Re[3]: 34 ICT's (and more...)

[Toby Erkson <Toby_Erkson@ccm2.hf.intel.com>]

BA brings up a good point:  Unless you're going for more power *and* larger 
displacement, stick to FI.  It can be a pain but, as I have found out with 
my 914, once you start working with/on it your understanding will become 
clearer and so will trouble shooting.  I almost have the entire FI system 
memorized and can draw a diagram of it -- a good visualization can help you 
in trouble shooting even if you're not with the car.

I'll repeat what I said and BA said:  Pull all of your FI wires that aren't 
needed (I had a wire meltdown, too).  In fact, remove the FI box and keep 
it for later (ya just never know) or, if it's still good, sell it.

If you go for carbs always go for 2-barrel (a.k.a. 2-throat) carbs, one 
carb per head.  Basically give each cylinder its own barrel.  You will get 
better response, power and fuel economy this way (nothing major, but still 
there nonetheless).  Intake runner lengths will be the same (generally a 
problem on single carb engines) and there will be less problems associated 
with fuel standoff and other sonic phenomenon due to the pulses produced 
from the intake valve closing.  Also, unless you have a 4-barrel single 
carb for your T3, the intake runner length will always be too short.  If 
you were to take any carbed T3 engine and toss it in a Bug of the same 
weight but add longer intakes you would notice more "umph" (power).  This 
is why FI in a T3 is the way to go since a long runner isn't required.

As for BA's problem: The other cylinders *may* have been getting some fuel, 
because there is a vacuum created when the intake valve opens, but there 
wasn't a sufficient enough *draw*.  This would cause the fuel to remain as 
small droplets (bigger than being properly atomized) and possibly the 
quantity of fuel would be less than what is needed.  Add the Bosch ignition 
system, which is fairly weak, and the fuel doesn't ignite.  The cylinders 
get washed with raw fuel and engine life begins to become affected.

Another problem, since the FI was removed, the previous owner could have 
installed a non-stock cam, possibly a slightly more wild one.  This would 
really affect the car's idle -- even more so if the carbs were not properly 
tuned for idle.  Just a thought.  If every thing is properly set and the 
problem is still there just bump up the idle a little more.  My 2.0L, with 
wilder cam and dual 2bbl carbs idles at 1200-1300RPM (as set by 
professional engine builder) -- a stock 900-800RPM is possible but the car 
is shaking like it was in an earthquake.  This is one reason why full race 
vehicles have a higher idle.
     Toby Erkson
     air_cooled_nut@pobox.com
     modified '72 VW Squareback 2.0L
     stock '75 Porsche 914 1.8L

______________________________ Reply Separator _________________________________
Subject: Re:34 ICT's
Author:  type-3-errors@umich.edu at SMTPGATE
Date:    10/11/96 10:03 AM


Marty Gray,

...
MAKE SURE TO DISCONNECT THE POWER TO THE FI BRAIN!

and remove the FI relay under the back seat ( opposite side from the 
battery, next to the rear defogger relay.) to be sure.
...
Personally, I would have kept the FI and tried to repair it first.
The new dual 34's have such a short intake manifold, it WILL run rough 
at idle.  It will smooth out as soon as you hit 2000 rpm. Since I ran 
it as a daily driver, I got sick of it shaking at every stop light or 
sign.  The problem is that at idle the vacuum is not strong enough to 
pull the atomized gas down into both of the cylinders(on each side) and as on 
mine, only cylinders 1 and 3 got gas at idle.  As soon as I hit the 
accelerator, all cylinders got gas and fired. A set of dual 2-barrel 
carbs might help? maybe?

Hope this helps.

Big Al
awpresley@earthlink.net