Bosch Motronics V Rover GEMS

[Franc Buxton]

Roderick Warner wrote:
> 

>       Having said that I would not rule out a GEMS  system -- but is there any
> info to allow diy programming ? .  A quick search of the web didn't reveal much
> of interest.
> 
>                     Rod
> 
	Hi, Guys,

	I may be able to offer some small insight into Rover GEMS. It isn't an easy
system to hack, or indeed to put on any custom application, IMHO. The whole
system is
based on measurement and calculation, in that it measures the airflow
_accurately_
and calculates the _mass_ of fuel required per injection event based on
programmed-in
knowledge of the flow characteristics of the injectors (which knowledge it
adapts
on the fly according to the feedback from the oxy sensor system). It does have
maps,
but they are related to things like _desired_ AFR rather than actual injector
times.
It even has mathematical models of things like intake tract volume and
wall-wetting
characteristics to calculate transient fuelling during acceleration and overrun.
Add to this the fact that it has several versions of some of these maps, which
can
be used in different combinations depending on the selected vehicle programmed
into
the NVRAM, which references _another_ map to determine the actual combination
(!),
plus the on-board diagnostics (OBD2 spec) which can bite you quite hard, and the
dual-processor architecture where the two processors interact in the
diagnostics,
and believe me it's possible to get in a hell of a mess! I have had help from
one
of the guys who developed its firmware, and even he wasn't sure how it all
worked!
	- Oh, yes, and it has a security feature whereby if it doesn't receive the
correct ID from the body control unit security system on startup it won't go.

	I have some of the factory development stuff (which I'm not at liberty to
reveal - sorry - I could tell you but I'd have to kill you ;>) ), and it's
_still_ 
hell to get right. You can't even get it to _run_ without the dealer hardware to
reset the security code! Anybody who can do a successful hack without any
factory
help has my undying admiration - good luck, but if I were in your position I'd
stick
with good old hackable Bosch Moronic!

	(Just my two bits-of-the-lowest-denomination-of-local-currency-worth. Please
hack it and tell us the results, just don't take it on lightly!)  :>)

	Best regards,
		Franc.
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