Knowing your Spark Plugs

Berto

Regular Member
The OEM spark plugs for the Z22SE are GM 91 990 38 == Bosch HLR 8 STEX

As weird as it sounds all those alphanumeric characters in the code 'HLR8STEX' have actually a meaning, but we need a Rosetta stone for decyphering the hieroglyphs:

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Now courtesy of Champollion we can get more intimate with the OEM spark plugs:

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I'd like to call your attention on two interesting points, ladies & gents:


· The 'H' in 'HLR8STEX means that the seat shape is CONICAL WITHOUT WASHER (as opposed to flat with washer).

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^ Conical seat spark plugs interface with the cylinder head in a different way than flat seat ones, and require less tightening torque.

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If we switch from conical to flat seat spark plugs (like for instance any Bosch one whose code starts with the letter 'F'), the results will be anyone's guess, from 'no problem' to 'cracked cylinder head', and anything in between.



· The 'S' in 'HLR8STEX' indicates the thread length, and the center electrode protrusion into the combustion chamber.

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Again, if we switch to spark plugs with different thread length and/or different center electrode protrusion, the results will be anyone's guess, from 'no problem' to 'preignition' / 'detonation' / 'fried coil pack', and anything in between.



My humble friendly advice: Unless you're confident you know very well what you're doing, stick to the OEM Bosch HLR8STEX.
 
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Berto

Regular Member
The direct alternative from NGK Europe for the standard Z22SE is the LTR6B-10T.

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^ They look very like the Bosch HLR8STEX (conical seat, 25mm thread length, similar protrusion, triple electrode). Gap is slightly smaller (1.0 vs 1.1mm, nothing to write home).

But curiously they are one grade colder than the Bosch HLR8STEX:

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This is tactically interesting for heavy footed drivers / warmer climates / moderately tuned up engines.

Not so interesting for passing MOT emissions, however.
 

Berto

Regular Member
Bosch catalogue recommends FR6KPP33X+ for SAAB B207 engines.

NGK recommends PFR6T-10G for SAAB B207 engines.


No idea if that's still optimal for a B207 head on top a Z22SE block hybrid, however. Probably yes, but that's just a guess. Some guru here around may know better.
 

evocarlos

Stupid Bollocks
Staff
one thing we know is bosch are crap with plugs :)
the platinum plugs from ngk for the z22se have been tried and test for 60k miles on one set the bosch multi point need doing every 20k miles

the information on the fitting nm is paramount the taper seat plug drive there way in to the head putting pressure on the head there have been 100's of cases where the head cracks the thread from fitting the plugs to tight on a z22se
 

corsaZ22se

Senior Member
in correct torque and the fitting of plugs to hot engine's as i have seen done many times by "so called experts" in the world of vauxhall tuning can lead to cracked heads. :facepalm:
 

Berto

Regular Member
Yep no wonder the NGK PTR5A-10 last longer in Z22SE engines.

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They're the same heat range than the Bosch HLR8STEX.

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