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V8 S15 PDM Output Opinions

PDM Installation & Configuration

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Hey guys,

Long time lurker first time poster here.. Been making my way through the Club level wiring & PDM Installation courses which have been fantastic. However I am brand new to the electrical side of automotive and have not wired anything prior (not even a speaker) - hence I was hoping to get some outside opinions before I go attempting to wire up my entire car. Full disclaimer - I do have some far more electrically experienced friends helping out but with the amount of variables I'm still finding myself posting here.

Car is an S15, has a dry sumped LS1 swapped in it - race car built for the Sports Sedans category here in Australia. I have an Emtron KV8 and a Motec PDM15, along with un-terminated flying harnesses for both these units (PDM Loom from GR Motorsport Electrics, ECU Loom from Emtron direct). Also have the Motec Keypad, a Cartek XR Isolator, and for now still sticking with my trusty old Racepak IQ3 Dash.

The LS1 has no forced induction just E85 and a big cam/supporting intake & head work - I'm finding it hard to accurately select PDM channels for my Coil Packs & Injectors (which I've currently split each bank over separate channels - unsure if correct or I'm over doing it, obviously would like them all on 1 channel to save some outputs) , just wanted to see if people might have some suggestions for me based off this list.

When googling LS1 Coil Draw the "10A per coil" information keeps coming up on Haltechs website which I thought sounded very excessive, maybe if in a high boost/power situation? I'll be trying to crack 300kw with the NA engine on E85, probably not revving higher than 8k.

Output 1 20A - ECU

Output 2 20A - IGN Coils Bank 1 (4 x LS1 Coils)

Output 3 20A - IGN Coils Bank 2 (4 x LS1 Coils)

Output 4 20A - Starter Motor Solenoid

Output 5 20A - S15 Wiper Motor (thinking just wiring high speed with direct method depending if I have any outputs left)

Output 6 20A - Fuel Pump Main (Walbro 460)

Output 7 20A - Combined with Output 6 as expecting more than 20A from some other peoples experiences

Output 8 20A - Lift Pump (another 460 but hopefully not working as hard, if it does I'll swap out for a sub 20A pump)

Output 9 8A - pre wired to Motec Keypad connector along with another spliced wire was thinking for Racepak Dash

Output 10 8A - LED Headlights (3.5A each)

Output 11 8A - LED Brakelights

Output 12 8A - Fuel Injectors (4 x Bosch 980cc)

Output 13 8A - Fuel Injectors (4 x Bosch 980cc)

Output 14 8A -

Output 15 8A - Alternator Field Wire

Inputs, I honestly haven't come up with many that aren't CAN switched, aside from Wiper Motor input & Cartek Kill Signal which I'm thinking will send to PDM.

Few other bits I haven't mentioned on the PDM list,

- Davies Craig EWP and its controller, running the loom it comes with and a 30A fuse for the thermo fan just to free up the PDM outputs/save myself programming the EWP smarts into the PDM

- Rain light, Hazard LEDs, cheap little rear view camera & some cabin LEDs are just running off separate Emtron AUX outputs so hopefully can be switched via CAN

- Astra Power Steering Pump running direct battery positive with an 80A Circuit Breaker, IGN switch for this off Emtron AUX Output too

- ECU, PDM & Dash all going into a CAN Hub

If anyone's up for telling me what I've messed up/if I could possibly merge some channels or what I've forgotten, that would be greatly appreciated! My biggest hope is that I could merge either Coils, Injectors or Alternator Field so that I could wire the Wiper Motor properly as per the PDM course/leave some outputs for future additions.


The LS cars that I have PDM logs of have never exceeded 20A for the ignition coils. And same for the injectors, they are more like 4A. Those are all comparable N/A LS's with near stock rev limit and one was race gas.

I'd want the EWP on the PDM personally, get the logging and potentially an alert if it trips a fuse kinda thing. Get some flexibility with the programming if needed too.

Might be missing something, but why aren't you using the ECU for all the engine related loads, and reserving the PDM for the functions that the ECU can't power?

Thanks Tyson that's really great to know! Combining the seperate injector & ignition channels was what I was really hoping for.

Gord, honestly I'd only put the super low drawing stuff on the ECU as again - I've never done this before, PDM Outputs I was virtually copying off the channels given in the course example. Would you be suggesting moving the injectors onto the ECU channel or something similar?

KV8 isnt a PDM, its just an ECU. Well a great ECU but lol it's not designed to power ignition coils or injectors.

You thinking of a Nexus Gord?

In general I favour combining the ECU and Injector's on a circuit so that the ECU's reference of battery voltage is the same as what the injectors are seeing which keeps the deadtime calibration accurate. I haven't found separating them to be an issue as PDM's are usually a cleaner source then older factory wiring. Some OEM's separate them, some combine them onto the same circuit.

I certainly may be wrong, Tyson - I was going by this, where there are the injector outputs, ignition triggers and several aux' outputs shown and listed, that I assumed would cover the engine side and possibly a bit more, depending on re-configuration options - leaving the PDM to handle what the ECU couldn't?

Injector and ignition triggers are low side control, they still need 12V on the other side.

KV8 and many other ECU's only have 1 or 2 +12V pins, they are to power the DBW H bridge , O2 heaters and the processor. But they have many pins connecting to ground as that is where most of the current is flowing to.

I would move the Wiper to Output 9, this is a special pin on the PDM that allows for motor braking of the wiper. Look through the help in the Output 9 Wiper control tab for more information.

The Keypad should be powered on with the PDM, I have never wired the power for the Keypad on any of the installations that I have done to an output on the PDM.

I would also combine the Ignition coils into a single output, an 8A outputs should be able to support them, they may draw a peak of 10A, but depending on the version of the LS coils used, the peak is less than 1ms, and the average draw on the coils is around 3A for ~5ms per firing.

What injectors are you using? If they are Saturated injectors then the current draw on them will be quite low and not needing to be on two outputs.

Hi Stephen,

Yes I was a bit disappointed when I read through the Motec manual that Output 9 was the dedicated motor braking channel, as the loom I've got for the PDM has output 9 wired up to power the keypad (already comes terminated for the keypad) along with a spliced power wire that they suggest for the Dash. I'll have a look at the plug next time I'm down at the workshop, hoping I can repin that power supply to a different channel so Output 9 can be used for the wiper motor.

Injectors are Bosch 980cc EV14's so that should be all good with 1 channel then. Also measured my brake lights that turned out to be a tiny draw so moved them to ECU AUX. This has also freed up some space to maybe move the water pump and thermo fan onto the PDM.

New list looks like this,

Output 1 20A - ECU

Output 2 20A - IGN Coils (8 x LS1 Coilpacks)

Output 3 20A - Starter Motor Solenoid

Output 4 20A - Thermo Fan (single SPAL, measured an inrush of 36A but running about 16-18A)

Output 5 20A - S15 Wiper Motor High Speed (try move to Output 9 if enough loom length to re-pin)

Output 6 20A - Fuel Pump Main (Walbro 460)

Output 7 20A - Combined with Output 6

Output 8 20A - Lift Pump

Output 9 8A - pre wired to Motec Keypad connector along with another spliced wire for Racepak Dash

Output 10 8A - LED Headlights (3.5A each)

Output 11 8A - Fuel Injectors (8 x Bosch 980cc)

Output 12 8A - Davies Craig EWP

Output 13 8A - Combine with Output 12 (guessing would need this as DC loom had a 15A fuse but love to hear other peoples experiences?)

Output 14 8A - Power Steering Pump Trigger

Output 15 8A - Alternator Field Wire

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