[Diy_efi] Continuous VVT system

[Adam Wade]

--- Alexei Pavlov <alexis.pavlov at st.com> wrote:

>> That would make good sense.  I suspect the
>> controller used will need modification, if not
>> replacement.

> No except ignition, as it's a MAF/RPM system.

I meant the valve timing controller.  I doubt they
used an infinitely-variable design architecture for
what is a binary system.

> You may find a Hall-effect sensor to be a more
> robust sensor for that application.

> The problem is to mount the magnet on the camshaft.

Is the car EFI already?  If so, it may well have a
Hall effect sensor on the camshaft already, although
in many cases, it's a simple engine phase indicator,
rather than an angular indicator.

If it isn't, you may find that epoxy and some magnets
may give you the desired effect.

> I'm afraid if I do that steel pieces will stay on
> cams and destroy the cam/tappet surfaces,

I doubt you'd be using magnets powerful enough to do
that, even if ferrous particles were to make their way
to the top end.  Hall-effect sensors have been used on
cams to detect engine phase for several decades witout
incident.

> while without magnets they are washed by the oil.

This is actually where Hall effect sensors show an
advantage over magnetic sensors.  They are far less
snesitive to trigger-to-sensor distances than magnetic
sensors, making them ideal for locations where there
may be fairly dramatic thermal changes over time.

>> An infintely-variable system doesn't seem trivial
>> to me at all.  I think you may be in for some real
>> mechanical engineering challenges.

> Mechanically it's not complexe, you just have to
> control the oil pressure in the VVT device.

I was more meaning adapting the cams, cylinder head,
and hardware on the vehicle now.  Unless it has
infinitely-variable design cams already, that's a big
one.  The Valvetronic system uses not only a different
cam timing, but a different duration as well,
necessitating very unusual-looking cam lobes that
change shape as the cams move laterally.  It would
probably be easier to have infinitely variable
advance/retard.  I'd be interested to see how much
difference that made in comparison to the Valvetronic
design.  My own experience with cam timing tells me
that there's not a tremendous amount of power to be
gained from changing timing alone, in many cases.

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