Megasquirt S5 BAC valve question
12-24-05, 02:09 AM
#1
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S5 BAC valve question
I have a question about using the S5 BAC valve with Megasquirt. Can it be used and if so what do I need to make it work.
12-24-05, 07:10 AM
#2
RX-7 Alumni
Originally Posted by BlastinSideways12A
I have a question about using the S5 BAC valve with Megasquirt. Can it be used and if so what do I need to make it work.
Originally Posted by muythaibxr
the fidle wire goes to the bac valve... and there's a +12v wire that goes to the BAC as well...
From what I've been told, you basically have to duplicate the v2.2 modded circuit to control the BAC valve.
1) First, remove Q20 and R39. Replace Just jumper R39 instead.
2) Replace R19 with a 510 ohm resistor.
3) Replace Q4 with a ztx688 (orient it with the flatter side the same direction as the flat spot on the silk screen) Leave a little bit of space under the ztx688 when you solder it.
4) remove D8
5) Using a 1N4001 Diode, jumper pin 3 of the ztx688 to a +12v source. The banded end of the diode goes to the +12v source.
That's it, just run the wire from the fidle pin on the db37 to one of the pins on the BAC valve, and make sure the other pin on the BAC valve has a +12v power source.
The instructions above basically duplicate the V2.2 circuit with the ztx688 in it. At one point or another, I'll try to do it with less mods, but there is a person on the megasquirt forums who tried it several ways, and destroyed several ztx688's to come to the conclusion that duplicating the v2.2 circuit but using a 510 ohm resistor instead of a 1k resistor for R19 works the best.
From what I've been told, you basically have to duplicate the v2.2 modded circuit to control the BAC valve.
1) First, remove Q20 and R39. Replace Just jumper R39 instead.
2) Replace R19 with a 510 ohm resistor.
3) Replace Q4 with a ztx688 (orient it with the flatter side the same direction as the flat spot on the silk screen) Leave a little bit of space under the ztx688 when you solder it.
4) remove D8
5) Using a 1N4001 Diode, jumper pin 3 of the ztx688 to a +12v source. The banded end of the diode goes to the +12v source.
That's it, just run the wire from the fidle pin on the db37 to one of the pins on the BAC valve, and make sure the other pin on the BAC valve has a +12v power source.
The instructions above basically duplicate the V2.2 circuit with the ztx688 in it. At one point or another, I'll try to do it with less mods, but there is a person on the megasquirt forums who tried it several ways, and destroyed several ztx688's to come to the conclusion that duplicating the v2.2 circuit but using a 510 ohm resistor instead of a 1k resistor for R19 works the best.
Oh crap, I just realized I didn't do step 5 with the 1N4001 diode, I just used D8. Maybe Ken will chime in and explain if that diode is absolutely necessary.
Look in the thread https://www.rx7club.com/megasquirt-forum-153/v3-board-idle-control-please-485656/, they are talking specifically about using the BAC and a version 3.0 MS board.
HTH,
Scott
12-24-05, 07:14 AM
#3
RX-7 Alumni
And here it explains more--even about the D8 diode needs to be changed.
http://megasquirt.sourceforge.net/extra/pwmidle.html
http://megasquirt.sourceforge.net/extra/pwmidle.html
12-24-05, 08:46 AM
#4
MegaSquirt Mod
don't use those instructions from the sourceforge site. The instructions I got were from the v3 board assembly instructions at http://www.megasquirt.info/ms2/V3assemble.htm
The instructions you quoted from me originally are correct. You can't use the diode from D8 because it's a zener diode (I believe) and won't work correctly. You MUST install that diode as you are PWMing a device with an electrical coil in it... which will cause some flyback.
The instructions you quoted from me originally are correct. You can't use the diode from D8 because it's a zener diode (I believe) and won't work correctly. You MUST install that diode as you are PWMing a device with an electrical coil in it... which will cause some flyback.
12-24-05, 10:33 AM
#6
RX-7 Alumni
Originally Posted by muythaibxr
don't use those instructions from the sourceforge site. The instructions I got were from the v3 board assembly instructions at http://www.megasquirt.info/ms2/V3assemble.htm
The instructions you quoted from me originally are correct. You can't use the diode from D8 because it's a zener diode (I believe) and won't work correctly. You MUST install that diode as you are PWMing a device with an electrical coil in it... which will cause some flyback.
The instructions you quoted from me originally are correct. You can't use the diode from D8 because it's a zener diode (I believe) and won't work correctly. You MUST install that diode as you are PWMing a device with an electrical coil in it... which will cause some flyback.
I read this as saying the diode is installed straight across the BAC valve with the banded end on the hot side, and the non-banded end on the ground side that goes to MS. Right now the 12v hot side of the BAC does not go into the ECU so I presume the diode should be installed right at the BAC.
