Megasquirt MS1/Extra Rover V8 – Troubles Starting

Broken Bosch Ignition Driver Legs

As many regular readers know, I’d had my Megasquirt MS1/Extra Rover V8 starting within a couple turns of they crank. So why the picture above? – Once you spot it, it’s obvious!

The next evening, with 2 wires on the idle valve reversed, I tried again.
Absolutely nothing. It didn’t even try to start. I swapped the idle valve wires back and still nothing.
It was like there was no fuel or spark.

The previous night I’d fitted the headers and p-clipped down the loom so maybe I’d trapped or broken some wires?

I checked the wiring, fuel pressure and finally the spark. It appeared I had a weak spark on 2 cylinders (same coil pack). I had spare leads and coils so I swapped them in, but now the spark was almost non-existent on the same two cylinders. Huh!!??

I disconnected the Megasquirt from the engine and connected it to the JimStim. It appeared I had identical coil/spark driver signals on all 4 outputs. So nothing odd there.

My suspicion was still something inside the Megasquirt wasn’t quite working right, so I pulled off the lid. There was no obvious signs of burnt components so I contacted some experts for help and credit to them, lots of advice was given.  However, still no faults were found.

I was totally stumped.. After all, it had started easily the previous night.

Bosch Ignition Drivers (BIP373)

Three evenings later, whilst playing with Tuner Studio I spotted a potential problem. In the picture above there are small copper coloured stripes across the legs of the Bosch Ignition drivers – they are stress fractures due to flexing. The broken halves were touching so a signal was getting through, but under load hardly any current could flow. Hence a very weak spark.

The heat-sink is flapping in the breeze. So I’m making some mods to the case with a fixed heatsink so hopefully the problem doesn’t happen again.

I’ve ordered new BIP373 drivers from the US, but in the meantime I soldered over the cracks.


I swapped the idle valve wires back around and the idle dropped from 2400rpm to 1600rpm. Still not good, but a step in the right direction.

Tuner Studio

Whilst learning Tuner Studio, I noticed just about everything in the various maps was wrong. The required fuel pressure seemed to be set for a 355ci V8. The sensors also appeared to match a Chevy and the VE table had KPa values up to 150Kpa. It appears my map was for a turbo’d or supercharged Chevy V8. This megasquirt had come from a Triumph Stag – so an odd choice of engine! A super-charged, fuel injected 355ci Stag? HHHmmm the classic car boys probably wouldn’t approve.

Chevy 355ci Required Fuel

With the high VE values and the required fuel wrong, it explained why the exhaust smoke was a bit black and possibly the high idle.

Megasquirt MS1/Extra Rover V8 – Required fuel

Here’s my GEMS P38 Rover 4552cc / 477.8ci required fuel settings. If you copy someone else’s VE map without these set, you’re onto a looser.

Megasquirt Ms1 Rover V8 Required Fuel

Megasquirt MS1/Extra VR Sensor Set-up

During de-bugging, I’d re-checked the crank signal from the standard Rover P38 VR sensor and it appeared fine. I’d used the MsExcel spreadsheet to set up my Megasquirt MS1/Extra to the 32nd tooth. E.g. 3 before the missing tooth on the 36-1 flywheel. My custom manual flywheel has the missing tooth in exactly the same position as a standard P38 automatic flex-plate. I’ve spaced out the sensor with two plastic spacers instead of one, but essentially everything is standard GEMS Range Rover P38 automatic. No toothed front pulley for this engine ๐Ÿ™‚

Wheel Decoder Excel Megasquirt

Megasquirt MS1 – Calibrating Sensor Values

I’d used non-standard CTS and IAT sensors from FAE. After reading the documentation, I thought I could simply use easyTherm to re-calibrate my MS1/Extra to them.
I was very wrong!
Panic set in as everything seemed Dead! – Again!
Except this time the Megasquirt had no lights on and no outputs!

It turns out on a Megasquirt MS1/Extra rev029y4, hitting ‘Download to Megasquirt’ wipes your firmware and .msq and you need to re-program from scratch.
BEWARE!!!! I hope you have project and msq back-ups!


I had data-sheets so I didn’t need to measure resistances, so I entered my values into easyTherm.

    1. Click ‘Write .inc files and .s19 Files’.
    2. Find the 3 new .inc files in the Easytherm Directory (e.g. C:\Program Files (x86)\EasyTherm) – Thats for the inlet Air Temp sensor – Thats also for the Air temp – this is for the coolant temp sensor
    3. Download and create a copy of the latest firmware directory (e.g. 029y4-copy)
    4. Open up your firmware folder and go into the ‘src’ directory (e.g. 029y4-copy/src)
    5. Overwrite the 3 .inc files with your new ones
    6. Double click ‘compile.bat’
    7. This batch file will generate a new ‘msns-extra.s19’
    8. Copy ‘msns-extra.s19’ to 029y4-copy (One directory up) – overwriting the existing
    9. Pop the lid of your Megasquirt and short the 2 ‘boot’ pins or holes (I used a paper-clip)
    10. Power Up Megasquirt (I had mine on the JimStim)
    11. Double click ‘download-firmware.bat’
    12. Select your comms Port
    13. It counts up to 1480+
    14. Once complete, power down the Megasquirt and remove the boot short.
    15. Open up Tuner Studio and re-install your current project / .msq
    16. Hopefully you’re ready to go.

Tuner Studio – Auto Tune

I have the Ultra Version of Tuner Studio, so I’m going to type in some more realistic values into the VE and Spark tables ( Read All This! ). Then I’ll try the auto-tune facility. Sure, with the car immobile the results won’t be great but they have to be better than what I have. After reading endless blogs and forums I know Auto Tune isn’t going to give the results of a rolling road session but I should be ‘in the ball park’.

Rover V8 ExtraEfi Megasquirt

I need to get my custom water pump fixed first. – Watch this space!!


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