data aq (loooong)

Brett Dikeman brett at
Tue Dec 3 02:10:55 EST 2002

Yep, it's long.  You've been warned.

At 12:38 PM -0800 12/2/02, Mihnea Cotet wrote:
>I need to know as well what can be datalogged with
>VAG-COM from a 3B ECU

Look in the Bentley.  See those 11 registers?  That's it, and half of
them are adaptation values for idle and lambda.  None have units, or
mappings, associated with least nothing has been documented

>, I know the AANs are more
>complete in these regards, offering more values that
>can be logged

  I've said it before, I'll say it again- the 3B is about as bright as
a doornail(the Hitachis were about as bright as rocks with
Alzheimer's.)  What convinced me was when my ECU declared a toasted
WGFV as "bad throttle position sensor."  I understand WHY(it didn't
get boost when it thought it should, so it thought the throttle
wasn't opening fully, so therefore, the throttle sensor must be
BS'ing it), but a simple resistance check would have been nice(after
all, the thing can tell you in exquisite detail anything about any of
the 5 injectors, grrr.)

Still, Audi 1991 engineering beats Volvo 1995 engineering hands down.
My mother's 960 actually KILLS the engine if the coolant temp sensor
goes dead.  Yeah, that's safe(left her smack in the middle of an
intersection on the busiest road in town.)

>, but maybe someone who has tested it
>knows and will let us know... Brett??? I know you're
>using it but did you try to do some datalogs with your

I played with it maybe a year and a half ago, roughly...actually
older than that I think.  I was pushing Uwe hard to develop
logging(as were others I'm sure), it didn't even exist yet.  I
presume it logs the 11 registers just fine, and yes, actually, one of
the registers IS timing if I remember correctly.  Coolant temp is
also one of the registers, but that's fairly useless; it's mostly
given to you so you know if the engine is in range for various tests.
Keep in mind- data rates are quite low, at MOST a FEW samples per
second...and they're at most 8-bit(256 values.)  Not exactly a lot of

>Did anyone ever try to make a separate "blackbox" that
>logs all the inputs/outputs from the ECU and can
>display them graphically?

I've toyed with the idea.  One major issue is getting to everything,
easier said than done with such an odd connector to the ECU.  To be
honest, I have no idea if that kind of connector is even available to
mere humans; I imagine AMP makes something similar, but who knows if
it's still available.  Audi has a breakout box for most ECU
harnesses, but they're $$$.  Nothing else is very practical;
modifying the ECU?  Eeerrrrr...maybe....  Modifying the harness?

If you solve the connection problem, then comes the actual electronic
interface work.  Boost?  Easy, $50(or less) sensor and an A/D
converter.  But then what else do you want?  Coolant temp?  Easy.
Timing?  Uh...might be doable, but you're going to want all
three(crank, RPM and hall sensor) sensors to be really useful for
troubleshooting odd stuff, and logging the timing is going to be
tricky. Injector pulse width?  Pretty easy, a lot of uC's have
PWM-sensing builtin these days.  MAF sensor?  I think that wouldn't
all that tough to tap either, not sure.  Whatever you do, in every
case, you've got to be 'invisible' to the ECU so to speak.

The work snowballs quickly.  Each sensor may be doable, but when
you've got 10 of them(or more), component count, cost, and
programming complexity gets to be a serious issue.  Even overworking
the uC can get to be a problem- even the fastest run at around, or
under, 100mhz, and have very little in the way of math(VERY few have
floating-point calculation capability for example.)

If I can find a pair of connectors, I could at least explore the
possibilities- we just happen to have a uC development kit in the
house now.

It's even got ethernet and a full TCP/IP stack.  Wouldn't that be weird?

To: Owner
From: Car
Subj: O2 sensor

"When the hell are you going to replace my #@$# O2 sensor?"

GE has it all wrong- they're trying to make smart fridges that know
when they're out of stuff(yeah, people have a real hard time telling
when they're out of OJ.)

   The real money is in cars that electronically predict failure of,
and order for you, all the expensive little electronic sensors and

(couple get in car)
Missus: "Oh, by the way, UPS delivered something this morning, I
didn't look at what it was."
Husband: "I wonder what for."
Car: "!"


However, I think a lot of new 7-series owners would simply be happy
with a car they could actually use.

   We must truly thank BMW.  The phrase "#$@! BMW driver's don't know
how to drive!" is now undisputable.  The real question, now, is which
side of the equation the problem is on.

"They that give up essential liberty to obtain temporary
safety deserve neither liberty nor safety." - Ben Franklin

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