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Old 03-05-2005, 21:07   #1
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Warning when Checking Injectors

I couldn't remember where our thread on checking injectors was, so thought it best to start another thread. More and more electronicly controlled Desiel are entering the market place now, and I believe it is starting to become more common to see them in the Marine environment. So what I hear you ask. Well the way the Desiel is being controlled is becoming very similar to an electronicly controlled Petrol engine. A computor is monitoring the performance of the engine and making changes all the time to how it runs, making it more fuel efficient and reducing emmisions. Well that tecnology has found it's way to the Deisel world as well. Desiels used to work very much in the "rule of thumb" world. It's size and fuel injected was always in a ball park firgure of resulting horepower. This was because the injectors were mechanical in operation. The pump would deliver a metered amount of fuel to the injector and when the pressure was high enough, usually a few hundred pounds, it would lift the injector seat and spray into the cylinder. Well things have changed. We now have electronicaly controlled injectors. This means a computor can now monitor all the work aspects of the Deisel and open the injector at the precise time and for a precise duration to allow a precise meterage of fuel in. Uh ha, so what, I hear you mutter once again. Well apart form that change, there is one other major change, that makes life for the person playing around there deisel engine, just a little more seriuose. These designs have one other addition. It is called a coomon fuel rail. Just like on any multi point injjected car engine. But on a deisel, the difference is the pressure found in that rail and thus at each injector. Now on a conventional Deisel, you will have a pressure at each injector rangeing from say 100psi upto say 300psi. You can crack that nut and allow the air bubbgle to escape or see if a cyclinder is firing and all you get is a fine misty drible of fuel. I should suggest that you still wear glasses to protect your eyes from an accidental spray of fuel. BUT, on t acommon rail electronicaly controlled Deisel, that rail pressure can be as high as 35,000psi. Wearing safety glasses would be meaningless at those pressures cause the fuel jet being shot out at that pressure would quite happily drill a hole in your safety hear and right on through your head. At the least, it could cause deadly damage to hands and fingers in close proxcimity to the injector nut you just losend off. A common rail system is easy to recoginse. It will have one very heavey walled pipe(called the rail) running the length of the engine injector system. A smaller pipe runs off along the length of the rail to each injector. Each injector will have a pair of wires running to them. And finally, your engine will have an electronic management system wired into it somewhere.
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Old 03-05-2005, 21:55   #2
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New diesels

I think the big problem for sailors is gonna be all the electronic stuff that could be a problem to figure out far from home.
Michael
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Old 22-05-2005, 17:30   #3
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35,000 psi is this correct
Just a question, seems very high
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Old 22-05-2005, 20:33   #4
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Yes and yes, It is very very high. Water/concrete cutting type pressures. Thats why the caution. Crack open a nut under those pressures and you run the risk of losing fingers hands neck etc etc.
Now before everyone panics, these engines, "common rail deisel" are still rare in the marine market. But some do exist and I expect them to become common place. This is because the economy and combustion/emission can be controlled via a computer.
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Old 22-05-2005, 23:42   #5
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Common-rail injector controversy

I've recently read that with inspected vessels for commercial use USCG approval for common-rail injected engines may not be forthcoming due to the safety issues. Aside from the safety problem of personnell in proximity of a failing common rail, there is the safety issue of having ALL cylinders fail to fire instead of just one should a pressure leak occur. At least the latter issue could be met by having a backup engine.

There is little doubt that the future will be with electronically controlled injectors the question will be just how to address the safety issues in the marine envionment at sea. Any further info in this regard?

Rick
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Old 23-05-2005, 07:36   #6
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Interesting. Plus I am of the age, that we didn't have computers running cars in my day. If it broke down, you could usually get home with the aid of some twin and fencing wire. Nowday's, if even you change gears funny, the computer decides something is wrong and either shuts the engine down or puts it into a limp home mode, of which home does'nt want to be too far down the road.
I also don't like the idea of electronics running engines in a Salt water environment. I guess the marine engine companies are going to make that part reasonably foolproof, but you know the saying. Just when someone makes somtheing foolproof, someone else makes a better fool.
But interesting the point you made Rick. I have often wondered about a similar device now being seen in an electronic form. The Throttle and gear controls. And I suppose in bigger boats, steer by wire, systems. I guess if they can be approved, I see no reason why and engine management system couldn't either. And a last comment, I suppose also, the driving force will eventually come from environmental controls. I would think we will eventually see the fuel/engine managment systems as the norm, just as we have seen in the petrol market. I think in the end, it doesn't matter who complains about safety, if all you can buy is CR type engine systems, then the argument becomes a mute subject.
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Old 23-05-2005, 19:12   #7
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Engine computer technology

Like you, Wheels, I am from a time when I could fix my own car. No longer. Yet there is a compelling reason to look forward to the technology.

It is the development of robust communication busses which make processor control workable and reliable. Mercury Outboards, for example, makes a wonderful two-cycle, light weight (as to compared to a four cycle engine) engine which beats the CARB emission requirements and is very efficient.

This engine uses processors to controll just about everything. Developed for the automotive industry, the communications bus is called CANbus and is quite a technical development. The standards work for various data rates and priorities.

The highest priority bus is not available for users to "tap" into because it would control the anti-lock brakes, for example, or the injectors.

