[Diy_efi] Continuous VVT system

[Adam Wade]

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

> Of course, I'll use an additional ECU to control
> VVT.

I wasn't sure if you meant to adapt what you already
had or not.  It occurs to me now that the system
currently in place may be strictly mechanical in
nature, as the simpled Honda system is.

> The original ECU does not check if the VVT is
> working.

Very handy to have them seperate, in such a case as
yours.

> It's EFI but without cam sensor as it's 2s per
> cylinder.

Ah, waste spark and bank fire injection.  In some
ways, this offers extra flexibility, since you don't
need to accomodate two cam position sensors, one for
the VVT and one for the EFI.

Check and see if the end of your camshaft could accept
a drilling and tapping.  Some cams come with a tapped
and drilled hole on the end already.  Fixing a trigger
wheel of some type to the end of the crank would then
become a matter of physical space.

>> 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.

> Yes, but they are not in direct contact with the
> camshaft.

The magnets?  Yes, they are attached directly to the
camshaft.  I can show you pictures straight out of
some motorcycle service manuals I have lying about. 
Attaches with a cap-head screw onto the end of the
(ferrous) crankshaft.  You don't need a very powerful
magnet.

> I would have to fix magnets on the camshaft, as the
> front of the camshaft is 'unshifted' (the VVT device
> is here).

Is there room at the rear?  I don't have a clear
picture of the cylinder head layout, so let me know if
that is a ridiculous question.  ;)

> And I'm not sure the epoxy (120 degres tolerant)
> will stay for a long time if the oil is at 110
> degres.

There should be industrial epoxy capable of doing what
you want, assuming there's no way to attach a trigger
wheel to the end of the camshaft.  You could also
theoretically cut grooves near the end of each
magnet's outside surface when installed, and run two
loops of safety wire around to prevent losing a magnet
should the epoxy fail for any reason.

> Another point is that magnets loose their
> 'magnetism' when heated.

Not all of them, as is apparent from their use in cam
position sensors by default.  It might require some
research to locate ones suitable for the task.

> The better would be to put sensors on the back of
> the camshaft,

External to the cylinder head?  I gather so from your
further comment on engine packaging.

> The Alfa Romeo engine without VVT should deliver
> something like 90HP from a 2L engine. The VVT brings
> the power at the 150 hp level on a 2s/cyl engine at
> 6000RPM, not so bad !

> The gain come form the overlap and IVC
> modifications.

So other than the VVT changing the advance or both
cams, nothing else between the cars is different (save
for fuel mapping)?  Same intake, same exhaust, same
cams?  If so, I suppose they must have deliberately
set the valve timing to give fairly poor performance
on the base model!

> Of course I would prefer to also have the variable
> lift.

If you really want to get complicated about it, you
could get a late-model Valvetronic head and control
system from a BMW, and saw off two cylinders.  :D 
Stranger things have been done!

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