nitrous colder plugs-

[MES]

I've used NGK plugs for 10k miles now (2 sets at 5k each) and had no problems. I've never noticed a sound change in the exhaust over stock plugs. If you do have a quieter car maybe one of your old plugs were going bad

I wouldn't be concerned about the noise reduction as long as the car is running good.

Edit: I'm using ZFR6F-11 #4291 not FR5-1 I think the 5 is stock and 6 is one step colder (but could be wrong)

 

[Flyin Phil]

I recently looked into getting colder plugs for nitrous also. I found that most of the manufacturers decrease their heat range number as the plug gets colder. However, NGK was the only manufacturer I found that REVERSED this and raised their number as the plug got colder. FR6-1 would be 1 range colder and FR7-1 would be 2 ranges colder for NGK. From what I could find, the FR5-1 is the recommended stock heat range plug from NGK.

I ended up going with Champions.

 

[Jack B]

The FR5 is definitely a colder plug than the stock Champions, in addition, it is not the extended tip (as the stock is)and the additional mass of the electrode helps retard the glow plug effect. The electrode on the NGK is .010 heavier and only projects .320 versus .450 for the Champion. Because the electrode is closer to the plug mass there less chance to glow.

The car pulls 447 hp/495 ft lb (motor)with either the champions or the NGK. If you use the stock plugs with N2O it is an accident waiting to happen.

As far as the noise - is it possible that you were experiencing some light detonation prior to the installation of the NGK's, I know that is a stretch.

 

[fast?]

just put in ngk fr5-1 spark plugs last week as recommended. now my car seems to be quieter. is this normal for my car to sound this way? less back fire on normal cruizin. i hope mes or jack can chime in on this.

 

[fast?]

thanks for the replies. i guess i shouldn't worry about my sound difference.