[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

dopping da bomb (long)

>Frank J. Bauer writes:               
>Subject: bad bomb warning
>i have a question for y'all concerning the above.
>for those who get this warning, is it the red triangle that flashes (from
>system check computer) or the amber ABS braking symbol among the idiot light
>array?  i commonly get the amber ABS light coming on at times i would expect
>see it if the PA were bad and i shut it off by hitting the ABS switch twice.
>however, this morning i saw the red triangle warning once (but not since on
>two starts).  i thought the triangle was brake fluid level warning.
>this is on my 86 TqW.

......  The red triangle is the brake pressure (one circuit) and brake and
hydraulic  fluid level indicators (second circuit).....  The abs has low
pressure deactivation in it as well, and defaults to off (lite on)....  The
common malady of ABS being able to be "reactivated" is usually a sensor out
of alignment, however, I would suppose the ABS could be reactivated by a
"recharged" pump/bomb....  REGARDING THE BOMB

I have received quite a few inquiries into the whole bomb deactivation
thread.....  Here are some thoughts:

*  Bad Bomb will give you intermittent/no power brake assist if the car
*  Bad Bomb will give you intermittent/no power brake assist when you have to
make an evasive manuever with the steering wheel as well....
RDH hit the delta change right on the head.....  Yes, I suppose you could run
the car without the bomb.  However, contrary to some net thinking, it is NOT
going to give you linear braking properties if you disconnect the bomb.....
 The following 4 ways can be considered in connection with the hydraulic
1)  Disconnect the bomb exclusively
2)  Disconnect the braking system from the HP system
3)  Disconnect the Steering from the HP system
4)  Run with bad bomb

1)  Disconnecting the bomb exclusively.
Gains:  Money savings (bombs are bux)
Losses:  Stalled motor braking assist, intermittent ABS performance,
intermittent steering assist, inconsistant braking assist
The Hydraulic systems in the audis have two measurable criteria Volume and
Pressure.  Disconnecting the bomb will retain only Pressure at feed line
Volume (it goes from large feed to small after the bomb), Post bomb Volume
will be lowered.  Significantly.  Assuming a static variable of straight line
steering and braking exercise, the bomb is prolly sufficient to provide
constant braking under most conditions, tho I would have my doubts with hard
panic abs assisted stop.   Regardless, add in the steering input (esp in a
panic abs stop/avoidance scenario), and the pressure drop is too high for the
pump to provide adequate volume, hence pressure loss...  And altho the Skippy
school may teach brake then turn in racing (and I am of that school as well),
real world scenarios don't always allow that....  This means the loss of
something, i.e. a massive addition of steering effort when you need it most,
a massive deletion of hydraulic (and quite possibly abs) braking assist when
needed most, and most likely a massive NON linear braking response.....
  None of these look good....  Let's go to the next one...

2)  Disconnect the braking circuit from the hydraulic circuit
Gains:  "brake feel,"  really really good extra steering boost, MacGuyver
Losses:  Never having brake boost, really really good extra steering boost, a
MacGuyver nightmare getting the 11mm post bomb fitting to attach to the 17mm
feed, a modification to the low pressure switch on the hydraulic circuit.
Interesting idea, but my guess is that no one here has done this mod.  And if
so, just avoiding the inevitable, since the sale of this modified machine
might get Aukermann et al. (plaintiffs) the RS2 avant in addition to his
current cool machine....  

3)  No hydraulic circuit period.
Gains:  Steering effort, braking effort, money in the bank
Losses:  Steering effort, braking effort, hitting the abs threshold, the back
of significant others hand when parrallel parking
Not sure this one is worth addressing, but is a scenario

4)  Hydraulic circuit with bad bomb
Gains:  Money, braking effort, added excitement to audi experience
Losses:  Braking effort, a crap shoot as to when you loose all the bombs
retention, inconsistent abs/steering/braking performance, Aukermanns bill

Well, not sure the solution is as easy as posted....  For those of you that
have done one of the above, please enlighten me as to how YOU got it to be a
gain over losses...   Not meaning to make light of this whole thread, but
maybe en-lighten this whole idea.  The audi is expensive to maintain (F1
key), and the whole hydraulic system is one of the worst gougers to the
wallet, and the most consistent:  HP, lines, accumulators, Steering racks....
 But when it is working, it works well, and I wouldn't trade it for a vaccuum
system despite it's shortness of life....  So my argument is with those who
change it to save the money, the trade-offs there in safety and performance
would make your insurance company sick...  For those who want to do it, knock
yourselves out, but beware of your liability exposure, from all fronts....
 Want braking performance, get one of the Brembo/Wilwood/Nissan/ etc. brake
conversions or slap on a set of cool carbons ,drilled rotors and SS lines,
those increase PERFORMANCE and feel.....  Keep the bomb, the HP pump and the
steerring rack tho.

Some have addressed the Steering racks construction in aleviating that audi
tithe....   Sounds to me like someone could make some good change by fixing
the other parts of this Hydraulic system....  A gander at the BMW cars might
be a first start, esp in the bomb department.  

The abs is a very sensitive component, and one that assures you of utmost
braking control, and audi designed it to default to off with the slightest of
input variation, HP pressure, Low alternator voltage (those selenoids need
all the voltage possible), sensor alignment and wave variation, as well as a
host of other fault perameters....  Not sure I'd want to be the one
compromising any of those for the sake of pedal feel.....   And certainly not
while I or someone else driving my car might have the Expectation that the
abs will be there in an emergency.  Shop the price of the bomb, put it in
yourself if you need to save some $$$$, it takes all of 30 minutes tops....  

My .02 as always