Best spark plug gap
07-13-2005 | 03:46 PM
#1
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Best spark plug gap for turbo
So Mazda recommends a plug gap of 0.047", if I remember correctly, and Greddy is recommending a gap of 0.030". Well I had some thoughts on this.
0.030 seems like a very small gap, for Iridium plugs since they tolerate larger gaps better than other plugs. The smaller the gap the less efficient the burn, hence less power, but a larger gap increases the chances of misfirings, but also lessens the chance of detonation.
I have tried both 0.047" and 0.030" gaps and I've found the 0.030" gap does seem to provide a better running engine, smoother revs, less hesitation, but I think it may be at the cost of some ponies. So I think the ideal gap is somewhere inbetween. I was hoping some more experienced tuners could chime in on this.
0.030 seems like a very small gap, for Iridium plugs since they tolerate larger gaps better than other plugs. The smaller the gap the less efficient the burn, hence less power, but a larger gap increases the chances of misfirings, but also lessens the chance of detonation.
I have tried both 0.047" and 0.030" gaps and I've found the 0.030" gap does seem to provide a better running engine, smoother revs, less hesitation, but I think it may be at the cost of some ponies. So I think the ideal gap is somewhere inbetween. I was hoping some more experienced tuners could chime in on this.
Last edited by rkostolni; 07-14-2005 at 03:43 PM.
07-18-2005 | 09:58 AM
#3
Consiglieri
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From: yourI'mgirl
Originally Posted by rkostolni
I have tried both 0.047" and 0.030" gaps and I've found the 0.030" gap does seem to provide a better running engine, smoother revs, less hesitation, but I think it may be at the cost of some ponies. So I think the ideal gap is somewhere inbetween. I was hoping some more experienced tuners could chime in on this.
As long as the gas mixture burns, there is no reduction in HP. A stronger spark, as from a cap. discharge tyope ignition, does not give any additional HP. Once you light the mixture, its out of the plug's hands at that point.
07-18-2005 | 11:57 AM
#4
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I agree that a stronger spark does not increase performance, but a larger spark I think does. By increasing the gap you increase the size of the spark, and ignite more fuel helping speed the combustion.
07-18-2005 | 01:35 PM
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I remember reading a suggested rule that you should reduce the gap by 0.003" for every 1 psi of boost. I'll try to find the rule again to make sure I am remembering it correctly. Has anyone else heard something like this.
07-18-2005 | 01:58 PM
#7
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From: yourI'mgirl
The reason for reducing the gap when you add FI is that air/fuel mixtures under high pressure are harder to ignite. The smaller gap helps here.
You don't gain HP by adjusting the gap. You can merely prevent the loss of power. THe loss of power will occur when you get misfires as a result of too large a gap.
directly from NGK:
You don't gain HP by adjusting the gap. You can merely prevent the loss of power. THe loss of power will occur when you get misfires as a result of too large a gap.
directly from NGK:
Originally Posted by NGK
Q: How much of a performance improvement can I expect from changing plugs?
A: A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle's computer can make adjustments so that vehicle operation seems smoother and more seamless.
Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don't understand is that most newer cars' engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can't burn more fuel because there is no more fuel to burn.
When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.
----------------------------------------------------------------------------------------------
Q: Do I need to set the "gap" when installing a new set of plugs?
A: Maybe. A spark plug part number might fit hundreds of engines and, although the factory will typically set the gap to a pre-selected setting, this may not be the right gap for your particular engine. Insufficient spark plug gap can cause pre-ignition, detonation and even engine damage. Too much gap can result in a higher rate of misfires, loss of power, plug fouling and poor fuel economy. It is always best to check the gap against the manufacturer's specifications.
Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005".
If you have any questions, please contact the NGK Sparkplugs Tech Staff here. The manufacturer of your vehicle, the company that produced the aftermarket products you've used and/or your mechanic are all additional sources of gapping information if you've modified your vehicle.
A: A common misconception is that changing spark plugs will result in a large power increase. In most cases, removing even seriously worn out spark plugs will only result in very modest power gains, typically about 1-2% of total engine output. This could be even less for computer-controlled vehicles, primarily because most newer vehicles have more powerful ignition systems and the vehicle's computer can make adjustments so that vehicle operation seems smoother and more seamless.
Many people think that simply supplying more spark to the firing tip can and will combust more fuel. What they don't understand is that most newer cars' engines are so efficient that they are already burning all of the available fuel. Simply adding more spark voltage can't burn more fuel because there is no more fuel to burn.
When a stock or near-stock engine is given a fresh set of spark plugs, peak efficiency is restored. The power gains that come from this restored state of tune are usually minimal. Any company that tells you that their spark plug will provide significant gains in power in a stock or near-stock engine is making blanket statements that may not be supportable.
----------------------------------------------------------------------------------------------
Q: Do I need to set the "gap" when installing a new set of plugs?
