NGK Spark Plug Question

Temperature - more specifically, the distance between the base of the porcelain insulator and the main plug body. The longer this is, the hotter the plug runs.

Plug temperature is very important, especially in a high compression ration engine, and doubly so in a turbo. Too cold, and the plug will foul easily because it won't burn off accumulated crud. Too hot, and you'll get predetonation.

Your car needs NGK BCP7EV. You can get away with NGK BCP6EV, but definitely the 5.

Which plug is the hottest plug of the three ?

You wrote :

"You can get away with NGK BCP6EV, but definitely the 5."

Do you mean: definitely *not* the 5 ?

IOW, do you mean the NGK BCP6EVand the NGK BCP7EV are okay but do *not* use the NGK BCP5EV ?

Thanks,

jon

BCP 5EV = 900 16v non turbo without cat, BCP 6EV = 900 16v non turbo with cat, BCP 7EV = 900 16v Turbo. That is up to 1993, HTH Tom, Saabtech.

I picked up a Bentley manual last night. It mentions using the NGK BCP 5ES for 1989 - 1993 Normally-aspirated. What is the difference between the NGK BCP 5ES and the NGK BCP 6EV ?

jon

5 is the hottest.

Yes, yes I do :-) Sorry, it was late.

Yup.

Got it. Thanks for the help,

jon

Check out this link:

Alex

the higher the NGK number the cooler the plug

S = nickel alloy electrode tip; good plugs at cheap price

V = gold palladium tip (fine wire, IIRC)

cost more than S, will last longer than S, _may_ offer slightly improved performance in short operating conditions, w/frequent on/off of engine

for 89 900S non-turbo use (assumes in good tune)

BCP5ES \ for all-around normal driving BCP5EV /

BCP6ES \ for more aggressive driving, extended high-speed, towing BCP6EV / (some techs recommend 6 heat range for normal driving)

between the two heat ranges, inspect the new plugs after a few hours of run time (respectively), to see how they are burning (color condition - google search). NGK home page has a FAQ

Lance

The ES range of spark plugs are copper cored, whereas the EV range sports a platinum tip, The EV range costs twice as much as the ES range but lasts twice as long, Saab recommend using the EV range but with a DI pack you have to use a resitor plug, eg BCPR 7ES on a Turbo as NGK do not make a resistor EV plug. Under normal use it does not matter if you use ES or EV it works out the same in the end. If you are in the states or elswhere with tighter emmission controls than the UK you may find that there is a different heat grade of plug depending on the configuration of the particular emission control of that engine, eg, twin lambda sensors bla bla bla. Dont allways trust bently and haynes manuals as being gospel, even the

2003 NGK catalogue has a couple of differences of opinion with SAAB as to what plug fits what car. Best place to look is your owners handbook or ring yer dealer............. T.

I use the bcp 6es on non turbo cars.

its the reg plug, no platunum

Okay, Lance. I went with the BCP6EV

Thanks,

jon

Thanks, Tom. For $4.50 a plug I and went all out and got the platinum tips. ;>) Thanks for the breakdown of what comprises the different plugs. Very helpful.

jon

Okay, Alex will do. Thanks

jon

The variable here is the number that NGK uses to rate the "heat" of the plug. A "hot" spark plug will have a deeper recessed "groove" separating the center porcelain core insulator from the steel, threaded shell. This empty space becomes filled with intensely hot gas upon combustion and, with limited paths to export this heat, the tip of the plug remains hotter than a similar plug constructed with a more shallow "grove". Hot plugs stay cleaner. The objective is to run the hottest plug you can with out the porcelain turning "toasted brown" after hard driving. DANGER. Run a too-hot plug for too long and you destroy pistons (Rare). If you use high octane fuel you can run a hotter plug. If you drive HARD use a colder plug. All the plugs you listed are "mid range " plugs. Not "cold" (racing) plugs or hot (anti-oil-fouling) plugs. With NGK, the LOWER the number the HOTTER the plug. Opposite with Champion. Check your plug's color. Black or nearly so... too cold. Toasty brown.....too hot. Warm tone of light grey....juuuuuuuuust right. HINT: If your '91 uses a distributorless direct ignition system, do not use BOSCH Platinum Plus plugs!! They eat ignition cassettes. I learned the hard way. Twice. Fool me once, shame on you. Fool me twice, shame on me.

Hyperdog

The car does have a distributor. I don't see any advance mechanism though. Thanks for the tips on plugs. I went with the BCP6EV. The old plugs do have the light grey color you say is "juuuuuuuuust right". :>)

Thanks again !

jon