Champion Spark Plugs

[e21Mark]

I've recently been looking at competition spark plugs as a friends rally spec BMW E30 M3 has been getting through them at quite a rate.

BMW actually do a Grp A competition grade plug but they're £400+ a set of four.

http://www.ebay.co.uk/p/Genuine-BMW-CMSP-Saloon-Ig...

Champion do the QA55V, which is also listed as a competition plug for the EvoIII but I used to hear bad things about Champion.

http://www.ebay.co.uk/itm/4X-CHAMPION-RACING-SPARK...

Are concerns justified or is it just a case of people having their favourites?

[e21Mark]

By all accounts the plugs are fouling to the point of misfire. I know it's quite common to use a set of plugs to start and warm an s14, before swapping for a fresh set, but I'm unsure you wouldn't still need to do this even if you were running ridiculously expensive "because M car" plugs at £100+ each?

The engine in question is a full rally spec s14/ 2.5 with suitable cams, flowed/ported head, dual injectors etc. It a bit of a beast and combined with a Drenth sequential box, is a pretty awesome thing to see. Actually make that hear!

[e21Mark]

The engine is fresh from a rebuild and certainly not consuming any oil. It's on DTA and running 'wasted spark' with mapping by Sandy Brown. It's certainly making the sort of power one might expect from an s14 of this kind of spec' but I don't know whether there might be an issue with plug gap?

Can the gap be altered on the plugs linked above?

Is there any formula to gapping plugs or is it a case of just seeing what works?

[e21Mark]

I wasn't trying to suggest plugs would no the difference, but that there's no fault or obvious reason for fouling. As I said, it's quite common for s14 to be started with one set of plugs before swapping to another. I know even stock engines can foul their plugs if you have to start, stop and re start in quick succession.

I'll mention the gap but I'm also thinking this might have been a common issue for BMW to have their own race plugs?

[e21Mark]

I had that exact cold start issue with my first M3, when the seller had moved it prior to collection but never warmed it through. I had to call the RAC to remove the plugs etc.

I'll check and see what exact plug he's using Steve. (This isn't my engine) I spoke to a couple of other people racing M3 and they all use one set to warm their engines and another set to run with. None use these Group A plugs though, which it turns out have no adjustment. Do you run 4 or 8 injectors?