# VEMS iac help



## chrgdVR (Aug 2, 2004)

ok so i have a 1.8t awp engine code 
im using a 24v75mm vr6 cable throttle body 

im trying to figure out how to wire the idle motor on this TB 
some info from the bentley... 

pin8/1 br/li~ grd 
pin8/2 ro/li~ im thinking thats my power 

and then pin 8/3 and 8/7 are my idle switch 









now my problem is in the bently it looks like theres power and grnd to a motor in the throttle body along with an idle tps and an idle switch 

i wired my tps no problem but the motor to control my throttle im pretty confused cause it doesnt look like the iac types shown below from the vems website 

got this info here....http://www.vems.hu/wiki/index.php?page=InTake/ThrottlePlates/VAGPassiveThrottle 

im trying to figure out how to wire this up and control it with my VEMS 
heres the info on the iac off the vems website....hopefully someone can help and this will prolly help anyone else in the future trying to do this 

Idle Air Controller (IAC) 
An Idle Air Controller (IAC) is used on most fuel injected engines to provide a method of controling the engine's idle speed. When the car is warming up or an additional load is put on the idling engine such as the additional current of an electical fan or air conditioning compressor it is necessary to raise the engine's idle speed to stop it from stalling. 

IAC Types 

There are a number of different idle speed controllers: 

Wax is the simplest and most common on Japanese cars and are not controllable by the ECU in that they use a wax filled piston which opens the throttle slightly when cold and closes it when the heat causes the wax to expand. 

Solanoid IACs use a single coil to open or close a valve in the inlet (in some cases to actually move the throttle plate). The simplest can be either opened or closed and will cause small increase in idle speed. More sophisticated types can be pulsed to provide a variable increase in RPM. 

Multicoil and Stepper motor IACs allow a more complex level of control, in its simplest form it will have two coils to open and close the idle valve. 

Choosing the correct IAC connection 
Single coil types are relatively simple to connect, the only thing you need to know is the resistance of the IAC's coil by measuring it with a DVM. Once you have the resistance value use Ohms law to calculate it's current load. I=V/R. 

Examples: 

The IAC coil for a Nissan 200SX is measured at ~11 ohms a voltage of 13.8V would mean a current of ~1.26A (13.8/11) which means that a spare high current port (EC36-pins6, 9, 17 or 18) would need to be used. 

The Toyota "Idle Up Valve" found on the early 4A engines has a solanoid coil with a resistance of ~44ohms, which gives a current of 313mA(13.8/44). As this is less than the maximum 350mA value for EC36-pin3 (Fast Idle) it would be possible to connect it, but this is only advisable if you are using all the other high current pins. In all other cases its advisable to use one of the spare pins. 

Dual Coil Solenoid IAC Control 
Found in some BMWs (Bosch) along with Toyota & Subaru, These have three pins, one of which is common, one is a solenoid that opens the idle valve, the other is a solenoid that closes the valve. If neither coil is activated the valve remains in a 50% open poisition (preset-spring type), or moves freely between opened/close position (no spring type). 











EC36-pin6 to IAC close pin 

EC36-pin17 to IAC open pin 

Configuration 

Set IAC actuator speed/pwm freq 

stepper speeds : 0 - 976 steps/s, 1 - 488, 2 - 326, 3 - 244, 4 - 195, 5 - 163, 6 - 139, 7 - 122, 8 - 108, 9 - 98, 10 - 89, 11 - 81, 12 - 75, 13 - 70, 14 - 65, 15 - 61. 

pwm freq: 0 - 244 Hz, 1 - 195, 2 - 163, 3 - 139, 4 - 122, 5 - 108, 6 - 98, 7 - 89, 8 - 81, 9 - 75, 10 - 70, 11 - 65, 12 - 61, 13 - 57, 14 - 54, 15 - 51. 

Stepper Motor IAC 
One of the most common types of IACV after the single coil solenoid is the Stepper motor type. The 4 pins of the 2 coils are connect to the 18pin Econoseal plug. 









The coils are preferrably connected between A-B and C-D stepper outputs: 

EC18-pin4 Stepper-A 

EC18-pin10 Stepper-B 

EC18-pin5 Stepper-C 

EC18-pin11 Stepper-D 

Configuration 

Using the dialog Extras->Idle Settings General 

Set Control Type to PWM/Stepper 

Initially IAC actuator speed/PWM freq should be set to 10, this number will need to be reduced to speed up the stepper, this needs to be done once the idle control is working. 

