[Diy_efi] Continuous VVT system

[Adam Wade]

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

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

>> Ah, waste spark and bank fire injection.

> No sir, bank fire but twin spark twin distributor
> ignition :-)

Aha.  Yes, I suppose that fits with the period.  I'm
os un-used to seeing vehicles with EFI and
distributors these days...

Which, of course, makes me think about scrapping the
stock EFI and distributors and replacing them with a
single box.  ;)

>> 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.

> Yes, there are, but only on the 'wrong' end. I have
> to remove the engine head to modify it if I want to
> put a sensor on it.

I'm afraid that this may be your only real option. 
You will be lucky indeed if you can fit a sensor
entirely within the cylinder head, maybe cutting a
notch in the cam cover for the sensor lead.

>> The magnets?  Yes, they are attached directly to
>> the camshaft.

> Ok, a good news. I'll think about that.

Most cam sensors I have seen are Hall-effect with a
small magent trigger attached to the nose of the
crank; the Hall effect sensors are less sensitive to
the size of the gap between magnet and sensor, which
can be important with the temperature difference
between cold and hot in a cylinder head!

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

>> External to the cylinder head?

> yes, external.

You'd need to drill a "window" where the sensor could
be inerted, and I'd worry about oil leakage unless you
designed some gasketing for it.  But it's possible. 
I'd look into a motorcycle cam sensor, as they tend to
be very small and robust.

>>> 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 !

> I was talking about the same engine with the VVT
> system disconnected and connected. Just a wire to
> disconnect and you have 2 different engines.

Wow, if it is running that "poorly" at high speeds
with the VVT disconnected, I'm almost afraid to see
the emissions.  ;)

> But in fact I'm not very honest in the case of Alfa
> engine as the IVC is too late when VVT is
> disconnected. :-)

Ah, so, very little overlap and thus reduced
scavenging.  :D

>> 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

> And not very reliable for now. Toyota's system is
> simpler and does the same I believe.

Hm.  I haven't seen Toyota's system...  What markets
is it in?  I'd love to have a look at it.

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