Mercedes OM616 Control Unit

[WStayton]

As you all know by now, I am putting together a 4 cylinder, 2.4 liter, indirect injection Mercedes engine (almost a 240D engine) and an ST-24 Generator-Head to suply the necessary "extra" power for my whole house sytem.

In as much as the engine started out life as a marine engine, it has a few things that are improvements, over the strictly automotive engine, such as: It has an lube-oil to cooling-water heat-exchanger, has an exhaust heat exchanger, which also handles main engine rejected heat, it has cute little (well, sort of "little") feet for the whoile thing to set on and has no throttle butterfly like an automotive 240D engine (Who ever heard of a throttle butterfly on a diesel engine, anyway?).  One thing it does lack, however, is any form of rpm control.  The fuel control has an overspeed governor built into it, but it is set so high, as it comes from the factory, anyway, that is useless - its starts cutting back on fuel at 4500 rpm and essentialy cuts it ALL off by somewhere between 4800 and 5000 rpm - unless I can get into the governor and adjust that down, it is totally useless to me, because I think I will have pieces of ST-24 flying all over the shop LONG before it gets to cut off.  Also, there is NOTHING to even attempt to keep the engine at a useful rpm - which in my case would be either 1800 rpm of 2560 rpm, depending on whether I have the four speed transmission I going to put in the drive train engaged in 3rd (1.41:1) or 4th (1:1) gear.

  To hold the neccessary rpm for generator operation, I was considering/planning upon using a Generac generator control, part # Generac 098647ASRV (98647), Governor Control Kit, Stepper.  This unit runs completely on electricity, so there is no need to have vacuum to provide actuation for the throttle and it takes its speed signal directly from the frequency of the AC current being generatred.  It has controls for "gain", "droop", and "stability" as well as dip switches forfrequency (50 Hz or 60 Hz) and direction of rotation of the control actuation shaft, either CW or CCW.  I think that the fact that it takes its speed information from the frequency of the current being generatred is good for me, in that I could shift from third gear to fourth gear and just wind it up close to the desired speed and engage it and it SHOULD be good to go.

  Of course, Generac publishes nothing about the amount of force that the stepper-moter cum actuator actually generates, but they do use the unit on a 2.4 liter natural gas four cylinder generator, so I hope that it has enough "oomph" to do the job.

  I do have a couple of questions, though, just on the of chance that one of you guys, in your mis-spent youth, has ever played with one of these!  <grin>

  First, if anybody knows, how much output force does the stepper motor actually generate.  I did send Generac a nice email asking them that same question and their return email was they didn't certify anything they made to run on any engine that they don't actually sell, so they couldn't provide me with any information.  Sort of sounded like:  "Good luck, now get lost!" to me!  <grin>

  Also, the directions for the set up say to put the three controls ("gain", "droop", and "stability") in the middle of their ranges, start the generator and adjust "as neccessary".  Never having rigged and run a diesel generator anything like this one before, how do I know what is "as neccessary"  I suppose I could just twiddle knobs and see what happens, but I'd really rather have some algorithm to follow, like If "it wanders, increase gain 1/4 turn" or "if it loses more than 0.5 cps, going from 0 to 75% output, reduce droop 1/4 turn".  If I don't have some sort of algorithm, it's just kinda "poke and hope"!  <grin>  Anybody have any recommendations beyond, wind it up and try it?  <smile>

  As always, all comments are hereby solicited!

  Thanx for reading!

Regardz,

Wayne Stayton

[SteveU.]

Hello Mr WayneS.
Look here:
http://www.generatorservices.com/Generac_Stepper_Motor_Gov.pdf
Regards
Washington State Steve Unruh

[WStayton]

SteveU.:

   Thanx for the link to Generac_Stepper_Motor_Gov.pdf.  The first (upper) page of that is part of the stuff that Generac show everybody, but I just KNEW there had to be more that, that they just weren't showing us/me!

  That's definately an improvement over "poke and hope"!! <grin>

Thanx for the input!

Now, has anybody actually used one of these and able to give hands on info about suitability, rigging, etc., etc.??

