Re: TAP vs IA Chip/Boost mods

[Orin Eman <orin@wolfenet.com>]

> only problem that I've ever had with TAP box is that the car will 
> ping somewhere around 16-17 PSI boost as seen on the VDO guage 
> mounted separately in the center console. If you leave your right 
> foot planted as this Ping is happening, It will turn to a studder or 
> slight cutout.

Ouch.  The computer will normally retard timing on detecting knock,
but this takes a while... two to three seconds for full retard,
not a problem at _stock_ boost levels, but definitely not good
at higher boost levels. 

Part of the retard process drops you down to the Regular fuel timing map...
this may stop the ping, but it's going to take a long time before it
goes back to the Premium fuel map, so you'll be stuck at massively
retarded timing long after you backed off the throttle.

Eventually the computer will try to reduce boost using the wastegate
frequency valve.  For those with wastegate springs, this is mostly
ineffective, about .1 bar reduction.

My 86 5kCSQ tends to ping above 2.0 bar with stock timing, so I have
it set up to stay below 2.0.  I haven't tried changing the timing in the
computer yet.

The above assumes that the TAP box has kept the knock sensor functionality...

>  After installing Neds IA Stage II box and running it hard for 5 
> laps, I found the following. The boost needle would immediatly jump 
> to 15 psi, back off to 14 psi and stick there no matter what rpm or 
> gear I was in. So, although I was getting a few pounds less boost 
> than the TAP box, it was consistant at 14 psi which let me keep my 
> right foot planted at all times.

15psi would be boost  determined by the wastegate spring, then the
computer is probably holding it at 14psi.  This is either not high
enough to cause a problem, or the IA box has the timing retarded for
high boost levels (or both).

> Stock bar guage read 1.7 bar all the 
> time. The power difference was barely noticeable between the two so 
> which one would I prefer? It depends. If you use your car mostly on 
> the street and for short periods of boost, I'd have to say advantage 
> is to TAP for the slighlty higher boost level-but just remember to 
> back off some if you hear the ping. If you run your car on the track 
> all the time and want good consistant lap times, then IA would 
> probably be my choice. BTW, 91 octane at all times-track or street!

Well, personally, I don't like hearing ping at high boost levels.  The
computer is set up such that you shouldn't be able to hear it.  If you
do, then you are outside the abilities of the computer to manage the
engine properly.

I prefer a setup where I can keep my foot planted without worrying about
listening for ping...

BTW, (your turn Scott) I hear that over 2.0 bar isn't doing much for
you with the stock turbo, another reason to keep it below 2.0.

Orin.