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View Full Version : Engine Frequency Valve Adjustment (and Idle Hunt)


TripleZeroFilms
10-09-2012, 08:06 PM
Well, technically a mixture adjustment, but one that affects the FV.

My question is this: during NORMAL warm running conditions what should the FV be doing - always buzzing, buzzing most of the time, buzzing intermittently, or not buzzing? I've been adjusting my mixture to attempt to get the right result but I've been reading differing accounts on-line as to what exactly I'm shooting for. At the moment it is buzzing almost constantly, but I've also (before my adjustments) had it never buzzing.

I would love to get a straight answer on this so I can finally get my FV operating correctly. Once this is sorted I need to find out why I have such a strong Idle hunt (800-1500 every 1-2 seconds) in park. I've already replaced my Idle speed motor and checked for (obvious) vacuum leaks with no avail.
Bitsyncmaster
10-09-2012, 08:15 PM
The FV should always be buzzing. On warmup it buzzes at a fixed duty cycle of 50%, full throttle 60% and after warmed up will vary between 30 to 40% if adjusted properly. If not adjusted correctly, you may not hear the buzz after warmup.
TripleZeroFilms
10-09-2012, 09:10 PM
The FV should always be buzzing. On warmup it buzzes at a fixed duty cycle of 50%, full throttle 60% and after warmed up will vary between 30 to 40% if adjusted properly. If not adjusted correctly, you may not hear the buzz after warmup.

Could you elaborate on "fixed duty cycle?" I'm not quite sure I know what you mean.
82DMC12
10-09-2012, 09:46 PM
Fixed duty cycle, as in the cycle is set by the lambda ecu and it is not taking input from the lambda probe.
Bitsyncmaster
10-10-2012, 06:02 AM
Duty cycle is the percentage of time on and time off at the rate it switches (50 cycles a second?). So 50% would be on for 20 ms. then off for 20 ms. Duty cycle and Dwell meter time are almost the same terms used on out cars. Four cylinder dwell is a percentage of 90 degrees of angle but it comes out to almost the same thing.

The voltage on the FV is always switching on and off at a fast rate. I think the rate was 50 Hz but that was just the number from memory.

Dwell is read in degrees, 0 to 90 deg. = 0 to 100% duty cycle.