I’m tuning my 2005 Mini Cooper S with a larger supercharger running an ECUmaster EMU black PnP and I’m chasing down a voltage issue. I’m getting 14.1v at the main battery post in the engine bay but only 13.2v at the main power wire for the engine fuse box and reading around 13v on the ECU log. I’ve checked and cleaned all the grounds in the engine bay and all grounds are reading less than 1 ohm. Does anyone have any suggestions for where to look next?
is there a fuse or some connection in between the two points you’re measuring?
do voltage drop tests for both power and ground side, with the engine running. resistance tests aren’t all that accurate that low of resistance, and when the engines running it’ll be different.
you’re looking for something that’s adding a bunch of resistance before the ecu. Can be corrosion on a connection, up a wire, something loose or a failing device.
The main power wire going into the fuse box goes from the battery through a 250a fuse and then into the fuse box. I’ll do a voltage drop test on that wire. If that’s the main source of power and I’m only seeing 13.2v where it terminates then that should be the culprit, right? Unless it could be a bad ground.
put one lead on the battery positive and the other on the whatever point you’re measuring, before and after fuse for example. Measured drop should be pretty low, like 0.0X volts.
You did say you checked the ground connections, but same test can help you find an issue there
I measured a 0.64v drop from the battery to the main fuse box power wire. I circled what two points I measured in this photo. I’ve been talking to a few mini cooper experts and they think the hydraulic power steering pump (circled blue) is pulling a ton of current causing the voltage drop. When not running a stock ECU the pump operates in a fault state and runs at 100% all the time. If that really is the issue I’d like to figure out a way to control the pump speed with the ECU.
hmm, weird to me the cooper S has a fuse and the normal cooper doesn’t.
0.64V for what should be a large run with nothing but a fuse in the way is a bit odd, and probably where most of the 0.9V drop is occurring then.
are you able to measure both sides of the fuse?
Epas at 100% can suck a lot of amps, i believe those pumps are CAN based and I don’t have data for them. I actually make a controller under my other company Hang Tight, but don’t have much CAN data for those units.
I feel like that shoulf be covered on the base map for that PNP ecu, might be a CAN setting that needs changing. worth reaching out to Ecumaster Poland and see what they say regarding that.
Is your mini USDM or a different market?