Plug gap
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Road Warrior
Joined: Oct 2009
Posts: 1,346
Likes: 3
From: Dallas, Texas
Plug gap
OK, what's the recommended spark plug gap for an '08 1200. I know - it can't be closed but seriously what's the minimum and how much does it really matter? You guys mull it over, in the mean-time I'll be turnin' my garage upside-down looking for my #@?%ing gauges.
Really, I gotta get a life, dickin' around with this **** at this hour & the alcohol ain't helpin'. Really is some dang good Scotch though.
Thanks in advance.
Really, I gotta get a life, dickin' around with this **** at this hour & the alcohol ain't helpin'. Really is some dang good Scotch though.
Thanks in advance.
Road Warrior
Joined: Jul 2007
Posts: 1,898
Likes: 67
From: Saint Amant, Acadiana
The gap less than recommended will probably reduce overall performance a little bit.
The gap more than recommended is bad for your ignition system. As you probably know, high voltage is required to create a spark. There are two factors that determine how high that voltage has to rise. First - the gap, second - the pressure in cylinder. Bigger than recommended gap will result in overvoltage, which puts more stress on insulation in coils and wires.
The gap more than recommended is bad for your ignition system. As you probably know, high voltage is required to create a spark. There are two factors that determine how high that voltage has to rise. First - the gap, second - the pressure in cylinder. Bigger than recommended gap will result in overvoltage, which puts more stress on insulation in coils and wires.
Stellar HDF Member
Joined: Oct 2010
Posts: 2,597
Likes: 180
From: east texas
As a plug ages, and the metal of both the tip and hook erode, the gap will tend to widen; therefore experienced mechanics often set the gap on new plugs at the engine manufacturer's minimum recommended gap, rather than in the middle of the specified acceptable range, to ensure longer life between plug changes. On the other hand, since a larger gap gives a "hotter" or "fatter" spark and more reliable ignition of the fuel-air mixture, and since a new plug with sharp edges on the central electrode will spark more reliably than an older, eroded plug,
experienced mechanics also realize that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs; therefore, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace or re-gap the plugs more frequently, as soon as the tip begins to erode
experienced mechanics also realize that the maximum gap specified by the engine manufacturer is the largest which will spark reliably even with old plugs and will in fact be a bit narrower than necessary to ensure sparking with new plugs; therefore, it is possible to set the plugs to an extremely wide gap for more reliable ignition in high performance applications, at the cost of having to replace or re-gap the plugs more frequently, as soon as the tip begins to erode
Stellar HDF Member
Joined: Aug 2009
Posts: 3,212
Likes: 212
Also, with less of a gap you don't achieve as large of a flame front in the cylinder when it combusts. This reduces your overall chamber pressure and will lead to less efficiency and poor power. It could be too small to even ignite at all.
Too large of a gap can lead to misfiring (flame won't ignite) at high speeds or may not fire at all because it can't jump the gap. This obviously leads to low performance as well.
The gaps are pretty important and are unique to each engine. Sometimes when you modify an engine you need to change your gap accordingly, but this is usually only when you start messing with compression ratios and engine operating speeds. The ignition system is also set to put out a certain electric potential that achieves a specific spark when gapped properly. The wrong gap can be bad for the ignition.
Too large of a gap can lead to misfiring (flame won't ignite) at high speeds or may not fire at all because it can't jump the gap. This obviously leads to low performance as well.
The gaps are pretty important and are unique to each engine. Sometimes when you modify an engine you need to change your gap accordingly, but this is usually only when you start messing with compression ratios and engine operating speeds. The ignition system is also set to put out a certain electric potential that achieves a specific spark when gapped properly. The wrong gap can be bad for the ignition.
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