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MG MGA - Fuel Injecting a 'B' series BMC Engine

I am also new to this cite.
But I have fiddled with TC's, MG B V/8's and now an ex-Californian imported '59 build MG A Coupe'--all of this beginning away back in the late 60's.
I am not a young person--but keeping fit mentaly and physically, through the MG hobby. [And poor!!].
My interests presently centre round Fuel Injection. My first attempt at this conversion was a most satisfying improvement.
So much so, that I have moved on, and now there have been 2 major alterations to the system ---MK 3 version is fine.
5 port cylinder heads were never intended to be fitted with EFI's.
Balancing the fuel to each cylinder is a huge challenge.
So, if there is another enthusiast on the cite who is playing with EFI, who might be interested in swapping stories with me--that is the purpose of this note.
For general interest sake---
Building an EFI system offers many challenges. I used an American Ford Electronic Distributer Ignition System--- a 36 tooth cog wheel fitted to the front crank pulley---a Cam Sensor fitted into an old distributer body---2 Suzuki motor cycle throttle bodys-- a specially made fuel tank---and a well known American ECU that more or less suits this engine. The ECU is available either built up, ready for mapping or as a DIY kit to solder up onto a printed circuit board.
I chose the latter. All very satisfying, to accomplish.
There is fitting and machining--reading electronic circuits---soldering up electronic components--fabricating moving linkages to fit and work properly--- And programming/mapping the completed system, involved.
It runs better, because it is set up correctly. Its performance is strong, but limited to fuel in use, Cylinder Head design and other 50's limitatioms. Tossed the Choke Cable!!
I.W. Cowen.

It looks like you are just about the only person smart enough to attempt this Ian.

I was going to suggest that you should look up this section of Barneys Website on the subject. http://mgaguru.com/mgtech/fuel/fu301.htm

Then I realised it was your article!

According to MGA Guru, another Aussie has fuel injected a CrossFlow head on an MGA with a 1950cc engine but I expect you have already seen this.

Do you fit an individual injector directly into each cylinder or do they inject into a common plenum chamber?

Colyn
Colyn Firth

Hi IW

I'm not planning to fit EFI to my car but I used to manage a team of engineers in the 1980s developing EFI for race cars with Lucas, Jaguar XJR5 winning Le Mans and Metro 6R4 Group 3 rally car amongst others. With EFI you need to measure air mass flow. Is that is what is fitted to the Suzuki throttle bodies?
You can estimate air mass flow with a throttle sensor and an air temperature sensor. You should also have a pressure sensor on the inlet manifold to measure load. Without these you won't be able to get the air fuel mixture right. A mass air flow sensor is ideal but is expensive.

We used to map throttle position against engine speed and load (manifold depression). Systems are much more sophisticated these days. The first EFI systems used to dump fuel into the manifold all at once. We developed the first fully sequential software so each cylinder was delivered with the right amount of fuel at the right point in the cycle.
John

John Francis

Good Day Colyn and John,
Nice to hear from you again, John.
Colyn, the Injectors and the breathing of a 5 port head, have been the issue.
In the developement process, it was considered --- to place an injector in the cylinder head in the induction chamber and above each of the inlet valves. It is possible to machine this, however properly sealing the water jacket under pressure, and conversly the manifould vacc. combined could cause reliability issues.
So, this time it uses "Timed Injection", rather than John's earlier experiences with "Dumped Fuel".
The ECU had to be altered to provide 2 timed injector shots from each injector , rather than one dump from each injector per cycle.
In the original "one dump" arrangement, the first inlet valve that opened grabbed the available fuel charged waiting in the induction. When the other valve in that port opened, it received the remainder, only, of the fuel charge. So, due to the engine's firing order, the 2 inner cylinders had first go at the fuel charge, and the 2 outer cylinders tended to run lean, since they received only what charge remained.
For tuning purposes--mapping--- the exhaust manifold has plugs fitted in each of the 3 outlets to take a wide band Lambda analaliser. This accurately reads the cylinder's out put.
The ECU normally runs with a narrow band lambda , fitted in the beginning of the exhaust pipe.
Its all fascinating stuff.
Kind regards, ian C.
I.W. Cowen.

Hello Ian,
I have fitted fuel injection to replace SU's on a Triumph GT6 engine but not on a BMC B Series.
As you say your main problem is having only two inlet ports for four cylinders. Your method of injection timing sounds like the best compromise, but for optimum results from sequential injection you need a Derrington head or similar.
The Triumph has six inlet ports for six cylinders and so I have optimum sequential injection.
I use 36 dowels in the flywheel and a magnetic sensor in the engine block rear plate.
I have completely removed the ignition distributor and use six ignition coils.
A dowel fitted to the cam lobe which used to drive the fuel pump gives the camshaft position.
I use the Australian Motec ECU.

http://www.motec.com.au/home

I will contact you offline.

Mick
M F Anderson

Ian,

Attached is an image of the wiring layout.

Mick


M F Anderson

Ian,

And the ignition wiring layout.

Mick


M F Anderson

This thread was discussed between 16/07/2016 and 17/07/2016

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This thread is from the archive. The Live MG MGA BBS is active now.