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Nick Jones

Quick and dirty EFI guide

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Lots of ways to skin this particulat cat, depends on what you want from it and how deep your pockets are:  Note even if you are buying a 'bolt-on' system there is more than a weekends work here.  Your own 'bespoke' system will take alot longer - took me about 3 months to do mine although the car was only of the road for a couple of weeks.




Three main divisions:


1. Throttle body injection - which means one big injector serving several cylinders, a bit like an electronic carb.  You might have just 1 feeding a 4 cyl engine or two feeding a 6 perhaps.  Cheapest solution allowing full electronic control (and thus emissions compliance) but is still reliant on a decent manifold design to give equal fuel distribution.  Tend to get used on cheap modern stuff but have also been (quite ingeniously) adapted to fit into carb bodies to give very easy conversions for classics using SU or Stromberg carbs.


However, remember the manifold limitations.  IMHO anyone going to the trouble of converting their classic for performance reasons should aim higher than this!


Pros - relatively cheap and simple, minimum spend on hardware and could look near standard if done carefully.

Cons - limitations of standard manifolds make this a bit of a compromise performance wise although should be possible to gain usefully on the economy front.




Plenum type manifold with single throttle.

The system used for the majority of modern injected cars.  Each cylinder has its own separate runner and injector fed from  a common chamber (plenum) which a single throttle assembly.  The runners can be sized and shaped according to taste but ideally as long as can be fitted under the bonnet, equal for all cylinders and with bellmouths in the plenum for best flow.  Plenum size can be chosen for low down torque or top end power.


On an old Triumph you will most likely have to make your  own (not so very hard in fact!) although on the 6 cyl there is the possibility of using the PI throttle bodies and plenum as starting point but remove the individual butterflies, seal up the holes and put a single throttle body on the inlet to the plenum.


Pros: Allows equal length runners for each cylinder and individual injectors for each cylinder ensuring even fuel distribution.  Single throttle keeps any linkage and balance issues at bay and keeps costs down.  Single sensibly sized throttle allows decently progressive throttle and eases mapping.

Best power/driveability/cost compromise IMO.


Cons:  More complicated than TBI throttle bodies and is not going to look remotely standard when done.  You'll probably have to make your own manifold or have one made.  Slight loss of throttle response and outright power compared to 3 below.


3.  Individual throttle bodies

As used on racers and high-end sporting machinery.  Similar to the plenum system above in that each cylinder has its own injector(s) and runner ensuring even fuel distribution but with the addition of an individual throttle butterfly per cylinder too.  This last improves throttle response by reducing the throttled volume of the inlet tract and removes the small restriction of the plenum allowing absolute maximum airflow and thus power.


They ways of arriving at this are slightly more varied.  If you have (very) deep pockets you could just buy a set of aftermarket throttle-bodies on the relevent manifold and bolt them on.  You could use motorbike throttle bodies and come up with your own design of manifold and linkages which will be cheaper but potentially tricky to get right or, on a Triumph six you can modify the PI throttle bodies to take modern injectors etc.


The big pitfall to watch out for is oversizing things which although superficially attractive, is likely to spoil driveability and response and make it very hard to set up.  Note that the standard PI throttle bodies are a bit big - you are probably looking at 32 - 36mm on most Triumphs.


Pros:  Best power and throttle response.  Can be bought off the shelf at a price.  Looks impressive (if you care)


Cons:  Most costly and complex.  Performance gains over good plenum setup will be small on a road engine.  Correct sizing of the throttle bodies is important and the linkage and balancing arrangements need to be excellent or you'll never get it running right at low rpm/small throttle openings.




Again, lots of choice, ranging from Megasquirt at around £ 130 if you build it yourself (£ 200ish assembled) through Emerald at £ 600ish and on up.


Megasquirt is perfectly adequate functionally but does require some basic electronics and computing aptitude (or at least a determination to learn!) whereas the other aftermarket ones are presumably more user friendly (why else pay extra?!).  You may also find some tuners (and rolling road operators) anti -MS mainly because they don't sell it or understand it.  Actually, the tuning process is no harder than any other but of the initial setup is a bit more involved.

