How completcated does Efi HAVE to be? Not that complicated!

[Rich M]

DIY_EFI Digest         Friday, October 8 1999         Volume 04 : Number 568

Date: Fri, 08 Oct 1999 09:40:33 -0700
From: Will McGonegal <McGonegal.Will at etc.ec.gc.ca>
Subject: RE: How completcated does Efi HAVE to be? Not that complicated!

>>>to do a reasonable job of EFI. However, you WILL need the crankshaft
position
>>>sensor, which means you need the flywheel, transfer case and the actual
>>>sensor.

>>Surely it doesn't have to be *that* accurate? Why not use the coil? 2 per
>>Rev should be enough, you only need speed not accurate position?

>>Ade

>I'd agree, you DON'T need the crankshaft position sensor (flywheel,
transfer case and >the actual sensor).  An input from the spark ignition
will sufice (distributor?
>surely that's already on the engine).


Bosch LE/LE2 based systems have been taking EFi trigger signals from the
ignition for years..
Don't lose sight of the big problem with mini's - siamesed ports! For those
not so familiar, the head has two inlet ports which each split in two to
feed two inlet valves; Cyls 1&2 are fed by one inlet tract and cyls 3&4 fed
from the second. Throw the firing order into the equation, and you will
appreciate the problem of mixture distribution, specially from a throttle
body injection arrangement. for this reason, Mini's run with uneven mixture
across the cylinders even with carbs that feed fuel into the airstream
continuously. Consider what happens when you inject pulses of fuel into the
airflow way back at the throttle body, synchronous with the engine cycle.
This is why I believe some (if not all) TBi sytems inject 'asynchronously'
(randomly?). Certainly Vauxhall/Opel Multec TBI systems inject 5 pulses per
cycle to try and spread out the uneven distribution so that each cylinder
gets a fighting chance of seeing reasonable mixture on average.

Multipoint systems with an injector per cylinder obviously overcome most of
these problems, but on the mini's siamesed ports it's difficult to
physically arrange this as the port split is in the head.

Don't let this put you off - Rover obviously achieve reasonable results;
indeed if you 're not using the 'A' series engine, and you've got an 8-port
head, then please bung this message in the bin...

Good luck!

Rich