manual boost controllers, and ECU functions

[QSHIPQ at aol.com]

I'm not a self proclaimed anything on these lists (except "idiot").  That 
said, let's take my position, and make it perfectly clear, there is *NO* 
conflict in my opinion or assessment of ABC (aftermarket boost controllers) 
since day 1.  Many quattros thru my shop since, hasn't changed things at 
all....

ABC's are good additions to cars that don't have any WGFV function, Gary, 
which includes the audi 10vt motors pre 86, and my 87 4Runner turbo.  Both of 
which use spring tension against manifold boost only as a boost control 
device.  

The *problem* with audi WGFV is their function in terms of leakage and 
ability to control what they were designed to control.  Neither WGFV, the top 
feed (slow/inaccurate) nor the bottom feed (leaking/inaccurate) accomplish 
boost control as well as a stepper motor.  That said, the problem with ABC's 
is (for now at least, the gap is getting closer) that they don't have as many 
inputs to boost control as the factory units, IOW, the ABC's have a primary 
function only (boost), they don't care about secondary inputs to 
accomplishing primary directives.

So, in an audi, when the CAT goes up, the WOT isn't activated, the engine 
temp is too high, the knock sensor is howling foul, the altitude is too high, 
etc, there is modified or no boost profile to the WG.  In all the inputs 
above, the ABC doesn't care, you programmed in 20psi, you get 20psi, with 
extreme prejudice.

So, my position has been crystal clear in terms of ABC's vs WGFV, and what is 
really needed, is for a *real* techno nerd to figure out how to add an ABC 
stepper motor to the WGFV tables in the audi ECU.  It's a lot of work since 
ABC's and WGFV operate on different functions, but it's not impossible.  

Until that is done, the WGFV is better at accomplishing the *safety* 
parameters of the primary function of added boost.  ABC's add a higher degree 
of risk to the primary function of boost, especially if the knob is located 
near the nut behind the wheel.  

I've driven and evaluated several customer cars (esp S cars) that have 
installed the ABC, then disconnected it and installed a proper chip upgrade 
to a car with WGFV.  I found the ABC tends to ramp faster, give more 
consistent boost levels, and give greater flexibility to control upper limit 
boost.  HOWEVER, the fact that is does, isn't necessarily a good thing, a 
WGFV may be giving lower ramp up based on the secondary inputs to the device. 
 That said, I believe audis would have great gains in performance using a 
stepper motor to accomplish primary boost function.  

I own the profec B, cuz I was fascinated by a certain audi tuners religious 
application of them.  I put it on a vehicle that has the greatest potential 
benefit from it, my 4 Runner with no WGFV function controlling the boost.  It 
took me forever to get the thing dialed right, and I'm still convinced that 
it could be better than it is, but the technology of secondary boost 
functions isn't quite as sophisticated...  yet.  No doubt in my mind it's 
gonna go that way.  BTW, I will also be installing an ABC on my 83 Urq, since 
it has no WGFV function at all.

Controlling the WG is the key to optimum turbo performance.  Using that POS 
WGFV that audi uses is behind the technology, and it fails quite regularly on 
any tweeked turbo car.  I have yet to hear of a stepper motor failure on an 
ABC.  Kinda makes ya think...

HTH

SJ



In a message dated 2/1/01 12:44:38 PM Central Standard Time, 
erickson at teleport.com writes:

> I guess my question is this: if the ABC's are the great solution you
>  claim, why aren't you running them in any of your _Audis_?  
>  
>  I'm just trying trying to process conflicting advice from the original
>  self-proclaimed turbo nerd.  And it's making my head hurt.