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Discussion Starter · #1 ·
I received a set of four NGK V-Power BKR7E-4644 earlier this week as a birthday present from one of our Gearheads. Today's my birthday and I took the day off. It was warm enough to install them. They came gapped between 0.030 and 0.034" and I regapped them to 0.034-0.035". My coin gapper has gap loops at 0.030", 0.034", and 0.035" and I adjusted the ground strap so that I could slide the 0.034" loop through but not the 0.035" loop resulting in all four plugs being gapped to within 0.0004" of each other. Remember, the original spec in GM's Global Connect for dealerships for the Cruze 1.4T engine was 0.033"-0.037".

I had left my car where the front of the car would be in the sun this morning, which helped some, but it was still cold enough that I had to run the engine to warm up the EcoTec cover so I wouldn't break any plastic clips when pulling it off.

Pulled the cover off, then unscrewed and pulled out the ignition rail and boots. I unscrewed each of the four plugs and then took the rachet handle off and hand unscrewed the rest of the way. I put the new plugs in and hand tightened without my rachet. Then I used my rachet, which is set to 18 ft-lbs and tightened to slightly before the torque setting triggered - my plugs are sitting at 16-17 ft-lbs of torque each. Then I took a clean damp rag and wiped down the top of the engine block, the ignition rail valley and the ignition rail itself, paying close attention to the boots themselves. There was a lot of dust and dirt from winter driving on everything. I checked and released all four springs from where they were jammed in the sides of the boots and reassembled the rail. Before putting the cover back on I started the engine to ensure a smooth idle. Idle was smooth so I put the cover on and went for a drive.

Initial impressions - very smooth idle. Once the engine had a little warm up time I took it up to 6200 RPM in second and then when it was at operating temperature I took it to 6200 RPM again followed by 5700 in 3rd. I held the engine at 5000 RPM in third for half a mile. Based on throttle feedback there was no knocking or spark blowout basically from idle to the red line.

Since I was below a quarter tank gas and needed to go to Home Depot anyway I had planned on filling with Shell V-Power 91 octane at an extremely busy Shell station just down the street from Home Depot. However, with the car driving like a car should - no hesitation, throttle pulsing, etc., I put in 87 octane which is about 13 cents less per gallon. Remember, the standard octanes in Denver are 85, 87, 91. Last winter I tried dropping from 91 to 87 octane and went back to 91 because as soon as the temperatures rose above 65 the ECU would switch to the low octane maps and the car would run like a slug. I'm going to give 87 a good test to see if I can now run 87 at least in cold weather and I'll even give it a try as the weather warms. If I can run 87 for at least three months of the year the fuel savings will pay for a set of Copper plugs each spring.

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Now for the old OEM NGK IFR7X-7G plugs - I gapped them to 0.035 around 35,000 miles ago. Over the past month or so I noticed a small amount of high RPM spark blowout and a very slight uneven idle before the engine warmed up. I had attributed the idle to the cold weather because cars simply don't idle as well in very cold weather. However, upon measurement I discovered three were at 0.037-0.038 and one was at 0.040".

I also find it interesting that NGK listed those plugs as 0.028" gap yet when I pulled them out at 6,000 miles two were at 0.023" and two at 0.025". Those plugs weren't gapped correctly based on what GM ordered and NGK's own on-line spark plug part decoder. This is a supplier error that given the statement in the 2014 US Cruze owners manual about the 0.025"-0,028" applying only to replacement spark plugs (bottom of page 12-3, second printing, 2014 Cruze Owners Manual).

I was going to take and post a picture of my old plugs but when I looked at them they are only marginally darker than the ones I put in and there is no indication of excessive heat on the plugs.

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Comments on GM's original spark plug gap spec found in GM Global Connect vs. http://www.cruzetalk.com/forum/10-p...cial-statement-regarding-spark-plug-gaps.html to XtremeRevolution.

I gapped my OEM plugs to 0.035" around 6,000 miles on my odometer and when I measured them after removal today three had gaps of 0.037"-0.038" and one at 0.040". Assuming I screwed up the regap on the one plug this still leaves 0.002" electrode erosion over 35,000 miles. Extrapolating this to 60,000 miles this means you don't want to start your OEM spark plugs more than 0.032" and for 100,000 miles more than 0.029". Giving a small amount of engineering wiggle room and the standard coin gapper's loops this means that for the 2011 to 2013 US Cruzen with their 97,000 mile spark plug replacement schedule (owners manual) you don't want to start larger than 0.028". For the 2014 with the 60,000 mile spark plug replacement you don't want to start larger than 0.030". The standard OEM brand coin gapper has gap loops at 0.028", 0.030", 0.034", and 0.035". This erosion rate, combined with the spark blowout I was starting to experience is our first evidence that GM's official response has some honest engineering thought behind it vs. just marketing and legalese to save money by not having to print and send out a page change to all the 2011 & 2012 owner manuals. I wish this had been communicated in their response as it is critical information for the DIY crowd. Instead the mealy mouths in their marketing and legal departments dumbed down the response and frankly, made GM look bad.

