Cant believe

[98svtlocal80215]

i know it takes hours to do this but its worth it ....read it and tell me what you think....:shrug:

well i cant beleive how much of a diff it makes when you go through the sensors inspect clean wrap ect, and all the maintance you can do to the car as a hole........ including maf,egr,tb, intake and ..................what i found to be one of the best things you can do...!... gaping the plugs at .45 rather than the factory .60 to which they come i mean i dont really know how it works but smother running shifting everything.......ive always been a do it right kinda guy from the start and doing All that you can will not only improve your knowledge of the car and help the car....
]

 

[BrApple]

um stock plug gap is suppose to be 54 thousanths not 60 ....

 

[98svtlocal80215]

Chit ejimacated and dislexic Chit Chit Chit got to pull it apart again........now to spend the next ten hours thinking of what else i can screw up the old hard drive is a little sloww these days...Chit...:nonono:

 

[Big Jim]

The gap is supposed to be between .052" and .056". It is my practice to gap plugs at the wide end of spec, so I gap mine at .056".

Spark plug factories do attempt to gap plugs at the same setting for any particular spark plug. Often it is the setting anticipated for the most common use. What they intend to set it at might not match the specs for your engine.

Also, the purpose of the gap is to provide the right spark intensity to light the fire in the cylinder. Wider is better up to a point, that point being where the ignition system doesn't have the available power to jump the gap.

Their are two main things to look at about coil output capability. One is available voltage and the other is required voltage. Available voltage is static and depends on coil design. Required voltage is the voltage required to jump the plug gap. Required voltage varies greatly depending on engine load, engine speed, atmospheric pressure, humidity, boost (if blown or turboed), engine deposits, spark plug condition, condition of air filter, fuel mixture, and a few other possible variables. Required voltage is highest under hard load (hard acceleration or climbing a grade). When required voltage exceeds available voltage, it doesn't fire. Gaping a plug too wide moves the required voltage graph up. Gap a plug too close and there may not be enough spark intensity to light the fire.

Unless you have made modifications that can effect plug gap, use the manufactures specs. Adding boost usually requires closing the gap a bit.

Any other questions?

 

[98svtlocal80215]

no thats great thank you very much im just wondering what my motor will do cause the gap is .45 :shrug:i must admitt im a little dislexic at times but my main concern is that they are gaped corectly this time i got exspensive plugs and want them to last.....
so your gap is .10 diff not much to the naked eye but what does it translate into when in the car....:shrug:the car seems to shift better rpm moves quicker not much but small diff and i got 10 more miles to my quarter tank......i appreciate all of your help and insight thank you....

 

[98svtlocal80215]

Spark Gap .45 with 91 sct tune

Spark Gap .45 with 91 sct tune

Come on guys lets get some good responses....

well a small update im now getinng 12.5 more miles to the Quarter tank on the .45 gap and more as i should say i dont go past the avarage 5600 when im shifting but the throtal response is quite different (better) shiftin smother too dont really know how all this plays cause i dont have a dyno in garage but ive come to the concluson it does many things even to which i have no idea do you think any of you tuners could exsplain this to me now remeber im in colo and les ox here so.......and the real difference between .56 and .45 in the cunbustion chamber relating to the pcm what exactly it does and how it compesates and how it works......hey i would really appreciate the feed back from who ever has the time i need to figure out this all be fore i start to get my parts for the summer .....:drool:

Rocky Mtn Runnin
98svt #2800 08/06/97 SF/MDB
2nd Owner......:laugh:

 

[Reebs]

Your tight gap won't hurt anything, but it is pointless. You should open them up to factory spec. I'm running a .039 gap, but I have good reason to.

 

[BrApple]

Your tight gap won't hurt anything, but it is pointless. You should open them up to factory spec. I'm running a .039 gap, but I have good reason to.

is your good reason the same reason, again, and why I would be running .035 ?

:laugh:

 

[BrApple]

Come on guys lets get some good responses....

well a small update im now getinng 12.5 more miles to the Quarter tank on the .45 gap and more as i should say i dont go past the avarage 5600 when im shifting but the throtal response is quite different (better) shiftin smother too dont really know how all this plays cause i dont have a dyno in garage but ive come to the concluson it does many things even to which i have no idea do you think any of you tuners could exsplain this to me now remeber im in colo and les ox here so.......and the real difference between .56 and .45 in the cunbustion chamber relating to the pcm what exactly it does and how it compesates and how it works......hey i would really appreciate the feed back from who ever has the time i need to figure out this all be fore i start to get my parts for the summer .....:drool:

what is there to discuss? the stock gap is fine unless you are running boost. chances are the improvements you are seeing is because you replaced worn out plugs.

 

[Reebs]

is your good reason the same reason, again, and why I would be running .035 ?

:laugh:

But dang, you are running a really tight gap. .040 should be tight enough for 14 or 15psi on our motors. Were you blowing out spark and tightened the gap even more, or did you set it at .035 when you first put it all together?