Set Max steps to extend to a low number, as this defines the number of steps that the controller will allow the stepper to make, too many steps will cause the controller to open too far and potentially jump the IACV. Initially start at 50 steps and increase the number once you have stable idle. 

Under Iac Hardware setup 

Set Type to Stepper 

The stepper pattern is defined as a binary pattern where: 

Coil A=00 Coil B=01 Coil C=10 Coil D=11 

So to define your pattern use the Windows Calculator in binary mode and convert to decimal mode, then put the result in the Iac step sequence box. 

For example the typical patterns are 

D->B->C->A which is 11->01->10->00 11011000 or 216 in decimal. 

D->A->C->B which is 11->00->10->01 11001001 converted to decimal is 

201


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## Crispy222 (Mar 10, 2008)

Good questions, but I'm not quite there yet with my configuration.

Find anything new somewhere else? Looks like VEMS developement isn't quite there as a whole yet.


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## chrgdVR (Aug 2, 2004)

Oh wow hey man I just replied to your pm... I didn't see this post until now. 

This thread is from when I first started with my vems install

I'm not using the TB motor for idle control as implementing an idle switch to disable the tps isn't there in the vems firmware yet... Hopefully in the future they will have control for this type of idle control.

I'm actually controlling my idle via the ignition by using 10* advance and retard to control idle... Works great but stalls when cold at times

I'm actually trying I install a Iacv from 034. It's a gm stepper valve.. Hopefully I'll have it working tonight when I get home from work..

If you need help with your coils and config setup let me know. I'd be more than happy to help you out with what I can.. I know it took me forever to figure out alot I things when I first started


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## need_a_VR6 (May 19, 1999)

Tps is pins 4,5,7 just like the diagram. 1/2 is the iac, its a 2 wire, controlled dc motor. The best driver seems to be a half h-bridge but one side pwm can work in open loop.


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## Prof315 (Jan 5, 2009)

need_a_VR6 said:


> Tps is pins 4,5,7 just like the diagram. 1/2 is the iac, its a 2 wire, controlled dc motor. The best driver seems to be a half h-bridge but one side pwm can work in open loop.


Actually I'm finding that one side pwm works better with closed loop, at least with MS3. It's not perfect and if someone could decipher the components needed here: http://www.msextra.com/forums/viewtopic.php?f=67&t=47346 , I'd be willing to have some boards made up and sell them at cost.


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## need_a_VR6 (May 19, 1999)

That thing seems overly complicated, it would be more useful on an OBD1 car where you can't change the idle frequency. 

I am bench testing a push/pull TIP120/125 pair once I find another tb that isn't broken.


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## Prof315 (Jan 5, 2009)

need_a_VR6 said:


> That thing seems overly complicated, it would be more useful on an OBD1 car where you can't change the idle frequency.
> 
> I am bench testing a push/pull TIP120/125 pair once I find another tb that isn't broken.


I have several Paul.....


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## chrgdVR (Aug 2, 2004)

need_a_VR6 said:


> Tps is pins 4,5,7 just like the diagram. 1/2 is the iac, its a 2 wire, controlled dc motor. The best driver seems to be a half h-bridge but one side pwm can work in open loop.


 Haha all this electronic talk is Greek to me.. No idea what an hbridge is lol


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## chrgdVR (Aug 2, 2004)

Prof315 said:


> Actually I'm finding that one side pwm works better with closed loop, at least with MS3. It's not perfect and if someone could decipher the components needed here: http://www.msextra.com/forums/viewtopic.php?f=67&t=47346 , I'd be willing to have some boards made up and sell them at cost.


 Wait so you've gotten the idle control to work with the vw TB and ms3 or are u still working on it?


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## Prof315 (Jan 5, 2009)

chrgdVR said:


> Wait so you've gotten the idle control to work with the vw TB and ms3 or are u still working on it?


 It works, just not perfectly.


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## chrgdVR (Aug 2, 2004)

How did you get it to work? Hardware changes? Do u have to short the tps to ground somehow?

I'm interested in knowing how yours is working?


