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One PDM vs two

EFI Wiring Fundamentals

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Discussion and questions related to the course Motorsport Wiring Fundamentals

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I’m looking at PDMs for my road, track and sprint car. The top candidates are the HP Electronik HP8441 and a pair of ECUMaster PMU16s, and I’m after some experienced opinions on which would be best. The cost is about 10% higher for the pair of PMU16s over the single HP8441.

I’m swaying towards the pair of PMU16s for the following reasons:

- I have an ECUMaster display so am familiar with their software and half of the setup is done for you.

- I’ve not found much recent mention of the HP Electronik units, so I don’t know if they’re somewhat abandoned?

- Having two PDMs could simplify the wiring, with one controlling lights, dash, stereo, fans, wiper etc at the front, and the other handling pumps, engine etc at the rear. Done right, I think I’d only need a suitably large power supply cable and CAN lines between the front and rear of the car, unless I’m missing something?

Pretty common in Motec land. I am going two PDM15's. Being mid engined the loads are pretty evenly balanced. Means I have a couple of big cables and one thin one running front to rear, rather than a couple of big cables and about fifteen small to medium ones.

For info, my current plan -

Front -

1 Fan

2 Dipped

3 Main

4 Side?

5 Heater



8 Wipers F?

9 Wipers S?

10 LH Ind

11 RH Ind

12 Horn

13 Washer

14 Dash etc

15 Stereo etc

Rear -

1 Ignition/Injectors A1/10

2 Fuel pump 1 A3/12

3 Starter A5/14

4 ECU A7/16

5 Brake (A9/17)

6 Reverse (B3/B9)

7 Fog (B5/B11)

8 SPARE (B7/B13)

9 Camera/transponder (A2)

10 Int light A4

11 LTCD A6

12 Tail (A8)

13 Fuel pump 2 A11

14 RH Ind (A13)

15 LH Ind (A15)

This would be for an Elise, so a very similar setup.

Hi guys im also real interested in PDM’s

And will do those in my next build for sure..

I struggle however to understand Front and Rear speaking in this post.



I see a car like this, 3 zones.

Front: Engine bay compartment

Middle: Passenger compartment

Back: Trunk

So why would you put to Back(trunk), PDM for ECU and Starter, Ignition/Injectors ??

This is for a mid-engined car (Lotus Elise), so the engine bay is at the back, with the fuel tank/pump, rear light clusters etc.

Ahh i see, now it makes more scene.. thanks for clarify :)

Mine is mid engined as well.

For a front engined car a single larger PDM would probably make more sense. Or a largish one at the front and a small 10 output unit at the back.

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