Re: So Slow

[ejfluhr@austin.ibm.com (Fluhr)]

> > 5) Franco industries variable-cam-timing gear.  As I understand it, this
> >    adjusts the camshaft timing as a function of rpms (some kind of inertia
> >    mechanism?).  Having advanced my camshaft forward and back one tooth
> >    and seeing how it affects the power band, this option appears very
> >    attractive.  It is not inexpensive, however, and I have not heard of
> >    any first-hand reports from those who have tried it.
> 
> The major issue here with the N/A I5 engines is that the distributor is
> run off of the back of the cam shaft.  When you fiddle with the cam
> timing, the ignition timing is going to change as well.

Yup, yup.  But as the sprocket retards the cam timing, does it not also 
(via the distributor gears) retard the ignition timing?  (and same issue
regarding cam timing advance...)  And is not retarded ingition timing
preferable for higher rpms?

> I have not ever played around with it to find out if the change would be
> helpful or detrimental.

I advanced my camshaft 1 notch and retimed to factory specs.  The torque
on the low-end was really strong, but the engine basically died above
3500rpms.  I also tried it the other way...retarding the cam by one notch
on the cam sprocket and retiming the ignition.  The engine was terrible
at low rpms, barely getting out of its own way, but was very powerful in
the 4-6K rpm range.  I ended up leaving it at stock, because that felt
the best for daily driving.

This leads me to believe that the variable cam sprocket, assuming it
starts the camshaft slightly advanced and then retards it as the rpms
increase, would keep the engine at this peaky point of its powerband
(try saying that 5 times fast).
 
Is there anyone out there that has used the Franco sprocket on an I5,
or even a VW 4-cylinder?  Anyone who knows how it works?

Later,
Eric
'85 Coupe GT
---
Eric J. Fluhr                                Email:  ejfluhr@austin.ibm.com
630FP Logic/Circuit Design                   Phone:  (512) 838-7589
IBM Microelectronics Div.                    Austin, TX