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Stock Spark Plugs - heat range?

Looking at the stock plugs (Denso FXE24HR11), they are a "24" heat range (equivalent to an NGK "8" heat range). Any idea why our NA V6 has such cold plugs

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Old 06-27-2010, 11:17 AM   #1 (permalink)
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Default Stock Spark Plugs - heat range?

Looking at the stock plugs (Denso FXE24HR11), they are a "24" heat range (equivalent to an NGK "8" heat range). Any idea why our NA V6 has such cold plugs stock? From my research the GT-R has basically the same plug specs (heat range 8) but a different tip/electrode.

I'm just used to heat range 6 plugs in N/A V6's. I know the VQ35HR uses the same plugs, except 1 range hotter. I can't imagine having to run a "10" heat range plug with 200 hp over stock; that's not streetable at all.
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Old 06-27-2010, 09:34 PM   #2 (permalink)
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I generally don't know anything about the spark plugs. but I have been wondering would installing "stronger' ones improve the performance?
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Old 06-27-2010, 11:17 PM   #3 (permalink)
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Originally Posted by Vegitto-kun View Post
I generally don't know anything about the spark plugs. but I have been wondering would installing "stronger' ones improve the performance?
No, very likely not. There were major gains with ignition upgrades before cars starting coming with full coil on plug systems... now, you'll really only see any ignition system performance gains if you're running boost (and lots of it).

The stock ignition system, including spark plugs (with dropping 1 heat range), is probably adequate for up to a bar or so of boost.
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Old 06-28-2010, 12:26 AM   #4 (permalink)
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Probably because the motor is high compression and tends to run on the hotter side given the occasional oil temp issues.

Hotter plugs are probably prone to some pinging. Although, if you run 93 AKI (or higher) you would probably be fine with slightly hotter plugs -- remember, the engine is tuned and set up to run on 91.

That said, read p. 9-4 of the owner's manual... they claim some light knock under load acellerating up hills is normal

You could also try playing with the gap, I suppose, but if it runs good, why mess with it?
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Old 06-28-2010, 01:40 AM   #5 (permalink)
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Originally Posted by Jordo! View Post
Probably because the motor is high compression and tends to run on the hotter side given the occasional oil temp issues.

Hotter plugs are probably prone to some pinging. Although, if you run 93 AKI (or higher) you would probably be fine with slightly hotter plugs -- remember, the engine is tuned and set up to run on 91.

That said, read p. 9-4 of the owner's manual... they claim some light knock under load acellerating up hills is normal

You could also try playing with the gap, I suppose, but if it runs good, why mess with it?
Honestly I've been building and tuning boosted engines for the past 5 years... I really don't think this setup needs 8 heat range plugs. A 13:1 engine might, though. There must be something about the cylinder head design that allows Nissan to get away with running such a cold plug with no fouling issues. That's more of the info I was interested in getting - I just read most of the service manual today, and nothing there.

The heat range of a plug dictates how much heat the spark plug can carry away from itself and the area surrounding the electrode. Really, it's just a way to prevent detonation and pre-ignition by eliminating the spark plug as a potential hot spot in the cylinder. I haven't spent much time looking at stock AF curves, but maybe the motor runs lean enough stock to warrant this extra protection.

I know my Evo X has basically the same plug design, and heat range (8) stock. But it essentially runs 20+ CR (boost PR * combustion chamber CR) under full boost stock (19-ish psi). At 32 psi, I was only needing a 9 heat range plug. Similar modern combustion chamber design, but I know it's not the same engine at all.

But you have a good point with the owner's manual comment and such. A 3.7 L V6 making 332 bhp on 91 octane stock is pretty much pushing the limits to begin with.