  As always, thanx for any input guys!

Regardz,

Wayne Stayton

[SteveU.]

Hi again WayneS
Yes I have used one of these systems - but it was on a 17.5kW Generac 999cc factory (Chinese) V-twin engine. The engine was aircleaner box mixer converted to fuel with woodgas utilizing the factory carburetor as the mixed volume control throttle. I DID break the engine in on gasoline for two loaded hours varying the load and on and off and using the the idle rest function. Stepper motor governor system worked great. Then pulled the gasoline tank, and all lines off, plugged the carb bowl vent and circuit air bleeds for a positive proof of NO CHEAT fuel anywhere possible when woodgassing. NO governor changes were needed with this fuel change over. With the governor stepper motor link disconnected the "felt" force of movement seemed good enough for any throttle body or injector pump I've used.
We almost chose this engine for the good price point, quality and the excellent govenor system for production units. I felt this would have hurt us with the EMP prepared people - I am one of those. And then a "Chinese" to have to explain-a-way with our Made in America manufacturing claim. Ha! Ha! Canadian and Mexican products ARE Nord American, eh?
Regards
Steve Unruh

[WStayton]

SteveU:

  Thanx for your insight - its really good to hear from somebody who's actually used the unit and not just read about it somewhere - like me!! <grin>

  When I discovered the unit, it seemed like the answer to a prayer, because what should work better to control a generator, thatn a generator control!  I expecially liked the fact that it used the line voltage to sense the speed so you are, more or less, assured of getting 60 Hz, no matter what the relationship is between your engine rpm and your generator rpm.

  The Mercedes has a real light throttle, so I didn't think there would be any problem using this unit on it - but, again, iots nice to have somebody who has actually hooked one up validate that!

  As to using U.S.Parts -Good Luck!  It seems like most of the diesel world is anywhre other than here, in the USA, unless you are talking about 6 liters and above.  Somehow, we always seem to think that bigger is better - I not so sure that is true!  <grin>

  As for something to run on woodgas, I know practically nothing about the subject, so I'll shut up and not display my ignorance! <smile>

  Anyhow, thanx for your insight and for validating my decision to use the Generac unit - at about $185 for the ECU and $50 (I think!) for the stepper motor, I just couldn't see anyway that you could get anything that cost less that would do the job!

  Again, thanx for the insight - it is always good to hear from somebody who has actually done what you're contemplating doing!

Thanx again for relating your experience!

Regardz,

Wayne Stayton

[BioHazard]

That's a neat little governor control, I have seen something similar although much smaller built into carbs by Walbro. I'll bet all small engines will have electronic governors before too long...

I definately want to hear how it works out for you!

[WStayton]

I kind-of have conflicted emotions here . . .

  In general, I prefer things mechanical to things electrical (I AM a Mecanical Engineer, after all . . .) but I am also a fan of KISS AND KICS (Keep It Cheap, Stupid!) and, in this case, I think that the electrical unit wins if only from a KICS standpoint.

  Also, the mechanical systems are all derivative type systems, in that they require that you be some didstance OFF of the setpoint before/in-order-to generate a restoring signal.  The electrical/electronic systems are all digital and whatever you (or, in this case, the factory) set you get - exactly, or as close to there as it can get.

  The electrical system is more complex, from the standpoint of fixing it, in that you can't just apply two U.S.Standard eyeballs and figure out what a problem is - but, that being said, electronic/electric systems are much more apt to have an all or nothing probelm, so the smart/easy fix is to keep a spare unit (wrappped in foil in an ammo can, under the workbench - for EMP protection, donch know!  <grin>) and i9f the original twitches, change it out - also helps an electronic semi-dummy (ME!) trouble shoot problems . . . system doesn't work - change control box - system stilll doesn't work - voilea, problem was NOT the control box!  <grin>

  Flyball governors are attractive in thier simpkicity and mechanical types, like me, like to see them spinning around, but function and ease of installation/maintenance and CHEAP wins out in this case!

  As always, thanx for the input!

Regardz,

Wayne Stayton

[SteveU.]

