tveltman

Is there any problem with running injectors with a switched 12V supply rather than a fixed 12V source? I have the TecGT system and I am going to switch my power supply for the flappy valve over to switched power, but I am wondering whether I can power ignition coils and fuel injectors with switched power, or if that will prevent the car from starting (if the switched power is interrupted during cranking, for instance).

Also does anyone know of a source for replacement plugs V and W (or any letter, I don't really care) for the wiring harness?

Thanks in advance!

WallyP

Not clear what you are trying to do...

The 12 vdc power to the injectors is switched on by the LH relay (Relay XXV), and the injectors are grounded (pulsed) by the LH ECU.

Are you trying to pulse the supply voltage against a hard ground?

The ignition coils are supplied with 12 vdc from the 15 bus, which is switched by the ignition switch.

123quattro

He put an entirely new engine controller in and is looking for a good place to grab power for the coils.

Switched power is what you want. If in doubt, put a meter on it, turn the key to run, and then to crank, to verify it's continuous.

RCinXS

Coils?? or DFUs?

tveltman

DFU to be accurate but I didnt think it would make a difference. I can easily run fixed 12V to injectors and DFUs and switched to everything else if that is more appropriate. Right now everything is running on 12V fixed, but I have the flappy disabled because it seems to be drawing current despite the switch being turned "off" inside the control box. The easy fix is to move the power supply for everything one pin over and make it all switched power, but if that isn't likely to work, then I can arrange it however I like, since I have plugs V and W at my disposal. Thanks for the responses, I'll try cranking while clipped to switched and see how it functions and report back for anyone else working on similar projects

danglerb

What do you mean when you say switched and fixed?

Switched controlled by ignition key?

Fixed direct to the battery?

Normally with the ignition key off or removed the engine has no electrical power, only a few lights etc have power. On supplies normal operating electrical power, and Start provides additional or replacement power necessary for starting.

Doesn't the aftermarket stuff come with fairly specific instructions for power?

tveltman

It does come with instructions, and I followed them. The CE panel provides battery voltage at all times on plug W pin 22, but also provides 12V at pin 23 only when the ignition is on, hence fixed vs switched. If my terminology is confusing, I apologize, that just seemed to make the most sense to me.

I personally think it makes more sense to wire everything from a switched power source so that with no key in the ignition, nothing inside the engine bay gets power. It seems to me that that is the safest way to do it, but as I mentioned before, I wasn't sure whether this might cause starting difficulties. I'm going to go out in about 10 minutes and check things out.

Tampa 928s

On the mega squirt if the Ecm does not receive pulses from the crank sensor it stops power to the injectors and fuel pump. What you don't want is getting in a wreak the motor disabled and injectors still pumping fuel. I am assuming your engine controller has the same safety feature?

john gill

My reccommendation would be to interface your existing relays into the aftermarket system , if you have removed the ezk and lh ecus you can use theae relays to switch whatever you want so the field devices are only supplied after you ahve cranked the ignition key , you also ahve the fuel pump circuit , this is activated after the ecu detects a pulse being recieved from the crank angle sensor , i.e. the engine is being cranked , after the pulses reach a preset level everthing else is put in motion.
Note that the ezk relay is turned on after the igntion is turned on , hope this helps .

tveltman

I have removed the EZK relay and am tapping power for the ECU from that socket, where the power is switched on after the ignition is turned. My fuel pump relay is interfaced with the ECU so that the system functions as stock. The LH relay provides a sourwce of switched power to pin 25 on plug W, and this was what I was contemplating switching over to. I could just move the whole power supply wire over, or I could separate the two and used the constant voltage to drive the injectors and DFUs. After some more thought, I think this is what I will do, because I dont want to pass too much current through one pin on the CE panel. Porsche had multiple 12V outputs from the central electrics, so I ought to do so as well.

In regards to earlier concerns about injectors firing with the engine off, the ECU will not drive anything without a crank signal, so as long as the engine isn't turning, injectors won't fire. The only reason I was contemplating using switched power was as a backup fail-safe, so even if somehow the ECU, which is pull-to-ground on the injectors, shorted out causing one injector to spray constantly, turning the ignition off would kill the 12V supply to the injector, so there would be a 0% chance of injectors firing with the ignition off.

How much current do we think each pin at the CE panel will tolerate? Maybe I am ju st being overly cautious, but I prefer to be safe than sorry

john gill

Have a look at the gauge of the wire that is exiting the plug, this will give you a good indication of the current carrying capabilities .
Most of the wires have a fuse in the circuit from them anyway, but not all some of the wires are live from the battery terminals without fusing , so be aware , consult the wiring diagrammes .

Alan

I think you should care - the plugs are not only color coded they have a coding mechanism on the side that interlocks with the socket - the wrong plug won't fit the socket - in fact not every plug is unique but there are 16 combinations - so only 2 different plugs will fit any socket and they won't be the same color or close to adjacent...

I think switched ignition (15) will be fine for everything, but you should use a relay to reduce current through the ignition switch and of course fuse every circuit (basically like stock config.). The current capacity of the CE panel hardware is theoretically 30A max but I'd split anything over 20A to 2 CE circuits. The actual current capacity of a pin already wired is limited by the wiring installed - so rewire if you need to.

Alan

928DK

I run my coils,dfu's and injectors switched (with relay)

TecGt has been installed and working for almost 1½ year now.

Also i have the same problem with flappy (so i've disabled it for now)

tveltman

You have the same problem with the flappy circuit as I do, but you are using switched power? Shouldn't the ignition being off kill the current drain? That was what I was banking on, otherwise I will need to use a relay to drive the flappy...

Oh also, I found out that the plugs are a three-piece assembly made by Porsche. Roger thinks that he can get them for me, so we will see if they are still available. The PET lists part numbers for them under the CE diagram, for those interested.

Alan

Don't you already have the plug shells? is it just the terminals you need? These are available and can individually be replaced.

BTW - you implied erlier is that you were running the new ECU from the coil terminal from the EZK relay socket -- Err thats NO NO! the coil wire is designed to supply only a few hundred mA and is likely not fused...

You need a relay to supply all that you want to be switched - just configure it like stock - you even have the relay sockets wired to the right things - you just need to swap around some coil connections to the new ECU.

Alan