Re: Some Boost Controller Info

[Richard Funnell <rfunnell@pobox.com>]

At 10:32 PM 10/5/98 EDT, CM1022@aol.com wrote:
>The Greddy, HKS, SARD, Apexi, Blitz, etc. are all pretty much the same.  They
>provide a more active control over the wastegate, but because of their
>electronic nature I don't know if it will work with an Ur Q.  Did the Ur-Q
>have an electronic timing valve?  

The urQ has a simple, spring controlled wastegate.  I'm told the valve and
stepper motor come with the controller.  When the HKS CPU wants to reduce
boost, it releases pressure to the existing wastegate.

>This valve, found on most later models of
>turbo kraut cars, is a simple device the modulates between either positive
>(boost) or negative (vacuum) pressure on top of the wastegate to more
actively
>control it.  This is esentially how an electronic controller wires- right
into
>the electronic timing valve.  I have seen pictures of the wastegate on the
Ur,
>and it seems that maybe it is just spring activated?
>
>Whatever the case, you might want to avoid the "fuzzy logic" controllers like
>the Greddy and HKS stuff, which I know have problems and take time to fully
>program.  Again, some very knowledgable people have told me the only
>difference in units is the color- pick one.

I'd love to hear what problems they have, especially before I receive my
unit and hook it up!!!  The programming seems fairly straight forward on
the current models.  A few full-throttle runs.  
>
>Another problem with these electronic controllers is boost hunting.  Most
>stock wastegate's are actually designed to leak, and the only solution is
>getting a new wastegate- one which is more agressive and performance
>orientied.  They can be relatively inexpensive- turbonetics has some decent
>prices.  The point is that the stock wastegate is inaccurate- leaking way too
>much, and the controller has problems with this, sometimes literally
searching
>for a stable boost pressure.

For the benefits I hope to see, a new wastegate would be a reasonable
expense.  I don't expect to have to replace the current one, however, but
maybe I'm too optimistic.  
>
>Greddy offers the simple Profec B, which isn't fuzzy logic but still requires
>a new wastegate in my opinion.  I would choose it for the simple reason that
>Greddy makes a steering wheel button activator- a great feature to use when
>powering into or out of a corner (switching between high and low boost
>settings).  

I've looked at this switch.  I really don't get it, but then I'm not a
racer.  I'd have thought the throttle a satisfactory control for this
situation.  Besides, GReddy don't recommend this unit for fast-response
turbos, which is one of the next steps.
>
>And then there is the manual boost controller- which is pretty foolproof but
>limited.  Everyone sells one- you can even make one.  It is a knob that has
>vacuum lines hooked up to it that goes between the wastegates vacuum/boost
>input, and the timing valve.  

Unfortunately the engineer in me objects to these.  I guess I've read too
many discussions of spikes, lag, broken diaphrams and peaky boost.  The
principle of the HKS-type controllers is seductive.  Apply sophisticated
logic to deciding when to hold a turbo to full boost, and when to release
it.  Compared to a spring, it seems as if the difference ought to be
noticeable.

I'm not knocking those who have opted for simple controls.  It's just that
I'm a coward.  This is my daily driver.  I don't just want power when my
foot is on the floor and the engine RPM is 5K+, and I want to keep the
engine in one piece.  This HKS unit actually has overboost limits built in.
 (For suspenders, I'm thinking of a popoff valve.)

>
>Chris Morlock
>
>86 951
>83 928S
>81 928
>81 931
>70 BMW 2800 CS
>and a Harley in there somewhere at sometime   
>
Thanks for the detailed input.  I'll let you know what happens.

Richard
'83 urQ