Boost controllers: Further Research

[Dwayne Cosby <dccosby@interlog.com>]

Further to Frank Amoroso's original post, and several very positive
experiences by other listers, I've become exteremly interested in the
instalation of a boost controller in my S4.

After doing a fair bit of online research  the boost controller market
seems to shake out as follows (in order of apparent "respect" amongst
tuners):
- 	A'PEXi
- 	HKS
- 	Blitz
- 	Greddy (Trust)

A'PEXi is a Japanese brand (they are all Japanese for that matter) that
I'd never heard of before. The unit in question is the "Super AVC-R". What
seems to make it unique amongst the other boost controllers is that in
addition to manifold pressure, and altitude, it also uses the fuel
injector duty cycle to determine the neccessary boost (it takes this
signal off one of the injector control signals from the ECU).

This gives me a little more comfort that it is not completely doing its
own thing regardless of what the stock ECU is attempting to over ride.
However, I am concerned about the "what if" questions that were raised by
Scott Mo.: 

<<
Question 1:
How will the HKS EVC know when the intake air temp is too high and reduce
the boost pressure? 

"Signals from the knock sensors are used by the Motronic control module
for cylinder selective knock control. The ignition timing of an individual
cylinder can be retarded if knock is detected. If knock continues, a
richer fuel mixture will be used and the charge pressure is reduced." 

Question 2:  
How will the HKS EVC boost controller know the engine is knocking so it
can reduce the boost pressure? 

Most pinging can NOT be heard by the driver until it gets pretty bad. If
the timing is retarded by the Motronic system but the boost level is
maintained by the HKS EVC, the exhaust temperature will climb.
<<

I spoke briefly today with local Toronto dealer (BC Auto) about the A'PEXi
unit. He didn't have much time to talk, as he was getting ready for the
AutoShow this week, but offered to spend some more time answering
questions next week.


QUESTION: In either of the 2 above conditions that Scott proposed, would
the stock ECU generate any type of external logical signal that can be
utilized by the boost controller to trigger a lower boost setting? Would
the check engine light be briefly triggered under engine knock?


The unit itself sells for about the same as the HKS controller; about
US$550. 

The website has the full product documentation/installation guide online. 
If anyone that is interested (or is more technically inclined than myself) 
could have a look and forward any concerns or questions, I'll try to put
together a list of questions I can ask the local dealer. 


A'PEXi website: http://www.apexi-usa.com/

Dwayne
94 S4