>
> Howdy folks,
>
> Took the Spit to work today thinking the fog would clear (not). Had
> the bonnet open to show off my new Earl's steel braided plumbing to a
> buddy, looked down and saw the vacuum line (from carb to dizzy) was just
> hangin' there...disconnected from the dizzy. As I had regreased the tach
> drive cable following the recent thread, I guess I knocked it off at
> that time. Thing is, I didn't notice any change in performance during
> my morning commute. I'm running the Crane electronic ignition and the
> Weber DGAV, and I'm wondering if the vacuum should even be connected
> now. Should I plug the vac on the carb? If so, what should my timing
> mark be (static and dynamic, please).
>
> I'd be much happier if the damn thing acted up when this kinda thing
> happens. Why didn't it?
>
Ok, here's my understanding. Somebody correct me if I'm off anywhere.
That's your vacuum retard line. It uses the vacuum created at idle to
retard the ignition way back. The theory is- you don't need the the engine
running at optimum advanced when idling, and if you retard it you reduce the
temperature in the cylinders, and therefore reduce NO2 emissions.
If the system is working properly, disconnecting the vacuum line while the
car is idling should make the engine jump up about 200-300 rpms. While not
at idle, it should have no effect.
While the system connected and working properly, your timing should be set
to 2 degrees ATDC (i.e. very retarded). With the system disconnected your
timing at idle should be about 10 degrees BTDC.
Now, as to whether you should have the system connected or not, well...
Supposedly with the system connected, there's a small lag time when coming
off idle as the dizzy moves back into the normal advance curve. I've never
noticed this myself, but then I'm not the type to remove my air pump for the
extra ~1 bhp it gains me either.
----
Jeremy DuBois jer@thlogic.com
Manager, Info Systems http://www.thlogic.com/~jer/
Thermalogic Corporation '60 TR3A, '74 MGB, '76 Spit
|