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Re: Fuel Injector Question
Are you talking about the air-shrouded injectors introduced in about 83 or
84 for the CIS (K-Jetronic) system? On these, yes, the entire injector was
moved back, relative to the earlier style injectors, to allow air into be
directed to the tip of the injector to promote fuel atomization--an economy
thing, nothing to do with cooling or leaking. (Since you reference the
Bosch FI book, see CI-Theory, pg 14-15)
The injector cooling fan on the 10v turbo engines is designed to help
prevent heat soak from vapor-locking the injector lines--remember that on
the 10v turbo, the exhaust manifold and intake manifold (where the
injectors are mounted) are pratically stacked on top of each other. On the
3B, the intake manifold and injectors are on the opposite side of the head,
so less issue with heat soak.
Can't answer Chi's question on life of fuel injectors (but if they leak and
the system loses residual pressure, the long-crank syndrome shows up).
TAPs sport injectors are supposed to allow more fuel to be delivered as
boost/volume (i know, not the same thing) goes up--lets you keep the
fuel:air ratios right so you don't fry the engine. No need for a Stage I
(or even Stage III) chip mod.
--Linus
At 14:32 4/1/99 -0500, Brett Dikeman wrote:
>I'm telling you exactly what I read from the Bosch:Fuel Injection book I
>have.
>
>The problem is not when the engine is running. It's when it isn't. The
>older, CIS and EFI injectors had the valve too close to the engine
>block and the fuel would get hot enough to decompose and clog the
>injector's seat with deposits causing it to leak and not fire properly.
>The fan keeps the injector, and the fuel inside, from heating up too much.
>Later EFI injectors has the whole valve assembly moved back, and this
>change happened right around 83-84 I think.
>
>Brett
>
>
>On Thu, 1 Apr 1999, Ti Kan wrote:
>
>> Brett Dikeman writes:
>> > The older CIS injectors had a design which put the rubber seal very close
>> > to the engine and hence it could overheat. The injector cooling fan
>> > completely compensated for this, I believe...
>>
>> I don't think the injector cooling fan serves that purpose. It is there
>> to reduce underhood temperatures near the injectors after shut-off, to
>> prevent vapor lock and hard starts. It is controlled by a thermo switch
>> which normally doesn't kick on while the car is moving.
>>
>> -Ti
>> 96 A4 2.8 quattro
>> 84 5000S 2.1 turbo
>> 80 4000 2.0
>> --
>> /// Ti Kan Vorsprung durch Technik
>> /// AMB Research Laboratories, Sunnyvale, CA. USA
>> /// ti@amb.org
>> ////// http://metalab.unc.edu/tkan/
>> ///
>>
>
>