Re: [T3] Injector interchangability?

["David V.N." <rmcevoy1@twcny.rr.com>]

>> As an aside ,Jim,Ive found some of your comments made a ways back on the
>> maximum sizes of engine that D-jet could support.They don't jibe with
other
>> opinions I've read in some respects. I know from reading this list for a
while
>>that you know as much as some posters from the shoptalk forum and was
>> wondering about your opinions/advice on the subject.

>It would help me a bit to know which comments you're thinking of. As far as
>general thoughts about going to a bigger engine with the D-Jet, I don't
have
>any experience with this. I'm just guessing that Bosch didn't build in
large
>amounts of "headroom" when they designed the system. As a good design
criteria
>I'd guess that +20% design ceiling would be a fair way to make sure that
the
>design could accommodate sample-to-sample variations in production. For
this
>reason I generally suggest that a 10% increase in displacement should be
safe.

Gonna make it quite the experience swapping in a 2110cc!
(30%increase)


>As for swapping in various other components to try to achieve the
performance
>of the donor engine, I think that approach is na?ve. Yes, you can probably
put
>in larger injectors and that may well fix things up where the OEM injectors
>leaned out but at the expense of running rich everywhere else.

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

>I understand that just setting up to run rich is common practice in many
>circles, but I dislike it for many reasons. It wastes gas and money. It
>pollutes our environment. It causes excess wear and tear on the engine.

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 system is too complicated for us to just swap in components
arbitrarily.
>The injectors, pressure sensor, brain, and throttle body all have to work
>together to get the right fuel/air ratio.

I would think that with a little fooling with this and that ,D-jet can be
very flexible.
(I may eat these words later.)

> I see a lot of suggestions to swap to
>a different injector, or different pressure sensor, but no one looks at the
>throttle body and the pressure drop vs. air flow across the different
throttle
>bodies. 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)

>All this could certainly be done by someone determined enough and with
enough
>time and money to do some real tests, but I don't think anyone other than
Bosch
>has bothered. It's just too easy to throw extra gas at the problem and say
>"that works" without really knowing or caring about the consequences.

>Just my opinion....

-- 
>Jim Adney
>jadney@vwtype3.org
>Madison, WI 53711-3054
>USA





"....the whole world , Chico. And everything in it."

David V. Nelson
1969 Fastback FI (no matter what!)


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