A friend of mine bought one of these engines to power an aluminum fishing boat. As a result, the required fuel and horseppower is less because the engine weight is significantly lower than a four cycle inboard or outboard. The max speed is higher. The weight to power ratio has a huge impact on the overall boat/engine design.

Lubrication oil is automatically varied as the engine runs through its break-in period. The remote display of fuel consumption is so accurate that a fuel guage becomes crude by comparison and is, therefore, omitted because one of the engine computers "knows" very precisely just what each injector has consumed. Totaled up you get to know fuel consumption very accurately.

These features are what we have to look forward to with all engine types in the future. Already today I cringe to hear that someone has paid for a "tune up" on their car. There just is NO tuning to do on cars anymore....all that the shop can really do is change the spark plugs (if that's what you have) and for that they charge for a "tune up" HA!

Rick
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Old 19-02-2010, 20:47   #8
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Thanks but no thanks! These modern gadgets fail enough on dry land so just imagine trusting your boat, life, and even booze collection to a computer at sea? Right. I can see it now blowing like mad, lee shore, anchors coming home, and the computer packs up because of a single drop of water. And then again there is the bit about the computer being supplied by the lowest bidder and manufactured a cheaply as possible. Nope! Not for the sea thinks I.
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Old 19-02-2010, 21:43   #9
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So Wheels - maybe you know the answer to a question coming out of the Miami Boat Show?

Several powerboat salespeople told me that the new common rail engines are great because you can run them at very low RPM with no worries - that the high injector pressure, even at low power, avoids carbon buildup. So if you want to run your boat with twin 500hp diesels 1500 miles at displacement speeds to save fuel - no problem! (..I left for another day the question of why anyone would buy a boat with twin 500hp diesels if fuel economy is a concern or why anyone would want to go offshore at displacement speeds in a planing hull form.)

I thought the carbon problem at low load had more to do with low operating temperature than injector pressure.

Is this just sales guy talk or a genuine change for the better?

Carl
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Old 19-02-2010, 21:45   #10
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why cant they just keep it simple, I do remeber the days when a car had points and carb, if it didnt run you check the carb for gas then check for fire at the plugs, keep a match book to clean the points and a inline filter you could always get home.

Computers in a car was a big mistake and now they are talking about puting them on boats. lol It seams to be a joke to me. just one more thing to break.

Dutch
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Old 19-02-2010, 22:54   #11
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Quote:
Originally Posted by johnar View Post
why cant they just keep it simple, I do remeber the days when a car had points and carb, if it didnt run you check the carb for gas then check for fire at the plugs, keep a match book to clean the points and a inline filter you could always get home.

Computers in a car was a big mistake and now they are talking about puting them on boats. lol It seams to be a joke to me. just one more thing to break.

Dutch
I agree! Simple is more independent, although not as efficient. But the gain is so little why sacrifice security in a off-shore vessel. Mechanical motors, one can here problems arising. Computerized motors quit without notice and just at the wrong time. Plus, one has more high tolerance parts to deal with/troubleshoot.

http://www.manbw.com/files/news/file.../p412-0503.pdf
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Old 19-02-2010, 23:29   #12
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The cars we were fixing that got 15 miles to the gal now get 40, still, last year my trucks motor sound sounding like something was going in the bottom end. I took it to a modern shop and the mechanic ran the computer diagnostics and said everything seemed ok. The battery was weak and I replaced it. Sure enough two days later and two hours out of town the cam shaft went. I remember how mechanics used to diagnose such things - a stethascope and a knowledgable ear.
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Old 20-02-2010, 00:55   #13
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All this is rather backwards. If they want efficiency then try copying the old slow turning engines that gave all the torque one could want on a tiny trickle of fuel. I had a 15 hp Alfa one cyl once that pushed a 45 mtr barge at 7 - 8 knts and gave about 2.5 miles per liter. My 215 hp Perkins will only give my current 20 meter boat about 7 knts and 1 (or less) miles per liter. You go figure! Oh and if something broke on the Alfa I went to the closest machine shop and made a new part. Then again at max 700 RPM it took a long time for things to wear out. Of coarse horses were stronger in those days and companies had a bit of pride in what they made. Seems like todays horse is more like a pony or perhaps colt. So perhaps we should say 500 colt power or 1,000 ponies?
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Old 20-02-2010, 03:55   #14
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Vega,
Absolutely spot on, great friends of mine changed from sail to power and installed a former bus engine from Hong Kong, a Gardener 4 cylinder it just ticks over delivering hull speed at around a L/nm. Where are you nowadays?
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Old 20-02-2010, 04:33   #15
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Great when that modern technology will enter the Marine market; it is hard to find a proper marine mechanic. When your car really acts up (where are the days you could simply file your points and get going) it is almost impossible to find mechanics who really understand modern car computers. Sometimes I get the opinion it is simply trial and error replacing parts instead of really fixing something.

Guess what will happen when we get computer controlled diesels in our boats...Can you imagine the 'fun' you will have dealing with engine troubles? Some persons who call themselves mechanics cannot even carry out a simple compression test.

My (ex) boat had a simple Volvo Penta MD7B engine using a liter (quarter of a gallon) per hour to push the 33 ft boat at 6 knots. The only maintenance it ever required was oil, filters and impellers.
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