Spark Plug Gap
- Thread starter Larry
- Start date
CoHPhasor
Active member
I just changed my plugs from .028 to .035 this weekend.
1st & 2nd & 3rd gear burnouts are fun.
You're running a tune with higher boost and no blow-out?
(And a performance gain)
Bogus
Senior Member
sx sonic
New member
Our cars are not equiped with an EGR system, the system is actually going the way of the do-do bird and thank god, it get problem matic with age (idk of a german car thats had one). cam phasing pretty much made it absolete as a more direct approach could be used to dilute the fresh charge with spent exhaust.
you had some good points, just saying the 1.4t doesnt have an EGR (atleast that ive seen)
-Tyler
you had some good points, just saying the 1.4t doesnt have an EGR (atleast that ive seen)
-Tyler
Swordsmith
242hp/252 ft-lbs BNR EFI
I just pulled and checked my plugs, all four were exactly the same, 0.028. Now I can stop lying awake nights worrying that the factory gremlins might have put a random set of gaps in.
I had called my local Chevy service dept to arrange an oil change, and asked about checking the gaps while they had it in. They did some research and could find no notice whatsoever about a problem, and said they would have to charge me to look. I offered to make a bet with them, I'd pay if they were all gapped the same, but they would pay if there were any differences, and they were game. But I would have had to leave the car overnight so they could work on it cold, and in the end it was simpler to just do the job myself.
I'm still interested in whether increasing the gap to say .030 or .032 might help performance, but in the end I left them at the factory setting since there doesn't seem to be a consensus, other than that -different- numbers would be "bad"
I had called my local Chevy service dept to arrange an oil change, and asked about checking the gaps while they had it in. They did some research and could find no notice whatsoever about a problem, and said they would have to charge me to look. I offered to make a bet with them, I'd pay if they were all gapped the same, but they would pay if there were any differences, and they were game. But I would have had to leave the car overnight so they could work on it cold, and in the end it was simpler to just do the job myself.
I'm still interested in whether increasing the gap to say .030 or .032 might help performance, but in the end I left them at the factory setting since there doesn't seem to be a consensus, other than that -different- numbers would be "bad"
ChrisJ
Active member
Ok what exactly is 'blowout" when talking about spark plugs on a forced induction engine?
http://www.ipdusa.com/techtips/10002/spark-blowout-or-is-it-my-birthday
Apparently people actually think wind or turbulence can "blow out" an electric spark? Come on now
I also see why it could have trouble consistently jumping a wider gap unless you increase the voltage.
http://www.ipdusa.com/techtips/10002/spark-blowout-or-is-it-my-birthday
Apparently people actually think wind or turbulence can "blow out" an electric spark? Come on now
I also see why it could have trouble consistently jumping a wider gap unless you increase the voltage.
Last edited:
If you have no issue with them where they're at, I say leave them be. The only reason I upped my gap is because mine were all wrong and I figured I might as well try the large gap while I had them out. No problems so far so I'm leaving them.
sx sonic
New member
As compression pressures increase there is an increased resitance between the electrode and ground strap (the gap). Forced induction engines have much higher dynamic compression ratios than NA engines (static compression is checked with a gauge and is what the CR ratio is based off, dynamic CR is. While the engine is running). This increased cylinder pressure and an excessive gap which also increase the resistance across the gap can result in the spark being extinguished before full combustion has been completer...
A shorter gap lowers the resistance across the gap. Or in other words required less voltage to fire the plug succesfully
A shorter gap lowers the resistance across the gap. Or in other words required less voltage to fire the plug succesfully
CoHPhasor
Active member
Ok what exactly is 'blowout" when talking about spark plugs on a forced induction engine?
Spark blowout or is it my birthday?
Apparently people actually think wind or turbulence can "blow out" an electric spark? Come on now
I also see why it could have trouble consistently jumping a wider gap unless you increase the voltage.
It's a term to identify something that is in most respects above the average driver's head.
Why do they call it a burnout when nothing becomes 'burned out' and there's no actual flame?
*sheesh*
air has varying resistance, it varies on content, humidity, density, etc.
It takes higher voltage to cross pending the variables and one of those variables comes into play on a turbo car... (guess?) density. *spooky noise*
Making the gap smaller combats the increased resistance, but when the density is lower (not boosting) if the gap is too small the spark will be weak, making a smaller area of the chamber directly exposed to the spark kernel as well, making the burn less complete making power and mpg suffer.
Papasonic
Active member
On the subject of spark plug gap: Back in the mid 1970s GM specified a spark plug gap of .060 on some of their engines equipped with the then new HEI electronic ignition system. The reasoning was improved performance, better combustion, reduced emissions etc. The HEI system was capable of delivering in excess of 50,000 volts in the secondary ignition system. The coil was indeed capable of firing the wide gap plugs, but the problem was that the spark would jump the path of least resistance, which wasn't always the plug gap. Spark would discharge right through the spark plug wires and boots to nearby manifold heat shields, and sometimes the intense voltage would discharge right through the distributor rotor to the distributor shaft; drilling a hole through it and shutting down the engine. Opening the hood at night with the engine running would often provide a light show of sparks from the plug wires. The fix was to reduce the gap to a more modest .045
Todays modern engines with coil on plug technology, and no ignition distributors, have fewer problematic components, and are more reliable.
---------------
Papasonic
Todays modern engines with coil on plug technology, and no ignition distributors, have fewer problematic components, and are more reliable.
---------------
Papasonic
Last edited:
sonicR
New member
Don't fret. I'm reading these complaints and I realized that I had I same problem. The dealer isolated the issue and said that this is a factory problem that the cruze was having. Replacing the valve cover corrected mine. Air was leaking in. It was equivalent to opening yours oil filler top while the car was at idle. Hope this is helpful. I am going to get new plugged thou it can't hurt.
