Re: How safe is above normal boost?

[Dan Bocek <dan@di.com>]

OK, I can't stand it anymore.  I wasn't going to mention this, but my
conscience got the better of me and I thought that the record should be
set straight here about the TQC Intended Acceleration mods.  In a recent
post, Glen Powel wrote: 

>The big features that you miss with the home-brew and TcrAP-type mods Vs 
>the IAmods are:
>
>1) more agressive ignition timing (critical for max HP increase)
>
>2) overboost protection
>
>3) rev limit increase
>
>I think the IA mod is a win,

Recently I've started fixing dammaged TQC engine computers.  Two 
computers sent to me turned out to have the IA mods.  Here's what I found 
in both computers:

1) Stock EPROM left in place and obviously left unsoldered, but with the 
part number sanded off to make it look like something had been done to 
it.  Needless to say, I unsoldered it anyway and dummped the code.  You 
guessed it: **COMPLETELY STOCK**!!!

2) A resistor soldered between the output of the boost pressure 
sender and ground.  This, as many of you know, divides down the boost 
signal going into the A/D, tricking the computer into thinking it has 
less boost than it really does.  This serves to advance timing across the 
board and will allow you to run at higher boost pressures (not 
necessarilly a bad thing) but could also rid the computer of any 
overboost protection at all.  Why?  Well, the boost sender only has a 
limited dynamic range... i.e. it outputs it's maximum voltage at about 
14.5 psi above atmospheric (1 bar).  Any more boost than that and the 
sender still outputs it's maximum voltage because the detector is now
saturated.  If any of you with the IA TQC computer are operating above 
that pressure and haven't experienced fuel cutoff, chances are you never 
will, because that extra resistor will always keep the boost the computer 
thinks it sees under the critical overboost threshold.

3) A different resistor in the oxygen sensor circuit to make the engine
run a bit richer.  This one is interesting, because the car only uses the
O2 sensor under the relatively mild conditions of closed and part
throttle.  If you're WOT, the computer runs open loop and ignores the O2
sensor entirely, relying on a table of fuel vs. boost values it has stored
in it's (stock!) memory.  But, it's presicely at WOT where you'd want more
fuel (*ESPECIALLY* at increased boost levels!!!).  Yet, the IA computer
has a C.A.R.B. exemption number... I don't get it. 

4) Stiffer wastegate spring.

So, if y'all want to spend 750 hard earned bucks for Ned to sand the part 
number off of your EPROM, solder in a couple of resistors, and sell you
a stiffer wastegate spring, be my guest, but you can buy your own spring 
from someone on this list (sorry, I forget who) and you can certainly buy 
two resistors for less than $750!!!

So, I'm sorry for all of you who've bought the TQC IA mods over the TcrAP
or Superchip mods for peace of mind, but you could have saved 500 bucks
and had the same mods done to your computer.  Buyer beware!

Note:  I've *ONLY* looked so far at what Ned has done to the TQC
computers.  So, for all of you with the 5000 turbo IA mods and such,
there's still hope...  Merry Christmas! 

                                                         Dan Bocek
                                                         dan@di.com