Welcome to the North American Subaru Impreza Owners Club Saturday July 26, 2014
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Technical > Engine Management & Tuning > Other Engine Management

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
Reply
 
Thread Tools Display Modes
Old 03-02-2006, 08:28 AM   #1
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default IAC on Hydra, 75mm TB

I'm using a 75mm Mustang TB on my project, and the very few who have successfully done this are not forthcoming. Don't worry, I will be. It's not rocket science, for Pete's sake.

What I'd like to know before I purchase the TB is:

-Is the IAC on the stock WRX or STi (DBW) a stepper motor, or solenoid? Is it on/off, or does it have a range, relative to idle speed desired?

-How does the Hydra control this? PWM output? Can a IAC be "remotely mounted", i.e. not on the TB machined surface?

Thanks to the great minds on this forum,

S.
* Registered users of the site do not see these ads.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 09:00 AM   #2
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

Quote:
Originally Posted by n2xlr8n
-Is the IAC on the stock WRX or STi (DBW) a stepper motor, or solenoid? Is it on/off, or does it have a range, relative to idle speed desired?

-How does the Hydra control this? PWM output? Can a IAC be "remotely mounted", i.e. not on the TB machined surface?
steve, i can give you SOME information on the IAC on the stock rig:

1) i believe it is a stepper motor--it's certainly not an on/off solenoid.
2) it does have a range of flow rates from wide open to fully closed.
3) it seems to be controlled via a single conductor, which would indicate PWM control. the 03 ecu pinout from http://www.northursalia.com/modifica...ng/wrxpin.html seems to back this up, showing possible values of either 0vdc or battery voltage, and having a "waveform" shape.

hth
ken

edit: oh yeah, one other thing: there is NO discreet iac on the throttle by wire setups, since it just uses the throttle plate itself as the iac.
ride5000 is offline   Reply With Quote
Old 03-02-2006, 09:04 AM   #3
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Somehow I knew you'd be the first to know.

Thanks, Ken. I suppose that Phil will have something to say about this, as well.

S.



Quote:
Originally Posted by ride5000
steve, i can give you SOME information on the IAC on the stock rig:

1) i believe it is a stepper motor--it's certainly not an on/off solenoid.
2) it does have a range of flow rates from wide open to fully closed.
3) it seems to be controlled via a single conductor, which would indicate PWM control. the 03 ecu pinout from http://www.northursalia.com/modifica...ng/wrxpin.html seems to back this up, showing possible values of either 0vdc or battery voltage, and having a "waveform" shape.

hth
ken

edit: oh yeah, one other thing: there is NO discreet iac on the throttle by wire setups, since it just uses the throttle plate itself as the iac.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 09:19 AM   #4
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

Quote:
Originally Posted by n2xlr8n
Somehow I knew you'd be the first to know.
not the first to know, just the first to goof off while "working" and make yet another post to nabisco!

i enjoy following your build up as it progresses. you'd better be a chatty cathy with the info when it's done!
ride5000 is offline   Reply With Quote
Old 03-02-2006, 10:30 AM   #5
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

ok, did a bit more research:

first, did some reading on stepper motors. they all generally require multiple connections so that more than one coil/winding may be fed current. this is how they are able to move in discreet steps and retain precision and repeatability.

so, i went out to my car and popped the hood. three wires are connected to the IAC itself. but only one wire is pinned out from the ecu... hmm. where are the other wires going?

then i hit the old FSMs i have on my computer.



there are the three connections to the iac on the tb. pin1/white goes right to the ecu, so there's one down. follow the S and T connections to another page...



there's T. the thing labeled GE1 is just an engine ground point. two down, one to go... S. S appears to be a power supply rail, feeding purge control solenoid, and the 4 injectors. it also branches off from injector 1!


point R feeds the wastegate solenoid and the mass airflow sensor, then continues on as point O.


point O hits the main relay and ECU. it also continues on as point E:



point E feeds the drain valve and pressure control solenoid valve:



when the main relay is energized, point A is shorted to point E. point A is battery, thus feeding ALL of the above sensors and actuators with 13vdc.

if by now you are thinking as i am, then you'll be thinking that this is some crazy assed wiring path. obviously it was intended to be easy to install as a complete harness which enabled the engine to be easily pulled, but, electrically speaking, it absolutely sucks. there is no reason to have four injectors, a purge solenoid, an IAC and a wastegate solenoid (all constantly switching on and off and drawing a not inconsiderable amount of current) sharing a power supply rail with the MAF sensor!!!

back to your original question, i found this here http://www.megasquirt.info/ms2/IAC.htm:
Quote:
Note: Beginning in 1985, Ford multi-port EFI uses an Idle Air Control (IAC) valve, which allows air to bypass the throttle plates. Unlike the stepper motors used by GM and Chrysler, the Ford units only have two terminals and one winding. These units regulate IAC plunger position using pulse width modulation (PWM). The idle speed is controlled by applying varying duty cycle percentages.
judging by the lack of multiple control terminals for our IAC i have to conclude that this is probably what we're talking about.

what to do about the mess of electrical current paths is for another thread.
ride5000 is offline   Reply With Quote
Old 03-02-2006, 10:55 AM   #6
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Wow.

