Spark Plug Wear Rate R1200RT 08

[racer7]

Changed some plugs on my 08 RT today that had been in the bike 26K miles.
They (OEM type NGK DCPR8EKC) were worn out of spec at an interval approx equal to the 40K kilometer recommended factory change interval though the bike was running and starting fine.

Spec gap is 0.8 - 1.0 mm and needs a wire gauge to measure due to shape of ground electrodes. The removed plugs measured 1.1 - 1.2 mm and both wear and appearance were similar for primary and secondary plugs.

The wear is primarily erosion of the center electrode to produce a taper. It is easily visible as a slightly tapered or conical appearance to the center electrode and actually does not require measurment to see.

I replaced the OEM type with DCPR8EKP - same as stock except with a platinum electrode instead of nickel. It will be interesting to see if they wear at a slower or same rate. They are a little cheaper than the nickel ones but have the same diameter center electrode- a bit unusual in that most platinum and iridium plugs have smaller diameter center electrodes than nickel equivalents.

Anyway- see photo below for a comparison of the worn OEM plug and the new replacement.

It seems that the factory interval for plug replacement is right on target for OEM types.

 

[mpmarty]

Great Photo! would it be possible to bend in the ground electrodes to cheat a few more miles out of these worn plugs?

 

[roborider]

I was discussing with a buddy why you can't compare miles on auto plugs to those on a bike. The discussion raised a question that maybe someone here knows the answer to.

First:

1) The revs on a car are much less than a bike. I cruise down the highway at about 2500 RPM in my car, and about 4500 RPM on my bike. A spark plug on my bike fires therefore about twice as much as it does per mile on my bike vs. car. And the life of the plug is proportional to how many times it fires, not distance. So right there 20k on a bike is like 10k in a car in terms of spark plug life.

2) The old boxer engine fired every time the piston was at TDC, regardless of whether it was the compression or exhaust stroke. A car only fires when it is at the compression stroke. So on an old boxer, plug life was 1/2 a car for that reason. That makes 10k miles on an old boxer equivalent to 40k miles in a car.

And that raises my question. Does the oilhead/hexhead boxer fire the plug at every TDC like the old airheads, or, does it only fire on the compression stroke? I would assume with modern ignition, it would be the latter, but I don't really know for certain.

Anyone know?

 

[mpmarty]

Hall effect sensor only fires the plugs on the cylinder that is tdc compression.

 

[ragtoplvr]

Great Photo! would it be possible to bend in the ground electrodes to cheat a few more miles out of these worn plugs?

If you were exceptionally unlucky you could have one of the electrodes break off, not common but it can happen. That would not be good. Plug is cheap compared to tires.

Rod

 

[racer7]

Adjusting those electrodes is a little fussy and as noted, I wouldn't want to take the chance on having one break afterward. They are heavier and stiffer than on many auto plugs so harder to adjust and the need for a wire gauge makes it slower. At what plugs cost, not worth it to me. Could be done as an emergency measure I suppose but you really don't want an electrode to end up in your motor. Have seen the results of this on race engines and it is not pretty.

 

[hjsbmw]

I replaced the OEM type with DCPR8EKP - same as stock except with a platinum electrode instead of nickel.

I, too, am thinking about going the platinum route. The OEM plugs are hard to find and expensive. May I ask where you bought the new plugs? I haven't looked yet locally in auto parts stores, but see them online.

Are there implications by using a platinum electrode vs. nickel?

 

[racer7]

The platinum NGKs are used in some BMW car engines and can be bought at pretty much any autoparts place that has NGK stuff or on the web at about half the price of stock.

The general theory is that platinum electrodes erode slower (and iridiums slower yet) but whether that is the case with the NGKs in the bike I can't say, yet. The platinums are exactly the same as stock except for electrode composition and there is no obvious reason why BMW doesn't use them. The stock plug is a "BMW bike only" item though.

There are no iridiums with the same physical config as stock though some folks use single electrode iridiums in these engines. Whether that config can deliver a longer life I don't know- would want to see photos and measurements.

 

[greenwald]

Changed some plugs on my 08 RT today that had been in the bike 26K miles.
They (OEM type NGK DCPR8EKC) were worn out of spec at an interval approx equal to the 40K kilometer recommended factory change interval though the bike was running and starting fine.

Spec gap is 0.8 - 1.0 mm and needs a wire gauge to measure due to shape of ground electrodes. The removed plugs measured 1.1 - 1.2 mm and both wear and appearance were similar for primary and secondary plugs.

The wear is primarily erosion of the center electrode to produce a taper. It is easily visible as a slightly tapered or conical appearance to the center electrode and actually does not require measurment to see.

I replaced the OEM type with DCPR8EKP - same as stock except with a platinum electrode instead of nickel. It will be interesting to see if they wear at a slower or same rate. They are a little cheaper than the nickel ones but have the same diameter center electrode- a bit unusual in that most platinum and iridium plugs have smaller diameter center electrodes than nickel equivalents.

Anyway- see photo below for a comparison of the worn OEM plug and the new replacement.

It seems that the factory interval for plug replacement is right on target for OEM types.

Yup - service interval for OEM plugs is 24,000 miles - right on the money!
(Bosch YR 5 LDE) - BMW Part #12127671301