marine engine FI

[nhoj at cd.chalmers.se]

Stuart Hastings wrote:
> > The Ficht has a whole lot of other parts to break. (And it seems to be
> > doing so with gusto...:))
>
> Hmmm. Oddball injectors, computer to drive them, special alternator,
> and an oil injector in the crankcase... I guess you have better
> sources than I do, but I had understood that most (catastrophic) Ficht
> failures were related to internal engine parts, like pistons, rings,
> and cylinders. Stuff that was supposed to be well-debugged by now :-) .

I don't think anything really breaks when the injectors stop working. After  
all, oil is passed another way. That's why you don't hear much about it, I  
guess.

>
> I doubt the marine engine manufacturers would fit a compressor unless
> required by smog regulations. It adds weight, complexity, and cost.
> But I personally would consider owning such an engine.

Well, in theory they could move to slip bearings and a conventional crank.  
That would save a good pile of dough...

> > This may be true. I read somewhere that it is doubtful that a significant
> > amount unburnt gasoline passes into the environment because of the high
> > temperature of the exhaust gases.
>
> It has been definitively shown here in California that most of the
> MTBE found in surface water (lakes, reservoirs) came from non-DFI
> two-cycle engines.

OK.

> Here in the Silicon Valley, the local water authority permits
> powerboats on three of our ten drinking water reservoirs. One of these
> is open to Personal Water Craft (e.g. Jetskis(tm)) at the beginning of
> every season, and promptly closed to them after the MTBE concentration
> rises above a certain threshold. PWC dealers in Northern California
> have mostly been driven out of business. My four-cycle boat is still
> permitted on all three reservoirs.

Well, having any boats on water reservoirs is asking for trouble, IMHO.

> When DFI manufacturers claim 25-30% improvements in fuel economy,
> they're talking about raw fuel that was formerly blown out the
> exhaust. This is a settled issue.

Yes. My point was that the high temperature of the exhaust gases would cause  
oxidation of the hydrocarbons in the exhaust stream once they leave the low  
oxygen athomosphere of the engine.

> > That can easily be fixed with a holesaw, if you're worried. :)
>
> I'm not worried, because I insisted on four-cycle power when I bought
> my boat. I'm not a "greenie," but spitting oil (and/or gasoline) into
> the water dismays me, in spite of all genuine advantages of two-stroke
> engines on a boat.

If there is a significant environmental problem with spitting fuel into the  
water, it should be avoided, of course. The problem with DFIs and two strokes  
is that there are none in the really high output segment. (Unless OMCs 250  
has been released.)

> Most marine engines (in the U.S.) exhaust underwater because it's
> essentially required by the U.S. Coast Guard for basic
> safety. Boat-engine exhaust is typically mixed with water shortly
> after it leaves the engine.

I know. Dry stacking changes the tuning characteristics of the pipe, since  
the exhaust gases have different acoustics, and more engergy, at the higher  
temperature.

> Most sterndrives (marinized car engines)
> have many rubber parts in the exhaust just downstream of the water
> port; if the water supply fails, the rubber parts promptly melt.

I have no experience with sterndrives; Swedish gas prices are about four  
times higher than American prices, so we try to keep boat sizes reasonable...  


> If nothing in the boat is hot enough to start a fire, there should be
> fewer boat fires. Nobody was thinking about ecology when these rules
> were established.

Of course. The situation is a bit different with an outboard, though, since  
it hangs a fair bit behind the boat. (I have about 40cm offset, for example.)

Regards,
John Hornkvist