K-Jet on the water (well, maybe not)

[Bernd Felsche]

Ken Thompson writes:
>From:
>Kevin Jaeger (Ken's Associate)

>Bernd,

>I apologise for my apparent heaviness of comment in relation to your
>statement "K-Jet would be OK for boat". ...

Apology accepted. We all have our "hot points".
You touched one of mine when you called K-Jet a "diabolical mouse-trap". :-)

It does appear that you read too much into what I wrote - I did
actually express concerns about corrosion resistance (I thought it
was zinc used for the flow-meter body and have been subsequently
corrected).

>All pleasure boats induct the spray of salt water (ocean going), it is the
>nature of the beast. ...

Salt corrosion could be the big problem. Although the systems have
to cope with a small amount of salt in the air, the airborne amounts 
in the spray are more persistent than the seasonal rituals
experienced in the the colder parts of the world.

Excluding the spray would be difficult. The system simply
has to be tolerant of it and/or require greater maintenance.

>I am sure you could do a great job rigging up a K-Jet that would function
>wonderfully on the water (the first day). Two weeks later, I will bet the
>second days fun will not be as much fun. One can construct well designed air
>boxes, centrifuges etc and salt spray is still going to be induced. Seizure
>of the actuator, the arm roller etc is likely to be a problem (air valve
>arm). Might be fine the day of commissioning, but put it away and come back
>in two weeks, rust will be a problem. Benz' and others you mentioned have
>got pretty good air filtration systems, but I do not see one system in
>amongst them, that could double as a watercraft water excluder (for want of
>a more suitable description).

What is in a car would be largely unsuitable to exclude the spray.
I've never designed an air induction and filtration system for such
a task; I'd be tempted to do it in a couple of stages, starting with
the inlet tube - directed to minimise spray induction. A cyclonic
arrangement can then be used to get rid of most of the larger water
droplets carrying the salt. The air would then be ducted to a large
box around the exhaust manifold to evaporate the remaining droplets
followed by another "cyclone" (a couple of sharp bends should do the
trick) and filter to capture before a "charge cooler" and the final
air filter leading to the metering unit.

Most of that stuff doesn't need to weigh much; it just takes space.

Before you put the boat "to bed" after a run, open up a trap-door in
in the duct to the metering unit and give it a squirt of WD spray
with the engine revving.

>Who cares if Lucas' A/F ratio is not perfect, never said it was. It can be
>set up pretty good www.kinsler.com Lucas was used in Formula One on down,
>was very big in boats. A pleasure boat is more like a performance engine
>than a street trim BMW. Not much stop start driving or gear changes. If 3000
>RPM is where it will be driven, would be nice to tune for max torque there.

No arguments here. But BMW owners might have frowns on their brows ;-)

>The Lucas (Triumph) bodies do lend themselves to simple set up for tuned
>length runners. After a day on the water, give the each port a spray with
>non waxing, dewatering compound. The Triumph runners would have plenty of
>velocity to purge any water that would be inducted. The velocity in the
>nooks and crannies inside the K-Jet main box (I call it this, for those not
>familiar with K-Jet) would not be great, based on the cross section area of
>parts of it. You know what happens when a carburettor induction manifold is
>badly designed? Fuel separation, uneven combustion etc (carbie V8s now),

I don't understand what the carb discussion has to do with K-Jet.
Maybe I missed something.

>sump dilution, bla, bla, bla. You have seen the crap that collects inside
>K-Jet's air / fuel reg. with normal driving?

Not much if you have an adequate filter. Most of the gunk comes from
the engine side. What is left under the fuel-metering unit, which is
the space I think you're talking about, is in a low-velocity region
- it's a stagnant area. The main corrosion problem which I
understand would arise is with the pivot and base of the control
plunger. 

One could reduce the stagnant volume by drawing air in from that
side, instead of the sensor-plate end. i.e the air would run in the
direction of the sensor-plate lever. That would be an "unusual"
arrangement.

>How / where will air / fuel reg be mounted on boat?

Far enough away (perhaps separated by a thermal barrier) from the
engine and a "long way" from the air inlet. One should try to get it
as close as possible to the inlet tracts - the total duct length of
meter to manifold is less than one metre in most cars.

>At what temp will it operate at? 

Hopefully, about 25 to 30 C. That's the desired inlet air
temperature.  The metering unit may in part be 10 degrees hotter but
the cooling effect of fuel and air flow should mean that it's
somewhat cooler than the surrounding environment.

>Under the bonnet, it operates at under bonnet temp, less what ever cooling
>effect may come from fresh air, depending on where air is tapped. Remote

The "air box" with metering unit often have provision for accepting
pre-heated air.

>mounting on Clair's motor would be an interesting exercise. Check operating

Don't know. Haven't seen the engine, nor the engine compartment.

>temp of box in the car, then on the boat. This will play a part as to how
>quick the thing will rust out. ...

How hot doesn the engine compartment get on a boat? Over 120C?

>I stand by what I have said, no amount of 250,000 trouble free km over the
>road will convince me that K-Jet will function perfectly on water on it's
>second trip out.

>Try this :
>Pull the air cleaner off your Merc. Jam the throttle at 2,500 RPM. Stand

It's a VW. It doesn't have K-Jet.

>back with a kero cleaning gun with the pick up hose in a 205 litre drum of
>salt water. Direct the spray toward the engine and run the experiment for
>half an hour. Shut everything down and come back in two weeks. Pull the air
>valve box apart and inspect all parts.

Why on earth would I want to destroy an engine like that?

Experience tells me that you can't run an engine for any length of
time without an airfilter _on the road_ without severe damage.

That's what I told the SBG Rally team when they brought their cars
into WA in 1997. They ignored me and the engine failed to start on
the second-last day because they had NO compression. The thing had
been re-bored by the dust - total competitive running time at that
point was about 3 hours.

They had filters in the following year.

>The LUCAS throttle bodies on the other hand consist of a butterfly and shaft
>and ram tubes if one has opted for tuned length runners. A rev and a squirt
>with CRC down each throat would be the sum total of post service required on
>our Lucas system, but I think with K-Jet user would always find himself /
>herself reaching for his / her tool box.

I wouldn't run K-Jet without adequate filtering.

If the Lucas system copes with it, then good.

>My previous comments were all about reliability on the water = safety.

Now all you have to do is to stop them running out of fuel, or
getting the fuel contaminated.

>The pic is not a Lucas system, it is Autronic. The turbos are
>Garrett ball bearing type, which by the way reduces back pressure
>for a given boost on the same compressor. This should be a factor
>to consider, with the on going discussion on turbo charging and
>water injection.

And you have nothing to say about the low mounting of the alternator? :-)

-- 
Real Name: Bernd Felsche
    Email: nospam.bernie at perth.DIALix.com.au
     http://www.perth.dialix.com.au/~bernie - Private HP
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