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## Prof315 (Jan 5, 2009)

chrgdVR said:


> How did you get it to work? Hardware changes? Do u have to short the tps to ground somehow?
> 
> I'm interested in knowing how yours is working?


 Actually it wasn't too hard. I wired up the idle motor part of the throttle (pins 1 and 2) backwards so pin 1 is PWM control and pin 2 is switched 12V. Then I set the MS3 PWM idle control to run inverted. I'm running the valve at 200hz and the DC range is roughly from 40% to 100%.


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## need_a_VR6 (May 19, 1999)

I have customers running those tb as well, 200hz seems to work ok.


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## chrgdVR (Aug 2, 2004)

Prof315 said:


> Actually it wasn't too hard. I wired up the idle motor part of the throttle (pins 1 and 2) backwards so pin 1 is PWM control and pin 2 is switched 12V. Then I set the MS3 PWM idle control to run inverted. I'm running the valve at 200hz and the DC range is roughly from 40% to 100%.


 when do you have the idle motor set to come on around 3% tps or so? how does it affect the tps? since the motor is moving the blade and all the tps must obviously move too right...and it seems to be working alright? 

im thinking i might wire mine up and give it a try sometime, im curious to how well it works. i dont really need it since im using a gm stepper valve to control my idle, but if i like the way it works maybe ill ditch my current iac setup.. thats one less thing in the engine bay.


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## need_a_VR6 (May 19, 1999)

For all the iac's I have run, i have left them active all the time. No downside that I have seen from this. 

TPS changes a bit when active but at least with ms every critical setting is %tps change so the little it moves is insignificant.


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## chrgdVR (Aug 2, 2004)

cool are you guys using any ignition advance to help control idle or can the tb motor control it well enough on its own? 

i think i'll try this out this week and see how it works. i might need some help with the settings, so you guys are prolly going to hear from me about this.. cool to see that people are using this kind of idle control


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## Prof315 (Jan 5, 2009)

chrgdVR said:


> cool are you guys using any ignition advance to help control idle or can the tb motor control it well enough on its own?
> 
> i think i'll try this out this week and see how it works. i might need some help with the settings, so you guys are prolly going to hear from me about this.. cool to see that people are using this kind of idle control


 Yeah I'm using MS3's Idle Advance feature. I run a seperate 4x4 table for idle only.


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## need_a_VR6 (May 19, 1999)

I would just lock advance at a tps threshold and let the valve do the rest. Depends a lot on the setup, how much cam it has, etc. I was running a 24v with stock cams at the time and it idled really nice compared to other things I have tuned.:laugh:


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## Prof315 (Jan 5, 2009)

need_a_VR6 said:


> I would just lock advance at a tps threshold and let the valve do the rest. Depends a lot on the setup, how much cam it has, etc. I was running a 24v with stock cams at the time and it idled really nice compared to other things I have tuned.:laugh:


 Essentially that's what I do with the idle advance table.


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## ChrisAudi80 (Apr 18, 2011)

Prof315 said:


> Actually it wasn't too hard. I wired up the idle motor part of the throttle (pins 1 and 2) backwards so pin 1 is PWM control and pin 2 is switched 12V. Then I set the MS3 PWM idle control to run inverted. I'm running the valve at 200hz and the DC range is roughly from 40% to 100%.


I have followed these instructions, but my idle speed is even lower now. I am not sure what I am missing.

TB pin 1 to VEMS EC36-6 inv. and TB pin 2 to switched 12v. Valve at 200hz and DC range 40 to 100. It now idles with AC on at 620rpm, AC off 830 which better than before (1050).
My IAC DC shows 83%.


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## need_a_VR6 (May 19, 1999)

Do the whole sweep of idle duties and watch the TB behavior. It sounds like you need the output non-inverted.


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## ChrisAudi80 (Apr 18, 2011)

need_a_VR6 said:


> Do the whole sweep of idle duties and watch the TB behavior. It sounds like you need the output non-inverted.


It's getting better. 
Seems like the IAC motor and gears needed to get unstuck. It helped to spray the butterfly and venturi with WD40 and cleaning it. Maybe some WD40 went into the IAC part and lubricated a little.


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## need_a_VR6 (May 19, 1999)

Most of the TB are like this put the push-pull driver in the factory ECM can actually free it up during the adaptation if it isn't too bad.


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