A: Maybe. A spark plug part number might fit hundreds of engines and, although the factory will typically set the gap to a pre-selected setting, this may not be the right gap for your particular engine. Insufficient spark plug gap can cause pre-ignition, detonation and even engine damage. Too much gap can result in a higher rate of misfires, loss of power, plug fouling and poor fuel economy. It is always best to check the gap against the manufacturer's specifications.
Another consideration that should be taken into account is the extent of any modifications that you may have made to the engine. As an example, when you raise compression or add forced induction (a turbo system, nitrous or supercharger kit) you must reduce the gap (about .004" for every 50 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology) you can open the gap from .002-.005".
If you have any questions, please contact the NGK Sparkplugs Tech Staff here. The manufacturer of your vehicle, the company that produced the aftermarket products you've used and/or your mechanic are all additional sources of gapping information if you've modified your vehicle.
07-18-2005 | 02:03 PM
#9
Originally Posted by guitarjunkie28
.028 leading and .050 trailing is what i use on gappable plugs.
give a good blend of smooth idle, with less chance of high rpm breakup.
give a good blend of smooth idle, with less chance of high rpm breakup.
07-18-2005 | 04:06 PM
#10
port hacker
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From: socal
^ i should have mentioned i do mostly turbo cars.
you'll more than likely be able to increase your gap. i'd probably start at about .050 trailing, and .045 leading.
be careful with those iridium plugs though...they're delicate and easily broken!
you'll more than likely be able to increase your gap. i'd probably start at about .050 trailing, and .045 leading.
be careful with those iridium plugs though...they're delicate and easily broken!
07-18-2005 | 06:59 PM
#12
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From: Topsail Island, NC
Originally Posted by MadDog
The reason for reducing the gap when you add FI is that air/fuel mixtures under high pressure are harder to ignite. The smaller gap helps here.
You don't gain HP by adjusting the gap. You can merely prevent the loss of power. THe loss of power will occur when you get misfires as a result of too large a gap.
directly from NGK:
You don't gain HP by adjusting the gap. You can merely prevent the loss of power. THe loss of power will occur when you get misfires as a result of too large a gap.
directly from NGK:
07-18-2005 | 08:22 PM
#13
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I think NGk's rule sounds right. i heard a similar rule somewhere else. I could be mistaken, but I don't believe the temp range of the plug will effect the required gap size. I'm just not sure why Greddy is suggested a 0.0030" gap. The is a huge difference from stock and is a very small gap, especially considering were using Iridium plugs which usually tolerate larger gaps.
07-19-2005 | 12:59 AM
#14
port hacker
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From: socal
if you have the time to dyno it for a few hours (and can stand your hands getting burned), try setting the widest gap possible without misfiring at high rpm/load.
some guys would disagree with me, but why not a bur9eq for the trailing? there's such a small hole between that and the combustion chamber that i'm not happy about using "shrouded" plugs in the trailing slots. helps with rough idle in a lot of cases.
AND they're only $5 each at kragen
some guys would disagree with me, but why not a bur9eq for the trailing? there's such a small hole between that and the combustion chamber that i'm not happy about using "shrouded" plugs in the trailing slots. helps with rough idle in a lot of cases.
AND they're only $5 each at kragen
05-06-2011 | 12:06 PM
#15
Sorry, i am bumping this.
From NGK
So what is the answer? Is the way they come fine or is it possible they need to be checked?
From NGK
3. Gapping
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
Since the gap size has a direct affect on the spark plug's tip temperature
and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap settings (to ensure ignitability
in these denser air/fuel mixtures). As a rule, the more power you are making, the smaller the gap you will need.
A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.
With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think.
05-06-2011 | 12:10 PM
#16
The Angry Wheelchair
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From: In da woodz, lurking after you
Since they say they're not pre-gapped I would advise to check them when they come in, no harm in doing so to make sure they're within the spec. If you're turbo'ed that's another story and will vary based on tinkering with them while using a tuner and dyno to see what gives the best performance.
05-06-2011 | 12:31 PM
#17
Since they say they're not pre-gapped I would advise to check them when they come in, no harm in doing so to make sure they're within the spec. If you're turbo'ed that's another story and will vary based on tinkering with them while using a tuner and dyno to see what gives the best performance.
I looked in the FSM but could not find the gap. Is it on the box for the plugs?
05-06-2011 | 12:42 PM
#20
07-31-2011 | 03:26 PM
#21
The Angry Wheelchair
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From: In da woodz, lurking after you
Just an update:
I checked the NGK ones that came in and they were quite a bit below Mazda's recommendation, at the most they were around 0.04in for one, the rest were below that. Since the gap can be adjusted with these plugs I recommend checking them and setting them to the proper gap.
I checked the NGK ones that came in and they were quite a bit below Mazda's recommendation, at the most they were around 0.04in for one, the rest were below that. Since the gap can be adjusted with these plugs I recommend checking them and setting them to the proper gap.
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