Jay,
Sorry to have confused.
>I am confused about the recent comments on overdrives. I recently
>installed a SV OD in my Series V. I left the 3.89 rear end in. I
couldn't
>be happier with the results. The car is like a dream on the freeways.
Great, you have quite a bit more low end torque than the average
Alpine due to your camming.
>Yet, Jarrid and Dick have mentioned that I have reduced my top speed
and my
>fuel economy. I don't understand. I thought that my 4th gear now is
>exactly the same as my 4th gear before. So then my power and output
should
>be the same. Unless, even in 4th with the OD disengaged, I am still
being
>effected by the OD. Is my 4th now somehow not really "direct" as it
was
>before, and I am getting some slippage even in 4th direct?
4th is 4th in non OD.
You should measure only a very slight loss in performance in
all non-od gears due to oil pumping losses in the OD.
It can be no less than 1/1 due to the locked cone clutch
and the one way overrunning clutch.
BUT, when you clunck it into OD, you are working on the ODs oil,
and have more friction do to the spinning planetary gears.
It has been suggested that you will lose around 5BHP at the rear
wheels in OD due to this condition.
This means that you would be able put more horses to the wheels
without OD because the OD is not as efficient as the straight gear
box.
>I will say that my gas mileage has definitely improved since installing
the
>overdrive. But, then maybe my Holbay engine can pull strong enough at
the
>cruising range.
Perhaps because now you are running at higher speeds, and keeping
your motor at the RPM range where it is most efficient.
>I also am not sure why I would want to install the 4.22 (which the
factory
>itself discontinued on SV Alpines with OD's). It seems that I would
lose
>much of what I gained in highway comfort by doing so.
You get 10% better acceleration, with a sacrifice of 10% higher RPM
at a given speed.
Jarrid
This archive was generated by hypermail 2b30 : Tue Sep 05 2000 - 09:56:33 CDT