SPi 16v to MPi conversion
Most early 16v Metros where Single Point Injection (SPi) with a single injector. Some people have found to increase performance you can convert these to have 4 injectors by fitting the later type Multi Point injection (MPi).
88Difficulty7Tools required9Time required7Price
I recommend working in conjunction with the Haynes manual, as some of the procedures set out below could be considered sparse and may need going into more detail if you are not familiar with the metro k-series engine. This conversion guide is exactly that, a guide only, and is probably relevant for the early metro MPi single socket ECU management system without integrated alarm and immobilser only. You carry out the conversion at your own risk, all work carried out is the sole responsibility of you!
The 16v SPi:
- MPi Loom
- Early Metro GTi (J or K plate)
- MPi ECU From early Metro GTi (J or K plate)
- 16V MPI Inlet Manifold from 100,200,400, or any MPI k-series
- 16V MPi injector throttle body assembly including ancillary items such as throttle housing assembly, injectors, rail, etc (100,200 or any MPi k-series)
- 16V MPi Water elbow from 100,200,400, or any MPi k-series (see picture below)
- 16V MPi fuel filter housing assembly (see picture Below)
- MPi exhaust manifold Metro GTi, 200 series will be ok but will need to use 200 series down pipe
- Lambda sensor (one that is attached to exhaust manifold (check)
- MPi exhaust down pipe Metro GTi, (200 series known to be ok with some mods)
- Charcoal canister purge relief valve 100,200,400, or any MPi k-series
- MPi coolant pipe the pipe that is connected to the water coolant elbow
- 16V MPi fuel pump not sure if 200 series pump will fit in fuel tank without modification
- Charcoal canister that connects up to purge relief valve.
- 16v MPi Cam Cover Only as the SPi example looks odd with out the airfilter
- Disconnect the battery, then remove the SPi air filter assembly.
- Disconnect the water hoses to the inlet manifold and drain the coolant Remove SPi inlet manifold and injector throttle body assembly complete, the loom plugs and disconnect the throttle cable.
- Remove fuel filter housing assembly and associated fuel pipes noting feed and return.
- Remove SPi exhaust manifold.
- Remove SPi water elbow that connects to passenger side of cylinder head and temp sensor loom plug. Remove SPi engine loom cross referencing the old to the new if required. The easiest way to do this is to line the two looms up side by side, making any notes you feel relevant when replacing the MPi loom.
- Remove the SPi ECU, leaving the ECU harness as well as the relay module located behind the ECU harness. Disconnect the loom plug from the inertia switch. The old loom should be almost out now except for where it goes into the fuse box near the battery, then terminating as a ground wire (see picture below)
Starting to add MPi parts
- Connect the MPi inlet manifold to the head using a new gasket. Start to put the MPi loom in place. Connect up the alternator plug and oil pressure plug which is at the start of the loom. Feed MPi loom in existing location as SPi loom.
- Connect MPi throttle body assembly to inlet manifold using new gaskets. Injectors, rail, pressure regulator, etc and associated sensors were already bolted on in this case. The existing throttle cable needs modifying to fit onto the new throttle assembly (See picture below).
- Connect the loom plugs up to the relevant sensors and then sECUre the loom to the chassis using cable ties.
- The SPi fuel filter housing needs to be replaced with the MPi version, I think it has a different connector type going to fuel rail. I'm not absolutely sure I just know there was a problem with the SPi filter assembly at the fuel rail end, and I had a MPi filter with fuel pipes available.
- Connect the fuel pipes to the filter pipe connector and the fuel pressure regulator which is attached to the end of the fuel rail. Be careful that the fuel pipes are sECUrely fastened as these are pressurized so could potentially be a fire hazard. It would be wise to look at the Haynes manual for reference when assembling the fuel pipes in conjunction with this conversion.
- Connect the tdc sensor plug to the TDC sensor which is located on the engine block, and connect the white reverse light plug to the gearbox sensor on the top of the gearbox housing.
- Now connect the MPi water elbow to the head, changing the gasket as a matter of cause. There are two sensors on this elbow; coolant temperature sensors. One sends the temp to the gauge on the dash; the other sends the temp to the ECU. I originally left this part off, the dash sensor was plugged in but the ECU didn't know the temp and assumed a pre-defined temperature. The result was an engine that wouldn't start well in the mornings, was flat on acceleration, as well as storing fault codes and retarding the ignition. Not good!
- One of the coolant pipes that was connected to the SPi inlet manifold needs to be connected to the new water hose which in turn gets connected up to the water coolant elbow; in my case I used a 214 coolant pipe. I used some 15mm diameter aluminum pipe to connect the two coolant hoses together, securing both ends with jubilee clips. This allows coolant to pass through to the other side of the engine which used to get diverted through the SPi inlet manifold; There is no provision for this on the MPi inlet manifold, hence the routing using aluminum pipe.
