quattro digest, Vol 1 #4526 - 15 msgs

[Larry C Leung]

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Ben,

I chipped my MC2 200Q at about 150K. No adverse effects, and it was
most definitely fun. For entertainment purposes, you can shim your
wastegate spring (I used Bicycle bottom bracket spacers), just use
care that the spring can still be located by the centering rings (you'll
understand) and you can raise boost to .... 1.4 bar. Yup, it won't raise
peak boost (it's still controlled by the WGFV) but it helps limit waste
gate cracking, so you get boost sooner. This is a good preview of
what a chip'll do which is only more :-). As I just posted, effect on
fuel economy (measured, gallons, miles measured by odometer) is
really minimal, although I don't get full on it too often. I do use the
throttle
though, and I live in moderately hilly country, so you figure out how it
fits your terrain. Generally, in mixed driving (suburban mall traffic
with
some highway) I get about 20 -22 MPG, on the real open road, at
75 MPH (still hilly) I get about 24-5. Really hasn't changed too much
since chipping. I may have gotten a solid 22, and solid 25 before,
haven't
looked in my records b/c I didn't notice enough of change to care.

As for high altitudes and turbos, since your car is wastegate pressure
controlled (as are most turbo cars) the turbo will try to spin faster in
thinner air in an attempt to meet the absolute pressure that the car's
intake computer expects to create with the turbo. On our cars, the
pressure is measured as absolute pressure, which is compared to
zero pressure. If the air is sufficiently thin enough, the turbo will not
be able to acheive the pressure it is attempting to provide, so it'll
spin past it's designed spin rate (bearing life, rotational stresses)
(a.k.a. overspin). What this means to owners of turbo cars when
operated at high altitudes (of which I'd say 12K ft qualifies) is either
a) set your boost limits low enough that the turbo will be able to
keep up with the boost demand at the higher altitudes, or b)
if you have a high boost car, watch your boost gauge when getting
to high altitudes religiously. This, of course, is hard to do.

If you only occasionally find yourself at 12K ft, I'd still chip, and
when you plan to go to the high peaks, put in your stock ECU and
wastegate spring and happily tool around essentially care free. You'd
need a stock ECU as a chipped one will still adjust the WGFV to the
higher boost levels, the spring just effects wastegate cracking.
(I think the stock boost settings provide plenty of margin even to
12K feet, other listers please chime in here)

HTH!

LL - NY


LL - NY




> Date: Sun, 26 Jan 2003 20:33:25 -0700
> To: quattro at audifans.com
> Subject: Mileage - more numbers, and upgrades?
> Reply-To: bwpearre at alumni.princeton.edu
> From: bwpearre at alumni.princeton.edu (Benjamin Weste Pearre)
>
> For what it's worth, my stock 1990 200TQA's computer tells me I get
> about 27 hwy at 75 mph or so, about 19 in the suburbs between San
> Jose
> and San Francisco, and rarely more than 14 around Boston.  Doesn't
> change a whole lot with temperature, seems to drop an mpg or two in
> heavy rain (more rolling resistance over wet pavement?)
>
> I'm thinking of chipping the old car, and I was wondering what
> experience people have had with mileage post-upgrade.  I'd think
> that
> it would help somewhat given the same driving style, but I've heard
> conflicting reports.
>
> Also, someone mentioned something about ECU upgrades and high
> altitudes - apparently the turbo can spin too fast?  I live in
> Boulder
> and not infrequently drive up to about 12000' (briefly).  Is that
> considered "high altitude"?  I don't really understand what the
> problem is, whether there are things I can do about it, whether
> it's
> something I have to worry about with an ECU upgrade, whether I have
> to
> worry about it already...
>
> Cheers!
>
> --
> Ben Pearre          1990 200TQA          http://hebb.mit.edu/~ben
>
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