CIS mixture tweaking Q

[pfcs49]

The CPR (cntrl pres rgl) is a straightfoward/normal regulator whose pressure is a function of the pressure of the internal spring and the augmentation of the bi-metallic strip that the spring reacts against it. If you arrange a threaded rod to react this spring base at the bimetallic end, you have made it adjustable. You can improve it's position and arrange a controlshaft into the cockpit. If you make the CPR adjustable, you'd better install a pressure guage in the side of the circuit that has the larger banjo bolt, or you'll drive yourself crazy trying to know whats going on if you have a (mixture) problem. (also, if you have a significant fuel starvation problem, you will see it-when system pressure reaches control pressure, the contol pressure will be system pressure; since injector pop off {operating} pressure is 35-37psi, and the metering pressure drop accross the metering plunger is only 1.5psi, CIS will fuction with lower system pressures until they get quite low. When you see a stable control pressure start diving, this is indicating fuel starvation. You will notice how control pressure jumps around when you suddenly accelerate as the airflow plate jams up the metering plunger and momentarily influences pressure in the circuit, and you will quickly see what is normal.
However...I still can't think of a scenario that would explain the huge fatness top end on the dyno; with CIS the problem is usually leaness. Is it possible you had an instrumentation issue? Unusual as most problems will drive a wideband to read erroneosly lean (exh air leak, misfire, etc).
A simple and super reliable way to monitor system and control pressures: take 14mm and a 13mm headed banjo bolt; drill !/8" hole thru middle of both, then counterbore that hole from the top w/ a 5/16" bit just enough to stand a short (3/4")piece of 5/16" steel tubing in it; braze the tubing to the banjo; put the 14 in the CPR, the 13 in the cold start valve and connect 2 100psi guages w/8mm fueline and miniclamps.
Good luck-I'm curious what will be the answer here! phil

[jlinfert]

The CPR (cntrl pres rgl) is a straightfoward/normal regulator whose pressure is a function of the pressure of the internal spring and the augmentation of the bi-metallic strip that the spring reacts against it. If you arrange a threaded rod to react this spring base at the bimetallic end, you have made it adjustable. You can improve it's position and arrange a controlshaft into the cockpit. If you make the CPR adjustable, you'd better install a pressure guage in the side of the circuit that has the larger banjo bolt, or you'll drive yourself crazy trying to know whats going on if you have a (mixture) problem. (also, if you have a significant fuel starvation problem, you will see it-when system pressure reaches control pressure, the contol pressure will be system pressure; since injector pop off {operating} pressure is 35-37psi, and the metering pressure drop accross the metering plunger is only 1.5psi, CIS will fuction with lower system pressures until they get quite low. When you see a stable control pressure start diving, this is indicating fuel starvation. You will notice how control pressure jumps around when you suddenly accelerate as the airflow plate jams up the metering plunger and momentarily influences pressure in the circuit, and you will quickly see what is normal.
However...I still can't think of a scenario that would explain the huge fatness top end on the dyno; with CIS the problem is usually leaness. Is it possible you had an instrumentation issue? Unusual as most problems will drive a wideband to read erroneosly lean (exh air leak, misfire, etc).
A simple and super reliable way to monitor system and control pressures: take 14mm and a 13mm headed banjo bolt; drill !/8" hole thru middle of both, then counterbore that hole from the top w/ a 5/16" bit just enough to stand a short (3/4")piece of 5/16" steel tubing in it; braze the tubing to the banjo; put the 14 in the CPR, the 13 in the cold start valve and connect 2 100psi guages w/8mm fueline and miniclamps.
Good luck-I'm curious what will be the answer here! phil
[/b]

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