41 985 spark plugs

[c5 joe]

Hi was wandering if i switch to the new irradium 41-985 plugs does the pcm have to be reprogramed i am getting mixed answers thanks Joe

 

[zagger]

I've just changed mine and was told reprogramming the PCM is recommended but not necessary, so I didn't. When talking to local dealers they didn't even know about the upgrade. I can tell you that I'm not happy with the switch and new gap setting. It has made the engine feel more sluggish (does not pull rpm as before) and I've noticed some detonation at about 5500 to 6000 rpm. This might be a directly related to reprogramming the PCM but I'm not willing to spend the money to recalibrate and loose my custom tune in the process. For me it's back to old, it has treated me well till now. Good luck, Zig.

 

[Hib Halverson]

What is the source of the recomendation to reprogram the PCM when changing to iridium tipped spark plugs?

 

[zagger]

http://www.corvetteactioncenter.com/forums/showthread.php?t=100804

See this thread I started earlier, C4C5 gives all the update information. Its more than Iridium tip, the gap and temp . are different on the -985 plugs.

 

[c5 joe]

spark plugs

I've just changed mine and was told reprogramming the PCM is recommended but not necessary, so I didn't. When talking to local dealers they didn't even know about the upgrade. I can tell you that I'm not happy with the switch and new gap setting. It has made the engine feel more sluggish (does not pull rpm as before) and I've noticed some detonation at about 5500 to 6000 rpm. This might be a directly related to reprogramming the PCM but I'm not willing to spend the money to recalibrate and loose my custom tune in the process. For me it's back to old, it has treated me well till now. Good luck, Zig.

Thanks Zig aftter talking to my dealer 3 plus hour he said not to use the tune or plugs with my turbo and nitrious Again Thanks

 

[c5 joe]

Thanks Zig aftter talking to my dealer 3 plus hour he said not to use the tune or plugs with my turbo and nitrious Again Thanks

Hey my good freind is running the bosch platinum 4 plugs and swears by them no gap I cant try them as for the nitrious, any one like em or they just another mind game:eyerole:booty:eek

 

[zagger]

The +4 plug is a gimmick. The basic design surrounds the spark (source of ignition) with four electrodes. That has a choking affect on igniting air/fuel within the chamber and drastically decreases timing. Without going into details, this plug will not increase any performance, if anything it will decrease it. I'm in the process of testing the NKG T55's, They are spaced little longer than 985 so there might be some effective timing retardation but I'll see what it means in real world. One thing about NKG is that they have to be replaced more often than iridium ones.

 

[c4c5specialist]

Hi there,
The original calibrations for use with the 41-932 were using the .060 plug gap.
When they changed the recommendation to the 41-985, we were also instructed to reflash the PCM with a calibration that optimizes the new spark plug for use with the engine. While its NOT a requirement, its what is suggested by GM since that bulletin was introduced on all Generation 3 small block. TSB is 03.06.04.060A for the spark plug update.
Allthebest, c4c5