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Re: [T3] Injector interchangability?

On 30 Nov 2003 at 23:14, David V.N. wrote:

> From: "Jim Adney" <jadney@vwtype3.org>

> > If you try to cure this by just increasing the fuel pressure, you can make
> > things work right at some single point, but the mixture at 36psi will be
> 20%
> > rich across the board at low throttle and RPM, and the PS will still be
> maxed
> > out at high air flow conditions (open throttle and higher RPMs.)
> Of course, this would be true if the engine was stock.But it is not.It will
> work out to be 30% larger in disp.Which may compensate.......or not.

It's the increased displacement that means that the PS will be maxed out. At 
any given rpm and throttle position the engine will be trying to suck 30% more 
air. At some point the "needle" in the PS is going to peg, which means the 
engine starts to lean out. Not a good thing at WOT.

I assume that if you have a stock engine the FI will handle the full range of 
airflow and load that might arise. 

> PS=pressure switch?  

Sorry, just my shorthand for pressure sensor.

> Just between me and thee,when I received the car,unbeknownest to
> me,the pressure switch wasn't even connected.As far as I can tell,it had
> little effect.Of course,now that I've learned a bit,it is connected and
> functioning. 

The pressure switch (68-9 only) was just a full load enrichment device. In 
normal driving you'd never notice that it was disconnected. If the vacuum hose 
had been pulled off it might be hard to adjust the idle, AND the engine would 
always run a bit rich. That's not a good thing, but you'd probably never notice 
it unless you kept track of your gas mileage.

Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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