Quote:
Originally Posted by parsonsj
So I've got another couple of questions for those in the know.
1. Anybody connect a "clutch-in" sensor to the ECM? It seems that the key to not having decel pop in the exhaust during clutch-in (like a gear shift) is for the ECM to know what the clutch is doing.
2. Any thoughts on adjusting the AC torque vs AC pressure table? The factory AC compressors are variable displacement... while our after-market Sandens are clutch-controlled. Does that make a difference in how much torque is consumed by the compressor for a given amount of AC pressure?
thanks!
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Clutch position sensor allows you to enable and use CFCO (clutch fuel cut off) similar in function to DFCO (decel fuel cut off) but obviously triggered off clutch position.
Popping can still occur if spark / fuel criteria when entering CFCO / DFCO is wrong. Many calibrators turn off DFCO to eliminate decel popping as an 'easy' fix - but why fuel an engine that you are not asking to create torque? Takes some time to get CFCO/DFCO entry / exit criteria correct to eliminate pops.
Biggest benefit from CASS (clutch apply sensor switch) is ability to rapidly drop engine RPM's with clutch apply (which puts less load into trans syncro's as well) as CFCO cuts fueling to engine. BTW - later calibrations use potentiometer style CASS - while earlier systems used Top-of-Travel and Bottom-of-Travel switches (separate). You typically cannot change the type of switch used with your particular software.
Your second question while correct - you
could adjust table that relates AC compressor torque to pressure, but really makes no difference as you are likely not using torque model (or it is vastly incorrect) if you have modified your engine. The slight load from AC compressor is nothing to the engine (assuming V8's.....). This does assume you do not have spark advanced at idle so much as to remove all reserve torque (which is ability of engine to absorb additional torque loads with negligable effects).
Dave