Issue with Bosch Platinums and Coil pack ignitions
12-01-2005, 06:30 AM
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Issue with Bosch Platinums and Coil pack ignitions
I came across this by chance, very interesting:
http://au.geocities.com/ozbrick850/e...boschplat.html
http://au.geocities.com/ozbrick850/e...boschplat.html
Bosch acknowledges a problem with using their Bosch Platinum spark plugs in engines with ignition systems that employ 1 coil for each pair of spark plugs (also known as a "waste spark ignition system").
The problem that Bosch has acknowledged when using their Platinum plugs
in engines with waste spark ignition systems stems from the tendency of
electrode metal to get transferred depending upon the polarity (direction
of current flow) of the spark. In waste spark ignition systems, 1/2 of the
plugs always see reverse polarity sparks. Given the very narrow platinum
center electrode of the Bosch Platinums, performance will be degraded more
significantly when reverse polarity sparks will cause material to be
transferred from the large ground/outer electrode onto the narrow platinum
center electrode's exposed end surface.
In cars with conventional (1 coil) ignition systems, every spark is of
the same polarity, for which the Bosch Platinums are optimized, leaving
them to deliver their designed-in advantages, which include:
o reaching self-cleaning temperature faster ("than any other plug")
o maintaining the spark gap and low firing voltage requirement throughout
their service life. (even in my high-stress turbocharged application
The problem that Bosch has acknowledged when using their Platinum plugs
in engines with waste spark ignition systems stems from the tendency of
electrode metal to get transferred depending upon the polarity (direction
of current flow) of the spark. In waste spark ignition systems, 1/2 of the
plugs always see reverse polarity sparks. Given the very narrow platinum
center electrode of the Bosch Platinums, performance will be degraded more
significantly when reverse polarity sparks will cause material to be
transferred from the large ground/outer electrode onto the narrow platinum
center electrode's exposed end surface.
In cars with conventional (1 coil) ignition systems, every spark is of
the same polarity, for which the Bosch Platinums are optimized, leaving
them to deliver their designed-in advantages, which include:
o reaching self-cleaning temperature faster ("than any other plug")
o maintaining the spark gap and low firing voltage requirement throughout
their service life. (even in my high-stress turbocharged application
12-01-2005, 08:51 AM
#2
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Very interesting.....I always wondered what the cause was behind the Bosch Platinum plug issue. That sheds alot of light on why NGKs and Densos seemed to have far less problems in certain engines.
Last edited by MTL_4runner; 12-01-2005 at 08:52 AM.
12-01-2005, 11:01 AM
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This explains why some Toyota owners, depending on the engine, have no issues, but our 3rd gens and above with the coil packs sometimes have degraded performance. It is more of a compatibilty with the ignition system than actually bad plugs. They just don't work well with coil-pack ignition systems. That is OK as long as we are aware of it. The Bosch plug issue has been a big bone of opinion here, it looks like this clears it up. 
12-01-2005, 03:23 PM
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Originally Posted by paddlenbike
To go a step further does anyone know why Toyota uses different plugs on each engine bank of the 5VZ-FE?
if they do my parts dept knows nothing about it.. I've changed the plugs on my 96 a few times (due again) and I always get 6 of the same.
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12-01-2005, 03:56 PM
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Originally Posted by paddlenbike
I saw rapid Bosch plug degradation in both my truck and Supra after less than 10k miles (both use waste spark ignition).
To go a step further does anyone know why Toyota uses different plugs on each engine bank of the 5VZ-FE?
To go a step further does anyone know why Toyota uses different plugs on each engine bank of the 5VZ-FE?
(ie 1 bank had 3 NGKs and the other bank had 3 Densos)
Would be nice to know what the story was on that too.
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