That seems to be my conclusion, as well.

I'm thinking the Mustang TB will work fine regardless, because the Hydra's control of IAC is PWM.

I determined a while back (with the grounding mod, lol) that my Subaru wasn't EMC / UL compliant. Junior engineers with no RFI experience on the harness.

Thanks for the help, Ken. I appreciate it.

Steve
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 11:09 AM   #7
Element Tuning
NASIOC Vendor
 
Member#: 54918
Join Date: Feb 2004
Location: 673 WHP Element ProComp Engine
Default

The WRX has a solenoid valve and not a stepper ISC valve. The Hydra controls this via a PID algorithm so itís not a straight forward PWM map that the user can adjust. You will have control over the proportional, integral, and derivative of this function along with a minimum PWM duty, a maximum PWM duty, and if you upgrade to software 2.16-2.17 it also adds maximum PWM duty based on coolant temperature.

I donít see you running into any problems that cannot be tuned out.

Thanks,
Phil
www.elementtuning.com
Element Tuning is offline   Reply With Quote
Old 03-02-2006, 02:10 PM   #8
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Quote:
Originally Posted by Element Tuning
The WRX has a solenoid valve and not a stepper ISC valve. The Hydra controls this via a PID algorithm so itís not a straight forward PWM map that the user can adjust. You will have control over the proportional, integral, and derivative of this function along with a minimum PWM duty, a maximum PWM duty, and if you upgrade to software 2.16-2.17 it also adds maximum PWM duty based on coolant temperature.

I donít see you running into any problems that cannot be tuned out.

Thanks,
Phil
www.elementtuning.com

Wonderful news

Thanks, guys!

S.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 03:55 PM   #9
offset
Scooby Guru
 
Member#: 32636
Join Date: Feb 2003
Chapter/Region: MWSOC
Location: Dayton, OH
Vehicle:
2004 Impreza STi
Silver/Silver

Default

Sorry, but I will have to be the one to ask the dumb question. What will swapping to the Mustang TB do for you overall?

offset
offset is offline   Reply With Quote
Old 03-02-2006, 04:07 PM   #10
PHATsuby
Scooby Guru
 
Member#: 13617
Join Date: Dec 2001
Chapter/Region: MWSOC
Location: MN
Vehicle:
2001 Legacy GT back
to stock is a project too

Default

n2xlr8n-can I ask where you got the TB and how much? I am needing one for my H6 project and a true 3" TB would be ideal, especially if they sell TB flanges for these things too

thanks

Ben
PHATsuby is offline   Reply With Quote
Old 03-02-2006, 04:13 PM   #11
ride5000
Scooby Guru
 
Member#: 32792
Join Date: Feb 2003
Chapter/Region: NESIC
Location: lincoln, ri
Vehicle:
2003 GGA MBP
12.9 / 105+

Default

ben, a quick search turned up these:
http://www.mustangtuning.com/ac75pothbo9g.html
http://www.carshopinc.com/product_in...ducts_id=43302
http://www.lildevilmotorsports.com/f...dy-p-9240.html

looks like around 225 or so. i suspect making your own mounting plate will be required to interface to your intake plenum of choice.
ride5000 is offline   Reply With Quote
Old 03-02-2006, 04:26 PM   #12
PHATsuby
Scooby Guru
 
Member#: 13617
Join Date: Dec 2001
Chapter/Region: MWSOC
Location: MN
Vehicle:
2001 Legacy GT back
to stock is a project too

Default

thanks ride5000, I was checking ebay too. Will these use our stock TPS sensors, or will that need to be sourced as well. Sorry for the semi hijack.

Also, I am fabricating my own intake manifold, so basically whatever TB I choose I either need to model a flange in solid works and have CNC'd or if I can find one to buy that would save some time

thanks for the help.

Ben
PHATsuby is offline   Reply With Quote
Old 03-02-2006, 04:55 PM   #13
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Quote:
Originally Posted by offset
Sorry, but I will have to be the one to ask the dumb question. What will swapping to the Mustang TB do for you overall?

offset
At the power levels we're seeing, it's likely to be the next restriction.

I figured I'd try it out.

Normally, I wouldn't go to a larger TB unless I had extended my upper rpm range, but I think in this application, it warrants a test. In FI applications, TB size is not as critical as Carbureted.

S.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 04:59 PM   #14
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Quote:
Originally Posted by PHATsuby
thanks ride5000, I was checking ebay too. Will these use our stock TPS sensors, or will that need to be sourced as well. Sorry for the semi hijack.

