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Spark plugs

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Beemingallover
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Spark plugs

Post by Beemingallover » Sat Aug 25, 2018 9:34 am

How many miles are spark plugs good for on a Z4M? Mine were last changed at 48k (insp 2), I'm now on 73k.
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srhutch
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Post by srhutch » Sat Aug 25, 2018 9:52 am

They are generally changed at inspection 2 time as the schedule dictates, which is approx every 50k.

Of course many will say you need to change boefre that time.
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Post by Mangozac » Sat Aug 25, 2018 10:15 pm

I was getting occasional cylinder shutdowns due to misfire so changed the plugs as they were looking quite worn. This was about 15k kms before the inspection II was due (at around 90k kms), so if you have reason to it's definitely valid to change them earlier.
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Post by Beemingallover » Sun Aug 26, 2018 9:22 am

Thanks. The car seems to perform well enough, though if the performance has deteriorated over a lengthy period it wouldn't be that noticeable. I recently had it on a dyno which indicated 307hp, as against BMW's factory output of 343hp. Whilst the factory figure might be overstated by BMW, I was advised that some loss was down to the friction of the good Michelin Pilot Sports, but also possible spark plug age.
:driving: Z4MR 2006 Interlargos Blue/Sepang Bronze SUMMER
E92 M3 coupe manual 2009 Silverstone Blue WINTER
M635Csi 1986 manual Lachs silver. GONE.

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Post by Mangozac » Sun Aug 26, 2018 10:03 am

It's quick and easy to pull one and inspect it - mine were noticeably deteriorated. I'd do this before replacing.
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Post by Ewazix » Sun Aug 26, 2018 10:15 am

Beemingallover wrote: Sun Aug 26, 2018 9:22 am Thanks. The car seems to perform well enough, though if the performance has deteriorated over a lengthy period it wouldn't be that noticeable. I recently had it on a dyno which indicated 307hp, as against BMW's factory output of 343hp. Whilst the factory figure might be overstated by BMW, I was advised that some loss was down to the friction of the good Michelin Pilot Sports, but also possible spark plug age.
Mentioning tyres as a possible drain on the figure suggests your 307 was at the rear wheels? I thought the factory 343 figure was 'at the flywheel', the loss to the wheels is usually rated at about -15% which wouldn't be far off the figure you had.

TBH plugs within their service age/mileage either work fine or fail under load which is generally quite noticeable somewhere in the rev range or show up on a real-time diagnostic.
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Post by Beemingallover » Sun Aug 26, 2018 12:07 pm

Ewazix, Yes 343 at flywheel but dyno guys seem to suggest the 307 at the wheels maybe could be a bit better, I pushed them on that and they said a change of plugs would help if the plugs were old.
:driving: Z4MR 2006 Interlargos Blue/Sepang Bronze SUMMER
E92 M3 coupe manual 2009 Silverstone Blue WINTER
M635Csi 1986 manual Lachs silver. GONE.

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Post by Bodyboarder » Sun Aug 26, 2018 3:08 pm

If you got 307 at the wheels I’d leave it all alone ! That’s a very good number , as you generally loose 50-70bhp from fly to wheels

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Post by Beemingallover » Sun Aug 26, 2018 3:56 pm

Bodyboarder, Yes, thinking now I mustn't get greedy.
:driving: Z4MR 2006 Interlargos Blue/Sepang Bronze SUMMER
E92 M3 coupe manual 2009 Silverstone Blue WINTER
M635Csi 1986 manual Lachs silver. GONE.

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