CIS injection question

[isham-research.freeserve.co.uk at pop.pol.net.uk]

>>On every CIS injected car that I have seen, there has always been a fuel
>>hose from the fuel distributer to each injector. So..an I5 engine has 5
>>hoses etc. My question is - why? Since all the injectors are merrily
>>squirting fuel all the time when the engine is running, wouldn't it save
>>money to have a single fuel hose into a fuel rail connecting all the
>>injectors, just like the typical pulsed injection system?
>>The Bosch guys are a smart bunch, so I'm sure there's a good reason. Can
>>anyone tell me what it is?

> The flow isn't strictly regulated by pressure. Each injector is a bit
> different, and takes a bit more or less pressure to flow a certain
> amount. Therefore, the way fuel is metered is that it's run through a
> calibrated orifice in the metering head (the size of which is
> controlled by the airflow plate position) and the pressure drop
> across this is maintained at a specific value. Thus the flow rate to
> all the injectors is the same, regardless of minor variations in
> injectors.

The plunger controls the amount of fuel going into the engine as a
whole - it doesn't meter the flow to individual injectors.  That is
done by the funny little 'top hat' things (you need to take a metering
head apart) resting on the diaphragm.  Their function is to ensure that
no one injector gets more than its share, even if the injector's
internal valve breaks down.  The German word for the metering head
translates literally as 'quantity distributor'.

--
 Phil Payne
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