marine engine FI

nhoj at cd.chalmers.se nhoj at cd.chalmers.se
Thu Oct 14 13:37:51 GMT 1999


Stuart Hastings <stuart at hal.com> wrote:
> > More like 200, IIRC. Also, Ficht's solenoid driven injector is not very  
> > precise; the pressure varies a lot.
>
> I suppose there is no way to really know without measuring it, and
> this would be difficult. One imagines a small, closed chamber, filled
> with an incompressible liquid, and a Ficht injector screwed in one
> end. Perhaps you could repeatedly fire the injector until the pressure
> stopped rising...

That would only tell you the maximum pressure, not the sustained pressure  
through a burst. Pressure in itself is NOT a good thing in a gasoline DFI,  
though. OMC and Yamaha use the pressure to get atomization. If they could get  
that atomization with lower pressure, they would.

The penetration rate (velocity of fuel entering the cylinder) is
too high when the pressure is raised enough to provide reasonable
atomisation. This is coped with by putting spray deflectors and
bowls in the piston and cumbustion chamber, but these are all
band-aids trying to slow the spray down and contain it near the
spark plug to achieve stratified charge conditions (i.e. rich near
the plug and lean elsewhere).

Orbital does not have this problem, since it uses compressed air to shear  
the droplets.

> > Note that compressed air contains far more energy than pressurized
> > fuel, which means that Orbital gets by with a far lower pressure.
> > Thus, they avoid a few of the drawbacks of DFI.
>
> Speaking as a potential customer, the extra belt and air compressor
> used on the Orbital design look like additional parts to break.

Of course. But a belt driven air compressor is not exactly rocket science...

> The Ficht design has none of these parts.

The Ficht has a whole lot of other parts to break. (And it seems to be doing  
so with gusto...:))

> My point was that DFI two-stroke engines are still blowing oil out the
> exhaust. If the emissions have dropped by half, that's great, but it's
> still disconcerting.

True. They could have moved the precompression out of the crank case, using  
a conventional "wet" crank case, and a screw compressor instead. That would  
have given more efficient scavenging, and gotten rid of all oil in emissions.  
In addition, they would probably be able to get a fair bit more power out of  
the engines since the problem of piston overheating would not force them to  
run rich at WOT. At least one of the car manufacturers that worked on an  
Orbital engine did this.

> More specifically, EPA is interested only in *air* pollution from
> marine engines. When they mandated oxygenated fuel, they indirectly
> required California fuel to incorporate MTBE, and nobody realized it
> would contaminate the *water*.

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. Since I'm not American, I won't claim to  
know how the EPA thinks or works, though.

> Hello, EPA, most marine engines exhaust
> *underwater*, even if most of their smog immediately bubbles to the
> surface!

That can easily be fixed with a holesaw, if you're worried. :)

> I'll guess that EPA isn't yet concerned about oil emissions because
> much of the oil stays in (or on the surface of) the *water*.

That is possible. They may also be taking on one problem at a time.

> OMC claims to have fixed their problems, and I haven't heard of any
> Ficht owners out of warranty yet.

Neither have I. Even if you are under warranty, it is quite frustrating to  
be left drifting on the ocean, though. That's one reason why it is a problem  
for OMC; they get a bad reputation out of the failures, and they have to pay  
for the repairs...

As far as I know, its the 60 degree V6 engines that have caused almost all  
of the trouble, particularly the 175. The 90 degree V6 and V4 engines seem to  
do OK.

An OMC rep told me that in order for your Ficht to survive, you should block  
the oil return line the first time you start it, as well any time it hasn't  
been running for a while. Otherwise there is a significant risk of hurting  
the rings and sleeves during startup due to oil starvation. Further, it is a  
good idea to give it some extra oil during the first few seconds it runs. The  
OMC rep suggested spraying fogging oil into the intake, or running a rich  
pre mix.

Since many retailers (and hence customers) don't know about the startup  
procedure, many Orbital engines are severely damaged the first time they are  
started...

The rep also claimed that OMC is having a lot of trouble getting mechanics  
to diagnose the (old fashioned) mechanical problems people are having with  
the engines. As soon as the built in diagnostic system can't tell what's  
wrong, mechanics tend to give up.

The second generation Ficht system should take care of the problems, and OMC  
are upgrading the old engines, starting with the 98's, IIRC. The 97's have  
been less troubling, but there is or will be a kit out for them too.

It seems that OMC are pushing Ficht onto new engines a lot faster than  
Mercury is pushing Orbital. It could be because Ficht is easier to retrofit  
than Orbital, but I suspect that it is because OMC are less scrupulous about  
testing than Mercury.

> OMC has said as much on their website in the past.

OK, I got the info from an Orbital engineer and an OMC rep.

> They also listed a
> bunch of problems they had with it, all problems that were adequately
> solved by Mercury. This leads me to believe they prefer Ficht because
> they were able to buy the technology outright and avoid paying
> royalties.

Another reason may be that they wanted a technology of their own, rather  
than being an "Orbital also ran"... Yet another may be that by the time OMC  
canceled their Orbital engine, it was clear that Orbital would not be a hit  
in the automotive world. Thus, economies of scale didn't look significanlty  
better for Orbital than for a home brewed system.

Orbital is working hard on the (four stroke) automotive market these days,  
with the selling point that their DFI system runs unthrottled, which makes  
the engine more efficient at the low power levels where cars spend most of  
their time.

Regards,
John Hornkvist




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