I have a 2005 R50 with 169k miles and I have always used the Platinum4 plugs. Recently I installed a set of Iridium plugs and noticed when starting the car it takes a little longer for the car to start. ~ 5-8 seconds longer than the Platinum4 plugs...is this normal?

What advantage does one plug type have over the other?

Also when I changed the plugs I noticed that the plugs were loose.
Should I need to torque them periodically?

 

Is the heat range correct on the plugs?
Mini plugs do have a tendancy to loosen is not tourqed correctly...shooting the plug out, causing $$ dammage.
Plugs don't make power (start the great debate ((going from a worn plug to a new plug will)), but just ignite the mixture, and if too hot a range, may cause a ping (preignation)....
Never noticed a differance iridium/platinum ...the conductive level of the materials are different, but at the ampages and voltages used in a modern ignation system, it should not matter.

 

Yeah I agree with ZippyNH,
I've used both in my MCS and there is no noticeable difference. Currently using Platinum, one step cooler because of my mods.
One important thing here is that you take the time to check the gap. Even with pre-gapped plugs, I've never found all plugs correctly gapped right out of the box. Except the ones with multiple pins that spark horizontally against the side of the main electrode (like I'm using now). I believe iridium plugs are single electrode and traditional configuration with which you might have gapping issues.

 

You have to crank your car over 8 seconds before it starts????

 

Iridium tip will last longer but it carries more resistance.

 

5-8 seconds is obscenely long to start any nice automobile. I'm the third owner of a probably-abused R53, and it turns on like a light every single time - no stuttering, no stammering, unless I've flooded the thing with Seafoam...

While I would guess you might have some other issues, I would recommend checking the gap on your iridium plugs. My NGK Iridiums were all off; I opened them all up to .045" and my car has run much, much smoother since.

 

While I would guess you might have some other issues, I would recommend checking the gap on your iridium plugs. My NGK Iridiums were all off; I opened them all up to .045" and my car has run much, much smoother since.[/QUOTE]

I gaped the plugs to .032" as stated online. What benifit does opening th gap up do?

The start up time had drastically been reduced to what I have experienced as normal. Not sure why??? I didn't do adjustments.

Thanks to everyone for all the feedback.
Mark

 

From our experience I've seen more problems with Iridium plugs than gains. We've found the tips to actually wear out faster. Yes I know this goes against their marketing, but I've seen so many worn out with my own eyes that I won't use them. The other thing is out of all the plugs we've seen come loose in cylinder heads, most of them were iridium.

 

Don't know, really. I had just read that (in theory) one should run the largest gap that won't misfire. Not sure what opening up the gap did, but it definitely ran smoother afterwards - but this could be equally due to the fact that my plugs went from variably gapped (.028"-.036") to consistently gapped (.045"), and in fact had nothing to do with the gap itself.

Having said all that, based on much of the reading I've done on this board and elsewhere, I'm changing out my NGK Iridiums for NGK BKR6EQUP (stock heat range for Cooper S, one up from JCW, MEG). I should get to it today or tomorrow, and will post here if I see any incredible difference or benefit.

 

Thanks everyone for all your inputs.

The start up time is back to normal....not sure why, didn't make any adjustments.

I'll keep everyone updated on any other issues.

Thanks again,
Mark