BAC operating freq
11-11-12, 08:23 AM
#2
page F-45 of the FD service highlights document states that the FD idle speed control/bypass air control valve operates at 244hz. Given that based on first-hand experience the FD Power FC computer works fine with the FC solenoids, sensors, etc (for the most part) we can safely assume that the FC BAC valves operates at 244hz, or at least operates well enough. You can certainly try different frequencies, but 244hz is a good starting point.
11-11-12, 08:52 AM
#3
I did this with the MS2, but am hardly getting any results. It's set to 91.5 right now and seems to work - though I haven't pulled the BAC to actually look... I may do that today. The reason why I'm asking is that when I set it to 244Hz I got nothing - no ability to raise/lower idle by changing duty cycles.
11-11-12, 09:19 PM
#5
page F-45 of the FD service highlights document states that the FD idle speed control/bypass air control valve operates at 244hz. Given that based on first-hand experience the FD Power FC computer works fine with the FC solenoids, sensors, etc (for the most part) we can safely assume that the FC BAC valves operates at 244hz, or at least operates well enough. You can certainly try different frequencies, but 244hz is a good starting point.
They're 2 completely different valves.
I have limited control over my idle speed. At "100%" open, it only revs up to at most 1500 rpm, and that's stone cold with the thermowax holding the throttle plates open a tad. I doubt that my BAC is doing a single bit of good.
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11-12-12, 09:53 PM
#9
I've read both yours and arghx's old posts in the last few weeks on this... I really would like someone to just go out and verify on an otherwise stock ECU and BAC to settle it... since Mazda didn't feel like including it in their original info.
11-13-12, 10:46 AM
#11
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i'm pretty sure its in the service highlights books, its the same as the FD
11-13-12, 06:17 PM
#14
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11-13-12, 06:52 PM
#15
With that said, like 104324923098432904 people could have gone out and checked this for us by now... but I'm sure most don't know what the hell we're talking about
11-14-12, 11:44 AM
#16
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Come on man! I'm no n00b! There isn't a copy of 2nd gen service highlights on there... which is where it may be. I found one elsewhere on the web, but it wasn't in there.
With that said, like 104324923098432904 people could have gone out and checked this for us by now... but I'm sure most don't know what the hell we're talking about
With that said, like 104324923098432904 people could have gone out and checked this for us by now... but I'm sure most don't know what the hell we're talking about
you're lucky actually, when we started setting these up in the 90's we didn't have the book, and had to experiment, the valves make all kinds of weird noises at the wrong frequency.
11-14-12, 06:16 PM
#18
USE 244Hz! Go from there. The trick is figuring out the various operating positions. It will operate at other frequencies, but lower will make more noise. Mine for example operates at 100Hz (10ms Pulse), but sounds a bit like a buzzer. I have to run it there because my old haltech (I think) doesn't have enough power to run the valve. At least I couldn't get it to work there...
11-14-12, 07:18 PM
#19
The issue he and I are both experiencing is that the BAC isn't doing **** for idle control. He's had his set at somewhere in the neighborhood of 80~ish Hz, and mine has been set at 244Hz since I first installed the MS ecu a little over a year ago. No matter what the setting, no matter how far open the BAC is commanded, it won't change the idle speed. So all we're trying to do is get an actual reading from someone with a stock ECU and a multimeter. I have some people "locally" that I can track down and I'll measure the damn thing myself if I have to Rob 
11-14-12, 08:30 PM
#21
Changing the duty cycle presently has jack **** effect on idle speed... not good.
When the engine bogs at idle, it opens and kicks the idle back up... so I know the valve works, I can hear the vacuum "leak" - its open to atmosphere so I can hear it.
I have run it as 30.5* X 3, because that's whats in AaronCake's writeup... but that aint 244Hz!
That would be 30.5 X 8, which I have tried... and doesn't work either.
11-14-12, 08:40 PM
#22
Try a multiplier of 5; meet it half way. As the car is first started and warming up, can you alter settings real time? Try a halfway duty cycle, and keep increasing it to see if the idle starts to increase.
Do you hear the valve buzzing at all?
On my old haltech, you would increase what's call the minimum position % (perhaps a duty cycle equivalent?) until the idle started to rise. Then you would know where the valve was effectively taking over the idle.
Do you hear the valve buzzing at all?
On my old haltech, you would increase what's call the minimum position % (perhaps a duty cycle equivalent?) until the idle started to rise. Then you would know where the valve was effectively taking over the idle.
11-14-12, 08:41 PM
#23
Yeah, the BAC does work. I can apply straight up 12v to it and it opens wide up. My Megasquirt has a rather robust TIP120 transistor to drive the BAC. Plenty of current capability at 8A/80W.
There are quite a lot of other settings:
Idle Open Duty %
Idle valve closed duty%
Idle activation RPM adder (rpm)
Ilde activation TPS threshold (%)
Close delay (sec)
Leave valve closed above: (rpm)
For this # of seconds: (sec)
Min Duty for PID(%)
RPM with valve closed(rpm)
RPM with valve open(rpm)
PID delay (sec)
Crank to run taper
PID ramp to target time
PID control interval
Proportional Gain
Integral Gain
Derivitave Gain
PID lockout rpmDOT threshold
PID lockout max decel load(%)
PID disable RPMdot
There are quite a lot of other settings:
Idle Open Duty %
Idle valve closed duty%
Idle activation RPM adder (rpm)
Ilde activation TPS threshold (%)
Close delay (sec)
Leave valve closed above: (rpm)
For this # of seconds: (sec)
Min Duty for PID(%)
RPM with valve closed(rpm)
RPM with valve open(rpm)
PID delay (sec)
Crank to run taper
PID ramp to target time
PID control interval
Proportional Gain
Integral Gain
Derivitave Gain
PID lockout rpmDOT threshold
PID lockout max decel load(%)
PID disable RPMdot
11-14-12, 08:44 PM
#24
Yeah, the BAC does work. I can apply straight up 12v to it and it opens wide up. My Megasquirt has a rather robust TIP120 transistor to drive the BAC. Plenty of current capability at 8A/80W.
There are quite a lot of other settings:
Idle Open Duty %
Idle valve closed duty%
Idle activation RPM adder (rpm)
Ilde activation TPS threshold (%)
Close delay (sec)
Leave valve closed above: (rpm)
For this # of seconds: (sec)
Min Duty for PID(%)
RPM with valve closed(rpm)
RPM with valve open(rpm)
PID delay (sec)
Crank to run taper
PID ramp to target time
PID control interval
Proportional Gain
Integral Gain
Derivitave Gain
PID lockout rpmDOT threshold
PID lockout max decel load(%)
PID disable RPMdot
There are quite a lot of other settings:
Idle Open Duty %
Idle valve closed duty%
Idle activation RPM adder (rpm)
Ilde activation TPS threshold (%)
Close delay (sec)
Leave valve closed above: (rpm)
For this # of seconds: (sec)
Min Duty for PID(%)
RPM with valve closed(rpm)
RPM with valve open(rpm)
PID delay (sec)
Crank to run taper
PID ramp to target time
PID control interval
Proportional Gain
Integral Gain
Derivitave Gain
PID lockout rpmDOT threshold
PID lockout max decel load(%)
PID disable RPMdot