Rover V8 MegaSquirt P38 4.6 – extraEfi

Rover V8 Megasquirt P38 4.6ltr

The original plan was to utilise a John Earle Engineering tweaked ECU, but along came a bargain cheap MS1 Rover V8 Megasquirt made by extraEfi previously fitted to a 4.6Litre Stag. A separate purchase gave me various hoses, brackets and pipes necessary.

This particular MS1 Megasquirt had built in IGBT coil pack drivers meaning I didn’t need to use that Ford Edis-8 ignition module I had stuffed under the bench. It also had a wiring loom.

A few minutes on the web found circuit diagrams, connector pinouts, photos, forum installation diaries and more.

Rover V8 Megasquirt

Confidence was high.

Once in the garage, confidence fell a little, as it was obvious that numerous connectors were missing from the loom. The hoses, tubes and brackets were obviously for a early 3.5 Land Rover, at best they’d need cutting up if not scraping.

After a few evenings of research it became apparent that although some have enjoyed Rover V8 Megasquirt success, many had become frustrated with what seemed like an endless series of issues. Several had employed specialist tuners and had still given up.

I’d recommend reading this post: Megasquirting a V8 – how to basics – long but worth it

Rover V8 Megasquirt Problems

  • Bad Grounding
  • Incompatible sensors
  • Poor idle
  • Unable to turn off
  • Constant resets
  • Wrong wire sizes
  • Wrong sensor pinouts
  • Old tuning software
  • Wrong firmware versions
  • Choice of Lambda sensors
  • Not to mention tuning

Rover V8 Megasquirt Observations

Once offered up to the engine it was instantly obvious that the wiring loom was the wrong length and designed for a different vehicle, I therefore decided to remove the heat-shrink sleeving and trace all the wires.

I noticed that the wire colours used didn’t seem to tie up with either Lucas wiring colours  or those used by Range Rover. To complicate things, even Range Rover changed their colours!

These are my colour codes:

B  – Black
G  – Green
K   – Pink
LG – Light Green
N  – Brown
O  – Orange
P  – Purple
R  – Red
S  – Slate  (grey)
U  – Blue
W  – White
Y  – Yellow

Having several injected Rover V8 engines, from a 1986 JEE tuned 3.5Ltr SD1 Rover V8 to a 2002 serpentine P38 4.6Ltr Range Rover V8, it became obvious that they all had slightly different plenums, different sensors, idle valves etc. There were different air feeds, crank sensor, fuel regulators….
The list goes on.

Added to which, many of the blogs I’d read, seemed to be from people using non-standard engines taken from a 20 year production span of TVR’s, Landies, Morgans, Boats and after-market tuners. Some were even dual fuel! It didn’t help that acronyms seemed to be the order of the day, complicated by everyone using different ones for the same device.

Part numbers for sensors seemed either thin on the ground, conflicting or obviously wrong. Helpful bloggers had suggested using the same sensor as their Toyota 4 pot, but with a lot of research I found they were the wrong thread or even the wrong type of sensor…… well you get the picture

Rover V8 Megasquirt Common Acronyms

EAV Extra Air Valve
PWM Pulse Width Modulation
MAT Manifold Air Temp (Bar)
AFM Air Flow Meter
AFR Air / Fuel Ratio
ATS Air Temperature Sensor
IAT Intake Air Temperature
IAC Idle Air Controller
CTS Coolant Temperature Sensor
TPS Throttle Position Sensor
VR Variable Reluctance
ECU Engine Control Unit
WB Wide-Band
NB Narrow-Band
MAP Manifold Air Pressure
FPR Fuel Pressure Regulator
ASE After Start Enrichment
WSE Warm Up Enrichments
WOT Wide Open Throttle
CO2 Carbon DiOxide
HC Hydro Carbons
KPa Kilo Pascal
VE Volumetric Efficiency
TS Tuner Studio
TDC Top Dead Centre
BTDC Before Top Dead Centre

Rover V8 Megasquirt sensors

At this point it, is important to realise I’m just starting out and realistically have barely started. I haven’t had the engine running, so this is a diary of mistakes rather than a ‘How To’.