 

[BrApple]

But dang, you are running a really tight gap. .040 should be tight enough for 14 or 15psi on our motors. Were you blowing out spark and tightened the gap even more, or did you set it at .035 when you first put it all together?

started there on suggestion.

 

[gorman]

Come on guys lets get some good responses....:drool:

Rocky Mtn Runnin
98svt #2800 08/06/97 SF/MDB
2nd Owner......:laugh:

Maybe you have a poor ground connection on your motor/battery/coil circuit. Closing the plug gap may mean that your lower voltage (caused by high resistance) is enough to jump the plug gap... G.

 

[98svtlocal80215]

well did change out the plugs but i had accel race plugs from jegs and they were fine but when i ran into the missfire thing i changed them went and got iridium had a dilexic moment and gaped at .45 when the accels were .60 either way it seems to work out good for now i like the extra miles so ill leave it and pull them in a 1,000 miles or so...to see how they look and all thanks for the input but i still need more info could you direct me to a forum that has info that would be great or just exsplain for me please how this all plays out and what effect it has.....so basicly the closer gap uses less gas....? i dont see the difference in hp or tq so i dont know but if you guys tink it would be finr im cool thanks again.....

 

[Dyoel182]

Nothing to do with gas. The larger the gap the larger the spark kernel you get and you get a "fuller" burn. But thats only if the coil can put out enough power to jump that larger gap. On a side note with a rotating distributor like older cars that was harder to do because there was less and less time for full spark as the revs went up.

 

[Ray]

a smaller gap is harder to "blow out" because it isn't traversing as much distance.. This is why those with a forced induced engine are required to gap tighter and tighter as boost increases.

A smaller gap, however, also does not produce as much of a spark (kernel) and complete ignition of the vapors begins to get harder and harder resulting in an incomplete burn (richer exhaust, less power, etc)

A wider gap means a further gap to jump and thus more voltage to jump the gap. This results in a more complete burn but requires more voltage to do so, taxing the coil and its abilities at some point on that scale.

a more complete burn means more energy in each cycle and more power, but also more chance of the spark blowing out (even an N/A motor can blow out spark) and reduced lifespan of the plug itself from stronger sparking, etc.

If your car is running fine, no hesitation and no pinging/missing under load then removing them later to increase the gap is not required.. keep in mind that your gap is NATURALLY increasing as the plugs wear anyway...

I personally would gap at the wider end of the spectrum (unless modifications dictate otherwise) but its not going to kill you to leave it..

 

[Big Jim]

a smaller gap is harder to "blow out" because it isn't traversing as much distance.. This is why those with a forced induced engine are required to gap tighter and tighter as boost increases.

A smaller gap, however, also does not produce as much of a spark (kernel) and complete ignition of the vapors begins to get harder and harder resulting in an incomplete burn (richer exhaust, less power, etc)

A wider gap means a further gap to jump and thus more voltage to jump the gap. This results in a more complete burn but requires more voltage to do so, taxing the coil and its abilities at some point on that scale.

a more complete burn means more energy in each cycle and more power, but also more chance of the spark blowing out (even an N/A motor can blow out spark) and reduced lifespan of the plug itself from stronger sparking, etc.

If your car is running fine, no hesitation and no pinging/missing under load then removing them later to increase the gap is not required.. keep in mind that your gap is NATURALLY increasing as the plugs wear anyway...

I personally would gap at the wider end of the spectrum (unless modifications dictate otherwise) but its not going to kill you to leave it..

Ray,

I respectively disagree with part of your explanation.

There is no such thing a "blowing out" the spark from boost. Higher cylinder pressure increases required voltage. Instead of blowing out the spark, it is simply not enough available voltage to fire the plug. Boosted engines raise cylinder pressure high enough that either there needs to be much more available voltage or the plug gap needs to be reduced.

 

[Ray]

It was my understanding (and yes, you are always very respectful, btw) that the increased pressures (while ALSO contributing to increased resistance to spark jump) could actually alter the flame front or kernel during ignition, thus prohibiting ignition not just the "jump" itself. Ie.. spark blow out, though I guess more accurately could be referred to as "FLAME blow out and not spark since the spark itself would have jumped already.



Thanks!

 

[Dyoel182]

There is no such thing a "blowing out" the spark from boost. Higher cylinder pressure increases required voltage. Instead of blowing out the spark, it is simply not enough available voltage to fire the plug. Boosted engines raise cylinder pressure high enough that either there needs to be much more available voltage or the plug gap needs to be reduced.

But if its not actually blowing out the spark, why is that the name of the term? I know on my modified mazda I had the full MSD setup to maximize spark because of the increased boost but I still misfired until I closed the gap a little meaning it wasnt an issue of voltage.

 

[Ray]

Well, actually it probably WAS an issue of voltage, though.

a decreased gap means less "required voltage" spec to jump that gap. Also, as Jim pointed out an increased in pressure will cause the voltage needed to jump that gap to rise.

 

[Dyoel182]

Not according to the MSD guys. That ignition box and coil should have taken care of any voltage issues that engine would ever see. I think voltage certainly plays a part but I also think higher cylinder compression has something to do with it as well.