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Discussion Starter · #1 ·
After 32000 Kms, I took delivery and installed a new set of plugs IOT evaluate improvements, if any...

The old Delco' came out in very good condition and remained gapped at 0.040". (20000Km) The new ones measured at 0.035" and were not adjusted.

As some of are you are aware, I am not all about HP and FT/LB's. I am more of a least amount of fuel for hills without looking for gears or loosing speed / cruise control.

I data log nearly every KM of travel and I have several hills where I hope to gauge outcomes live and confirm with instant mL / sec data logging and comparison.

I will eventually provide feedback with hard numbers averaged out of a few runs over a couple of steep hills.

They are Denso IK20TT, I have stepped into undiscovered country.

It will be interesting to see the reactions, here and in my car.
 

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I'm surprised your car would even rev past 3,000 RPM with spark plugs at 0.040". With the Cruze you're definitely in spark blowout territory there. Definitely give us a report on your new plugs once you have some mileage on them.
 

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This is the tool I use to give me a rough idea of the quality of the spark. An adjustable spark gap tester.

View attachment 173314

Good news is the Cruze is using one coil per plug, bad news is these coils are very small. With some ignition systems can get a very powerful spark with the gap set at an half an inch, lucky to get 3/16" with the Cruze and this is in a non-turbulent area. Cruze specification is 0.028" finally somebody with some intelligence, but I gap mine at 25 mils, high speed 17,000 rpm motorcycle engines are gaped at 17 mils. Bigger is not necessarily better, least for spark plug gap.

Not sure what idiot recommended a 45 mil gap on her new Kia Soul, also had a super tiny coil per plug. Gaped hers like the Cruze at 28 mils, her performance drastically increases and her highway fuel economy jumped from 27 to 33 mpg.

Another consequence, what fuel that does not burn in the combustion chamber burns up in the catalytic converter, drastically shortening its life.
 

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I'm surprised your car would even rev past 3,000 RPM with spark plugs at 0.040". With the Cruze you're definitely in spark blowout territory there. Definitely give us a report on your new plugs once you have some mileage on them.
How about it!! I was getting blowout at .032, doubt my car would even start at .040.
 

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Ha, remember all those crazy Splitfire commercials, my car runs like brand new again! While in truth, any brand new plug, well if properly gaped will make your vehicle run like new again. In particular if replacing the with one in your engine that is all carboned up, that is the major cause of spark plug failure.

Carbon is highly conductive, builds up on the center electrode insulator that shorts the spark back to ground. This resistance can be measured with a megaohmmeter. Another resistance that can be measured is that built in resistor inside of the plug, typically around 8,000 ohms. Depending on the quality of that resistor and how its mounted, that high voltage can cause arcs drastically increasing it value.

A good quality plug will hold that resistance, yet another factor is leakage between that ceramic and the steel base, will see a carbon like ring on top of that base that show leakage causing additional blowby that can blow out that spark.

Don't care what plug you put into your car, all subject to carbon build up, may be super critical on this, but use a ground walnut blaster to clean them. Really no definitions on top tier gas, more BS, still has carbon in it. And this is the key problem for misfires that not only decreases performance and fuel economy, but also fries up your way overpriced catalytic converter.

I still clean my plugs every 15K miles or so, and when showing signs or excessive resistance or electrode wear, replace them. One thing I love about the Cruze, very easy and even fun to do. Plugs should be torqued at 18 ft. lbs, I don't trust anyone to do this for me, with others, find a loose plug, talk about excessive blowby. Heck, can't even do a simple oil change properly.

Boots on the Cruze are very poorly design as are the springs, the end of he spring should fit tightly on the coil module, just barely making contact, using shoulders in the boots to hold them in, so those springs can hang up in the shoulder leaving a huge extra gap. Stretching out the springs about 3/8" help to prevent this, and look at all four to make darn sure they are extended.

Using simple math with 42K miles on my Cruze say driving at 70 mph at 2,400 rpm, each plug already fired over 43 million times, seeing running off the the platinum under my stereo microscope, time to replace them. Rounded off edges increases the ionization voltage required to fire the plugs. This also stresses the coils and the solid state components that drive them Plus increases the possibility of a misfire.
 

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Discussion Starter · #6 ·
Mine only had 13000 miles on them when I took them out.

I know that the gap is set at 0.028 on most Cruze's for trouble free operation for the next 150000 Km across the full power band. Therefore the spark gap has to be narrow enough to enable the ignition system to generate sparks yet wide enough to ignite the fuel, accounting for neglected wear by most drivers, I am assuming that .028 would be tuned to nearly 90% ignition capacity at 6500 RPM

WRT my plan... there is only one gas engine that I run at or near redline that being my Mercury 115 at 45 miles per hour across a lake. Imagine running Cruze 1.4T at 6100 RPM for 5 to 10 minutes at a time. With reference to running the Cruze at full bore, I do not regularly go past 3000, I have no need to, in my ECO.

Therefore I gapped out to, tune my ignition system to function a higher capacity at a lower RPM, I have taken the engine RPM up 4000 once an had no issues. I suspect that would be close to my redline, where the ignition system would start to fall behind in spark production.

No noticeable power loss, or buttometer misfires, and great mileage. I though I as monitoring misfire counts on my torque app but I guess the update cleared the enhanced PID list.

I will run the new plugs for a weeks worth of trips to work and log everything on Torque, and switch back long enough with the old plugs to confirm misfire counts. Might even do "few full power trials"

LOL I am willing to burn a couple extra liters in my car for CRUZETALK member science.