Air Temperature Sensor (ATS)

I’m using an FAE 33170 (page 81). It basically a thermistor; a resistor that changes impedance with temperature.
Pin1 – Red/Black 0.5mm (Ground)
Pin2 – Slate/Green 0.5mm

  • FAE – 33170
  • Renault – 77 00 737 572 or 30865366
  • Daewoo – 96279856 or 96253552
  • General Motors – 96279856
  • Siemens- S101431001
  • Beru – 0 824 111 007 or ST 032
  • Chevrolet – 96279856 or 96253552
  • Hella – 6PT 009 104-021
  • Volvo – 30865366
  • Cambriare – E375084
  • Blue Print – ADG07236C
  • Fuel Parts – AT1010
  • Intermotor – 55703
  • Kerr Nelson – EAT019
  • Lucas – SNB818
  • Quinton Hazell – XEMS600
  • 0824111007

I made up a 70mm steel tube for mine to sit in, with a 14×1.5 threaded insert.

Rover V8 Megasquirt P38 Inlet Air Temperature

The hose outlet is to the Extra Air Valve. I’d rescued the air fitment to the Extra Air Valve from a Megasquirt-V8 AFM tube. For some reason the fitting was 22mm, which was odd because the Bosch Idle valve is 19mm. I therefore bought a pair of silicon 22-19mm reduction hoses.

Coolant Temperature Sensor (CTS)

There are often at least two CTS fitted to a Rover engine. Before the thermostat and after. You want the one marked 6 in the following…

For the CTS I used a FAE 33370

FAE 333370 Rover V8 Megasquirt Coolant Temperature Sensor

Pin1 – Red/Black 0.5mm (Ground)
Pin2 – Green 0.5mm

  • Jaguar – EAC3927
  • Land Rover – EAC3927 or ETC8496
  • Rover ADU 7130 or ETC 8496
  • Saab 74 85 006

Throttle Position Sensor (TPS)

I’m using the smaller TPS, as fitted to a 2002 P38 4552cc Range Rover. The TPS is a potentiometer or adjustable voltage divider.

Megasquirt TPS - ERR7322

Pin1 – Red 0.5mm
Pin2 – Yellow/ Light Green 0.5mm (Wiper)
Pin3 – Red/Black 0.5mm (Ground)

  • Bosch – 0 280 122 016
  • Land Rover – ERR7322

Extra Air Valve (EAV)

From reading the forums, many after-market ECU have idle problems without an EAV.

I’m using a 3 wire Bosch 0 280 140 505

Pin1 – Black 1.0mm
Pin2 – Brown/Orange 1.0mm
Pin3 – Green/White 0.5mm

Lambda Sensor

My Rover V8 set-up has twin exhausts that don’t converge and the Megasquirt MS1 has only one Lambda input. Some modern V8 cars have sensors pre  & post catalytic converters. That’s a total of four. For my one Lambda sensor, I picked a position pre-catalytic converter on the near side.

There is an age long argument raging on the forums whether narrow-band or wide-band is better. It seems wide-band are more sensitive to vibration damage, but have a better measurement range. If wiring is routed badly, then they can be more prone to noise. Narrow band however, seems quicker to set-up and has a longer life span. Many argue as the Rover is so simple, a narrowband is useally adequate.

Then there is 2, 3 or 4 wire. Two wire lambda sensors aren’t heated. Three wire version are heated but the heater shares the same ground wire as the sensor. Four wire is heated and has separate ground for heater and sensor.

What did I chose? It was simple, I had a spare SEAT LEON Cupra 4 wire wide-band heated lambda sensor in a box on the shelf. It had the right thread for my stainless performance catalytic converters, so I’m using it.

021906262C 1K0998262C 07L906265F 07C906262AE 078906265N 077906265AE
022906262AF 1K0998262E 07L906265G 07C906262AG 078906265P 077906265AF
022906262AG 1K0998262Q 07L906265H 07C906262AH 078906265Q 077906265H
022906262AH 1K0998262R 1K0998262 07C906262AR 078906265R 077906265J
022906262BG 1K0998262S 1K0998262A 07C906262H 078906265T 077906265K
022906262BH 1K0998262T 1k0998262AB 07C906262J 079906262G 077906265L
022906262BJ 6A906262CM 1K0998262AC 07C906262M 079906262H 077906265R
022906262BQ 07D906262E 1K0998262B 07C906262P 079906265 077906265T
022906262BT 07D906262A 07D906262B 07C906262S 079906265A 078906265AA
022906262CE 07C906262T 079906265F 07C906262A 079906265E 078906265M
022906262CF 022906265B 030906262L 058906265B 06A906262AJ 06A906262AR
022906262F 022906265C 030906262N 058906265C 06A906262AK 06A906262BA
022906262K 023906262 036906262H 06A906262AC 06A906262AL 06A906262BB
022906262L 030906262 036906262P 06A906262AG 06A906262AM 06A906262BG
022906262S 030906262A 047906265B 06A906262AH 06A906262AQ 06A906262BL
06A906262C 06A906262F 06C906265 06D906265 06F906262S 077906262B
06A906262CN 06A906262P 06C906265A 06F906262AE 06F906265 077906262C
06A906262DQ 06A906262Q 06C906265C 06F906262D 06H906262A 077906262G
06A906262EA 06A906265M 06C906265L 06F906262E 06J906262A 077906265AA
06A906262ED 06A906265N 06C906265M 06F906262P 06J906262K 077906265AD

