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Interesting mechanical engineering tidbit

  1. #1
    Dictionary quoting knob stoinkythepig's Avatar
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    Interesting mechanical engineering tidbit


    I bought a boat with CAT 3208 diesel V8 engines and have been doing a lot of research to learn everything I can about them so that I will be able to maintain and repair the the engines myself. These are old fashioned, purely mechanical, fuel injected engines and I discovered that the fuel injection pump was really cool. It's basically a V8 piston pump that nestles in the middle of the V8 engine and looks like a miniature V8 engine. Each of the 8 pump pistons pushes fuel to the injector for the corresponding cylinder on the engine. I just thought it was clever and figured there were folks here that would like it. It's very different than the rotary piston pumps I'm used to on automotive diesels.

    Interesting mechanical engineering tidbit-l1600-jpg

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    Last edited by stoinkythepig; 05-01-19 at 12:54 PM.

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    Lifer Garandman's Avatar
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    Re: Interesting mechanical engineering tidbit



    Diesels are cool. The M60A3 tanks we had were 1,790 cig twin turbocharged V12’s That were air/oil cooled. 34 gallons of oil. Currently we only own a Kubota 1.5L and the MB turbocharged 2.7L five.

    What is the rpm range for the 3208?

    Caterpillar 3208 engines: not a throwaway

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    Last edited by Garandman; 05-01-19 at 08:23 AM.
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    TWINS! xrocket21's Avatar
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    Re: Interesting mechanical engineering tidbit

    that is very cool! Thanks for sharing. These motors use tech i didnt even know was out there.

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    Lifer ZX-12R's Avatar
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    Re: Interesting mechanical engineering tidbit

    It looks like a dual cam LS engine!

    As I look at it more, how is the actual volume of fuel controlled? Is the stroke of the fuel pump pistons adjustable?

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    Dictionary quoting knob stoinkythepig's Avatar
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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by Garandman View Post


    Diesels are cool. The M60A3 tanks we had were 1,790 cig twin turbocharged V12’s That were air/oil cooled. 34 gallons of oil. Currently we only own a Kubota 1.5L and the MB turbocharged 2.7L five.

    What is the rpm range for the 3208?

    Caterpillar 3208 engines: not a throwaway
    Mine are 375 HP versions that top out at 2800 RPM. The lower HP versions typically top out at lower RPM (and typically last longer). They made them up to 435 HP, but those were typically installed in sport fish boats, and run hard, so 3000 hours between rebuilds is typical. I'm hoping mine will last for 6000+ hours. They only have 1600 hours now.

    The boat came with an Onan Cummins 8000 watt diesel generator that happens to have a 3 cylinder Kubota engine. It runs at 1800 RPM and should last forever.

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    Last edited by stoinkythepig; 05-01-19 at 08:59 AM.

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    Backwoods lobster boy number9's Avatar
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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by stoinkythepig View Post
    It's basically a V8 piston pump that nestles in the middle of V8 engine and looks like a miniature V8 engine.
    Enjoy

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    Lifer Falko's Avatar
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    Re: Interesting mechanical engineering tidbit

    Most of these big diesels were built for longevity and reliability and not to some price point. I remember going to a farm show and seeing some 350hp tractors. The engines were absolutely massive, so much different than you'd expect for that hp rating. Definitely built for the long haul.
    1600 hours on those means they are babies. That should be an awesome boat for your plans, Stoinks.

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    Dictionary quoting knob stoinkythepig's Avatar
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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by ZX-12R View Post
    It looks like a dual cam LS engine!

    As I look at it more, how is the actual volume of fuel controlled? Is the stroke of the fuel pump pistons adjustable?
    My understanding is that the volume out each piston of the pump, per stroke, is fixed; the "throttle" is just a set of ganged bypass valves that control the amount of fuel that is returned to the tank rather than sent to the injector. More throttle just means less fuel returned to the tank and thus, more sent to the injector and more power. It's pretty clever since a purely mechanical, variable-volume, positive-displacement pump would be really complex and challenging to design for long service life.

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    Dictionary quoting knob stoinkythepig's Avatar
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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by Falko View Post
    Most of these big diesels were built for longevity and reliability and not to some price point. I remember going to a farm show and seeing some 350hp tractors. The engines were absolutely massive, so much different than you'd expect for that hp rating. Definitely built for the long haul.
    1600 hours on those means they are babies. That should be an awesome boat for your plans, Stoinks.
    Kinda funny you mention that, some diesel guys think these are "throw away" engines because they don't have cylinder liners. When you rebuild, you bore them .020" over the first time, .040" over the second time, then sleeve them for every rebuild after that. The reason CAT went this way was specifically to build them to a price point, from what I've read. They have a stellar reputation in the marine world.

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by Falko View Post
    Most of these big diesels were built for longevity and reliability and not to some price point. ////
    We researched Yanmar marine diesels, which are considered light and high rpm in the marine world. Most people were going 3-4,000 hours between rebuilds, and some were as high as 7,000.

