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Thread: Spark plugs on high hp high comp n/a ve setups

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2014-01-01 21:02:13
Spark plugs on high hp high comp n/a ve setups
I'm curious what plugs everyone are running in their high hp, high comp or even big bore setups? At what point would you go to a 7,8 or even 9 range plug and if anyone has noticed any behaviour or hp gains on certain heat ranges.

I'm currently running a 8 plug in my 12.x cr motor and I'm wondering if it's overkill. Can it hurt hp?
2014-01-01 21:49:19
Im running 7 on mine 12:1
2014-01-03 13:44:42
Technically running the hottest plug that you can will be best. A colder plug has a larger ceramic element to avoid overheating under higher power applications. That larger element will soak up heat around the spark. The initial light and burn (this is called kernel development) is the slowest portion of the ignition cycle so having a colder plug will slow it down even more (less heat, less speed). This means with a colder plug you are "safer" but a slower burn means more timing advance needed to get maximum work from each burn, and this means less horsepower.

As for a higher compression VE, I am not sure what the hottest plug you can run will be so sorry I cannot offer direct advice there. But I don't see why the standard heat range wouldn't run well with only a small bump in CR.

2014-01-03 14:22:54
At least on my 13:1 88mm motor I could not use Standard 5 Heat range plug since the tip of the plug touched the dome of the piston!! 6 or 7 are fine for ALL MOTOR 12.5-13:1 motor!!
2014-01-03 15:42:55
Ran both 6 and 7 on my 2.4 12.5:1 the 7 actually made 2-3 more Hp.

Sent from my GT-I9300 using Tapatalk
2014-01-03 16:35:02
Running 6's on my 12.5 88mm VE. Never tested 7's but i might the next time i am on a dyno.
2014-01-06 19:54:38
Thanks for the info dudeman. Also interesting to see you guys running 6's!

I'm must admit that my motor itself gets physically pretty hot. Hotter than I recall previous builds. Could be the 8 plugs transferring heat to the head I guess. I'm just trying to be safe and avoid any possibility of detonation. I'm running a maximum of 30 deg timing and around 28 at peak hp. Bear in mind we have shittier fuel and much warmer climates here.
2014-01-06 20:28:48
Docter G,

You're welcome. I always like a good question when I see one. Hope I was able to make things a little clearer. Just since I am OCD I'll throw in a little more info.....

I wanted to point out that if your are concerned about detonation you will want to run the hotter plug within safe limits. A hotter plug will help prevent detonation in two ways: First, as I briefly explained earlier, the quicker burn will avoid detonation. Second due to a quicker burn the engine's timing can be retarded to make maximum power vs a hotter plug which would "want" advance to make peak power. Both of these factors lead to less heat before the piston reaches TDC (a good thing). Suffice to say that you want peak heat right after TDC and the hottest SAFE plug will be best for this. One last note is that a spark plug likes to run within a temperature range to avoid carbon deposits forming on the surfaces so going too cold can lead to misfires also.

You would need to run a hotter plug as you increase power since as we know the increased temperatures from high compression/boost/nitrous/toomuchtimingadvance can lead to the plug becoming so hot you have pre-ignition which is NOT detonation. Pre-ignition simply melts your piston away since you basically have a burn beginning WAY before the piston reaches TDC. Cylinder temperatures will spike to an insanely high level as the piston is trying to compress, and melty melt poof....game ovah. This is extremely rare btw...

That said, those are the extreme's so don't think you are going to do any damage if you are running a relatively safe tune, which is always #1 to avoid detonation (your timing sounds within reason btw).

I wouldn't worry about it much but if other's are getting away with 6's or 7's I say go for it!

2014-01-13 11:49:58
I am running NGk bkr5eix , 5s iridiums..seems fine when i ran the drags (multiple passes) and now using them for daily

altough i should be using 6 for daily

i have stock bottom end with n1 cams, maybe ill be needing 6s with 16ve pistons?
Last edited by b12sr20ve on 2014-01-13 at 11-51-22.
2014-01-15 00:55:29
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