Black – Signal
White – Earth
White – Heater
Gray – Heater

022906262 Wideband heated Lambda sensor

Crank Sensor

Many MS1 Megasquirt set-ups use a Ford crank sensor and an after-market 36-1 trigger wheel mounted to the back of the front pulley. The P38 serpentine Range Rover, unlike early SD1 Vitesse’s has a trigger wheel mounted to the back of the flywheel. The 4.0 Discovery is available as a manual. When a 4.0 flywheel & clutch came up for a couple quid, I bought one. When it arrived, it was obvious I couldn’t use it, as it was twice as thick as the SD1 Vitesse. It also weighed 14Kg as opposed to my 8Kg JEE Vitesse one. The intention is to fit the Discovery trigger wheel to the Vittese flywheel and get it re-balanced. This guy’s done it.

The above picture shows the trigger wheel from a automatic flex plate. Whereas I want to use a manual trigger wheel on a manual flywheel.

Apparently, according to this forum piece the missing tooth is at 20° BTDC.

I’m a little confused by that article, as he’s trying to achieve 60° BTDC, whereas I want 50° BTDC

According to this post and this image, you need 5 teeth past TDC. That’s 50°, isn’t it?

I’ve got some measuring and phone calls to make

I’ll keep you posted on this one….


The above devices use 2 and 3 pin AMP connectors. It’s best to use new connectors and the proper crimp tool. Luckily I still had a pair from my days working for Magnetti Marelli on Renault Engine management design. The same 2 pin connectors are used by the injectors.Rover V8 Megasquirt P38 ip65 boots

I’ve added IP65 water resistant boots and small piece of adhesive heat-shrink. Being sensor wires I twisted them together for mutual inductance (better noise immunity). Where these wires passed close to anything hot, I made sure they were inside heat-resistant sleeving.

All sensor wires were kept in a separate loom to injector and ignition wires. I’ve even got some special RF shield wire mesh to wrap around sensitive wires. Range Rover didn’t feel the need so I’ll only go this far if there is a noise issue.

When looking at the above circuit diagram and from taking apart the loom I’d bought, not much attention had been paid to earth star points or ground loops. When you don’t use star points what you think is 0V (ground) may well be noisy or have a small static voltage upon it. This will cause false sensor readings. The 600volt+ ‘peak and hold’ injector waveforms will be visible on your various readings. If the noise is bad enough, the main micro-controller will simple sit in a permanent reset cycle. The circuit will visually appear correct, and even buzz through OK, but with a decent oscilloscope, the problem will be apparent.

To avoid that, for everything that is ground, run a separate wire back to a single ‘star point’ very close to the battery. If possible, keep the ECU close to that star point. Definitely do not daisy chain earth wires or use the engine block. Keep sensor wires away from Injector and ignition circuits and twist sensor and ground wires together.

Currently the loom is temporarily cable tied, but once I’m happy it will be bound in adhesive free looming tape, non heat shrink sleeving and heat reflective shield.

Rover V8 Megasquirt P38 sensors

A set of Magnecor spark plug leads came with the MS1 Megasquirt ecu. However, as you can see, they don’t fit my engine too well. They said Rover V8 – but what model I don’t know.
Therefore, I’ll be making my own 8mm silicon leads.

You’ll see in my wiring diagram I have added wire gauges and Range Rover wire colours. I have also shown multiple wires converging to star points. No daisy chaining here!Rover V8 Megasquirt MS1 Wiring Diagram

Engine run on

In the alternator circuit I’ve added a 1N5402 diode to prevent back voltages through the charge light keeping the ECU powered once the ignition is turned off.

Rover V8 MS1 Megasquirt

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