Is this correct? How could one install this diode inside the MS when the 12v side doesn't run into the ECU?
Edit: Ok so after thinking some more, the 12v side doesn't necessarily have to be the same one that feeds the BAC directly. So long as the non-banded end is on the BAC-MS ground side and the banded end is on any common 12v supply. Then I can see having it in the MS.
Last edited by Rex4Life; 12-24-05 at 10:45 AM.
12-24-05, 10:57 AM
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Yea please clarify on that diode. Im currently working on this too. I currently have a diode inside the MS from the ztx688 collector to 12 volts with the banded side facing the power source. If I need another one on the BAC itself please say so.
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12-24-05, 11:03 AM
#8
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Originally Posted by custom13B
Yea please clarify on that diode. Im currently working on this too. I currently have a diode inside the MS from the ztx688 collector to 12 volts with the banded side facing the power source. If I need another one on the BAC itself please say so.
12-24-05, 11:10 AM
#9
MegaSquirt Mod
hrmm, when I've mentioned the pwm idle valve, I've always mentioned the diode change... maybe you're talking about in the v3 assembly instructions?
I think you're fine running that diode to a +12v source inside the MS... that's how it is done by default on a v2.2 board.
I think you're fine running that diode to a +12v source inside the MS... that's how it is done by default on a v2.2 board.
12-24-05, 11:24 AM
#10
RX-7 Alumni
Originally Posted by muythaibxr
hrmm, when I've mentioned the pwm idle valve, I've always mentioned the diode change... maybe you're talking about in the v3 assembly instructions?
12-29-05, 12:01 PM
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I am working on this part right now on the V3 board. I have been following the instructions here: http://www.megasquirt.info/ms2/V3assemble.htm
I want to make sure that I have everything right before I solder anything. Here is what I know so far:
1) Replace R19 which is originally 1000 ohms with a 510 ohm resistor.
2) Jumper R39
4) Remove Q 20 (just leave it open?)
3) Replace Q4 with Transistor ZTX 688 (do I need to fabricate a heat sink or something for it?)
4) Remove D8 (do I jumper it, leave it open, or replace it with something?)
5) Jumper pin # 3 of the ZTX 688 (the one farthest from the heat sink) to a + 12v source. Can I just use a 12v source somewhere one the board and if so, can somebody point me to a 12v source?
Am I missing anything?
I want to make sure that I have everything right before I solder anything. Here is what I know so far:
1) Replace R19 which is originally 1000 ohms with a 510 ohm resistor.
2) Jumper R39
4) Remove Q 20 (just leave it open?)
3) Replace Q4 with Transistor ZTX 688 (do I need to fabricate a heat sink or something for it?)
4) Remove D8 (do I jumper it, leave it open, or replace it with something?)
5) Jumper pin # 3 of the ZTX 688 (the one farthest from the heat sink) to a + 12v source. Can I just use a 12v source somewhere one the board and if so, can somebody point me to a 12v source?
Am I missing anything?
Last edited by BlastinSideways12A; 12-29-05 at 12:19 PM.
12-29-05, 02:21 PM
#12
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1) Correct
2)Correct
4?) Correct, leave open
3?) ZTX688 is the same as the original Q4, so no heat sink is necesary.
4?) Correct, leave open.
5?) I used the 12V going to the MOV.
2)Correct
4?) Correct, leave open
3?) ZTX688 is the same as the original Q4, so no heat sink is necesary.
4?) Correct, leave open.
5?) I used the 12V going to the MOV.
12-29-05, 09:29 PM
#13
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I don't have any 510 ohm resistors so I'm gonna run 2 1000s in parallel. What wattage should I run? I have 1/4 watt, 1/2 watt, and 1 watt.
You mean that ZTX 668 is directly interchangeable with Q4 but is a different part, correct?
What does MOV stand for?
You mean that ZTX 668 is directly interchangeable with Q4 but is a different part, correct?
What does MOV stand for?
12-29-05, 10:03 PM
#14
MegaSquirt Mod
I guess you could run to 1k resistors in parallel, although I've never done it, and it'll probably turn out a bit sloppy...
1/4th or 1/2 watt should be fine.
ztx688/689 are direct replacements for the pn2222a or whatever other transistor your kit came with for q4.
MOV = Metal Oxide Varistor (spelling?) It's the big black disk with 2 leads near the back of the board (db37 side)
1/4th or 1/2 watt should be fine.
ztx688/689 are direct replacements for the pn2222a or whatever other transistor your kit came with for q4.
MOV = Metal Oxide Varistor (spelling?) It's the big black disk with 2 leads near the back of the board (db37 side)
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