marine engine FI

[nhoj at cd.chalmers.se]

>> At 05:00 11/10/99 -0400, DIY_EFI Digest wrote:
>> >Or - altitude could be faked out by reading the MAP while the engine is
>> >stopped.  Then you could account for it.  Of course this assumes that the 
>> >car is stopped every once in awhile (probbaly a reasonable thing).  I know 
>> >for a fact that some outboard marine engine controllers do this.
>
>Marine FI can probably get away with this, unless you run your boat
>down (or up) the side of a mountain with the engine running.
>"Over the falls," perhaps :-) ?
>
>> Outboard engines are FI???? Wow!! Things have changed in the past 5 years.
>> Why would they do this? Manufacturers are still putting ECUs in the engine
>> bay of cars. This is a pretty nasty place for electronics. I can see the
>> reason for putting FI in cars as it improves fuel ecconomy and power along
>> with controling the fuel so that it doesn't clog the CAT. But why on a
>> small outboard engine?

There have been fuel injected outboard engines for a long time. However, EFI  
2-strokes have been available only in the high power segment, starting  
around 200hp, and primarily from Mercury.

>>Surely you would want to keep the thing as simple as
>> possible using NO electronics as Sea water isn't electronics freindly by
>> any means.

It is difficult to get enough low and midrange power out of a highly tuned  
2-stroke engine using carbs. With EFI that problem decreases significantly.  
Remember that a boat needs good power at low revs to get on plane, and lots  
of power at high revs to be fast...

>The technology employed to fix this is DFI; injecting fuel directly
>into the cylinder, after the piston has risen enough to close the
>exhaust port.

As I recall, this is not really true; at high RPMs injection takes place  
before the exhaust port closes. Thus, at wide open throttle, the efficieny of  
DFI outboards gets close to the efficieny of manifold injected or carbed  
outboards. Note that two-stroke outboards are pretty efficient in their tuned  
RPM range. A problem that limits fuel efficiency of DFIs more than older  
outboards, IMHO, is that the limited cooling of the pistons forces DFIs to  
run rather rich.

>Mercury uses a system they licensed from Orbital (of
>Australia), OMC bought a company named Ficht (of Germany), and Yamaha
>has developed their own. As I recall, Ficht uses a special injector
>that develops about 450psi,

More like 200, IIRC. Also, Ficht's solenoid driven injector is not very  
precise; the pressure varies a lot.

>Orbital uses ~90psi mixed with a blast of
>compressed air,

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.

>and Yamaha uses ~700psi.

Yamaha's new offerings are interesting, because they designed a completely  
new engine for the DFI system, rather than retrofitting it on an existing  
construction.

>I haven't looked at Yamaha's web site; they may not have a writeup
>yet, as I don't think they've shipped yet.

There is a writeup floating around, but it says "Not for publication"...

>Curiously, while DFI reduces oil consumption, it doesn't really
>address the oil-emission question.

DFI as such sure does; reduced consumption leads to lower emmissions, after all.

Hower, due to technical problems, some current DFIs, and particularly  
Mercury's, tend to use surprising quantities of oil.

>Apparently EPA agrees this is not a
>major pollution issue at this time. Manufactures are quick to tout the
>reduced fuel consumption of DFI, and many satisfied customers agree
>it's real.

And quite a few customers are on their second, third or fourth power head on  
warranty... OMC's Ficht has been worse off than Mercury, in this respect.  
(Mercury found unexpected problems and quietly pulled back their first  
generation of DFI's, and came back with an improved design and a new name.  
OMC on the other hand, being somewhat financially challenged, let their  
customers do the testing for them, to the misfortune of a whole lot of  
people. OMC also had an Orbital license, and built but never sold an engine  
almost identical to Mercury's original DFI, by the way)

Regards,
John Hornkvist