Also, I am fabricating my own intake manifold, so basically whatever TB I choose I either need to model a flange in solid works and have CNC'd or if I can find one to buy that would save some time

thanks for the help.

Ben

I'd imagine it would depend on the EM, but it's standard 5v TPS sensor. If you are using a Hydra, it shouldn't be an issue, but I'd ask Phil, anyway.

For those that are interested, my friend makes billet TBs for the LS1/Mustang parts vendors (the big ones) on his CNC lathe / 3 axis machine. He is making mine. If the interest is there, he can make several. I'd imagine the cost to be in the neighborhood of $375. More expensive than cast, but it's billet.

HTH

S.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 05:02 PM   #15
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Quote:
Originally Posted by PHATsuby
n2xlr8n-can I ask where you got the TB and how much? I am needing one for my H6 project and a true 3" TB would be ideal, especially if they sell TB flanges for these things too

thanks

Ben

Sorry, I missed your post.

I couldn't find anyone willing to sell a adapter. Sponaugle had mentioned fabbing one, but I haven't heard anything back in months.

I think you're going to be in the same boat as I.

My Magnus manifold came with the needed 75mm flange

S.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 05:14 PM   #16
PHATsuby
Scooby Guru
 
Member#: 13617
Join Date: Dec 2001
Chapter/Region: MWSOC
Location: MN
Vehicle:
2001 Legacy GT back
to stock is a project too

Default

I am running the Hydra as well, just wondering if our TPS will bolt to the slot they have for TPS on the mustang TB.

I can fab a flange no problem, it is just more things to do on a an already high list, haha.

Thanks for the info.

Ben
PHATsuby is offline   Reply With Quote
Old 03-02-2006, 06:48 PM   #17
bboy
Scooby Specialist
 
Member#: 56468
Join Date: Mar 2004
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
04 Improved STI
Dirty White

Default

You got all the info.

How much bigger is the Mustang TB? Seems like mine is pretty close to 3 inches which would be 76 mm. Or......is it the same size and your building a new plenum-intake-manifold.....mmmmmmmmmm..
bboy is offline   Reply With Quote
Old 03-02-2006, 07:20 PM   #18
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Quote:
Originally Posted by bboy
You got all the info.

How much bigger is the Mustang TB? Seems like mine is pretty close to 3 inches which would be 76 mm. Or......is it the same size and your building a new plenum-intake-manifold.....mmmmmmmmmm..

IIRC, the stock WRX/STi is 65mm, so 1cm. The mustang TBs come in many sizes.

Magnus TGV-less manifold, 75mm TB flange, N2O bosses (for future expansion), and plenum rev 25,178. It makes power where I want it.

S.
n2xlr8n is offline   Reply With Quote
Old 03-02-2006, 11:59 PM   #19
boogerwrx
Scooby Specialist
 
Member#: 13448
Join Date: Dec 2001
Vehicle:
2002 wrx wagon
silver

Default

Just to add a quick note. Electromotive makes an adaptor so you can bolt on a GM IAC motor onto any aftermarket Mustang style throttle body if you want to go that way. I think they run $50-75 each and you can pick up a GM IAC from any local yard for $5.

Ron
boogerwrx is offline   Reply With Quote
Old 03-03-2006, 11:18 AM   #20
n2xlr8n
Scooby Specialist
 
Member#: 18960
Join Date: May 2002
Chapter/Region: South East
Location: Bama
Vehicle:
02 WRX MBP
It lives! ; )

Default

Quote:
Originally Posted by boogerwrx
Just to add a quick note. Electromotive makes an adaptor so you can bolt on a GM IAC motor onto any aftermarket Mustang style throttle body if you want to go that way. I think they run $50-75 each and you can pick up a GM IAC from any local yard for $5.

Ron
Thanks, Ron; that's great info.

I'm assuming you've done this also?

S.
n2xlr8n is offline   Reply With Quote
Old 03-03-2006, 04:37 PM   #21
bboy
Scooby Specialist
 
Member#: 56468
Join Date: Mar 2004
Chapter/Region: NWIC
Location: Seattle, WA
Vehicle:
04 Improved STI
Dirty White

Default

Well that sounds like fun. 1 cm will yield you a lot more flow capacity.
bboy is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
TOP FEED:***MAGNUS intake, 75mm tb and 1600cc fuel setup oneoverWRX Engine/Power/Exhaust 6 03-01-2010 08:01 PM
IAC on a 2002 suzuki4life Normally Aspirated Powertrain 0 07-01-2008 12:51 PM
Location IAC on 2002 RS imprezkid Normally Aspirated Powertrain 2 12-19-2006 10:13 PM
Help to eliminate knock on hydra RemlapaN Other Engine Management 14 11-20-2005 01:57 PM
funny idle oscillations on Hydra Matrix 1193 Other Engine Management 1 12-01-2004 09:54 AM


All times are GMT -4. The time now is 04:09 AM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2014 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.