what choice of FI setup?
Turbo Mini Forums

OK, i might be going FI on my GTM (standard carb spec 1275). currently i have going spare a built up megasquirt unit and a SPI injection manifold. wouldn't cost much more to get the full kit needed - eg trigger wheel etc

bear in mind i done plenty of reading on here about the issues of FI on siamesed engines etc etc, is it worth using these components or am i wasting my time. i'm not looking for ultimate power - just better fuel consumption and cold starting etc. should i sell off these items and go mpi/canems for instance?

OR....keep the su and go mappable ignition as i also have a spare omex 100 3D ignition system too.

the car is being built as a lightweight commuter car (my other mini has a redtop on MBE with busa TB's)

cheers
matt

Edited by maph2 on 9th Jan, 2009.

I'm sure you could get it work and it would run OK.

Matching SPi sensors and IAC arrangements may be tricky with the MS.

Set it up at four squirts per cycle and there is a remote chance that the fuel will spread equally amongst the cylinders.

However, I would not turbo it as you will not have sufficient control over trhe fueling.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Mapped ignition makes a massive difference to cold starting and mpg. I would start with that and see how you get on.

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A man without a project is like a like a woman without a shopping list.

My personal view, bearing in mind you have most of what is needed, would be do it....

Just bear in mind you simply aren't addressing the siamese port issues (just as Leyland didn't with carbs or SPi), you are simply building an electronic carburettor (wet manifold).

That alone has the potential to give you what you want in terms of fuelling and, as has already been said, you can also use decent mapped ignition.
Also for minimal extra cost, and a small addition to the MS unit, you can even have direct driven coilpack ignition and get rid of the dizzy too.

I would add a wideband Lambda to your shopping list though, both for setup and closed loop control if you do fuelling.

However, if it weren't for the fact you already have most of the hardware, I wouldn't be so sure.

But, remember, you can do mapped ignition alone with MS, and leave fuelling until later.

Schrödinger's cat - so which one am I ???

If the Megasquirt is a "standard" build it will only have one "ignitor" (VB921, coil driver chip) so you do away with the bottom bits of the dizzy and use a map to fire the coil rather than the mechanical advance weights, vacuum advance etc. but you still need the top half of the dizzy to distribute the spark.

So it gets rid of the vagueness but not the damp problems !

The modification to MS to instal a second VB921 and drive a coilpack direct completely doing away with the dizzy is very straightforward and you just have to use the "Extra" code instead.
There is also another way to get rid of the dizzy completely, which is to get MS to drive an EDIS module (like Megajolt would do) but, personally, I don't see the point compared to adding a couple of extra components in the MS box.

But, as you say, lots of other aftermarket ECUs have enough driver chips inside as standard to support a coilpack (or even COP) without any modifications.

Schrödinger's cat - so which one am I ???