spark plug discussion

[solaire]

so in a way this is a diagnosis session for me but maybe it'll help someone else in the future with spark plugs in these cars. I keep reading how sensitive the plugs are in our cars. so..

Exactly how sensitive are our cars to spark plugs? I've been working on 91 for awihle chasing misfires that tend to "move" all over the engine. Here's what I've got
In my car: PFR5B-11 Iridium platinums I got from the local store since I didn't know about Z1's plugs then.
In this 91: BKR5E-11 Copper plugs you can pick up for $2.09 at the local advance auto parts. This car was driven to me perfectly fine and after fixing the injector connectors it has a bad misfire. so back to my original question at hand.

Are our cars really that sensitive to plugs? Could copper plugs cause this issue?

[NolimitZ32]

YES, use the OEM plug.

[solaire]

Then what do you think would have made this car that's running NGK copper plugs pull harder than my 90 with 84k that runs perfectly?

[NolimitZ32]

Definitely not the plugs. the 90s had head machining issues from the factory, could be that, or could be that your rings are slightly more worn, or that your TPS is a couple degrees off from true, or that your cats are slightly blocked, or the oil you're running. Two identical 24 year old cars, even well maintained could easily have a differential in HP of 10% or more. Metal isn't everlasting, plus if the 2 cars are identical apart from having had the exact same life then there shouldn't be a massive difference in how they "pull". The reason you should use the OEM plugs or a fitting replacement is because the plugs in the VG are longer than other "standard" plugs so sticking in shorter plugs puts the ignition source for the fuel/air mixture in the wrong place, this causes the car to lose power. Can autozone plugs be ran in a VG? Yes. Will it always cause problems? No. But if you want your car to run right than you need to run the OEM set.

[solaire]

That's a bit more technical which is what i was looking for.

[t.mcginley.jr]

Basically Nissan partnered with NGK when they built these cars to have a specific spark plug made for the NA and the TT because no other plugs they tried would make the engines run correctly. So........ basically the OEM plug is always the best choice in this case. If it was any other car it wouldn't be that huge of a deal.

[solaire]

Makes sense. Anything else will mess with pretty much any newer Nissan with CoP ignition system also. I'm just trying to figure out how this car ran with NGK copper plugs before I got my hands on it.

[NolimitZ32]

We're not saying that it wont run, I ran mine for some time on the wrong plugs and it ran just fine without any misses or CELs but it wasnt running 100%, there was power loss is all.

[ThisIsSparTTa]

I was running the PFR6B-11B in my TT that everyone says to use, and that worked fine when I had my boost jets for ~14PSI. However after my rebuild and adding in an EBC, even running 12PSI I was getting misses. Greg@SpecialtyZ pointed out that they recommend BKR7EIX for running 9-16PSI for the extended heat range and gap. Said that the length difference wasn't an issue for them, and they had done dyno testing on the same car swapping plugs to show that the Iridiums actually produced more power. Anyways, I switched over to the BKR7EIX and the rest of my issues vanished. I keep on trying to spread that word around, because it comes from a reputable source, and a lot of people still say PFR6B-11B is the only plug to run in a TT.

[NolimitZ32]

You are absolutely correct, tuners and builders suggest running the NGK Iridiums (R7) once you up the boost, however once that's done the dynamics of combustion change and a colder plug will benefit the engine more that the longer factory heat range plug, TT and NA like their OEM plugs in factory trim and the TT takes the colder with raised boost . I am currently running 1 BAR on HKS2530s with the R7 plugs and 0 issues. But then I am tuned for higher boost. I could get into the engineering behind this but would honestly need a few days to polish up on the specifics. Page 18 of the Maintenance section in the FSM has the table.

Standard NA - PFR6B-11
Hot NA - PFR5B-11
Cold NA - PFR7B-11

Standard TT - PFR6B-11C (now 11B IIRC)
Hot TT - PFR5B-11C (now 11B IIRC)
Cold TT - PFR7B-11C (now 11B & no longer made IIRC)