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Cams (Was: Tales of turbos, part 3)
I have been looking into performance modifications and engines swaps for my
83 TQC and thought some of you might be interested in what I have found.
Good post, thanks for typing it all in. One quibble:
When asked about cams, he said he has not found a replacement turbo cam
which he would recommend. The stock cam is very good. He did mention that a
normally aspirated cam from the 5 cylinder engine from Germany seems to work
very well in the turbo engine. For the turbo cam, he said to look for one
with a very small overlap.
WRT U.S. stock cam, I have to disagree. It sucks. It "comes on" about 3,000
and has shot its wad by 5,000rpm. Installing Dan's Schrick cam in my '83
extends the top end to rev-limiter (6,500) and pulling strong, with no
real effect on bottom end (doesn't have one in stock form, still doesn't
have one). The Schrick really comes on about 3,000 (pretty much as stock),
with a secondary surge at 4,000 that seems to last all the way to 6,500.
This is a direct no-other-changes (except for changing the oil...) compari-
son 'twixt stock and Schrick cams, in a "stock" '83 UrQ motor with new
head (ported/polished/etc.) and pistons, stock valves, and S4 turbo with
stock (VDO boost guage 11psi) wastegate spring (and chip/computer).
I can't comment accurately on stock turbo with stock cam (as there were too
many other problems with the engine/car to reliably draw a conclusion), ex-
cept that my memories are that the power curve/behavior was the same 3,000
to 5,000 ballpark (had really run out of steam by 4,500, but that was before
new fuel pump, injectors, ground connections, vacuum lines, and just about
everything else that can conceivably fail being replaced...including engine
mounts, which shouldn't affect power, but this being a German beastie, I
figure it's heavily into Gestalt, so who knows...)
Without any doubt I'd say that the Schrick cam was the best bang-per-buck
engine performance enhancement I've seen. (My only complaint so far is
that the Schrick likes a *much* richer cold-engine mixture than I've so
far been able to coax out of my setup, but I think I know how to fix that,
once I've found the right switch, speaking of which, does anyone know of
a "thermo-switch" that will fit a "standard" oil/water temp sensor hole,
has two-terminals (insulated from ground), and triggers in the 140-160F
range? By the way, by "cold" I mean 10F to 20F temperatures.)
Standing on it's own, a 15psi wastegate spring would win hands down, but I
would really have to factor in the "chip", not to mention the new S4 turbo
et al... which will ultimately (when I have recovered enough to sink even
more money into this beast) win me far more.
For overall "driveability", it's a tie between the Schrick (extending the
top end) and the S4 turbo (much more responsive everywhere, although a
minor nuisance when it trips the computer overboost at 2000rpm with 7psi
boost...). They work very well together!
(Since this is my daily driver [and in fact *only driver* at the moment],
I am far more into "street behavior" than that last tenth on the racetrack,
just to let y'all know where *I*'m coming from.)