Bravo.
And well stated entirely. I didn't get back soon enough and probably could not have put it so well anyhow.
One thing that seems to be a misconception is how most prop valves work, so this might help you better visualize the pressure thing. Most of them work off total pressure. Thus if you put in 600lbs of pressure you get out 600 right? Wrong. This is the kneee Jim is speaking of.
Suppose you have a knee of 450. Now when you put in 400 all four wheels get 400, but when you put in 600 the rears might only get 300. How's that? Well, as the pressure input goes up; the pressure output to the rear goes down. Intentionally. Most factory valves have a preset knee and reduction, they generally just shut down the rears for safe measure. (*the Impala goes from 65/35 to 90/10 under hard braking! And with the weight and wheelbase of this you KNOW there's room for improvements!!)
So what's a manual valve do? It allows you to change the point which reduction occurs. BUT it does it differently than most 'cut off valves' in that it they go up to about 55% reduction total based on the set knee and input pressure. You change where you want it to cut out. Seeing your'e not going this way we'll leave it at that.
Ok. Now you sitll wonder what the hell all of this has to do with those sand bags in the trunk don't you?? With the weight over the rear wheels there is less dive and weight shift is not so quick. So what? Well, as you put in 400lbs of pressure all four wheels brake, as you increase this to 500 all four do some with the rears doing only slightly less...600lbs and they are begining to shut down. Fair enough. Now consider the stock 'nose dive' where the 400-600 input goes up real fast as there is no weight out back to hold down the rear LONGER thus immediate shift places nearly all the work up front.
To this end both shocks, springs, tires, ride height, weight bias and alignment can play on this. That's dynamic braking. What's the magic set up? The one that works best for your parts and car in those conditions operating in.
I'm done, fingers tired. I'll let Jim put in more data and correct any comments he feels I have incorrect. He's the engineer, I just try to improve on what he's done! \\
*excuse my spelling...
Last edited by Todd TCE; 03/16/05 02:10 AM.
