tigeo
Autocross Champion
- Location
- Richmond, VA area
7
Long Term Spark Plug Thoughts
- Thread starter Twist1
- Start date
tigeo
Autocross Champion
- Location
- Richmond, VA area
Love it man - science. I guess the point of my questioning is: has someone taken a tuned car with XYZracerboi tuner stage 2.45 (repeating) put it on a dyno with stock plugs at stock gap and run it then closed the gap incrementally to the final magic 0.024" and recorded if this is even necessary. I would say no. I would say it's just a good easy number to use that quells a lot of drama. But that drama - is it really b/c of plug gap or is it something else? Just asking questions.
CaptainRatty
Autocross Champion
- Location
- Winston-Salem, NC
- Car(s)
- MK7 GTI
Please ELI5!
victorofhavoc
Autocross Champion
- Location
- Kansas City
Certainly
.In general we're constantly under 1 atmosphere of pressure, which is 14.7psi pressing on us from weight of air and gravity. In our atmosphere and at this pressure the amount of voltage necessary to jump from one conductor to another conductor (like two metal plates) is approximately 75,000 Volts for every inch. It sounds like a lot, but there's not much current (amperage) behind it to sustain this spark so it just has a lot of "potential" energy and you see the blue spark as a result of this energy having nowhere to go but the next conducting hop. This jump from the electrode to the grounding arm is what causes the fuel and air mixture in the cylinder to go boom.
As pressure increases it takes more voltage to generate the same spark because the density of the air and fuel increases and more of the molecules have to be excited before the spark can happen. This relationship is fairly linear (barring humidity, air quality, and fuel quality factors) so the last bit of the equation is just accounting for the ratio in pressure increase.
When you multiply by the change in gap we're talking about, the equation reduces to the voltage necessary for just that gap difference. In this case we're talking about reducing gap size, so it's 830V LESS to generate the same spark.
From here, things get more complicated with knock sensors, ecu mapping calibration, pressure tables, and a myriad of other two dimensional factors which account for how and when the charge is delivered. These calibrations are the reason you're not running full boost at partial throttle and why you're able to accelerate smoothly. With less boost the coil packs need to deliver less charge and with a leaner fuel mixture (less fuel more air), there's less "excitement" that needs to happen at the atomic level for the spark to fly. These calibrations are what the tuner can and will mess with in order to deliver spark later ("moving timing"), dump in more fuel, reduce fuel, and increase boost pressure.
Does that help?
... Stop me or I'll go on for days.... Lol
Nineeightyone
Autocross Champion
- Location
- Pennsylvania
- Car(s)
- 20 CX5 19 GTI 10 MZ3
Don't stop, I'm almost thereCertainly
In general we're constantly under 1 atmosphere of pressure, which is 14.7psi pressing on us from weight of air and gravity. In our atmosphere and at this pressure the amount of voltage necessary to jump from one conductor to another conductor (like two metal plates) is approximately 75,000 Volts for every inch. It sounds like a lot, but there's not much current (amperage) behind it to sustain this spark so it just has a lot of "potential" energy and you see the blue spark as a result of this energy having nowhere to go but the next conducting hop. This jump from the electrode to the grounding arm is what causes the fuel and air mixture in the cylinder to go boom.
As pressure increases it takes more voltage to generate the same spark because the density of the air and fuel increases and more of the molecules have to be excited before the spark can happen. This relationship is fairly linear (barring humidity, air quality, and fuel quality factors) so the last bit of the equation is just accounting for the ratio in pressure increase.
When you multiply by the change in gap we're talking about, the equation reduces to the voltage necessary for just that gap difference. In this case we're talking about reducing gap size, so it's 830V LESS to generate the same spark.
From here, things get more complicated with knock sensors, ecu mapping calibration, pressure tables, and a myriad of other two dimensional factors which account for how and when the charge is delivered. These calibrations are the reason you're not running full boost at partial throttle and why you're able to accelerate smoothly. With less boost the coil packs need to deliver less charge and with a leaner fuel mixture (less fuel more air), there's less "excitement" that needs to happen at the atomic level for the spark to fly. These calibrations are what the tuner can and will mess with in order to deliver spark later ("moving timing"), dump in more fuel, reduce fuel, and increase boost pressure.
Does that help?
... Stop me or I'll go on for days.... Lol
Really though, this is great information, and I think provides a ton of valuable insight into what's involved in making tuning decisions on a car. I dunno if the rest of y'all are just engineering geniuses or something, but there's a bunch that I don't know about modifying cars, and would love to have more information like this for my own curiosity.
tigeo
Autocross Champion
- Location
- Richmond, VA area
Isn't the larger the gap the stronger the spark (but as you point out it take more electric oomph to get it to there)?Certainly
In general we're constantly under 1 atmosphere of pressure, which is 14.7psi pressing on us from weight of air and gravity. In our atmosphere and at this pressure the amount of voltage necessary to jump from one conductor to another conductor (like two metal plates) is approximately 75,000 Volts for every inch. It sounds like a lot, but there's not much current (amperage) behind it to sustain this spark so it just has a lot of "potential" energy and you see the blue spark as a result of this energy having nowhere to go but the next conducting hop. This jump from the electrode to the grounding arm is what causes the fuel and air mixture in the cylinder to go boom.
As pressure increases it takes more voltage to generate the same spark because the density of the air and fuel increases and more of the molecules have to be excited before the spark can happen. This relationship is fairly linear (barring humidity, air quality, and fuel quality factors) so the last bit of the equation is just accounting for the ratio in pressure increase.
When you multiply by the change in gap we're talking about, the equation reduces to the voltage necessary for just that gap difference. In this case we're talking about reducing gap size, so it's 830V LESS to generate the same spark.
