Members Page/Gergely Lezsak/Idle Control

MembersPage/GergelyLezsak/IdleControl (2005-07-13 22:06:33)

IAC

This is a 3-pin solenoid. I did some measurements to it:

Resistance between pins: (1)- ~~20ohms~~ -(2)- ~~20ohms~~ -(3) (So there are 40 ohms between pin 1 and 3)

Without connection it's opening can be changed by rotating or shaking the solenoid. (Guess there's no "default" position)

Checked wiring as below, and it should work: PWM switched ground to pin1 and pin3 moves the valve to opposite directions, if pin2 has stable 12V+ supply.

Q: Would this use two TO220 FETs for this function alone? 14V/20Ohms = 0.7A capability with flyback. On this 6 cyl machine that would use the two remaining high power FETs if you use the injector drivers, none to spare for other functions. What about the IGBTs? Can those be used for this too? /MS

Control it

Found some info in haltech docs:

BAC Hi

BAC high is a form of BAC idle control that is used for 3-wire BAC valves with two coils. These valves are

sprung so that when no coils are energised, the BAC valve sits at 50% open. Two PWM signals are used to

move the coils. One signal moves the valve from 0% to 50% open, while the other signal moves the valve from

50% to 100% open. The BAC Hi output moves the valve from 50% to 100%. When the target position for the

valve is between 50% and 100%, this output will provide a signal from 0% to 100% duty.

Sounds relatively simple. Some changes and things to-check required in idle_solenoid() :

2 channels must be used instead of config.iac_sol_channel. However, I don't see a reason to add a config variable to make them independent. Eg. config.iac_sol_channel and config.iac_sol_channel+16 would work well (that means if mdh02/mdh82 is used for one solenoid, mdh12/mdh92 can be used for the other).
if one solenoid is powered, the other must be unpowered. This can be remembered or done dumbly every time (SRAM/cycles tradeoff).
iac_conf can be cleaned-up (while merging the unipolar-iac support) as on GenBoard/UnderDevelopment/FirmWare/PowerRelated to make space for the new bit that activates BAC-mode.

All idle control tuning and setup is done with the BAC Hi output. Refer to section 3.13 for details on how to

tune your idle control.

BAC Low

The BAC low output is used to control the BAC valve when the target opening is 0% to 50% open. When the

valve target position is 0%, the output duty is 100%. When the target is 50% open, the output duty is zero to

allow the spring to return the valve to its default position.

BAC Inverted

For 3-wire BAC valves that do not have a spring to return the valve to the centre position, use BAC and BAC

Inverted to control the valve. Connect the BAC output to the coil that pulls the BAC valve open. Connect the

BAC Inverted output to the coil that pulls the BAC valve closed. The BAC Inverted signal is a complementary

signal to the BAC signal. If the BAC output is set to 70% duty, then the BAC Inverted signal is set to 30% duty.

All idle control tuning and setup is done with the BAC output.

pwm freq maybe in 200-1000hz range?

[original doc]

NOTE ! "Original" wiring ('0 280 140 509' valve (from E30 -89) is as follows...

Pin 2 -> 12V supply.

pin 1 -> to Motronic ECU pin 22 (white-green)

Pin 3 -> to Motronic ECU pin 4 (white-yellow)

wiring might be same with the '524' valve ?

Thanks Ben, I'm not sure where it came from, I think these are very similar ones. With motronic control it has some "Brrrrr" sound like the 50Hz on a transformator.

I have the stock(?) idle air solenoid:

But system has an EVAP purge canister valve (said 'auxiliary air control' earlier):

I'm not sure whether this is part of current motronic config or it comes from some jetronic system. Harness is connected however.

options

leave it out and block its connection from throttle body.
or you can control it from GenBoard. A purge canister can trap significant amount of gases (useful in the engine, unwanted in the athmosphere unburnt) escaped from the tank on a hot summer day (such as today).
- resistance is 46 ohms. This might be a useful idea, but has low priority at the moment :)
- actually I used the drill in throttle body for [IAT]