I strongly recommend that anyone who has gapped their OEM plugs to 0.035 or higher to check them at least annually or every 15,000-20,000 miles, whichever comes first.
 

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I am sure the car wil run better on 87 in the winter than summer.But no matter how you slice it it will go to low octane map no matter what with lower octane than 91
 

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Discussion Starter · #3 ·
I am sure the car wil run better on 87 in the winter than summer.But no matter how you slice it it will go to low octane map no matter what with lower octane than 91
I suspect you're correct but I'm still going to give it a shot. I know from last winter that as long as the temperatures stayed below 60 it didn't matter if I ran 87 or 91, but as soon as they started to rise above that point I could tell the difference. I'm hoping that the copper plugs will raise that transition temperature to a point that I can run on 87 for part of the year and save myself some money in the process. In addition, as a practicing hyper-miler I will be monitoring my fuel economy while on 87 octane - if it starts to dip without the corresponding dip in outside temperatures that will also lead me back to 91, and probably back to full iridium plugs since there won't be any fuel cost savings to cover the cost of the annual plug replacement.

Question - how can the car tell what the octane is? I suspect its by monitoring the engine for knocking and it switches to the low octane map when it detects a certain amount of knock over a moving time period. When I went to dinner this evening there was no throttle pulsing that you feel when the engine is using the low octane map, but since it was below 40F I can't say if this is because of the plugs or because of the temperature. The OEM plugs also didn't knock on 87 octane at these lower temperatures.
 

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A
I suspect you're correct but I'm still going to give it a shot. I know from last winter that as long as the temperatures stayed below 60 it didn't matter if I ran 87 or 91, but as soon as they started to rise above that point I could tell the difference. I'm hoping that the copper plugs will raise that transition temperature to a point that I can run on 87 for part of the year and save myself some money in the process. In addition, as a practicing hyper-miler I will be monitoring my fuel economy while on 87 octane - if it starts to dip without the corresponding dip in outside temperatures that will also lead me back to 91, and probably back to full iridium plugs since there won't be any fuel cost savings to cover the cost of the annual plug replacement.

Question - how can the car tell what the octane is? I suspect its by monitoring the engine for knocking and it switches to the low octane map when it detects a certain amount of knock over a moving time period. When I went to dinner this evening there was no throttle pulsing that you feel when the engine is using the low octane map, but since it was below 40F I can't say if this is because of the plugs or because of the temperature. The OEM plugs also didn't knock on 87 octane at these lower temperatures.
Pay attention when you fill up next time and listen to the engine closely (rev it up a little bit and put your foot into it - 2.5k or so). You'll hear/feel the engine running a little louder/rougher and may jump a bit in acceleration as it tries to figure out what timing map to use (it's listening closely to the knock sensors). It'll even do it to some extent on 93, but it's more noticeable at first on 87/89. It seems to figure it out after a half mile or so.

I'm surprised the iridium gap changed that much. They're not *supposed* to do that, but I guess it wouldn't be the first time advertising has fooled me. Watch out for that on the coppers - you may have to regap them in a few months since you set the gap on the high side. I typically had to regap these once in their lifetime in my last turbo car.


Sent from AutoGuide.com App
 

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Discussion Starter · #5 ·
I'll check the gaps around Labor Day or sooner if I feel spark blowout. It'll be interesting to see how these V-Power degrade over time and miles. It's not a traditional plug electrode tip and you can't use the coin gapper by putting the slot around the tip. I had to put the ground strap in the slot and carefully bend without touching the electrode. You can see a picture at NGK 4644 BKR7E Nickel Spark Plug.

I was also surprised at how much the OEM plug electrodes had eroded, especially after reading the expected erosion rate for iridium plugs. This was probably the underlying technical reason to switch the gap specification in the GM Global Connect system vs. changing the spec in the Owners Manual. I was also somewhat appalled when I used the NGK plug part number decoder and discovered the OEM plugs are supposed to be 0.028" vs. what we actually found. For those who weren't around when we were discussing and discovering the extent of the issues with the 2011 and 2012 Cruze spark plug gaps, here's a chart from 63 cars (252 plugs):

Text Plot Pattern Line Font


As we got more cars added the spike at 0.025" just kept growing. The plugs should all have been gapped at 0.028" according to the NGK plug number.
 

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Discussion Starter · #7 ·
The spike hasn't moved. It's gotten a little wider which tells me there is less consistency in the plug gaps.
 