Hey Wayne
You are absolutely correct in your observations.
For small woodgas fueled gen-sets although possible to use an American "brand name" the actual engine 80% gonna be made overseas somewhere else. Just like small John Deeres since the 80's; "American" cars since the 70's. Personally I have no overt problem with "Chinese" - got an R180 clone engine to prove it. And an Italian Mecc Alta gen head I bought for performance.
You are correct too it is impossible to make a trailing situational mechanical governor set-up as quickly reacting and accurately responsive as an electronic solution. Lord knows I've tried - oh, how I've tried. The best digetal can aticipate a needed resopnce from a demand signal. We are going a different route on this that will be KISS/KICS enough for the market that I'll be able to talk about openly in a couple of weeks.
Yep, Tin Foil Hat a spare on that board for sure - need a spare stepper motor too. ALWAYS KEEP the old take failure for a possible reparable and upgradable solution by the electronics wizard/amateur radio guy you need to be-friend. But hey, go easy on the old 70-90's Ford/Chrysler standard out of the manuals of "Replace with known good part". From back in the 70's GM and now all digital module units can blow like popcorn if your real problem was a motor or wiring short to ground or short to full hot voltage. Been there too. In the silicon wafer Fab plant I worked in for seven years I once saw an equipment maintenance man take down 4 out of 16 CNC four axis grinding machines one after the other doing this. Instead of just one machine down for a week it was the four down for the two days for new boards to be expedited in from Japan. Motorola, Intel and Fugitsu were NOT happy thier orders were late coming through.
Regards
Steve Unruh

[deeiche]

rm /

[SteveU.]

Yes. SEH-America. 90-97 or 91-98. I forget. Slicing/Edge Grind/Laser mark/Lapping "dirty" area. Only had to white nylon bunny suit up for process QA tracking. Ha! Ha! We virtually hand made the 1st 300mm wafers in the US in my last year there. Do we know each other Mr Deelchi? Your first name doesn't start with an "R", you made Tee shirt graphics and worked in maintenace, now did you?
Regards
Steve Unruh

[deeiche]

rm /

[SteveU.]

Amen to that Brother. One of those things you really have to experience to understand. Winter of 92-93 began with 29 days of 13 hours straight on covering production machine operator shifts who did have families wanting an little Christmas, New Years, Hanukah  time off at home with those families. Three days off. Then 17 days of 13-15 hours of "special" project time. Five days after that I was very sick and ended up in the Hospital. When working for companies that annually rotate out (dismiss) as a policy 10-15% of people annually to be replaced with new blood best to never slow down or be viewed as underperforming. And the top performing 10-15% get the lions share of annual pay raises. Moores Law rules: and his whips are SPC, CIP, FRTFT, minimum MTBF, ZDTG, patents applied for and won, etc, ect.
Honestly WS we are not highjacking your thread. These experiences are apt in automation decision choices. Consumer grade electronics are rushed to market and the bugs, weaknesses are geeked out there, or not; or just replaced with the "next improved generation". Only the Military and Industry use the old, slow, durability built-in proven and expensive stuff. There is good experienced learned reasons many here do follow a credo of minimal electronics dependancy, and make that in issues of 100's of thousands of world wide proven deployment, and what we do use better come from companies with a proven reputation for durability and longevity. And you gonna be paying for this. We ain't stupid - experienced.
I really do not know where the Generac electronics stand in this mix. But at least an open board - so potentially repairable/upgradable. Just like my 1996 Coleman brand unitized all in one electric furnace control board that has now failed TWICE - it does not like shorted out or open heating coils - and always just out of warranty time period.
Regards
Steve Unruh

[WStayton]

SteveU.:

  Hijack??? I'm rather viewing it as a chance to see another slice of the technological world I've never had the opportunity, or should I say "misfortune", to experience!  <grin>

  Interesting to see that every industry has their own set of problems/concerns and that they bleed over into everything that that particular industry does.

   Maybe we should have sub-forum: "Management/Mis-management", <smile>

  Last time I checked, the OP didn't have any veto rights, either!

Proceede!

Regardz,

Wayne Stayton