Re: Pinch valve question?
 

Ray,
We are actually using the term pinch valve incorrectly in this throttle stop application. It is usually a needle valve used to control the air flow.
Needle Valves

The needle valve is used specifically for accurately controlling the flow of fluids at low flows. The valve is basically a globe valve without the disc. It is generally used provided in small sizes of up to 20mm bore..


This is a good example of a pinch valve:
Pinch Valves

The pinch valve is a theoretically ideal solution for fluid on-off duties. The valve is simple a length of pipe made from an elastomeric material with a mechanical system for squeezing the tube closed when a shut off is required. The valve is a true full bore valve - there are no mechanical parts in contact with the fluid- The operation of the valve is ideally simple- The valve can be easily engineered as a tight-shut off valve..

The valve is often supplied with the pinch tube contained within a outer pipe between the end flanges. This option provides a method of monitoring for tube leaks and provides a degree of secondary containment

The valve has similar limitations to the diaphragm valve. The diaphragm valve is really a variation on the pinch valve principles.. Pinch valves are supplied is for diameters 25 mm - 1000 mm, temperatures -50 C - +160 C, and pressures 0 - 100 bar.

Sorry can't get the pictures to copy.

Re: Pinch valve question?
 

Speculate all you want.....but put a linear potentiometer on the cylinder and connect it to your racepak......then you will know if it's consistent....

Re: Pinch valve question?
 

I have a TPS sensor, logged in my racepak, and I have just looked back at 20+ runs on my Biondo stop, and it comes of the stop at exactly the same rate in each one. This is a small data set, admittedly, but I'm satisfied. I will keep an eye on it, because of this discussion, but I'm thinking is is a tempest in a teapot.

Re: Pinch valve question?
 

I have Rock and mine isn't (But what I don't understand yet is why?)

Re: Pinch valve question?
 

My guess would be that you have it opening up too slow. I had an issue with mine being inconsistant and spoke to Gary at 1 Stop and he had told me that. He told me how to set it properly because it needs to open back up within a specific amount of time, too slow and it will be enconsistant. Going off of memory (and that leaves a lot to be desired) I think he said it needs to be no slower than 6 tenths of a second. I hope this helps
Chuck

Re: Pinch valve question?
 

FWIW, here's five runs of ours. This is rpms coming off the stop with our Biondo stop. Only appreciable difference is the setting of the timer.

http://emdubracing.com/wp-content/up...09/offstop.jpg

Re: Pinch valve question?
 

Thanks CW that's the kind of info I am looking for mine is a lot slower than .6 actually it's in the .85-.87 range so per your experience and Gary's advice it sounds like I need to open the air control needle (i.e. pinch) valve to speed up the opening to the .5 to .6 range. I'll give it a try! again thanks.:D

Re: Pinch valve question?
 

sounds like you guys are on the right track.....bump the trace over so the lines are on top of each other...then you can see if it's acting the same.....just keep trying stuff till they lay on top of each other.....I have a pile of stops because of it........

Rock

Re: Pinch valve question?
 

I hate to tell you those are shyt.

Re: Pinch valve question?
 

Thank you for your thoughtful input.