    All those fishing boats in “The Perfect Storm” have one diesel and run for weeks straight.

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by Garandman View Post
    We researched Yanmar marine diesels, which are considered light and high rpm in the marine world. Most people were going 3-4,000 hours between rebuilds, and some were as high as 7,000.

    All those fishing boats in “The Perfect Storm” have one diesel and run for weeks straight.
    The fishing boats used John Deere/Lugger engines, for the most part. Supposed to go 20,000 hours between rebuilds. Very over-built and lightly stressed in the HP rating they use for commercial applications. You typically just run them at full throttle all the time.

    I think a lot of Yanmars are based on automotive diesels, pretty sure they use the BMW IL6 diesel for their bigger engines. I don't think they make any heavy duty commercial engines. 6000 hours would be like 200,000 miles of run time in a car.

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    Last edited by stoinkythepig; 05-01-19 at 12:33 PM.

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by stoinkythepig View Post
    Kinda funny you mention that, some diesel guys think these are "throw away" engines because they don't have cylinder liners. When you rebuild, you bore them .020" over the first time, .040" over the second time, then sleeve them for every rebuild after that. The reason CAT went this way was specifically to build them to a price point, from what I've read. They have a stellar reputation in the marine world.
    Interesting. I thought these would be more along the lines of industrial designs. We've been doing a few systems with CAT engines lately and they are pretty robust. Maybe too robust and weighty for the pleasure boat market?

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by Falko View Post
    Maybe too robust and weighty for the pleasure boat market?
    Depends if you value outright speed vs longevity and lower total costs I guess.

    I did find the different TBOs depending on service use interesting. I cant imagine a lot of boats those motors are in operate under continuous load for long.

    Even the fishing boats are constantly in and out of gear all the time.

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by stoinkythepig View Post
    My understanding is that the volume out each piston of the pump, per stroke, is fixed;
    I wanted to know why so I went searching. The engine uses a sleeve metering fuel system. Basically there is a fixed volume plunger that has an inlet and outlet port in it with an adjustable sleeve that covers the outlet. When in the fully lowered position, the fill port is exposed and the fuel transfer pump pushes fuel into the plunger. As the cam pushes the plunger up, the inlet is sealed off and fuel gets pushed out the top which is connected by lines to the injector. As the plunger moves upward, eventually the fuel outlet port is uncovered (from the sleeve) and fuel exits the plunger there instead of out the top to the injector. By controlling the height of the sleeve, you control the amount of fuel that is pushed into the engine.


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    Last edited by ZX-12R; 05-01-19 at 02:53 PM.
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    Dictionary quoting knob stoinkythepig's Avatar
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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by ZX-12R View Post
    I wanted to know why so I went searching. The engine uses a sleeve metering fuel system. Basically there is a fixed volume plunger that has an inlet and outlet port in it with an adjustable sleeve that covers the outlet. When in the fully lowered position, the fill port is exposed and the fuel transfer pump pushes fuel into the plunger. As the cam pushes the plunger up, the inlet is sealed off and fuel gets pushed out the top which is connected by lines to the injector. As the plunger moves upward, eventually the fuel outlet port is uncovered (from the sleeve) and fuel exits the plunger there instead of out the top to the injector. By controlling the height of the sleeve, you control the amount of fuel that is pushed into the engine.

    That's not at all how it was explained to me, but clearly right. Thanks!

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    Lifer ZX-12R's Avatar
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    Re: Interesting mechanical engineering tidbit

    I got most of my info from this manual for the vehicular version of the 3208.

    http://www.numeralkod.com/cross/arch...enr2764-01.pdf

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by ZX-12R View Post
    I got most of my info from this manual for the vehicular version of the 3208.

    http://www.numeralkod.com/cross/arch...enr2764-01.pdf
    Thanks, that's excellent; I just learned a ton from that (still waiting for my factory service manual to arrive). For instance, I had no idea the fuel injection volume varies relative to the boost for a given throttle setting, I just assumed it was controlled solely by the throttle setting like a normally aspirated diesel.

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    Re: Interesting mechanical engineering tidbit

    I grew up rebuilding Cat 3406s and Cummins BigCam 3s.

    Not only do you need to time the engine properly, you also need to time the fuel pump properly.

    We were running 425-450 HP on the 3406s. We'd expect to do a rebuild about every 200,000 miles.

    We got to a point where we could do a frame in rebuild (pistons, liners, bearings, injectors (technically injection pumps) and all of the seals/gaskets) with 2 people in about 6 hours. If we had to replace the valves, and could find a 3rd person to run the head, that could also be done in the same 6 hours, just add a person.

    Beautiful pieces of machinery.

    Assuming this is as similar to the 3406 as I expect, that fuel air ratio valve you want set right under where it's making a ton of black smoke, generally.