From here, things get more complicated with knock sensors, ecu mapping calibration, pressure tables, and a myriad of other two dimensional factors which account for how and when the charge is delivered. These calibrations are the reason you're not running full boost at partial throttle and why you're able to accelerate smoothly. With less boost the coil packs need to deliver less charge and with a leaner fuel mixture (less fuel more air), there's less "excitement" that needs to happen at the atomic level for the spark to fly. These calibrations are what the tuner can and will mess with in order to deliver spark later ("moving timing"), dump in more fuel, reduce fuel, and increase boost pressure.
Does that help?
... Stop me or I'll go on for days.... Lol
https://vasttuning.com/spark-plug-selection-and-spark-blowout
My guess is tuners recommend the narrower gap because they can't control the maintenance level of every car they tune. Narrower gap increases the odds of success over a larger population, and ideally fewer complaints/questions.
As others have said, if it ain't broke on your car, don't fix it.
My guess is tuners recommend the narrower gap because they can't control the maintenance level of every car they tune. Narrower gap increases the odds of success over a larger population, and ideally fewer complaints/questions.
As others have said, if it ain't broke on your car, don't fix it.
victorofhavoc
Autocross Champion
- Location
- Kansas City
It's not necessarily a "stronger" spark. It just takes more energy to cross the medium when the distance is larger. A longer spark does have more time and area to make contact with the combustion material, though, which can lead to a "cleaner" burn because there's less chance left over material will exist. This is also part of the logic behind the projected plug burning cleaner.
victorofhavoc
Autocross Champion
- Location
- Kansas City
Happy to share and I'm glad it's of use to you!Don't stop, I'm almost there
Really though, this is great information, and I think provides a ton of valuable insight into what's involved in making tuning decisions on a car. I dunno if the rest of y'all are just engineering geniuses or something, but there's a bunch that I don't know about modifying cars, and would love to have more information like this for my own curiosity.
I have many years studying physics, chemistry, thermodynamics, electronics, and software under my belt. A lot of people these days knock traditional schooling methods (like university), but there are some foundational knowledge things you can't pick up and understand without having a wider picture. As you pointed out, you're trying to learn and there's a lot of information out there that's top down (i want to accomplish z, so I did x and y), but once you learn from bottom up (how did you get to x in the first place?) things start to sort of click.
If you want to learn more about this specific thing, a great starting point is learning about basic physics of electricity and Newtonian mechanics. AP physics classes in high school cover it and the AP exams have wonderful resources and "cheat sheets" to reference out there!
Jovian
Drag Racing Champion
- Location
- Denver, CO
- Car(s)
- 2016 VW GTI
At least they acknolwedge the issues are less than 1% of the plugs. Everyone posting made it sounds like a garenteed fail and exploded engine.
jimlloyd40
Autocross Champion
- Location
- Phoenix
- Car(s)
- 2018 SE DSG
I meant if they are due to be replaced. Less expensive than stock also.
jimlloyd40
Autocross Champion
- Location
- Phoenix
- Car(s)
- 2018 SE DSG
I honestly don't know. I just followed the recommendation since joining the forum. Someone should test.
jimlloyd40
Autocross Champion
- Location
- Phoenix
- Car(s)
- 2018 SE DSG
I have a headache.Certainly
In general we're constantly under 1 atmosphere of pressure, which is 14.7psi pressing on us from weight of air and gravity. In our atmosphere and at this pressure the amount of voltage necessary to jump from one conductor to another conductor (like two metal plates) is approximately 75,000 Volts for every inch. It sounds like a lot, but there's not much current (amperage) behind it to sustain this spark so it just has a lot of "potential" energy and you see the blue spark as a result of this energy having nowhere to go but the next conducting hop. This jump from the electrode to the grounding arm is what causes the fuel and air mixture in the cylinder to go boom.
As pressure increases it takes more voltage to generate the same spark because the density of the air and fuel increases and more of the molecules have to be excited before the spark can happen. This relationship is fairly linear (barring humidity, air quality, and fuel quality factors) so the last bit of the equation is just accounting for the ratio in pressure increase.
When you multiply by the change in gap we're talking about, the equation reduces to the voltage necessary for just that gap difference. In this case we're talking about reducing gap size, so it's 830V LESS to generate the same spark.
From here, things get more complicated with knock sensors, ecu mapping calibration, pressure tables, and a myriad of other two dimensional factors which account for how and when the charge is delivered. These calibrations are the reason you're not running full boost at partial throttle and why you're able to accelerate smoothly. With less boost the coil packs need to deliver less charge and with a leaner fuel mixture (less fuel more air), there's less "excitement" that needs to happen at the atomic level for the spark to fly. These calibrations are what the tuner can and will mess with in order to deliver spark later ("moving timing"), dump in more fuel, reduce fuel, and increase boost pressure.
Does that help?
... Stop me or I'll go on for days.... Lol
victorofhavoc
Autocross Champion
- Location
- Kansas City
How much do they run? The last time I bought plugs from the dealer I bought 12 and they were ~38$ for 4 including tax and picked up within 20 mins of ordering online. This year all the parts have gone up and dealer is selling them for 12$/ea before tax...
I've generally found that for all oem parts the dealer has been significantly cheaper than any online stores. I know someone is going to shout FCP after reading this, but I just don't care to worry about tracking and boxing all the disposables I buy for their return process. I totally get it for anyone willing to go through the effort though...
victorofhavoc
Autocross Champion
- Location
- Kansas City
OK. I'll screw around with gapping when I get to my spring service.
Since I've been focused on rebuilding the top end of the racecar and rebuilding the splitter I broke, I haven't given the other two cars any love, lol. The gti might be shouting at me about its oil for a month now
. I've only driven it like 80 miles in that time though...