[T3] Cylinder Performance

[Jim Adney]

On 21 Jun 2011 at 21:06, Adriel Rowley wrote:

> > From: jadney at vwtype3.org

> > On 21 Jun 2011 at 16:01, Adriel Rowley wrote:

> My new ones were fine in length.  I think it was just an accident, as it 
> was about the length of the new's number three. ;)

Are you saying that it was the OLD #1 that was short? If that's the 
case, you would probably have to buy at least a new #1 wire and OG 
dist cap end, unless you can pry the crimped end off the old one and 
recrimp it.

> > > Only thing was it was hard to get it up to 50 M.P.H. as it run out of
> > > power to do it.  When coming back was able to persuade it up to 53
> > > M.P.H. but took feathering the throttle.  This reminded my I had not
> > > checked the T.V.S..  When I got back, I tested it, which was a bit of
> > > a challenge with the warm engine.  Idle circuit shows 0 Ohms along
> > > with the fourth test, and the second and third tests get odd results.
> > > Seems that might be my problem?
> >
> > The TVS is NEVER the cause of poor power. I don't know how this got
> > started, but for the last couple years it's been getting a lot of
> > unwarranted attention. If you think your TVS is bad or unadjusted,
> > just unplug it and see if your engine now runs better. If you don't
> > notice an improvement reconnect it and move on.

> Then where did the idea come from?  Or, one of those with no backing...

The idea arises out of lack of understanding, desperation, and 
grasping at straws. There's no backing for suspecting the TVS when 
you have a lack of power.

> > > Anyone have an extra four pin T.V.S.?  Been using a five, but switched to this four pin thinking it worked; now need to remember where I put it.
> >
> > A 5-pin is never an appropriate replacement for a 4-pin. That just
> > doesn't work. If you have your original 4-pin it is probably fine.
> > I've seen worn out 5-pins, but never a worn out 4-pin.
> >
> We have been down this road.  I used it for quite awhile, along with 
> others, so not sure of the validation of that id does not work. ;|

You can install it, force a connector onto 4 of the 5 pins, and drive 
the car, but the pinouts of those 2 versions don't match up such that 
the pin functions will be correct. So, yes, you can do it, but it 
won't be doing the job it was meant to do.

> I am confused then with this statement: "If you see any sign of 
> decreased resistance anywhere in the travel of the throttle, your TVS 
> may be worn out."  So, I guess I do not understand the instructions 
> clearly as all I want to do is check adjustment, not set it.

That part of the instructions is for determining whether your TVS is 
WORTH adjusting. If your TVS is worn out (something that seems only 
to happen to the 5-pin version) then it should be replaced if it 
fails that test.

If you pass that test, you can move on to the later part of the 
instructions that tell you how to adjust your TVS.

> "[...]slowly turn the TVS CCW until the VOM jumps from high to low 
> resistance."  "Make sure the VOM goes to low resistance every time 
> the pedal comes back to the idle position."  So, why do I have no 
> resistance and no change in resistance, i.e. always 0 Ohms?

If you're now quoting from the adjustment section, this would mean 
that your TVS is out of adjustment. Since you're using the wrong TVS, 
however, this is irrelevant, since it will not work correctly with 
your '71 FI system. You'd be better off just disconnecting it.

> "Connect your VOM across the 2nd and 3rd pin of the TVS. Slowly open 
> the throttle. You should see the VOM change from high to low 
> resistance several times as the throttle opens but not as it closes. 
> Repeat this test with the VOM connected to the 2nd and 4th pin."
> 
> I got this to some degree, but no not recall for sure that I got 0 
> ohms when closing.

You are not supposed to see the zero ohms when closing. That's what 
the word "not" means in the instructions above.

> "Finally, set your VOM to its highest resistance scale and connect it 
> across the 2 bottom pins of the TVS. Slowly open and close the 
> throttle several times while you watch the VOM. If you see any sign of 
> decreased resistance anywhere in the travel of the throttle, your TVS 
> may be worn out."
> 
> This one got all sorts of strange readings.

Not a good sign, but you don't want this TVS anyway.

> > Of course it's possible that your 4-pin was damaged by someone who
> > damaged it internally. That certainly happens, but there's no excuse
> > for it.
> >
> I believe I opened this one up, and all looked fine.  I open them to 
> set the adjustment according to another fellows method, but wanted to 
> compare the results. 

There's no harm in opening it up and looking inside.

I have several good used 4-pin TVSs, as well as some new ones. New 
ones are pricey.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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