"Charlie" springs

[Alan Cordeiro <cordeiro@avlna.com>]

>If there were a stock spring which would work for increased boost,
>I'd expect the price to be ridiculously cheap in quantities > 10,
>probably less than $5 each!
>
>BTW: my spring was 2.165" long, 1.460" OD, .115"  wire and the rate was
>     about 25lb/in.  
>
>     I figure a 2", 1.5" OD, .135" wire spring with a rate of 55lb/in
>     should do the trick for about .8bar boost (shim for a little more
>     boost) with a reasonable safety margin (rates are +/- 10%).
>
>Orin.

I did a lot of figuring and calculations about two years ago. I has some
spring catalogs from two manufacturers, and it seemed the prices were
about $7.00 in 10 piece quantities. I even had a part number.

But here my requirements differed. I intended to get the SAME SPRING RATE,
but increase the "preload" by 150%. since I was popping at 1.2 -1.3 bar,
I expected to pop at 1.7 or so if I trippled the preload. However, once
the desired boost point was reached, I wanted to OPEN UP at the same
RATE as originally designed by Audi.

Also you will notice that the spring companies offer the same springs
in PHOSPHER BRONZE or STAINLESS STEEL. Always use stainless steel since
their main advantage is a long(er) life under high temperatures. It adds
only $2 or so to the price.

The O.D. is not critical, but the I.D. is more critical. It needs to fit
reasonably snugly, but still have a bit of clearance.

Preload is determined by the spring rate, and the compression from
when the spring is "free" to when it is installed in place in the 
wastegate. ( It is quite a trick to put in a "springier" wastegate
spring into the wastegate after you get used to the original. Did
it many times while experimenting.... )

My advice ( not asked for by anyone, but given FREELY ) is for those
people who just want a peppier Audi without too many extra hassles
is to get a spring that "pops" at 1.4 to 1.5 bar. This adds about 20
or 30 HP over the typical 8+ year Audi which runs 1.2 to 1.3 bar.
Note: the same effect can be got by a two judiciously placed
"FENDER WASHERS", 1.25 I.D.  1/8" thick. ( a drop of super glue
on the one that goes in the top ).

Then for those that need 1.7 bar  ( 40-50 HP ) , 

use a stiffer spring, as described above,

REINFORCE THE INTERCOOLER with filament strapping tape 
(or nylon shipping bands used for packing crates.)

Be ready to buy new hoses to and from the intercooler....

Use only PREMIUM gasoline....

Modify the ECU, or fuel pump circuit to prevent it from
cutting out at 1.6 bar.

Finally, a bombshell. **************************

I had played with an electronic mini-circuit, and mentioned
details about it to a few people while I was testing it to
see if it had long term undesirable side effects. It seems
to have been reasonably stable for the last year.

So I purchased parts enough for perhaps 20 modifications,
and was going to do a descriptive writeup with perhaps
one or two photos to help. Of course Graydon ( his ECU actually )
was going to be my guinea pig, but we still never got together.
I know he has been busy, ( especially with the addition to his
family )  I so have I lately. So this scheme is still on the backburner.

The cost of the parts is minimal, and I was going to offer this
upgrade free to those who were willing to take a chance and hack 
up their MAC-11. Be sure you know electronic service techniques.

The only car it has been tested on is an '86 5kTQ.

Dashboard boost guage reads "correctly" ( i.e. you see the
boost going upto 1.7 or 1.8, even if the guage is notoriously
inaccurate ).

No changes to the behaviour below 1.0 bar, changes only come into
effect at boost, so emissions and gas mileage should not change under normal
driving conditions.


Finally, the BEST WAY to go is really the CPU CODE MODIFICATION with a stiffer
spring. I know at least two people are working on it right now. So my advice
is to be patient and wait for the better fix.

And for those who want the ULTIMATE, my gut feel seems to be Ned Ritchie,
but again, I have had no dealings with any of those guys......

Alan Cordeiro