This is just a question of curiosity and thinking about boosted applications on the Z, not looking to mess with anything; so I'm not sure how plug gaps are relevant. I don't really like messing with gaps on iridium-tipped plugs anyway; too much room for mistakes and potential broken plugs inside the combustion chamber!
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Old 06-28-2010, 01:51 AM   #6 (permalink)
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And BTW, stock plug gap spec seems to be 1.1 mm (0.043 in), which is actually pretty wide for a high compression engine. That said, you probably couldn't gain any power by opening that up at all. And I doubt you'd regain any power by closing it up (assuming any spark suppression is present at all with our COP system).

edit: oh, and on the oil temp idea: really, the oil temperature elevation on these engines is testament to how well the oiling system is carrying away extra heat from piston skirts, bearing surfaces, wrist pins, etc. under high load. The temperature in the combustion chamber is most directly related to coolant temperature, and I haven't heard of anybody reporting that ever spiking. Besides, 240-260 degrees isn't that hot as far as oil goes. Air-cooled Porsche engines were sustaining much higher oil temperatures back when automotive oil technology was relatively primitive.
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Old 06-28-2010, 04:12 AM   #7 (permalink)
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^^^ I'm really just speculating.

My old 11.5:1 2ZZ took IK20's -- although, it only made about 180 at the crank.

I can only assume the 24's clean up under load -- irridiums have a pretty wide range they operate well under, don't they?

You're proably right about it being tuned to run relatively lean at low load (and maybe even during cold enrichment) -- I think this motor is considered ULEV.
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Old 06-28-2010, 10:35 AM   #8 (permalink)
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^^^ I'm really just speculating.

My old 11.5:1 2ZZ took IK20's -- although, it only made about 180 at the crank.

I can only assume the 24's clean up under load -- irridiums have a pretty wide range they operate well under, don't they?

You're proably right about it being tuned to run relatively lean at low load (and maybe even during cold enrichment) -- I think this motor is considered ULEV.
Actually iridium-tipped plugs have really good anti-fouling properties because of the fine tip size (among other things I'm sure).

It's just really odd to me how the 370Z comes with the same plugs included with (essentially, minus the double iridium config and tighter factory gap on the GTR plugs) a boosted engine (the VK38DETT) that makes 40% more specific power.
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Old 05-01-2012, 01:02 AM   #9 (permalink)
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Anymore on the topic
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Old 05-02-2012, 02:42 AM   #10 (permalink)
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Nothing?

Usually we have experts on here.
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Old 05-04-2012, 11:54 AM   #11 (permalink)
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Talking NGK copper sparkplugs

I have a Nissan Motorsports oil cooler installed and went one step warmer. I run NGK coppers, LZKAR7A (6799) gapped @ 1.1mm.
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Old 05-04-2012, 04:36 PM   #12 (permalink)
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^^^ They won't last as long...

Why the switch? Any differences in how it runs?
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Old 11-08-2013, 12:37 AM   #13 (permalink)
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Not to bring resurrect an old thread but I think the reason why the vq37vhr uses basically the same plug and the vr38dett is that our engines are high compression and the vr is boosted which brings up compression
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Old 11-08-2013, 02:37 PM   #14 (permalink)
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Quote:
Originally Posted by Jordo! View Post
^^^ They won't last as long...

Why the switch? Any differences in how it runs?
They'll last ~30k miles. I don't want a spark plug in my head for over 50k miles PERIOD.
I switched because w/an upgraded oil cooler the stock heat range of 8 is to cold. It runs the same and I'm receiving combined ~17 MPG w/my 4.30 final drive.

Quote:
Originally Posted by Nuccigucci View Post
Not to bring resurrect an old thread but I think the reason why the vq37vhr uses basically the same plug and the vr38dett is that our engines are high compression and the vr is boosted which brings up compression
I agree w/this.
The VQ37VHR (11:1) uses the same plug cuz it runs hot in OEM trim. No oil cooler OEM 'till 2012 and then still inefficient! The VQ37VHR compression is 0.4 higher than the VQ35HR (10.6:1).
The VQ35HR uses a 7 heat range plug and doesn't have an oil cooler OEM -which I'm sure runs hot too.
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Old 05-13-2014, 01:50 PM   #15 (permalink)
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So, the best way to go with this is OEM replacement for plugs?

How about on a boosted system? OEM plugs will be fine?
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