FD BAC close loop idle control DELAY
 

hey guys,
i am wondering if anyone could post a screenshot or post some general settings they use for an FD using the stock BAC for closed loop idle control. i'm using a PS1k.

i am having a problem with the BAC not opening until the car has been running for more than 15 seconds. the first 15 seconds is when i need the BAC the most!

after the 15 seconds has passed, the BAC works as i want it to, but it is slow to react. and if i touch the gas pedal and let it come back to an idle, it waits another 15 seconds to start working again.

anyone? claudio/ludwig?

do you have the thermal wax? on my 3 rotor i kept the wax, and the BAC didn't work because the ecu didn't see zero throttle, because the wax was pushing it open...

^This is because of the throttle pump dead band (not sure what it may be called on the PS1k). Set it to around 2%. This way the BAC will ignore a tad bit of throttle to help the engine idle. Otherwise it thinks you are giving the engine gas, and it doesn't need to turn on.

That's just not true at all. The throttle pump deadband applies only to the throttle pump function. It's purpose is to stop enrichment from being applied during steady throttle conditions because of small jitters in the mechanism. Has nothing to do with BAC operation.

Jacob, think I asked for some info from you in my email reply. Did you ever get that?

Here's what I do to setup a BAC. All this said, as I told Jacob in our emails, I've seen the same thing happen where there is a delay in idle control on first start. The best you can do is set things up to minimize the effects during that first few seconds after startup.

First thing is to know that idle valves, like injectors, have a deadband at the top and bottom of the duty cycle range where you lose control of the air flow. Usually, the top and bottom 20-30% are to be avoided. So you want the active duty range to be 30-70%.

Get the engine warm and set the mechanical idle just below the desired idle speed with the BAC disconnected. Usually about 100 rpm below. Now connect the BAC valve and see what DC the valve needs to run to maintain desired idle. Lets say it settles at 40%. We then want to set the start duty slightly above this value. For this example, I'd set the start duty at 42%. The post start offset should add about 5%. What you end up with in this example is a valve that will run at 47% on initial startup, fall to 42% after a few seconds and hold there until the ECU takes control of the valve. Worst case, idle speed is a little high for the first several seconds after startup.

Watch that your post start enrichment isn't so lean or rich that is greatly effects the idle speed. Yoy can also use post start ignition timing to bump the idle speed up a bit until the ECU goes into closed-loop idle.

Not true.
not on the e6k at least
I spent HOURS on messing with the BAC. Set the throttle pump to 0% on an e6k and the BAC will not turn on. The TPS is so sensitive that with the themowax holding the throttle open just a HAIR, the BAC with "think" throttle applied, do not open.

Don't believe me?
Have something hold the throttle open 2%, then set the pump to 0% That BAC will not turn on.

It's been so long since I've fooled with an E6K, I won't bother arguing that point. You may be correct. Jacob has a Sport ECU though and that's what I'm discussing. Within the Platinum ECUs, Sprint, Sport, and Pro, throttle pump settings have NOTHING to do with idle control.

As J9FD3S pointed out, the thermowax can create issues with a non-zero TPS reading at cold startup. First, it's my opinion, that the thermowax be bypassed when employing engine management that allows for proper idle control. The ECU will do programmable cold start idle up, so why rely on the old analog system?

Now then, the zero throttle readings and what it means with the Platinum ECUs. There is a zero throttle value that is programmable in the TPS setup screen. Anything below this value is considered a closed throttle. The BAC will attempt to control idle below this value. If you're using a zero throttle fuel or ignition map, they will also be employed below this value. In the idle control setup page, there are on throttle vacuum and on throttle boost DC settings for the BAC valve. When the TPS signal is above the zero throttle value programmed in the TPS setup screen, closed-loop is turned off and the valve will run at the DC programmed in these two boxes. This is a handy feature that allows you to do some interesting tricks with the valve. For most purposes though, set the on throttle vacuum DC at the same value as the start duty value. That way, when you come off the throttle, the valve is already running at your start duty value. If the valve is vented to the atmosphere, then you will want the on throttle boost setting to be 0. Otherwise, I set it to the start duty value as well.

Agreed. It's the terminology open the E6k. It's called the throttle pump dead band, but it does have more purpose than throttle pump. They should really call it TPS dead band or something. Whatever :)

In OP's case, try upping the throttle dead band and see what happens. But don't go too high, the car will probably hesitate.

Once again, no.

ludwig, my last email from you did not mention a fix. maybe i didn't receive one.

right off the bat, i am thinking my duty% is too low, at about 20%.

i was particularly interested in the 3 strange values that had quite confusing explanations (the integral, etc.) that i haven't changed.

the strange thing for me is that when i start the car, the BAC literally does nothing (including while cranking, seemingly) and continues to do nothing for about 10-15 seconds, then rpm slowly climbs up to where i have the closed loop idle rpm set to (takes about 3-4 seconds to climb up). there are so many settings that i am looking for a good "base," as i'm not really sure where to start from.
but i will check into it much more tonight and tomorrow.

Log BAC duty cycle from startup until it stabilizes. Sounds like you have the start duty and/or post start offset are too low.

PID gets into a huge topic. I think I posted links to some tutorial videos on the Motec website about PID control. Watch them. It will give you a much better understanding. PID controls how fast the output reacts to change in rpm and how fast it will try to find the target rpm. The idea is to get the start duty as close to ideal as possible so the ECU doesn't need to make much of a change either way. If the start duty is way off, it can take a while for the valve to wind up and hit the target.

totally agreed, the haltech makes the thermowax redundant, although in 2001, i had to run into this problem to learn it!

ok ludwig, great.

i'll tinker tonight and post up results.

ok guys i have been tinkering with this some more, wanting to "start over" from zero.

i followed the instructions in the haltech manual to set the PID values, which state "set all three values to zero, then increase the P values in % increments of 5 until you see a slight oscillation in RPM, then raise the I values until the idle stabilizes."

so when i increase the Proportional, nothing happens unless i increase the Integral to a value other than zero...

i got a little sidetracked with a turbo project, which is now complete (thank god) and i'm back to getting this startup/idle perfect. i will post back in about an hour with some more info, including the results of increasing the start duty and base duty.

ok i have an update.

i had both the start duty and the minimum position way too low.

i used ludwig's numbers above as a starting point (~40% duty) and turned down the idle stop screw to set the idle up to where i want it while at ~30% duty warm (42% cold) and it's nearly perfect.

the PIDs still seem to be a shot in the dark though. i can raise the Proportional to infinity, looking for an oscillation in idle (according to the haltech manual), and nothing happens, then i change the Integral even a 10th of a percent and it goes crazy.

i currently have the P at 50 and the I at 20 and it seems to be working well, but it was a complete guess. anyone have

Watch the Motec webinars on PID control. It explains things about as well as possible. Its still a bit of a black art. Matt Wright told me years ago you usually want the I to be half of the P and that's always worked for me. But understand they are interrelated. Going up or down on one may cause you to also have to adjust the other. The most important thing is to get he start duty right. Do that and the PID control doesn't have to do as much.