the fuel filter back to front!!! I had a major service last september and the mech installed a new fuel filter as part of the service. Ive only just noticed. Could be contributory to the detonation & low power at high revs problems if there is fuel starvation.

 

Just replaced it.

 

Q. I am looking to replace my plugs. I am currently using Bosch/botch Platinum LOL. Has NE1 had problem using these plugs before?

 

Trying NGK PRF6B - ? (11b or 11c)

 

C is standard and I think b is a cooler plug. NE1 using them? What do you think?

 

Running 13.5 psi so I guess a cooler set of plugs are now needed?

 

Im also going to try some of this Redline Water Wetter that the guys in the US keep raving about. I will keep you all posted on the results.

 

Cheers,

 

Andy.

 

6B-11B's are the puppies to use, they have a longer shroud length which brings the heat of the initial combustion down lower in the chamber away from the cylinder head which limits detonation.

 

Rowan

 

 

 

I think that the 11c plug has the longer shroud length??

 

The 'B' plug doesn't mean that it's cooler.

 

If you want cooler then go to PFR 7B 11.

 

I bought some cooler PFR7B11B from the U.S and my Z ran like an old donkey.

 

I measured my original PFR6B11c plugs against them and the 11c plug shroud length was longer.

 

I spoke to NGK who said that the reason for the extra length was because of emission control.

 

I still run PFR6B11c now.

 

Steve.

 

I'm not sure where the -c's fit into the equation but here's my understanding (and a picture).

 

The 6b-11's are the "standard" plugs, these are what you buy off the shelf from Nissan/NGK.

 

Nissan commissioned NGK to make the 11b's to control detonation problems, the 11b's have a much longer shroud length than the 11's. In NZ and Aussie we can't actually buy the 11b's as they're a phenomenom only avaliable in the US (maybe Europe I'm not sure). You ask NGK down here and they say the thing doesn't exist... but it does and here's the proof

 

On the left the 6B-11, on the right 6B-11B:

 

God knows what the 11c is, never seen it. If you're running high boost with big turbos then you should consider going to the 7 series plug as the 6's may detonate. But with the 7's you'll get cold running problems. One of my friends who's running 7's if he's to eager on the throttle when cold will get big amounts of misfiring, and if the engine is running rich you may get hard starting problems as the plugs don't get hot enough to reach their self cleaning temperature. Eg one day after drag racing he couldn't get his car to start from carbon build up on the plugs.

 

Rowan

 

Thanks guys.

 

The NGK website states that the standard plug for the 300zx TT is PFR5B-11C. I also checked this with my local auto part supplier. This might be for UK spec Z's though! I stand corrected Steve, the 4th character relates to the heat range so PFR6B-11C would be one plug cooler which I think is what I need. The 5th character is the firing end contruction as NGK call it. The 11 is 1.1 MM gap. Last character - does not say.

 

The 11's are for the N/A's and the 11B's for the TT's (according to guys in US and NGK web site)

 

They have slightly difference engine specs in the US compared to ours in the UK and Japan I think Rowan. Their quality fuel is 92 octane! The heads might be different. hence 11b over 11c.

 

I will find out from NGK UK tomorrow on whether I should use 11B, or 11C but if yours is fine with the PFR6B-11C's Steve then I will probably go with them. I think we are running similar power.

 

Cheers,

 

Andy

 

REF. www.ngksparkplugs.com

 

 

 

FYI I've used 11b's on a daily driven Jap spec TT since August last year without any problems, including a couple of racetrack outings and a couple of drag day outings.

 

I wouldn't run it on the 5's though, that sounds like a recipe for disaster!

 

Rowan

 

The US octane is worked out in a different way. Take the UK octane value (RON)and -4 to get the equivalent US value.

 

So their 92 is actually 96 in the UK.

 

Ok, so here's the deal.

 

Standard plug PFR5B-11C

one step cooler PFR6B-11C (For anyone running 50+BHP extra)

 

PFR6B-11B is slightly shorter than the PFR6B-11C. This was requested by Nissan (US) especially for Z's. I think to reduce detonation. Rowan, I think you have compared the 11B to the 11 and not the 11C. 11 is the shortest, then the 11B and finally the 11C being the longest. (11B approx 19mm, 11C approx 21mm) The 11 being for the N/A. Anyone running serious BHP , and I mean serious or shifting around the track then you may need to go to PFR7B-11B/C (much cooler!)

 

One only thing to clear up is B or C. It looks like B is the way to go. The US guys swear by them and so does JWT. Thanks to Dave an his explaination on their fuel. It looks like we are running similar octane levels. Shall I be a guinea pig? .... unless someone in the UK already uses them!

 

Andy.

 

Just to add to the confusion, I was told by Jez that the standard UK plugs are colder versions than the standard US plugs, i.e. PFR6B-11. No idea whether that's B or C though.

 

So don't buy from the US and ask for the 'standard' TT plugs as you'll probably end up with 5s rather than 6s.