- Now the MPi exhaust manifold can be attached to the head, with the lambda sensor which needs to be attached to the lambda sensor loom plug.
- Replace the exhaust down pipe as the MPi exhaust manifold wont mate up to the SPi exhaust down pipe.(spi has single large down pipe, MPi has smaller twin down pipes) I used the manifold and down pipe off a 214 which wouldn't mate up to my existing center section. The down pipe was cut short and the flange was re-welded back on, and then secured to the center section.
- Instead of adding the standard MPi air filter assembly, a pipercross air filter from a rover V8 was put on to the throttle body which saved fitting time as well as increasing the maximum airflow available.
- Rather than connecting the charcoal canister assembly, I chose simply to connect the bypass valve to the associated piping, sealing off the vacuum pipe on the injector throttle body assembly with a small tapered plastic pin as shown in the pictures. A golf tee would be a good alternative also. The loom plug was also connected up to the purge relief valve just in case the ECU threw up a fault code.
- The fuel cut-off inertia switch was also re-connected to the relevant loom plug, although I have heard that some MPi GTi's do not have them. Again I wanted all the new loom to be connected up to the relevant parts so as not to throw up any fault codes.
- The MPi ECU needs to be attached to the existing ECU harness, the SPi ECU harness can be used as well as the small black relay module box located behind the harness. I checked the SPi and MPi relay module boxes and they had exactly the same serial number on them.
- Once the ECU is secured to the harness, connect the loom plugs up to the ECU and to the relay module box. The loom follows up to the last fuse in the fuse box near the battery.
- The old fuse, along with the old loom fuse wires and connector plugs can be removed from the main fuse box housing, replacing with the new loom wire and fuse if needed into the connector plugs which click back into the main fuse box housing.
- The end of the loom is a grounding point as shown in the pictures, disconnect the old loom ground wire and replace with the new, making sure the ground is suitably tight and not loose. The old loom should now not be connected to any parts or sensors and can be removed from the engine.
- Connect the battery, refill the coolant system.
Should I replace the fuel pump?
If choosing to replace the fuel pump, there are a few things to consider. The MPi pump has a higher maximum output of 3bar +/- 0.2bar as opposed the SPi pump which is 2.7bar +/- 0 bar. Some might argue that you could get a MPi pump with 2.8 bar max output which only has a 4% increase in max pressure over the SPi pump. Others could argue that you could get a MPi pump with 3.2 bar max output which equates to a healthy 18% increase in max fuel pressure.
At the end of the day the fuel pressure regulator, located at the end of the fuel rail, dictates the regulated fuel pressure available which is 3.0 bar. My advice is that if a MPi pump is available, or can be readily sourced, then it should be fitted, especially if the car has been modified as it will have a greater fuel requirement at higher revs. Moto-build have converted a 1.4 SPi metro to 1.8vvc spec without changing the pump and said the car ran fine. I would reserve judgment on this one, as I bet the 1.8 VVC pump has a higher pressure than the 1.4 MPi pump (The danger being the car could run lean at high revs and cause serious damage to the engine. You have been informed and warned, it's up to you!)
- Cut a circular cut-out using tin cutters on the top of the fuel tank, which will gain access to the old pump.
- Remove and replace with the MPi pump, noting the correct pipes for the main feed and return feed.
- I am not sure if a 214 MPi pump can be used due to the fuel sender gauge assembly probably being different although these are more readily available from breakers, etc, and at worst you could either “a-team” or graft the metro sender gauge onto the 214 pump or leave it off altogether at the expense of not knowing how much fuel is on the tank! (Not advised)
- If you can source a metro mpi pump then there will be no issues regarding the fuel sender gauge, and fitting issues.
I recommend replacing the oil, filter, and plugs as a matter of course, unless the parts are fairly new and the oil clean before driving, then driving the car easy for the first 50 miles, gradually working the engine harder though not too hard, i.e red-lining) for the next 50 miles All of my metro's have seemed to run a lot better after 100 odd miles, possibly due to the new ECU learning that particular engine characteristics and optimizing fueling and ignition to suit, this point is also mentioned in Haynes) then taking it in to a rover garage for a full system diagnostics check. They will remove any old fault codes, advise of current fault codes if any, and rectify as necessary at cost, as well as setting the mixture and idle correctly. This is worth the 30 to 40 pounds charged by rover for
- Better fuel consumption,
- Reliability, and most importantly
- Peace of mind.
To see the pictures click below
Also available as printable PDF
This is a guide written by Dean Challis. If you have any questions or advice on this conversion, or indeed any extra points that you feel should be included or left out, please email the site admin or post your query on the forum.
Constructive criticism and comments will be welcomed and appreciated. This conversion write-up was done for the benefit of Performance Metro Club Members and Metropower.