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Thread: Announcing the Merc 888

  1. #21
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    Forget the turbo......you don't need it. Having years of experience around 18 wheelers, and having owned and fixed up a classic International 9670, I can tell you that the venerable Detroit 6v and 8v series two stroke diesels were pressurized by a gear driven roots style blower. Later on the silver series models, a turbo was added, though it only added to the pressurization. It wasn't really necessary to make those engines work well. By that time, an 8V-92 Detroit diesel at 736 cubic inches would make from 435-600++ HP at 2100 RPM. It was a giant V-8 at 92 cubes per cylinder. Just some interesting stuff......

    Basically, what you can use is a roots style mini compressor/blower for a motorcycle engine. I think they exist if I'm not mistaken. That will give compression in the crank case without valves and is immediate and mechanically direct.

  2. #22
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    Default Decisions, decisions

    Quote Originally Posted by champ20B View Post
    Forget the turbo......you don't need it. Having years of experience around 18 wheelers, and having owned and fixed up a classic International 9670, I can tell you that the venerable Detroit 6v and 8v series two stroke diesels were pressurized by a gear driven roots style blower. Later on the silver series models, a turbo was added, though it only added to the pressurization. It wasn't really necessary to make those engines work well. By that time, an 8V-92 Detroit diesel at 736 cubic inches would make from 435-600++ HP at 2100 RPM. It was a giant V-8 at 92 cubes per cylinder. Just some interesting stuff......

    Basically, what you can use is a roots style mini compressor/blower for a motorcycle engine. I think they exist if I'm not mistaken. That will give compression in the crank case without valves and is immediate and mechanically direct.
    Indeed, there are many challenges and potential improvements for the opposed 888. As an engine of this type may never have been built before, a tall learning curve curve is expected. But, you've got to start somewhere. My thoughts are to start simple (and inexpensive), to determine if further investment is warranted.

    Among the many interesting comments: Dicks recollection about valveless generator engines (presumably 2-stroke) is very interesting: I've never heard of such a thing. And, Detroit Diesel 2-strokes are near/dear to my heart. As a suppler to DD in the 70's and 80's I became very familiar with the 53, 71, 92, and 149 series engines (cubic inches per cylinder for those who don't know). In fact, I built a two stroke, four valve Cosworth-Johnson using a similar principle (with crankcase scavenging) in the 1990's.

    So far as splitting the diffuser and intake tract, this may be needed in the future, IF the engine behaves itself. And while a blower would be preferred for its volumetric scavenging, I had a spare small frame Garrett on the shelf.

    All super-trick ideas aside, my larger concerns are survivability of the skinny little rods and lightweight crankshaft. Success is defined as successful/repeatable starting and idle performance, with light tank time on a test wheel to follow. My dream is that operation will be stable enough to push a boat around for 10-15 minutes without blowing chunks.

    Tim

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    I too have 'history' with Detroit Diesels; EMD railroad engines in my case. And they aren't puny 92 cube per cylinder, glorified 'lawn mower' engines: Think 645 and 710 cubes PER cylinder, and up to 20 cylinders! Now, that's an engine!

    Turbocharging a two stroke has a hidden benefit in that the exhaust back pressure it creates keeps the inlet charge from blowing out the exhaust system. Supercharging doesn't do that.

    Jeff

    PS: The thought of that crankcase, without vacuum/ pressure pulses going on all the time, is fascinating!
    "We live at the bottom of an ocean of air." - General Marvage Slatington

  4. #24
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    Default Whoa!

    Quote Originally Posted by Fastjeff57 View Post
    I too have 'history' with Detroit Diesels; EMD railroad engines in my case. And they aren't puny 92 cube per cylinder, glorified 'lawn mower' engines: Think 645 and 710 cubes PER cylinder, and up to 20 cylinders! Now, that's an engine!

    Turbocharging a two stroke has a hidden benefit in that the exhaust back pressure it creates keeps the inlet charge from blowing out the exhaust system. Supercharging doesn't do that.

    Jeff

    PS: The thought of that crankcase, without vacuum/ pressure pulses going on all the time, is fascinating!

    Now those are some BIG engines! Were they two strokes like the Detroit?

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    Hook your shop vac to the turbo exhaust while you are cranking it, the shop vac will get out of the way as soon as it starts (lol) Seriously though, it would be nice to be able to have a two stage starting process, dc motor coupled to the turbo shaft, spin it up throttle closed, then crank and open throttle. Just thinking out of the box.

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    Default Electric turbo & ignition

    Quote Originally Posted by daveswaves View Post
    Hook your shop vac to the turbo exhaust while you are cranking it, the shop vac will get out of the way as soon as it starts (lol) Seriously though, it would be nice to be able to have a two stage starting process, dc motor coupled to the turbo shaft, spin it up throttle closed, then crank and open throttle. Just thinking out of the box.
    Hi Dave,

    Yes, the shop vac is always possible. Actually, my leaf blower has a suction adapter, and may be used - LOL! Also, electric turbos were researched first (see videos on youtube). Generally, a high power electric motor replaces the exhaust turbine. Aside from the obvious problem marinizing electric motors on outboard engines, compressor output is limited. I'd given thought to adding one to the fore bank for starting only, but the weight, complexity, and cost ruled out the exercise for the prototype.

    What I really need help with is an ignition system, preferably battery CD or HEI (for reasonable $$$). The least cost method is twin, conventional, belt driven, (petite) VW Type 1 distributors & two coils. The next method is an under the flywheel crank trigger battery CD system based on readily available marine parts (available but pricey). Finally, I'm considering building my own with four inductive sensors, coupled to four GM HEI ignition modules, firing four Siamese ignition coils.

    Do any of you engine or ignition guru's have any experience with an inductive HEI?

    Tim

  7. #27
    Team Member R Austin's Avatar
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    Tim

    As long as you are considering building new rods, think about the rod configuration in the Allison and the radial engine with a master rod and a link rod.

    Dick

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    Default Master & link

    Quote Originally Posted by R Austin View Post
    Tim

    As long as you are considering building new rods, think about the rod configuration in the Allison and the radial engine with a master rod and a link rod.

    Dick
    You mean like this?
    Attached Images Attached Images  

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    Quote Originally Posted by R Austin View Post
    Tim

    As long as you are considering building new rods, think about the rod configuration in the Allison and the radial engine with a master rod and a link rod.

    Dick

    Regarding ignition: How do you fire the twin plugs on your Looper Beast?

  10. #30
    Team Member R Austin's Avatar
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    That's the setup on the rod. Obviously with a little more pin and a bearing in the rod link.

    The beast is just the standard ADI ignition with the primary coil feed connecting 2 standard coils in series. Not sure yet if that may be the problem with the ignition/fuel issue. I do not think it is but will not know for sure until I get it on the dyno.

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