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    Last edited by jasnmar; 05-02-19 at 11:24 PM.

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by jasnmar View Post
    I grew up rebuilding Cat 3406s and Cummins BigCam 3s.

    Not only do you need to time the engine properly, you also need to time the fuel pump properly.

    We were running 425-450 HP on the 3406s. We'd expect to do a rebuild about every 200,000 miles.
    How long did it take to go 200K and how many times would you rebuild thrm?

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by jasnmar View Post

    Assuming this is as similar to the 3406 as I expect, that fuel air ratio valve you want set right under where it's making a ton of black smoke, generally.
    I think the 3208 is quite different than the 3406

    3406: 14+ liter lowish RPM (2100 max) inline 6 with sleeved cylinders and low power relative to its displacement. Guessing it's used in big rigs.

    3208: 10.4 liter moderate RPM (2800 max) V8 without sleeved cylinders and moderate power for its displacement. Commonly used in garbage trucks, excavators, and dump trucks.

    Both engines are used in boats and both have similar HP ratings, but the 3406 weighs 1.5 to nearly 2 times as much and likely lasts twice as long. Guessing there are not many 3406s in non-commercial boats, it's a really rugged engine that would be a waste in most pleasure craft.

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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by Garandman View Post
    How long did it take to go 200K and how many times would you rebuild thrm?
    Generally less than a year and a half, but if we had one that was going to be in the shop for other significant maintenance we'd likely go ahead and rebuild if it was 150k+. I didn't actually track this, I was told when, so the numbers are a bit anecdotal.
    On average drivers were capable of about 50 MPH (this included all "on duty" time, not just driving).
    With a 60 hour / 7 day week (this was 30 years ago, so no electronic log books, so there was some fudging) you get 3000 miles / week. So math is easy figure 50 weeks per year (we wouldn't get that, but we'd target north of 45) you're at 150k / year.

    If the cam / crank got out of spec we'd send the truck off to Cat or Cummins for a rebuild. We weren't really set up for frame out rebuilds or for getting cranks out in frame.

    We never 'retired' an engine block and replaced it. I do remember a couple of time replacing heads, but even in those cases there was a core charge for the head, so I assume they got reused?

    Quote Originally Posted by stoinkythepig View Post
    I think the 3208 is quite different than the 3406

    3406: 14+ liter lowish RPM (2100 max) inline 6 with sleeved cylinders and low power relative to its displacement. Guessing it's used in big rigs.

    3208: 10.4 liter moderate RPM (2800 max) V8 without sleeved cylinders and moderate power for its displacement. Commonly used in garbage trucks, excavators, and dump trucks.

    Both engines are used in boats and both have similar HP ratings, but the 3406 weighs 1.5 to nearly 2 times as much and likely lasts twice as long. Guessing there are not many 3406s in non-commercial boats, it's a really rugged engine that would be a waste in most pleasure craft.
    Yeah, Over the road trucks was the primary application I saw the 3406 in.

    The difference you point out in the 32 vs 34 for weight, rpm, hp are valid. The V vs. I thing, for Caterpillar is way less important than you probably think. I did have a couple opportunities to be around some of the cat V blocks (a couple years ago I got to tinker around in a 3412 rebuild) and the V config, for all intents and purposes are a new casting around the crank with 2 "I" engines in it. Heads, turbos, pistons, and liners are all the same part numbers between the V and the I blocks. It's just a matter of how many of them you need. (the same thing is true of the fuel pumps).

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    Posting Freak caddydaddy's Avatar
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    Re: Interesting mechanical engineering tidbit

    What's the price on a rebuilt pump? I know the one on my Jeep has a high price tag!

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    Dictionary quoting knob stoinkythepig's Avatar
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    Re: Interesting mechanical engineering tidbit

    Quote Originally Posted by caddydaddy View Post
    What's the price on a rebuilt pump? I know the one on my Jeep has a high price tag!
    Looks like 600 bucks on ebay.

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    Re: Interesting mechanical engineering tidbit

    We were just transitioning from M60’s to the turbine M1’s when I was in the Army. My platoon had four M60’s. The power plant was the Continental AV1790, a twin turbocharged 1,790 cu in air/oil cooled V12. It weighed 4,880 lbs without its 34 gallons of oil. Rated output was 1,250 lb ft of torque and 810hp, but rumors were there was a combat setting that would increase output.

    But the King Of diesel tank motors was the liquid cooled MTU MB 873 KA-501. In the Leopard II they put out 1,500hp and 3,350 lb ft of torque. While the M60 sounded “diesel” and the M1 is very quiet, the Leo II sounds like “You better run!”


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    Last edited by Garandman; 05-05-19 at 07:49 AM.
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    Lifer Garandman's Avatar
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    Re: Interesting mechanical engineering tidbit

    Speaking of interesting mechanical doodads, some WWII German tanks had an emergency hand-cranked flywheel starter.


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