Plug Gapping - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

*sykikchimp* · 07-08-2002, 01:04 PM

I know that the smaller the gap of the plug the higher the chance of pre-detonation (pinging), but you should lower the gap the more HP you get with mods.. now my question.
How much does plug gap affect performance?  factory gap specs are like .039 - .043.  If you put in plugs that were gapped to .044 how would that affect performance?

uiuc240 · 07-08-2002, 01:47 PM

you might get slightly better gas mileage and a vague increase in power, but you also run the risk of the spark "blowing out"...especially as the plugs wear (causing the gap to grow).  the only good way to run bigger gaps than stock is to use hi-po ignition systems (crane and jacobs recommend big gaps...usually .050").  but that's because they have like 60 kV of juice to light the spark.  oh, but too small of a gap may cause the spark to be too small, therefore not burning enough of the air/fuel mixture.  go with OEM and you'll be fine <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt='

'>

Eric

*sykikchimp* · 07-08-2002, 03:21 PM

vg1. well.. I didn't have a plug gap gauge so I figured .044 (stock gap on NGK's) would be fine.  It's been working fine for about a month now. Since I put on my exhaust I feel like I've lost about 300rpm of power up top, and I was thinking maybe the plug gap was just a touch too big, and is getting pushed a lttle too hard in the upper rev range. do you guys think that could be it? or maybe something else?  I'm thinkin about getting an new ignition coil too..  like MSD or Jacobs..  

edit - stupidness

uiuc240 · 07-08-2002, 03:48 PM

well, that could be it...you might be losing spark up top in the revs.  it's easy enough to check gap.  get a gap tool at an autoparts store.  piece of cake.  just be careful not to f up the electrode when you do it.  oh, and how are your plug wires/cap/rotor??  fuel filter?  air filter?

by the way, skip jacobs.  i had one on an old jetta.  it did basically nothing.  your OEM ignition should be fine for now (unless you have a T88 and 30 psi and you just haven't told us yet <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt='

'>).  i'd say just freshen everything up and check plug gap and see how that does for ya.

Eric

bbp · 07-09-2002, 08:09 AM

now remember, by intalling an aftermarket exhaust with a larger diameter pipe, you may lose some top end power.  I doubt the plug gap has anything to do with it.

If your motor is stock, the stock ignition will work just fine....

*sykikchimp* · 07-09-2002, 03:43 PM

ok..  why would you loose top end with a larger exhaust?  It would seem like you would loose lowend due to lower gas velocities?

I already changed all the other stuff...  brand spankin new filters, lubes, wires, etc..  everything..  I was just to lazy to go to napa and pick up a gap gauge.

uiuc240 · 07-09-2002, 04:14 PM

i was wondering if someone was going to touch on that too.  i disagree with the lack of top end with a big exhaust.  in fact, it's totally the opposite.  small piping will give good torque but squeeze airflow up top.  no good.

i say check those plugs <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt='

'>

Eric

07-08-2002, 01:04 PM	#1
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 44 Posts: 6,525 Trader Rating: (0) Feedback Score: 0 reviews	I know that the smaller the gap of the plug the higher the chance of pre-detonation (pinging), but you should lower the gap the more HP you get with mods.. now my question. How much does plug gap affect performance?  factory gap specs are like .039 - .043.  If you put in plugs that were gapped to .044 how would that affect performance? __________________

07-08-2002, 01:47 PM	#2
uiuc240 Nissanaholic! Join Date: Apr 2002 Location: Naperville, IL Age: 46 Posts: 2,093 Trader Rating: (0) Feedback Score: 0 reviews	you might get slightly better gas mileage and a vague increase in power, but you also run the risk of the spark "blowing out"...especially as the plugs wear (causing the gap to grow).  the only good way to run bigger gaps than stock is to use hi-po ignition systems (crane and jacobs recommend big gaps...usually .050").  but that's because they have like 60 kV of juice to light the spark.  oh, but too small of a gap may cause the spark to be too small, therefore not burning enough of the air/fuel mixture.  go with OEM and you'll be fine <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''> Eric __________________ 2002 Mazda Protege5 1989 S13 w/SR20DET (sold)

07-08-2002, 03:21 PM	#3
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 44 Posts: 6,525 Trader Rating: (0) Feedback Score: 0 reviews	vg1. well.. I didn't have a plug gap gauge so I figured .044 (stock gap on NGK's) would be fine.  It's been working fine for about a month now. Since I put on my exhaust I feel like I've lost about 300rpm of power up top, and I was thinking maybe the plug gap was just a touch too big, and is getting pushed a lttle too hard in the upper rev range. do you guys think that could be it? or maybe something else?  I'm thinkin about getting an new ignition coil too..  like MSD or Jacobs..   edit - stupidness __________________

07-08-2002, 03:48 PM	#4
uiuc240 Nissanaholic! Join Date: Apr 2002 Location: Naperville, IL Age: 46 Posts: 2,093 Trader Rating: (0) Feedback Score: 0 reviews	well, that could be it...you might be losing spark up top in the revs.  it's easy enough to check gap.  get a gap tool at an autoparts store.  piece of cake.  just be careful not to f up the electrode when you do it.  oh, and how are your plug wires/cap/rotor??  fuel filter?  air filter? by the way, skip jacobs.  i had one on an old jetta.  it did basically nothing.  your OEM ignition should be fine for now (unless you have a T88 and 30 psi and you just haven't told us yet <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/wink.gif" border="0" valign="absmiddle" alt=''>).  i'd say just freshen everything up and check plug gap and see how that does for ya. Eric __________________ 2002 Mazda Protege5 1989 S13 w/SR20DET (sold)

07-09-2002, 08:09 AM	#5
bbp Zilvia Junkie Join Date: Apr 2002 Location: oHIo Age: 53 Posts: 477 Trader Rating: (0) Feedback Score: 0 reviews	now remember, by intalling an aftermarket exhaust with a larger diameter pipe, you may lose some top end power.  I doubt the plug gap has anything to do with it. If your motor is stock, the stock ignition will work just fine.... __________________

07-09-2002, 03:43 PM	#6
sykikchimp WOW addicted Join Date: Dec 2001 Location: the moon Age: 44 Posts: 6,525 Trader Rating: (0) Feedback Score: 0 reviews	ok..  why would you loose top end with a larger exhaust?  It would seem like you would loose lowend due to lower gas velocities? I already changed all the other stuff...  brand spankin new filters, lubes, wires, etc..  everything..  I was just to lazy to go to napa and pick up a gap gauge. __________________

07-09-2002, 04:14 PM	#7
uiuc240 Nissanaholic! Join Date: Apr 2002 Location: Naperville, IL Age: 46 Posts: 2,093 Trader Rating: (0) Feedback Score: 0 reviews	i was wondering if someone was going to touch on that too.  i disagree with the lack of top end with a big exhaust.  in fact, it's totally the opposite.  small piping will give good torque but squeeze airflow up top.  no good. i say check those plugs <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=''> Eric __________________ 2002 Mazda Protege5 1989 S13 w/SR20DET (sold)