Spark plugs

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.
 
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.
 
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.
 
It's quick and easy to pull one and inspect it - mine were noticeably deteriorated. I'd do this before replacing.
 
Beemingallover said:
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.
Click to expand...

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.
 
[ref]Ewazix[/ref], 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.
 
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
 
You must log in or register to reply here.
Back
Top Bottom