320i '85 Spark Plug Conundrum

[TheWolfman]

So I've just embarked on replacing the plugs in my 320i from 1985 and now a slight conundrum has arisen.... I was using NGK BPR6ES which was the recommendation of the Zone WIKI and then went to buy some replacements from Euro Carparts and without thinking just went with the NGK's that they recommended for my model as they didn't specify the actual part number I presumed they would just be BPR6ES . After picking them up and taking out my old sparks I then realised that they were quite different and they had a much deeper spark than the BPR6ES.These replacement plugs are NGK ZGR5A.


NGK ZGR5A on bottom, NGK BPR6ES on the top.

IMG_3910 2.JPG

After looking into this a bit on the NGK website I noticed that the NGK ZGR5A are the plugs recommended for post '86 E30's and have the 0.8mm Gap I see lauded as being the ideal gap for E30 bims.


http://www.ngkpartfinder.co.uk/car_comm ... engine=2.0

These plugs however are the recommended one from the original service information for M20B20's without a catalytic convertor and are the direct alternative to the BOSCH W8 LCR.

The plugs recommended for M20B20's with a catalytic convertor in the original service information is the BOSCH W8DC and the NGK equivalent is the BP5E which should actually have a gap of 0.6mm and from what I understand these have a lower heat rating than the BPR6ES. I'm not sure if I have a convertor or not but will have a ganders.....not something I've actually thought about to be honest!

So from what I can gather,I really don't want to be using the NGK ZGR5A's that I have as the deeper spark concerns me and I should also ditch the NGK BPR6ES and go with the BP5E with a 0.6mm Gap?? ....Or maybe I should just put a bloody plug in it myself and stop having sleepless nights about such matters!

What are other zoners with early 320's using?

[TheWolfman]

After more digging around I decided to actually go with the NGK ZGR5A's because as it turns out these are the direct replacement for the BOSCH W8LCR and as I don't have a Catalytic convertor on my 320i ( because I'm clearly an unashamed polluting scumbag with no morals) are what original service guides say I should be using.

Using these plugs with a deeper spark has actually markedly improved the running of the engine, it seem's much quieter, smoother and somewhat 'tighter' than using the BPR6ES plugs. I have also side-gapped the plugs and set the gap to just shy of 0.7mm and this has made a very slight but certainly welcome improvement in power and response.It mean's I'll have to swap the plugs out sooner, but I can live with that. I also learnt more than any scumbag needs to know about spark plugs in the process

Anyone with a 320 should definitely try this themselves in my opinion.

Some Info on plugs and gapping (...that sounds wrong!), should anyone be interested:

https://www.ngkpartfinder.co.uk/files/N ... hicles.pdf

http://performanceunlimited.com/documen ... pping.html

[Foe]

Interesting, and nice update.
I don't have a 320, but this side gapping, I've not heard of before, assuming this can be done on any engine?

[TheWolfman]

Yes Foe, Side-Gapping can be done on any plugs... speed-demons and racers have been doing it for years, basically just un-shrouds the tip of the plug so that the spark is fully exposed to the injected fuel for better combustion.£20 Premium Plugs have this as a 'feature'.Downsides are that the life of the plug is somewhat compromised.