Vist the Megasquirt website and have a good read because even if you end up buying something else, there is NOWHERE that covers the EFI process as comprehensively or accessibly anywhere else!


See: www/msefi.com




Fuel supply - EFI needs a high pressure supply - 2 bar +.  You will need a high pressure pump, filters, high pressure feed and a low pressure return and some kind of swirl pot or volume chamber to stop fuel surge causing misfires.  Obviously it's important that this part is done safely and well or you'll have an impressive bonfire.


Sensors and wiring - not particularly complicated or difficult but MUST be done well of you'll create a an unreliable moster.  If you've done the RBRR in the pissing rain without a hitch you can consider your wiring tested.


Ignition.  Most ECUS have the facility to control the ignition as well.  USE IT!  Its worth it - makes as much difference as the FI!




Megasquirt: http://www.msefi.com/index.php  (start at the beginning! also worth a trawl through the sucess stories)


Make your own manifold:http://www.sdsefi.com/techinta.htm  (lots of good info on this site - have a look around)


Jenvey throttle bodies:http://www.sdsefi.com/techinta.htm (wallet too fat? - these guys can help!!)


TBI system: http://topshamautoparts.com/tr6/tbi.htm


Here's one I did earlier: http://www.tengaston.plus.com/Megasquirt1.htm  (been going nearly 4 years now, works well)


Some other DIY systems:






This is in no way exhaustive - it's a big subject!


Should give you a bit of a start though!  :P



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Good article Nick, well done. Still like that vitesse, makes me think sometimes....

Not sure about the battery clamp you use though :P


Got a proper one now...... it's still a bit too shiny though :P



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Bloody good show Nick, one of the things that is stopping me plonking my Cosworth V6 into a car is the fact that I am going to have to take the wiring loom to bits as I do not understand this side of motoring.

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Thanks Jon.  I have read that the engine loom for the cars with that Cosworth V6 engine is mostly separate from the main loom.  This is so they can use the same main loom for all of the models and just vary the engine part.  This means it should be possible to separate without huge aggro.  Would also be relatively easy to megasquirt using the standard hardware although I would use the std ECU if at all possible.



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Hi Nick,

Finally I have found some good information on my project subject, I know much has happened since you wrote these wonderful notes, however, many of the links appear to no longer be available. Is there any chance you might update these. I found a great site selling a turn key kit for the TR6 but there are no contact details or phone details on the website http://eficonversions.co.uk/Index.html Nor do they reply to emails??? Any new information would be appreciated.



Canberra Australia

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I've not heard of these folks before and their website doesn't seem to show that they have actually sold any conversions. They also seem very expensive for what if offered being something over 3.5 x the cost of a DIY install. At £ 3,700 it is also 70% of the price of Revington's Weber Alpha system and doesn't even appear to offer altitude compensation (not a big issue in Oz maybe) or mapping.


My first conversion on the Vitesse (most similar to their MK2S) cost me under £ 500 although I did use alot of used parts (which are still fine 9 years later) and it took me a while.


My second conversion on my PI wasn't alot more and took less time due to only modifying manifolds rather than starting from scratch.


James' EFI conversion on his Mk1 2000 is well worth a look







1. My PI.

MS2 ECU, PI manifolds modified to accept modern solenoid injectors and single throttle

EDIS 6. Makes approx 148 bhp with std "132" PI cam, diy flowed head and TR6 cast manifold. Very flat torque curve and up to 35 mpg.


2. Vitesse.

MS2 ECU, Home made plenum manifold (steel exhaust tube) and single throttle.

EDIS-6. Makes approx 120 bhp with std Mk2 came (same as PI), diy flowed head and 6-3-1 manifold. Up to 42 mpg, 35 mpg average. Has done approx 30k with EFI - 100% reliably.


3. Friends Ex US TR6

MS1 ECU. PI manifolds modified to accept modern solenoid injectors and single throttle

EDIS 6. Power unknown but goes really well. He's in the aircraft industry and like to do things right!

PIe 006.jpg

Vitesse 09 004.jpg


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