[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: Improved S-Knob

> When we spoke on the phone a few months ago I mentioned that I was going
> to try putting a check valve inline with the W/G vacuum line to prevent
> engine vacuum from being applied to the W/G. 
> At any rate with the check valve installed I think there is a noticable
> difference in how fast the boost pressure comes up during gear shifts. I
> have a mechanical boost gauge and can see that the pressure comes right
> up to about 6 psi when shifting before it lags for a second or two and
> then takes off for 15 psi. Without the check valve the boost only comes
> up to about 2 psi before lagging and then taking off to 15 psi. I did
> put a small pin hole in the hose to the W/G to prevent any pressure
> spikes from gradually building up pressure on the W/G above what is
> required for the 15 psi of boost.
> I haven't tried any timed runs yet but the throttle response between
> shifts does seem a little better by the seat of the pants. 

... interesting note Russ ... thanks for posting it!  I don't know if I
necessarily follow everything you are saying, but when I thought about 
putting a check valve in the line to the top of the WG I decided that it 
would be a VERY good idea.  If you think about it, all that S-K was inten-
ded to do was to augment the WG spring with the addition of a little 
pressurized air on top of the WG.  If you have the pressure regulator in 
line before the check valve you will limit the pressure of the air supply 
to the WG such that if the pressure regulator can overcome the pressure in 
the WG it will supply additional pressure through the check valve, but 
when the boost is reduced the check valve will prevent the air spring from 
being deflated, so it is there even earlier on subsequent boost events.  I
can't say I'd be worried about "pressure spikes" given the pressure regu-
lator is in the circuit.  I suppose if you assumed that there were no 
leaks you'd have to do something to depressurize the WG if you ever wanted 
to decrease the pressure regulator output, but I'd bet that over time 
there would be sufficient leakage to allow the system to adapt to the 
lower pressure.  What would be interesting would be to put the pressure 
gauge on the WG side of the check valve to see how long the WG remained 
pressurized ...

I do think that your addition of the check valve is responsible for the 
perceived improvement in the boost performance at shifts ... it might 
even allow the boost to come on sooner from a stop!  Thanks again for 
the great idea!

San Jose, CA (USA)