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Re: Bosch W7 DTC vs Bosch Platinum?
I use the W5DTC in the 85 ur-q because the '5' heat range is correct for =
the ur-q. The 5K/200 turbos use the '7' heat range, hence the W7DTCs in =
the big Qs. I fergit if the 5 or the 7 is hotter/colder......my guess is =
that the 5 is colder for less detonation at high boost.
Bosch uses higher numbers for "colder" plugs (with "colder" generally meaning
suitable for use in "hotter" engines...); Champion uses lower numbers for
"colder" plugs (as I recall, my Lotus wanted N6Y plugs, while my urabuS
seemed to like N14Y plugs...).
In general, you want the plugs tips to run at a specific temperature to
keep them from fouling; "hotter" plugs hold heat more than "colder" plugs
(colder plugs conduct heat faster into the plug body, from there into the
cylinder head), and thus are suited for lower-stress engines which typi-
cally generate less combustion chamber heat overall, while high-perfor-
mance/turbo-charged/etc. engines tend to generate more heat, and so need
to conduct the plug tip heat away faster (both to avoid detonation from a
"glow-plug", and to avoid simply melting the tip...).
One of the typical problems of a "high performance" engine is running it
"around town", where the plug simple runs too cold and fouls (doesn't
"burn off the gunk"). Ergo the famous Bill Cosby schtick about blowing
the gunk out of the engine by driving 90mph in second gear . . . (In
fact, I would run N7Y plugs in my Lotus for "commuting" purposes, and
switch to N6Ys for track/autocross usage!)
I have not tried the Bosch platins in any Audi. I did try the Bosch =
platinums in some other cars (supajus) with bad results and have not =
experimented with them since.
My one experience with platinum plugs (they're more expensive, must be
better) was pretty much negative, or more to the point, non-positive,