STi spark plugs?

[Philip Procter]

With so many different styles and clains for "hotter sparks", etc,
does anyone know if one type of plug is actually better than the
others for the STi?

Philip

 

[Hallraker]

With so many different styles and clains for "hotter sparks", etc,
does anyone know if one type of plug is actually better than the
others for the STi?

From what I've read/seen/heard, a lot of those alternative spark plug styles
are as helpful as the fake blue "xenon" headlights. (In that, despite
packaging claims, they don't actually do anything better for your car, and
may in some cases be worse.)

I replaced the spark plugs on my '95 Outback a few years ago, and although I
originally bought Champion plugs, I heard some horror stories about Champion
plugs in Japanese engines. So the Champions went in the back of the wagon
(and, as far as I can remember, never got returned to the store, doh!) and I
ended up getting NGK (oem) plugs from my dealer - and they actually cost a
bit less. I've put on about 50,000 trouble free miles since then.

-Matt

 

[CompUser]

4ax.com>, (e-mail address removed)
says...

With so many different styles and clains for "hotter sparks", etc,
does anyone know if one type of plug is actually better than the
others for the STi?

The OEM stuff seems best, Bosch=horrors.

 

[Jim Stewart]

From what I've read/seen/heard, a lot of those alternative spark plug styles
are as helpful as the fake blue "xenon" headlights. (In that, despite
packaging claims, they don't actually do anything better for your car, and
may in some cases be worse.)

I replaced the spark plugs on my '95 Outback a few years ago, and although I
originally bought Champion plugs, I heard some horror stories about Champion
plugs in Japanese engines. So the Champions went in the back of the wagon
(and, as far as I can remember, never got returned to the store, doh!) and I
ended up getting NGK (oem) plugs from my dealer - and they actually cost a
bit less. I've put on about 50,000 trouble free miles since then.

I've always followed the common wisdom of US plugs in
US cars, Euro plugs in Euro cars and Japanese plugs
in Japanese cars. It's always worked for me.

 

[y_p_w]

I've always followed the common wisdom of US plugs in
US cars, Euro plugs in Euro cars and Japanese plugs

A good deal of the newer cars on the market are spec'ed
with high quality Japanese plugs (more often NGK but
sometimes Denso). My father's '96 Buick Regal actually
comes with (AC rebranded) NGK platinums for the 100K
mile change period. Some German carmakers are known to
use NGK plugs, and a lot of BMW/VW specialist shops use
them.

 

[Ignignokt]

With so many different styles and clains for "hotter sparks", etc,
does anyone know if one type of plug is actually better than the
others for the STi?

Philip

It's worth noting that while the beneficial claims of a "hotter spark" from
certain aftermarket plugs are almost certainly so much snake oil, there
really is such a thing as plugs that are classed as relatively "hotter" or
"colder" than others. "Hotter" plugs tend to be better for cold starts, but
are more apt to lead to pre-ignition in high-compression or forced-induction
engines. In such high-performance applications, you almost *always* want to
use *cold* plugs, so as to reduce the likelihood of dangerous pre-ignition.
"Hot" plugs are of a benefit only in old, tired engines that aren't running
very high combustion chamber pressures and don't like to start when it's
cold.

Unless your engine has been modified, use OEM plugs. The specious benefits
offered by other plug manufacturers don't outweigh the potential damage from
pre-ignition, IMHO. If your engine *has* been performance-modified, always
use the plugs recommended by your performance upgrade expert -- ask them, if
necessary. In most such modified engines, the OEM plugs will probably be a
safe bet, but colder plugs might permit higher boost at the theoretical
(though in practice unlikely) expense of difficult cold starts.

Whether the spark itself is "hot" or "cold" isn't nearly as important as
whether the fuel-air mixture actually begins its burn when the spark is
fired. If the burn tends to begin before the spark, you need "colder"
plugs. If the burn doesn't begin at all, you need "hotter" plugs. If your
engine is experiencing neither of these conditions, then changing to either
"hotter" or "colder" plugs will give you no benefit at all, and might
actually *cause* some problems.

- Greg Reed

[Not an automotive engineer, but did stay at a Holiday Inn Express last
night...]