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Re: [T3] Injector interchangability?

On 30 Nov 2003 at 20:13, David V.N. wrote:

> Naive?No.Optimistic?Probably.Looking forward to doing it?Definately!

I tend to be pessimestic about things like this, but I tend to believe that 
this is because I think I understand them better than most. Of course I may be 
wrong on both counts, but see below....

> It won't waste anything if used to feed a larger displacement (if you're
> refering to higher fuel pressure=max is 34 or 36psi,I think.)Either way an
> exhaust analyxer is in order,Can you suggest a source?

The PS measures the pressure DROP across the inlet. It uses that to indicate 
the amount of airflow. At low throttle and RPM this will be just fine with a 
large engine; air is air and a measured amount will get a measured amount of 
fuel. At some point the PS will max out, however, and then there will be no 
additional fuel as the airflow continues to increase. So you are lean.

If you try to cure this by just increasing the fuel pressure you can make 
things work right at some point, but the mixture at 36psi will be 20% rich and 
the PS will still be maxed out.

> >In my opinion, It MIGHT be possible to upgrade our FI to that of a
> >different car IF we also upgraded the throttle body either by machining out
> the
> >throat diameter to that of the other car, or by using the throttle body
> from that car.
> Is the porsche d-jet THAT dissimiliar?The internal volume doesn't appear to
> be that different. (The porsche bieng slightly larger)

Internal volume has nothing to do with it. It's simply the throat diameter and 
possibly a small effect from the air cleaner flow properties. I don't know what 
the relative throat diameters are, or what effects that might have.

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

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