engine quite a bit and end up with a doable 300 hp airplane engine.

    Now on the topic of jet fuel, the jet fuel diesel folks are all recommending lube additives for jet fuel to make their pumps live. Hmmm. I suspect that we have a way to make the common rail pumps live with jet fuel.

    You still have a LOT of engineering to do to make a truck engine into an airplane engine, but I would have to bet that a good performance diesel shop could get you most of the way there...

    Billski
     
    Streffpilot and Detego like this.
  9. Jan 22, 2010 #49

    pepsi71ocean

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    Very interesting view my friend!
     
  10. Jan 23, 2010 #50

    Starman

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    Yes, but car engines have displacement already, and I don't need 500hp. In order to not derail this thread check out another thread I started http://www.homebuiltairplanes.com/f...sion-discussion/6385-future-direct-drive.html and follow up there if you wish, I'm going to start in again on that one.

    In that thread be sure to watch the video in this post #13 http://www.homebuiltairplanes.com/forums/54438-post13.html
     
  11. Jan 23, 2010 #51

    Starman

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    Someone in this thread earlier said it would be a huge amount of work to make that switch and the power would be much lower due to it. It seems to me that it would be easy to make all parts of the injection system dual except probably the injectors themselves, but injectors will only fail one at a time, not all of them at once, and the crankshafts are so much stronger than aircraft engine crankshafts that having one cylinder out due to a non functioning injector won't break them at moderate power. Other than that you can have two entirely separate and complete electronic injection systems, just like with dual ignition systems, and switch back and forth between them. I don't see a problem doing that.
     
    Last edited: Jan 23, 2010
  12. Jan 23, 2010 #52

    wsimpso1

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    A constant speed prop has more usable rpm range, but then the project takes on added cost and complexity. Always a tradeoff...

    For any prop, you will need a front end with a prop bearing and oil flow in it (prop moments due to P factor and gyroscopics can be way too much for crank flange and last main bearing). For the common hydraulic CS props, you will need to build in a drive and pad for a prop governor, an oil supply and paths to the prop itself, plus connect the prop governor to the front end. If using an electric CS prop, it is simpler, as the you only need to add the mounts for the brushes.

    It all depends upon the priorities of the folks doing the work.

    Billski
     
  13. Jan 23, 2010 #53

    pepsi71ocean

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    Im going to say this again, HPCR's have nothing over mechanical injection. Look into the P-7100 pumped 12v cummins.
     
  14. Jan 23, 2010 #54

    pepsi71ocean

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    Yes, but look into my thread about it, there is a volume of information in there that details why the need for PRSU's even on engines with redlines at 3,300RPM.
     
  15. Jan 24, 2010 #55

    pepsi71ocean

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    While shifting though my paperwork i found this.

    For the "inline" P7100 pump ('94 to 98.5 12 Valve engines). P7100 pumps are internally lubricated by engine oil. These fuels are "OK": #1 & #2 Diesel, 1K & 2K Kerosene, Jet-A, Jet A-1, JP-5, and JP-8.
    NOT OK under any circumstances: Jet-B, JP-4, and Cite

    So yes the P7100 can run on Jet fuel.
     
  16. Jul 3, 2012 #56

    Fauteux

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    Right this is one of our chalenge in our project
    we plan to use the same variable prop front end bearing than the lycoming tio540
    direct drive the 2011 duramax deliver 350 hp. At 2600 rpm for take off that is more than the 310 hp
    in our navajo
    2200 rpm in cruise give much more hp than required for our project cessna 207
    Weight of duramax as remove from truck is 1000 pouds
    we are working to reduce weight by removing egr. And. Ure system
    Replace the one big turbo by two smaller one
    but still we will be 500 pound heavier. Thanks to cessna 207 gross weight
    we count on the better efficiency of this fantastic engine
    we hope for 50 litre of jeta1 per hour at 150 knots
    Guy
     
  17. Nov 26, 2012 #57

    T-51ls1

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    i'd love to use a diesel but you realize you cant run one at 3k rpm for more then a couple mins right? they are designed to run around 2k constant and will break pretty easily if you push them that hard without reinforcing the heads. they do have alot of torque and can make good hp but duramax's become unrelaible quick when you add more power above 450 fly wheel hp. i'm a diesel mechanic and i've worked with duramax's they are great in trucks but i dont think it would do well in the air.
     

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