Re: 3B Charlie Spring??

["Paul C. Waterloo" <74543.407@compuserve.com>]

Thanks Bob. After driving my car today, I found that the car did not hit
overboost once. The car was extremely fast again. I still used only a
quarter pedal in accelerating most of the time, with incredible results!
However, later in the day I tried putting my foot into it, couldn't get the
overboost to hit. Would hit 1.7 and a few times 1.8 (higher gears). The car
MOVED.

However, I'm concerned about wasting my engine, so I changed back to the
original 3B spring later today. When I took out the charlie spring, I found
that it was considerably less stiff than when I put it in yesterday, like
it had been excercised and loosened up a bit. I could now almost fully
compress it in my hands, but with a lot of effort, yesterday I could not.

The old spring only gets me 1.2 in 1st and 2nd gears, I get 1.4 about that.
Big change from 1.7, 1.8.

So is it that the new spring was getting closer to the proper mechanical
strength as it loosened up? If so, I wonder if I would being doing damage
to the engine if the computer can control the boost to 1.7 or 1.8?

Paul


*********************************************
Paul Waterloo
Brookfield, IL

91 200q

EMAIL: 74543.407@compuserve.com
*********************************************

>Paul, Be carefull with thatspring mod in the 3B. I am enclosing
>some info that I got earlier this year when I aksed about mods
>to a 3B.  Let me know what you think. Bob Russell

>From Linus Toy to Bob Russel:

> your second
>mod--charlie spring--helps address that.  Audi's wastegate
>design begins opening up the wastegate faster than necessary
>(again, another safety feature).  the stronger spring holds the
>gate shut longer with two results: 1) more boost sooner (this
>you really feel in low speed acceleration) and 2) more ultimate
>boost--an adjunct to your schrap knob.

>these two mods work well in the 10v turbos because the FI
>system, KE-Jetronic or Continuous Injectsion System as VW/Audi
>calls it, is more of a mechanical/analog system that monitors
>several parameters and reacts to them as inputs--the schrap knob
>and charlie spring simply alter the way the parameters are fed
>into the computer.

>the '91 200q(3B) uses a full-blown motronic fuel injection
>system.  as such, it

>is not as susceptible to tricks like the schrap-knob or the
>charlie spring.  as you're probably aware, the 20v not only has
>the dohc, but also a much higher CR:  9.3:1.   to deal with this
>(that is, modify it more) you really need a more precise FI
>system--thus, the motronic system.  this gives Audi full maps to
>control fuel and ignition, instead of simpler curves.  (since it
>is a pulse FI system instead of continuous injection, you can
>specifically change the fuel amount at any point in the spectrum
>instead of relying on changes to fuel pressure as in the KE-Jet
>system)

>so where's that leave you?  can you use DIY mods?  a few folks
>on the list have in fact changed springs--they have quickly hit
>overboost limits or find rapidly oscillating on-off boost
>conditions.  bleeding off air to the computer (schrap knob)
>doesn't sound like a good idea to me--you'll actually be
>boosting to say, 2 atm (1 bar boost) but the computer will think
>you're only at say, 1.5 atm (.5 bar boost) and not give enough
>fuel--good way to fry a piston (this, btw, is true for 10v cars
>as well, but since you only go from 5psi boost to 15psi, and not
>20psi, its' not as much a stretch for the car)--given the
>relative rarity of these cars (and the cost of engine parts)
>this is something to think about.