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Anytime you refuel the fuel level sensor will indicate a refueling event.Than the ecm selects a octane map based on its testing
 

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Question - how can the car tell what the octane is? I suspect its by monitoring the engine for knocking and it switches to the low octane map when it detects a certain amount of knock over a moving time period.
Every car/company is different, but I think you're right on the money. The high octane map is fairly agressive and from what I understand the car is constantly trying to get there. It constantly monitors knock levels and attempts to put timing back into the engine until the knock threshold is breached again, tossing it back down to the low octane map and then starting the process over again shortly after.

Only if operating conditions and fuel knock resistance allow will the engine operate on the high octane map for extended periods. Having said that, guys on the HPTuners forum are still trying to get to the bottom of a "phantom knock" condition present in the 1.4T in both the Cruze and Sonic. This is on throttle tip-in, not at steady state cruise or acceleration, and has the experts on that board stumped for the time being. The programming for this engine is much different than with older platforms like the original 2.0T and LS series engines.

Glad to hear those plugs are working out. :)
 

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Discussion Starter · #10 ·
I'm watching your experiment with the "colder" iridium plugs closely. I figure I'll only get one year out of these copper plugs.
 

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Discussion Starter · #11 · (Edited)
For the past couple of weeks I was noticing what felt like spark blowout when accelerating uphill in 5th gear between 2300-2500 RPM. I didn't mention it to my dealership because I figured it was a gap issue. Today it was warm enough to work on the engine so I took my plugs out and checked. Here's what I found:

1: 0.035"
2: ~0.038"
3: 0.034-0.035"
4: 0.040"+

I cleaned the plugs andregapped all to 0.030" as these are copper plugs and I'd rather not have to check them again before Lordstown and went for a test drive. Smooth as silk all the way up to 5500 RPM and I came up a 30 MPH hill in 2nd gear at 3300 RPM.

When I pulled the OEM plugs out back in January I found one plug had a significantly larger gap. I thought maybe I had mis-gapped that plug. Now I don't think so. I was extremely careful to consistently gap the new plugs before I put them in. This may explain some of the gap variations we have had reported. I also noticed that the two plugs that had the most gap growth had a lot more carbon buildup around their bases. This doesn't surprise me since the burn wasn't as clean in these two cylinders.
 

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Interesting. I'll have to pull my new plugs out and see how they're wearing. Maybe this has something to do with the reduced 60,000 mi replacement interval?

Usually when numbering cylinders you start at the crank pulley end and count up from there, so your #2 and #4 plugs are the ones with the highest gaps.
 

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Discussion Starter · #15 ·
Interesting. I'll have to pull my new plugs out and see how they're wearing. Maybe this has something to do with the reduced 60,000 mi replacement interval?

Usually when numbering cylinders you start at the crank pulley end and count up from there, so your #2 and #4 plugs are the ones with the highest gaps.
Reversed the numbers and removed the "Driver's Side" comment. Thank you.
 

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Discussion Starter · #16 ·
Spark blowout is gone. There is a hill that I climb every day and spend most of the climb in 5th gear at 2300 RPM as it's too steep for 6th gear. This morning she was a smooth as glass climbing that hill.
 

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Discussion Starter · #17 ·
I've been experiencing a small amount of spark blowout the last two weeks. Went out this morning to check the plugs. I ended up throwing them away as the plug in cylinder 4 had completely eroded to the point where the V was nearly gone. Fortunately I had kept my OEM plugs. I regapped them to 0.030" and when I get spark blowout again I'll replace them as one of the electrodes will be worn nearly all the way down at that point. I didn't put that plug into cylinder 4. The copper experiment went well but I'd prefer to not have to check the plug gap every three months - once a year will be sufficient. The NGK V-Power BKR7E-4644 worked well for performance and fuel economy. However, like all copper plugs, they just require a lot more attention. The BRK7Es lasted a little over 15,000 miles.

My ignition boots came out like they had just been put in - no tugging, pulling, etc. needed. Just a very light pry with a screw driver and the coil pack/rail came right up.
 

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im unsure about chevy but bmw does a fuel quantity test it does this by watching knock and how high it can bring the ignition timing up to without detonation so I think its safe to say that the cruze monitors that also if it has 2 maps for low and high octane fuel
 

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...I think its safe to say that the cruze monitors that also if it has 2 maps for low and high octane fuel
Someone can correct me if my understanding is not correct, but the way I thinkt he Cruze works is it's constantly monitoring knock and trying to get timing advanced as far as possible up to what is in the primary ignition map. If it detects knock it doesn't automatically run off the low octane map, it just retards from the primary table to keep knock in check.

My understanding of the Cruze's "low octane" timing map is that it's there to perform in a sort of "limp mode" if there's something wrong with the engine.

Some older cars would switch to the low octane map if they detected any knock whatsoever, and wouldn't attempt to switch back until a certain time had passed, the engine was shut off, or it detected a refuelling.
 
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