[s-cars] Cheapest boost controller evar!

[Calvin & Diana Craig]

It's a heck of a lot easier and more reliable to build one with a 555 timer
that puts out a set duty cycle at the same frequency as the ECU WGFV signal,
the output is enabled by a simple comparator tied to the TPS, so it's not
doing this all the time, only above a certain throttle input.  Obviously a
FET power stage is called for.  You vary the duty cycle, and therefore the
boost, by varying a pot in one of the numerous punch outs not used beside
the rear defroster switch, etc.  I am doing something like this as an
experiment on my '89 200 wagon.  I have tried it temporarily and it seems to
work quite well, I just haven't soldered the stuff down yet.

I tried going the chip route on this car.  The problem I have is a stinking
knock sensor that will NOT stop flagging a signal.  I have no knock and I
have had two mechanics check it out thoroughly, replaced just about every
component you can think of, and it still stays around.  One mechanic spent 3
days on it and felt so bad about it he didn't charge me.  VERY annoying to
spend $400 and get a chip that only goes to 1.6ish BAR because of the damn
sensor.  Since I know I am getting maximum retard (because of the false
knock indication), have a solidly rich fuel mixture at WOT, and it is an old
MC engine with 7.8:1 CR I have no fear of things going badly.  I may get to
it this weekend, but the Fuel Injection project for my '72 Pontiac is
looming large as well.

--Calvin


-----Original Message-----
From: s-car-list-bounces at audifans.com
[mailto:s-car-list-bounces at audifans.com]On Behalf Of FvAMI at aol.com
Sent: Tuesday, February 03, 2004 4:02 PM
To: gabriel at ts.bc.ca
Cc: s-car-list at audifans.com
Subject: Re: [s-cars] Cheapest boost controller evar!


In a message dated 2/3/04 12:02:31 PM Pacific Standard Time,
gabriel at ts.bc.ca
writes:


> I agree, but this guy is in college and he did the swap himself on a
> tight budget.  $20 for 240hp out of a 200 engine isn't a bad deal in his
> eyes.  Compared to $500 or so for a real chip.  I would never do it, but
> I thought it was pure genius to use the signal for the trip computer
> boost gauge as a boost controller.
>
>

I will be suprised if he even gets 180HP out of it.

With his circuit when the voltage hits 4.5 volts the relay will close
opening
up the WGFV the boost will drop and drop until the voltage hits 3.5...
3.6???
Who knows without characterizing the relay. Then the wastegate will close
again then the boost will rise until it hits 4.5 volts again and repeats the
cycle. This would provide an average boost of 4.0 volts +/- 0.5 volts ...
yikes!!!
The WGFV of the Motronics unit if programmed correctly would keep it at 4.5
and I bet it will not deviate more than +/- 0.1 volts.

A $10.00 restrictive orifice would work better without any electronic boost
control. So ... an A for attempted effort ... yes ... but an F for
functionality.

Best regards,
Feico van der Laan


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