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Porsche Crest Spark plug choices

The car is a stock 1987 924S in rehab. It runs but has a mild flat spot in the middle RPM range. I have not replaced the plugs yet because they look good. There appears to be several choices (both standard and high performance) for this engine. The main difference appears to be heat ranges. Historically, I've had the best results with NGK in all my cars but if there is a consensus plug that has the best track record for this engine, I'm all ears. Thanks.
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Last edited by rbuswell; 09-06-2019 at 04:14 AM.. Reason: More content
Old 09-06-2019, 04:12 AM
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I always used what Porsche advises in the manual which is Bosch Copper WR7's. Maybe today there are better modern options idk, subscribed.
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Old 09-06-2019, 04:22 AM
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The PO had iridium plugs in the car. I changed over to copper after a while, and saw no performance difference. I say save your money and stick with copper.
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Old 09-06-2019, 07:36 AM
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I like these in the '92.
Old 09-06-2019, 10:24 AM
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Ngk bpr6es
Old 09-06-2019, 01:40 PM
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Porsche Crest Thanks for the help

I'll let you know if they help with my flat spot.
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1982 911SC Coupe (Zinc Metallic w/ Dark Blue interior)
1987 924S (Black on Black)
Old 09-08-2019, 02:25 AM
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vacuum leak
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Porsche Crest Thanks

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Originally Posted by DannoXYZ View Post
vacuum leak

I have a smoke machine. I'll give that a try.
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1987 924S (Black on Black)
Old 09-09-2019, 02:22 AM
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The WR7DC plugs are great. In any case, I would stick with copper. I go with the NGK BPR6ES plugs because they dissipate heat more quickly than the WR7DC ones.
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Porsche Crest Best results with NGK

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Originally Posted by 944tothefloor View Post
The WR7DC plugs are great. In any case, I would stick with copper. I go with the NGK BPR6ES plugs because they dissipate heat more quickly than the WR7DC ones.

I've had my best luck with NGK. I bought BPR6ES and will put them in right away.
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1987 924S (Black on Black)
Old 09-09-2019, 12:59 PM
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I was surprised to learn that one of the most significant differences in spark plugs was its ability (speed?) with which it transfers heat from the combustion chamber to the engine head. So what's best for our 924s? This:

An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as adding a turbo or supercharger, increasing compression, timing changes, use of alternate fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature, necessitating a colder plug.
Source: https://www.ngk.com/learning-center/article/207/what-is-a-spark-plugs-heat-range
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Old 09-11-2019, 03:10 AM
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Quote:
Originally Posted by curtisr View Post
I was surprised to learn that one of the most significant differences in spark plugs was its ability (speed?) with which it transfers heat from the combustion chamber to the engine head. So what's best for our 924s? This:

An unaltered engine will run within the optimum operating range straight from the manufacturer, but if you make modifications such as adding a turbo or supercharger, increasing compression, timing changes, use of alternate fuels, or sustained use of nitrous oxide, these can alter the plug tip temperature, necessitating a colder plug.
Source: https://www.ngk.com/learning-center/article/207/what-is-a-spark-plugs-heat-range
Not only that, the addition of Ethanol to gas and the effect on spark plugs was also addressed in a TSB by NGK.


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Old 09-11-2019, 05:35 AM
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Quote:
Originally Posted by 9ff View Post
not only that, the addition of ethanol to gas and the effect on spark plugs was also addressed in a tsb by ngk.


+1
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1977 924 Guards Red (parted and sold)
1987 924s Alpine White (sold)
1987 924s Kopenhagen Blue (my Lowencash tribute track car)
1987 924s Garnet Red
1982 928 Silver (sold)
Old 09-11-2019, 06:03 PM
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I was always hooked on Bosch, but just installed NGK standard copper plugs (sparkplugs.com) that were one level cooler than OEM Bosch. It seemed that availability of various levels of heat range for NGK was better than Bosch, since I ran into Bosch heat levels that were discontinued. Several vendors also stated that QC seems better for NGK.

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Old 09-15-2019, 01:40 PM
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