compensator operation

From: tom-nooneofconsequence (milveh@carr.org)
Date: Mon Dec 02 2002 - 14:33:43 PST


ok, several people wanted to know about the compensator and if it should

be by-passed. first let me say a few things about the system. if you
like adding gauges there are 4 that i think are justified - a clock,
exhaust temp gauge, boost pressure gauge, and a 0 - 100 psi fuel
pressure gauge plumbed to the bleeder on the final fuel filter. this
last gauge will tell you some important information. fuel from the tank
first goes through a booster pump on the side of the injection pump. at

idle there should be around 35 psi and at full rpm around 70+ psi. if
this reading is a lot lower it shows dirty fuel filters or weak booster
pump. now this pressure is critical to the compensator working properly.

the pressure is applied to a piston in the top of the comp. and tries to

raise it. at the same time there is a calibrated bleed hole venting this

pressure back to the tank. the thicker the fuel the higher the piston
goes. on the bottom of the piston is a rod that raises a precision ramp,

and this ramp limits the range of the fuel control rod. the position of
this ramp is adjusted by the main fuel adjustment screw. if you bypass
the compensator you are in effect leaving the ramp at its lowest
position and giving the engine a lot more fuel. of course it will run a
lot better, but it may also melt the pistons......... if you choose to
by-pass be sure you check the exhaust temp. max 1200f on a hot day. the

boost pressure gauge will also give you valuable information at this
point. at full throttle and full load at 2300 rpm there should be 9 psi
at the manifold. this is the factory setting and is in my opinion very
conservative, but this will give you the factory performance.
tom



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