PWM wiring..

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69futura
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Posts: 5
Joined: Sat Feb 17, 2007 11:41 am

PWM wiring..

Post by 69futura »

Hey there everyone, got a couple of questions regarding the ford PWM.. The Manual gets me confused a bit, so I'd like to get some clarification on some things, if you don't mind...

1. When using Ford's PWM, do I still need to follow the following instructions, or is this just for the GM IAC?

* Connect (1A)JS0 (under the processor socket) to IAC1A (near the DB37 connector) - this brings out IAC1A on DB37 pin #25
* Connect (1B)JS1 (under the processor socket) to IAC1B (near the DB37 connector) - this brings out IAC1B on DB37 pin #27
* Connect (2A)JS2 (under the processor socket) to IAC2A (near the DB37 connector) - this brings out IAC2A on DB37 pin #29
* Connect (2B)JS3 (under the processor socket) to IAC2B (near the DB37 connector) - this brings out IAC2B on DB37 pin #31

If I don't need to connect these, Do I need to connect something differently (other than what's described in step #62)?

2. Which wire on the Ford IAC valve is which, or does it matter which wire goes to + and which one goes to the megasquirt? Is there a method to determine which way is which? I will be using a 1993 mustang IAC valve if that helps.

3. Where should I solder the diode, and am I right in assuming it goes across the wires like so?

Image

4. Will this wiring mod affect anything with regards using the megastim, and if so, is there a way to modify the megastim so I can still test my megasquirt?

Thanks in advance, as I really have no idea what I'm doing, and I'd hate to burn a trace or something like that as others have done..
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FiatFreak
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Posts: 24
Joined: Thu Sep 09, 2004 2:40 am

Post by FiatFreak »

The 1A, 1B, 2A, and 2B wires are for a stepper motor type IAC. For Ford type PWM IAC's, here are the instrunctions from the MegaManual:

Note that if you are using a PWM Idle valve, such as those used in some Ford products, the standard transistor is not sufficient to power the valve directly. Instead, on a V3 main board, you need to:


Obtain and mount a TIP120, TIP 121, or TIP 122 transistor (such as Digi-Key 497-2539-5-ND, 74¢ ea.). Mount it on either the heat sink (if you have a spare spot) or the case. You should use a mica insulator (4724K-ND, 93¢) and heat sink grease under the transistor as well.
Run wires to the Q4 connections as shown below:[/i]


Do not install Q20 or D8, and jumper R39.
Put a 1N4001 diode across the PWM Idle valve itself - the banded end goes to the 12 Volt supply, the non-banded end goes to the lead that goes to MegaSquirt (this diode is for flyback purposes on the idle valve).
To configure the software for the PWM FIdle valves:

Select the 'PWM Warmup' option for the algorithm under 'Idle Control' in MegaTune.
Note that the 'Start Value' and 'Time Based Afterstart' parameters in the same dialog do not apply to PWM use (the PWM% is dependent only on the coolant temperature),
Select the PWM% you would like to apply to the valve at each coolant temperature in the 'Idle PWM Dutycycle' under 'Tables' in MegaTune. 0% means no current, 100% means the full 12 Volts is applied. Apparently some valves are fully closed at 100% PWM, others are fully closed at 0% PWM, you will have to experiment to see which way yours operates.
If you are using PWM Idle control, you cannot use the FIdle relay on the relay board, and have to jumper the relay socket. The jumper goes from the relay socket hole nearest the CB1 polyfuse to the relay socket hole nearest DB37 pin #4.



I'm not sure about that mod with adding a diode. Seems like that would cause problems. Where did that suggestion come from?

-Patrick-
'81 Fiat Spider - Turbo charged, MSII, EDIS4
'04 SRT4 - Daily driver
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66fb

Post by 66fb »

FiatFreak

From the info you just posted...
Put a 1N4001 diode across the PWM Idle valve itself - the banded end goes to the 12 Volt supply, the non-banded end goes to the lead that goes to MegaSquirt (this diode is for flyback purposes on the idle valve).
Adding the diode limits the voltage spike (flyback) across the IAC.

AL
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FiatFreak
MegaSquirt Newbie
Posts: 24
Joined: Thu Sep 09, 2004 2:40 am

Post by FiatFreak »

Ah yes, that makes sense. Teach me to read everything I cut-n-paste before I paste it! :)
'81 Fiat Spider - Turbo charged, MSII, EDIS4
'04 SRT4 - Daily driver
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69futura
MegaSquirt Newbie
Posts: 5
Joined: Sat Feb 17, 2007 11:41 am

Post by 69futura »

So am I correct in assuming this is the proper way to wire this, or have i missed something somewhere?
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carjbre02
MegaSquirt Newbie
Posts: 6
Joined: Fri Oct 13, 2006 6:37 pm

Post by carjbre02 »

the flyback diode is still confusing to me. where or what is the PWM valve on your car? Is it the idle air control device right next to the throttel body? then how do you know which wire is going to the MS?? is it the one going to D22???? or D26?? then do you hook that up to D28??? I got a wiring harness for my car that plugs directly into the stock wiring and goes into the MS wiring. So if I could just hook up a flyback diode from D26 to D28 or something that'd be perfect.
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69futura
MegaSquirt Newbie
Posts: 5
Joined: Sat Feb 17, 2007 11:41 am

Post by 69futura »

Well I got the Megasquirt assembled, and everything thus far looks ok, but for some reason the fidle LED on the megastim lights very dimly.. Is this normal, or do i have something wired wrong? Do I need to change something on the stim, since it's not 'standard'? I'm using a TIP120 I think.
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FiatFreak
MegaSquirt Newbie
Posts: 24
Joined: Thu Sep 09, 2004 2:40 am

Post by FiatFreak »

What are you using to power MS? It should light up fine if you are using a 12 volt battery.
'81 Fiat Spider - Turbo charged, MSII, EDIS4
'04 SRT4 - Daily driver
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69futura
MegaSquirt Newbie
Posts: 5
Joined: Sat Feb 17, 2007 11:41 am

Post by 69futura »

Thanks for the reply.. I'm using a 9v battery, and all the other LED's light up brightly.. Only the Fidle light is dim, and it kinda intermittantly pulsates, but never gets very bright. Since it is a PWM and not an IAC valve I'm not that worried about it, but I guess I'm looking to see if this is a problem, or is normal for this circut.. It doesn't happen at the higher simulated RPM and Throttle levels, which I beleive is correct, but it does start to come on at the lower levels.. Therefore, I beleive that part of the circut is working correctly, I'm just not sure about the other part...
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69futura
MegaSquirt Newbie
Posts: 5
Joined: Sat Feb 17, 2007 11:41 am

Post by 69futura »

No one knows?
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66fb

Post by 66fb »

69futura,

I use the Ford PWM IAC also. I don't have MS on the stim right now so the following is a guess. Depending on how you have the IAC configured (temp, no. of steps, frequency etc) and the temp you have cranked in with the CLT pot the voltage pulse width applied to the FIDLE LED could be sorta narrow, i.e., dim light output. If the CLT pot is set above your WUE temp then the FIDLE LED may be turned off -depends on your configuration.

Mine is set so that at operating temp the IAC is closed, no FIDLE LED output.

I think it's ok...for what that's worth.

AL
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