Timing belt ?

[Richard van der Hoff]

On Sat, 19 Aug 2006, SJ wrote:

> I wouldnt be surprised if most of the car manufacturers use the same damn
> chip. The chip does everything you can think of. Each model car uses what it
> needs, the other chip functions are simply not used. This idea makes a lot
> of sense from an inventory and qty price break point of view - less parts to
> stock and a better price because of larger order quantity.

I used to write software for these things. It's not really true that all 
manufacturers use the same chip - generally the engine management unit 
will have a general purpose cpu with lots of i/o pins, and various bits of 
circuitry, of a more or less custom design, to drive the actual actuators 
etc.

Generally manufacturers will use a different cpu for their high-end cars 
than their low-end ones - if you can save a dollar per car by using a chip 
with less functionality, you're saving big bucks when scaled up to the 
number of cars the big manufacturers churn out - even when you take into 
account the need for completely different parts and software.

It probably is true that different manufacturers use similar, if not 
identical, chips though.

It's certainly true that most modern cars have plugs wired in pairs with a 
wasted spark at the end of the exhaust stroke. As SJ said, this means you 
don't need a distributor, thus cutting out a potentially unreliable 
component, and giving much greater control over spark timing; and you 
might as well pair them up, to halve the number of coil packs needed.

Cheers

Rich