Who else enjoys burning 25 plus liters of fuel an hour in a boat though, like me?
 

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Discussion Starter · #7 · (Edited)
Update,

I have 10000 Km logged on my Denso IK20TT. The gap did not change from 0.035 during this test. I do feel that I enjoyed slightly improved bottom end pulling (reduced need to downshift for a few hills), and no performance robbing misfire issues accelerating up the band beyond 5500 rpm. As for fuel economy, I averaged 43.67 MPG, for the entire 3 months of winter in Nova Scotia.

Yesterday was a fun day of ecomods, I am now operating at 0.045 gap, the 100 km drive in this morning was uneventful. This time around, I did coat the connection points and boots with silicon dielectric compound. I have been reading about people having torn boots, and I do not to be one of them.

The interesting thing to note, is how clean the plug insulators are so far....

https://www.dropbox.com/s/tcgramp2zglk9se/20160320_112001.jpg?dl=0
 

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Therefore I gapped out to, tune my ignition system to function a higher capacity at a lower RPM, I have taken the engine RPM up 4000 once an had no issues. I suspect that would be close to my redline, where the ignition system would start to fall behind in spark production.
Though spark blow out usually occurs at high RPM, however it can and will occur at any point your under full boost. Though not to the level of setting off your CEL yet I suspect if you data log your car you will see under load you are getting knock events. With a gap that large you may be able to open the drivers window and hear the knock about 2-6 seconds after you put the engine under load(hills). Listen for a metallic click or ping under load.
 

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Discussion Starter · #9 ·
Ignition failure should not generate Knocking, unless timing is out of whack. Sensor detected knock events are common, the ECU uses this as a wall for ignition timing, and will pull timing back once detected. I have logged them and have seen them show up in the file as Knock Retards in degrees, never been able to hear them.

Misfires is a typical outcome of failing ignition system and if bad enough would be noticable as hesitation or stumbling, be it deteriorating sparkplugs, ignition modules. Or in my case modification for a very specific operating range, which I have yet to find any issues.

A wider gap improves ignitablility at lower RPM, but the modules will not have enough stored energy for higher RPM spark generation. GM uses this trade off for the current gap of .028 and 6500 RPM redline and the plugs being neglected for 96000 KM.

my intent is to not operate the car beyond 4000 RPM and they get pulled out every 10000km.
 

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Sensor detected knock events are common, the ECU uses this as a wall for ignition timing, and will pull timing back once detected.
What fuel(octane/ethanol content) are you running? On 93E10 gas with properly gapped plugs rarely can I log any knock events. However lower that ethanol content and octane it becomes common.

One huge problem with relying on the ECU to control knock, it allows it to happen before it actually dials things back. It also will continually attempt to push those limits causing knock events in the process. Can drive 1/4 tank before the ECU fully gets used to any octane/ethanol changes, could do allot of damage in that time.
 

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Can drive 1/4 tank before the ECU fully gets used to any octane/ethanol changes, could do allot of damage in that time.
It takes well beyond the amount of knock that the sensors are set to listen for to do damage to an engine.

If you're running extremely crappy gas, hear audible knock, and there's nothing left that the ECU can compensate for, that's when you run into trouble (or with a poorly calibrated aftermarket tune).
 

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all you guys sound so smart and knowledgeable lol It's like reading chinese for me
It may seem that way to you but don't forget we as a forum have dealt with this issue pertaining to what brands, gaps, and heat ranges, seem to work best for those of us with 1.4L's auto and manual. We have had pages and pages of discussion and testing.
 
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Discussion Starter · #14 ·
What fuel(octane/ethanol content) are you running? On 93E10 gas with properly gapped plugs rarely can I log any knock events. However lower that ethanol content and octane it becomes common.

I am running 91 east coast Canadian ethanol free gas. The car is showroom stock with a few known tricks to improve MPG's. I have logged knock on Torque Pro and it will only pull back a couple of degrees of spark timing at the most.

On of the key things that I think about when considering my plan, is the fact this ECU is managing an engine that is designed to produce 1.65 horsepower per cubic inch, to coasting along at highway speed not burning any fuel. Knock detection is one of the key measurements IOT determine the effects of the combination and spectrums of fuel quality, coolant temperature, intake air temperature, and boost pressure while considering load. Basic research has lead me to believe that the ECU will manipulate variables to just touch the light knocking threshold, which is not detected by anything other than the knock sensor.
 

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Discussion Starter · #15 ·
It may seem that way to you but don't forget we as a forum have dealt with this issue pertaining to what brands, gaps, and heat ranges, seem to work best for those of us with 1.4L's auto and manual. We have had pages and pages of discussion and testing.

LOL Of course no forum is complete without a few that walk a different path, just to muddy the waters. I have been looking for ways to save gas and carry 3 other passengers comfortably since 1993 when I bought my new Fort Tempo 5M.
 

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Discussion Starter · #16 ·

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Discussion Starter · #17 ·
Update,

Enclosed are the pictures of my Denso IK20TT twin tip iridium sparkplugs after 5700KM. They kept the gap of 0.040 for 32000 km of which I lowered to 0.035. I m convinced these plugs are worth the extra few dollars due to the stability of the gap and exceptionally limited electrode wear. The engine, and the way I drive the car obviously likes them as the ceramic is very clean. (I did not clean these plugs)
 

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