lets talk spark plug gap for ls2 coils - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

quickdiversion · 06-08-2014, 04:03 PM

I am running NGK 7 plugs and have kept the spark plug gap stock, around .30

Now I am noticing possible light misfiring at idle and light town driving and smelling like fuel with when it reads lean. The car is not fully tuned yet, but will be soon. Also at 18 psi It feels a bit like a flat flooding, but still running feeling, yes part of the tune, but with 1000cc injectors, I need some more gap.

They are legit ls2 truck coils 120Mj.

I was thinking about starting the gap around .36 and going up slightly from there. Yes it seems large, but the coils pump a lot of juice and work high gaps in high compression v8's. I can go either way from there

Anyone with any ideas or inputs for other starting places and why?

quickdiversion · 06-08-2014, 07:45 PM

No one is thinking this is either to small or to large a starting point?

lol

Kingtal0n · 06-11-2014, 03:58 PM

The bigger the better. Always run as big of a gap as you can support. If it holds spark during boost then there is no reason it should misfire when lean.

If you are getting misfires from being lean you are either leaner than you think you are, or the spark is in the wrong place, (try indexing your plugs, make sure they extend into the combustion chamber and you are using the right part # for the head), or your fuel atomization is poor (common with large injectors at low duty cycles and low fuel pressure)

I thought you had an LSx engine. I see now you have an SR20DET so scratch that nonsense about the plugs location/index.
What sort of manifolds/camshafts you have that adversely affect air velocities and poor fuel atomization may be your culprit. try raising your fuel pressure just to see if it helps (reduce fueling at the ECU to compensate)

ultimateirving · 06-11-2014, 04:02 PM

I have lq9 coils myself and have the gap around .30 iirc, but i was getting some blowout if i gapped any larger when hitting around 20psi.

I have rewired a few grounds and cleaned all the terminals when i had the engine out recently. Once i get on the road and can do some pulls i can start to mess with the gap again and truly test my limit.

quickdiversion · 06-12-2014, 11:50 AM

Quote:

Originally Posted by Kingtal0n

What sort of manifolds/camshafts you have that adversely affect air velocities and poor fuel atomization may be your culprit. try raising your fuel pressure just to see if it helps (reduce fueling at the ECU to compensate)

I am running a greddy intake, and crx racing top mount manifold for the exhaust. Only reason for the CRX is due to it places the turbo between cylinders 1 and 2 and not 2 and 3, giving me much more room by the booster and keeping it cooler. Turbo is a HX35 7 blade. Cams are 270 in and 270 out tomei high lift, solid lifters, and yes, shimmed.

quickdiversion · 06-12-2014, 11:51 AM

Quote:

Originally Posted by ultimateirving

I have lq9 coils myself and have the gap around .30 iirc, but i was getting some blowout if i gapped any larger when hitting around 20psi.

I have rewired a few grounds and cleaned all the terminals when i had the engine out recently. Once i get on the road and can do some pulls i can start to mess with the gap again and truly test my limit.

I am gonna buy new plugs today and start around .30 maybe .31

quickdiversion · 06-14-2014, 11:19 AM

OK so I finally got my hands on a spark plug gapper, new plugs, and a nice day.
I get the new plugs all set up for .36 gap and start pulling the old ones. The old ones are at .42 gap.

So maybe I was backwards?
Its not fuel blowing out to small of a gap its air blowing out to large of a gap?

Haha no Idea why they were at .42 but thats gonna change.

ultimateirving · 06-14-2014, 09:09 PM

Just put new plugs in. Blew out the spark at 18.2 psi and .030 gap. I'm gonna drop to .028

EEDIT!!!
Fixed my blowout it was due to spark plug
Boot being loose.
Just ran up to 20.1psi with 0 hiccups!!
.030 gap was perfect.

quickdiversion · 06-14-2014, 09:49 PM

Old plugs were all at .42, nit sure why. At 18 psi I would read below 10 at 3/4 throttle.
New plugs from test were dropped down to .32 for test run. Normal driving they seem fine. Tomorrow I will be able to really boost. Who knows I might be going for like .50 gap for these coils packs.

ultimateirving · 06-15-2014, 09:15 AM

Quote:

Originally Posted by quickdiversion

Old plugs were all at .42, nit sure why. At 18 psi I would read below 10 at 3/4 throttle.
New plugs from test were dropped down to .32 for test run. Normal driving they seem fine. Tomorrow I will be able to really boost. Who knows I might be going for like .50 gap for these coils packs.

