theway007

Hi guys, I need help making decision on my spark plug change.

I would to change my spark plug to either original or iridium for my 981 CS.

Option 1. Bosch Original FGR-5-NQE-04
1.6mm gap
Nickel Material

Option 2. Denso VKH22, validated compatible at Denso Website
0.8mm gap
Iridium

How should I choose?

Currently I am using Brisk ER15YIR-1 and I am experiencing rough idle and juddle during 1-2.5 RPM on acceleration.

TEF

I put in the Denso iridium's about a year ago in my 987.1 BS and have no complaints. While Bosch was the OE plugs in other European cars that I've owned, I've found long ago that the Denso plugs (made in Japan) always performed better especially at lower rpm.

Bxstr

No experience with Denso. Have Bosch spark plugs in my 997.1 GT3. My theory is that the OE spark plug should last for the 4 year interval in which they're in the car, without issue. Unless you're driving more than 40k miles, or the recommended interval in that time. But I'm sure the Denso is good as well.

Marine Blue

The advice I have been given for the past 15 years as it relates to all Porsche’s is to stick with stock plugs. It’s unlikely you’ll gain much performance, if any with a different plug and from I’ve experienced the wrong plug can in fact fracture and get ingested into the cylinder, this happened to my volvo and the results were catastrophic. Why risk it?

Bluehighways

The brand of spark plug itself is unlikely to make any difference. BUT going from a 1.6 mm Gap to an 0.8 mm gap certainly will, if there are any "issues" in the Secondary Ignition Systems insulation. A smaller gap requires a lower voltage to bridge the spark plug gap. If any of the insulation in the secondary system is breaking down, reducing the spark plug gap may bring the voltage required to fire the spark plug below that at which it is able to compromise a failing secondary ignition system insulation. Ex: Coil(s), Plug Wire(s), Rotor, Cap.

KBell

Don't do the plugs twice.
I'd stick with OEM.
It has been covered recently that spark plug removal is painful on the 981.
I lost some skin doing it myself.
I would have been pissed if there was ANY problem with a NON OEM plug.
Thus, having to redo the plugs again! NO way.
Stay with OEM

theway007

I have changed my coil pack, they are new, hence ruling out the secondary system failed, which one should I pick? I believe 1.6mm gap can give me more stable idling and better acceleration? Or it's either way?

theway007

I have changed my coil pack, they are new, hence ruling out the secondary system failed, which one should I pick? I believe 1.6mm gap can give me more stable idling and better acceleration? Or it's either way?

1.6mm have higher spark power but 0.8mm have longer spark burn time. that put me in dilemma.

ga 951

Can't speak for your car, but I had Iridiums in my 944 . When I swapped to OEM (copper), I saw absolutely NO difference!
Recently did 80K mi service on my 987.2 and stuck with the Bosche OEM.

theway007

Thanks for your reply, that makes me thinking going for OEM.