Question about flyback to devices connected to INJGroup

ZoLtaR · January 30, 2011, 12:29:45 AM

My question is about connecting devices to free INJGroup channels. I want to run 4 injectors, so I have 4 outputs free at the moment. I need to drive boost solenoid, 3-wire (dual coil) ICV and variable cam solenoid.

I have ordered assembled VEMS with integrated 30V flyback. As we know, flyback must be connected to +12V after the fuse for the injectors. But I was searching viki for information about connecting boost control solenoid and i read that

"electronic driving:

* using a free injector channel recommended: Flyback is needed."

So my questions about that issue?
1) I guess I can't use already integrated 30V flyback that is in controller? It's only for injectors Vbatt+ ? So how should I wire-up second diode and make "second" flyback for those extra devices? How to connect it? (some diagram will be helpful)
2) Does other things connected to INJGroup such as variable cam solenoid or 3-wire ICV also needs flyback?

Sorry for my lame questions. I don't want to fry anything during first start up :)

jrussell · January 30, 2011, 02:03:11 AM

These other devices would need their own simple flyback. There were likely some 1N4001 or 1N4007 diodes included with your ECU, those would be fine for this application. Basically you want to install the diode between the power supply and the ground with the stripe of the diode on the +12V side. I actually made a diagram of this, but I can't find it at the moment. I did find the one below that Jorgen made for the fuel pump relay. Basically any device that is a coil of wire (relay, injector, solenoid, etc.) needs a diode to take the spike when the device is turned off. The spike is due to the inductance in the coil.

http://www.vems.hu/files/MembersPage/JorgenKarlsson/flyback_skydd.PNG

For your 3 wire ICV, you would use 2 diodes. Both with the stripes on the +12V line, and the other end to each of the other wires.

Hopefully that helps.

GintsK · January 30, 2011, 09:44:13 AM

If your ECU has built in 30V flyback - it is for all 8 INJ chanels. So for solenoids nothing additional is not needed. Everything is already connected.
Except IAC valve: for smooth operation flyback voltage must be clamped as low as possible. So use diode in parallel.
For boost solenoid such diode makes operation worse.

ZoLtaR · January 30, 2011, 01:35:23 PM

So I can connect +12v lines from IAC and Variable Cam solenoid to +30V flyback EC36 pin23 ? Or it should be used only for injectors?
Anyway. After reading some posts I try to make a conclusion

- 3pin IAC valve - Flyback needed for smooth operation
- Boost control, Variable cam (on/off types) - no flyback for faster operation (connected directly to ecu pin).

So IAC should be wired like this?

And what about fuel pump relay? Does it also needs flyback when driving from P259 chip?

GintsK · January 30, 2011, 02:18:08 PM

Pin 23? It is not injector output. It is ignition output. You should check is IGBTransistor mounted in your ecu for this output. If it is, then you can use it for solenoid control as is. IGBT has own flyback limiter built in. It is for high voltage around: 400V.

For 3-pin Bosch IAC I do not use diodes. It works with 30V flyback quite well from INJ outputs. So it works out of the box.

Regarding P259. Usual automotive relays has some internal protection for flyback voltage limiting. Sometimes diode (be careful with polarity), sometimes just resistor in parallel with coil. I never use additional diode there, just automotive relays.

ZoLtaR · January 30, 2011, 02:30:46 PM

Quote from: GintsK on January 30, 2011, 02:18:08 PM
Pin 23? It is not injector output. It is ignition output. You should check is IGBTransistor mounted in your ecu for this output. If it is, then you can use it for solenoid control as is. IGBT has own flyback limiter built in. It is for high voltage around: 400V.

For 3-pin Bosch IAC I do not use diodes. It works with 30V flyback quite well from INJ outputs. So it works out of the box.

Regarding P259. Usual automotive relays has some internal protection for flyback voltage limiting. Sometimes diode (be careful with polarity), sometimes just resistor in parallel with coil. I never use additional diode there, just automotive relays.

I think we misunderstood each other. As the diagram says, pin 23 is flyback (in my case it's already developed inside the case).
So if 3-pin Bosch IAC work just with integrated 30V flyback I can wire it like this ? (so it will just use TS diode that is already in the ECU)

For the fuel pump, radiator fan I will just use automotive relays as you recommend

GintsK · January 30, 2011, 03:04:19 PM

Oh, sorry, my fault. Pin 23 comes from inj supply for flyback.

Regarding fuse. Fuse shouldn't be separate for this wire. It should be common for this wire AND all elements driven by INJ outputs.

Yes, you can connect as drawn.

ZoLtaR · January 30, 2011, 03:38:52 PM

Thanks for your suggestions. Taking into account all the suggestions I put the final diagram of my setup. Now all INJOut devices are secured by one fuse, and 30V flyback is connected for injectors common and ICV. Hope everything will be ok with such a connections?

ZoLtaR · January 30, 2011, 07:32:54 PM

I just looked at that diagram and I think it doesn't make sense.

While INJGroup all devices should have common +12 feed with one fuse, it's impossible to feed only injectors and IAC with 30V flyback. Connecting flyback to +12V injectors feed = flyback goes to every device that is powered by that fuse.

So it doesn't make sense then.
Then I should feed +12v common injectors and IAC from one fuse (with flyback). And Boost Solenoid / Variable Cam from other +12v fused source.

GintsK · January 30, 2011, 10:30:22 PM

Main idea is pin 23 should always be connected with elements driven by INJ outputs. Even if fuse is blown.

ZoLtaR · January 30, 2011, 10:39:54 PM

Ok I get that, so it seems that the diagram above is correct? (every INJOut devices are feeded with +30V flyback on it's +12v lines)

z0tya · January 31, 2011, 09:14:36 AM

Quote from: GintsK on January 30, 2011, 10:30:22 PM
Main idea is pin 23 should always be connected with elements driven by INJ outputs. Even if fuse is blown.

So if I don't use additional flyback for iac and boost solenoid and switch on ecu with disconnected v3 harness injector loom, then fet blow up?

[email protected] · January 31, 2011, 01:43:39 PM

I'm not sure that is what Gints is saying.
You need to connect Pin23 to a point that will still be connected to +12 even if the main fuse blew.
If you connect your flyback diodes to the same wire as pin23 is connected to you should have no problems.

GintsK · January 31, 2011, 06:38:48 PM

z0tya, no.
Scenario: short circuit for injector. Fuse blown - no injectors, no 12V for flyback. If IAC at same time is still 12V powered from other fuse - ECU is not protected any more.
So there is two solutions: one fuse for all INJ outputs driven elements and pin 23.
Or - for pin 23 - no fuse at all.

ZoLtaR · January 31, 2011, 08:18:17 PM

Damn, I don't get it. This means that PhatBob user manual have a lot of mistakes in it concerning to the wiring.
So do I need to use 1N4001 diodes for 3pin IAC or not when is it being connected to +12v 30v flyback?

Gints, could make some diagram for me? I guess that diagrams posted by me few posts above are still not ok ?

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Question about flyback to devices connected to INJGroup