Not likely I had high hopes for running a huge gap. But the spark still gets blown out.

06-08-2014, 04:03 PM	#1
quickdiversion Zilvia Junkie Join Date: Aug 2012 Location: nj Age: 41 Posts: 341 Trader Rating: (4) Feedback Score: 4 reviews	lets talk spark plug gap for ls2 coils I am running NGK 7 plugs and have kept the spark plug gap stock, around .30 Now I am noticing possible light misfiring at idle and light town driving and smelling like fuel with when it reads lean. The car is not fully tuned yet, but will be soon. Also at 18 psi It feels a bit like a flat flooding, but still running feeling, yes part of the tune, but with 1000cc injectors, I need some more gap. They are legit ls2 truck coils 120Mj. I was thinking about starting the gap around .36 and going up slightly from there. Yes it seems large, but the coils pump a lot of juice and work high gaps in high compression v8's. I can go either way from there Anyone with any ideas or inputs for other starting places and why?

06-11-2014, 03:58 PM	#3
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,829 Trader Rating: (17) Feedback Score: 17 reviews	The bigger the better. Always run as big of a gap as you can support. If it holds spark during boost then there is no reason it should misfire when lean. If you are getting misfires from being lean you are either leaner than you think you are, or the spark is in the wrong place, (try indexing your plugs, make sure they extend into the combustion chamber and you are using the right part # for the head), or your fuel atomization is poor (common with large injectors at low duty cycles and low fuel pressure) I thought you had an LSx engine. I see now you have an SR20DET so scratch that nonsense about the plugs location/index. What sort of manifolds/camshafts you have that adversely affect air velocities and poor fuel atomization may be your culprit. try raising your fuel pressure just to see if it helps (reduce fueling at the ECU to compensate) __________________ 5.3/4l80e/turbo 240sx playthrough: tinyurl.com/4l80er

06-11-2014, 04:02 PM	#4
ultimateirving Zilvia FREAK! Join Date: Nov 2010 Location: arizona Age: 36 Posts: 1,521 Trader Rating: (1) Feedback Score: 1 reviews	I have lq9 coils myself and have the gap around .30 iirc, but i was getting some blowout if i gapped any larger when hitting around 20psi. I have rewired a few grounds and cleaned all the terminals when i had the engine out recently. Once i get on the road and can do some pulls i can start to mess with the gap again and truly test my limit. __________________ Z32 with lq4 swap Desert Street Scene \|\| Dssevents.com

06-14-2014, 09:09 PM	#8
ultimateirving Zilvia FREAK! Join Date: Nov 2010 Location: arizona Age: 36 Posts: 1,521 Trader Rating: (1) Feedback Score: 1 reviews	Just put new plugs in. Blew out the spark at 18.2 psi and .030 gap. I'm gonna drop to .028 EEDIT!!! Fixed my blowout it was due to spark plug Boot being loose. Just ran up to 20.1psi with 0 hiccups!! .030 gap was perfect. __________________ Z32 with lq4 swap Desert Street Scene \|\| Dssevents.com Last edited by ultimateirving; 06-16-2014 at 02:20 PM..

06-08-2014, 07:45 PM	#2
quickdiversion Zilvia Junkie Join Date: Aug 2012 Location: nj Age: 41 Posts: 341 Trader Rating: (4) Feedback Score: 4 reviews	No one is thinking this is either to small or to large a starting point? lol

06-14-2014, 11:19 AM	#7
quickdiversion Zilvia Junkie Join Date: Aug 2012 Location: nj Age: 41 Posts: 341 Trader Rating: (4) Feedback Score: 4 reviews	OK so I finally got my hands on a spark plug gapper, new plugs, and a nice day. I get the new plugs all set up for .36 gap and start pulling the old ones. The old ones are at .42 gap. So maybe I was backwards? Its not fuel blowing out to small of a gap its air blowing out to large of a gap? Haha no Idea why they were at .42 but thats gonna change.

06-14-2014, 09:49 PM	#9
quickdiversion Zilvia Junkie Join Date: Aug 2012 Location: nj Age: 41 Posts: 341 Trader Rating: (4) Feedback Score: 4 reviews	Old plugs were all at .42, nit sure why. At 18 psi I would read below 10 at 3/4 throttle. New plugs from test were dropped down to .32 for test run. Normal driving they seem fine. Tomorrow I will be able to really boost. Who knows I might be going for like .50 gap for these coils packs.