Fuel Injection - Options for B series Owners

(With thanks to Keith Clarke for inspiration and information)

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Options to fit EFI on a B Series

When considering fitting an EFI system to a MGB, most are doing it because the donor engine such as the M/T16 or K Series engines come fitted with it and making up custom manifolds to run with SUs is not an easy option.

A basic review of the parts needed for EFI is :

• A modified tank or swirl pot (with a low pressure pump feed from the main tank) with high pressure pump feeding the system.
• A return rail for excess fuel to return to the tank (although nowadays the internal high pressure pumps have a bleed-off valve for excess fuel directly back into the tank)
• An Engine Management system or ECU

The following sensors are needed:

• Engine temperature (usually from the coolant)
• Ambient air temperature
• Manifold Absolute Pressure (MAP)
• Throttle Position Sensor (TPS)
• Oxygen sensor in the exhaust downpipe
• A crank position sensor (usually on DIY systems, a toothed wheel to fit the crank pulley with 36 teeth and one removed aka 36-1)

So how easy is it to fit to the B Series?

Please see the discussion on charge-robbing issues of Siamesed inlets in the introduction to EFI and also, I suggest you visit Keith Clarke's excellent site.  

To summarise an email Keith kindly took the time to compose for me and to re-cap on the charge robbing issues:

On the siamese-ported engines, there have been some experiments with port injection (up near the head, so the manifold remains ‘dry’ only delivering air). The only hope for charge-robbing is sequential injection (expensive ECU that manages one squirt per cylinder, per induction stroke) but this requires large injectors dumping lots of fuel quickly (whilst only the correct inlet valve is open) & as engine speed increases this becomes impossible. This approach hasn’t been too successful – atomisation suffers as well as part throttle drivability, as big injectors have poor sensitivity when they are opening for very short durations at part-throttle. Most A-series & B-series converters therefore accept the limitations of siamesed ports & go for an aggregated, wet manifold approach.

A few ideas for you: 

• TBI (Throttle-body injection): This is the simplest approach as used with the EFI Metros (especially if you got a single-carb manifold with the O-series). This is a wet manifold approach, running a combined single throttle-body/injection (TBI) housing, as here on Werner's MG BGTi pages. This approach is effectively a straight replacement for a single SU, though with the carb’s venturi gone, the flow rate is much improved & the ECU provides a software based needle/jet adjustment. The combined TBIs tend to run at a lower pressure than individual injectors, so the HP fuel delivery side is also simpler. Here’s another B conversion using a single Individual throttle bodies (ITB) from a big bike.
• Port injection: Here’s a 1500 Midget conversion with a dry manifold, port injection set-up. The 1500 Midget has individual ports, so the manifold work is probably worthwhile. I considered chopping up a C manifold but the balance pipe gets in the way & as I had a triple Weber manifold, the motorcycle ITBs look a bit more ‘Sebring’. I don’t think I’d bother with port injection on a standard A or B-series head, though, as even if there was space on the shared runners for 2 injectors per port, the inlet port shape within the head precludes the injectors from spraying onto the back of the correct inlet valve. And indeed, shared injectors right at the port might exacerbate charge-robbing issues, depending on the spray pattern from the particular injector.
• Direct SU replacement: I was sorely tempted to take this approach to have more of a ‘stealth’ conversion. There are firms who offer throttle-bodies that can bolt onto SU flanges - Jenvey  do single ITBs with or without injectors, together with SU flange adapters, which work out less than the TWM kit. However, these are made exclusively for those with money to burn – again, you might as well get the cross-flow head & bolt on 4 bike ITBs or port injection!
• Motorcycle Throttles: Another option you might care to consider. I’ve taken 2 sets of GSXR-600 motorcycle ITBs http://msefi.com/viewtopic.php?t=6627 to create a 6-in-line throttle assembly, similar set-up to the Sebring triple-Weber configuration. These injectors are good for 50HP per ITB, so a pair of these might suit a not too hot B – mounted as direct replacements for the twin SUs. Indeed, as I used the central pair from one set of 4 bodies, I have a spare pair comprising the ‘end-units’ which have the throttle cable & throttle-position sensor. I had considered trying to get approval for a Midget or Morris Minor project for these but the ‘FD’ (aka Mrs Clarke) won’t sanction that. So, if you want to use a twin-SU manifold & fancy some experimentation for a ~100BHP B-series, let me know.

Courtesy of Keith Clarke.

So the simple answer appears that to fit EFI, you are looking at also fitting a newer engine such as the O series onwards or even...a V8!  That said, as mentioned above, Moss do a kit but the primary reason being the emissions control rather than any improvement in power.  Of course EFI also offers opportunity for improvements in economy, response and cold starting, and also as a cure to the run-on problem facing many B owners!

Off-the-shelf DIY EFI Kits

Note the photos below are from the respective websites.

Moss:

As mentioned in the introduction to EFI, some American States have such tight limits that Moss have started to offer a fuel injection unit for owners (see below).  Obviously this is not about making power, but maintaining tight emissions control.

Since the launch of the version above, Moss-Europe now offer this WEBCON kit below:

From the website:

Webcon have now developed a breakthrough in engine management systems for the MGB.

Based on an aluminium cross-flow cylinder head with side draft throttle bodies and Webcon’s Alpha management system it is the most advanced ‘out of the box’ solution to engine management for MGB models.

The system is mapped to suit the driving requirements of most road and fast road users, providing better throttle response and a more managed spread of torque and power making the MGB more tractable and enjoyable.

A further advantage of a more efficient engine management system is that an improvement in fuel economy will almost certainly be noted and, although not enabled on the display car, the system is capable of full closed loop lambda control making it suitable for use with a catalytic converter should the need arise.

The system features 2 x 45mm ALPHA throttle bodies fitted with State of the Art Weber PICO injectors and is controlled by the latest and most powerful Alpha PRO4 Electronic Control Unit.

Further mapping can be done by an approved Webcon dealer.

This kit includes:

• Aluminium cross-flow cylinder head 
• Inlet Manifold 
• Throttle bodies 
• ECU Injectors 
• Wiring harness 
• Remote Mounted High Pressure Fuel Swirl Pot

Extrudabody:

Extrudabody is another option that Bryn unearthed for me.

TWM Induction:

The TWM 2700 series is the one to go for on the SU carbs (most British sports cars and saloons!).

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