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Hesitation...GONE!

495K views 1K replies 175 participants last post by  Johnny B 
#1 · (Edited)
UPDATE: For those that don't want to read through the 2348972347892 pages of this thread, we have found that the following plugs seem to work best in the 1.4-Liter engines:
-BKR8EIX-2668 (iridium plugs), expect ~10-15k regaps on these, ~40-50k overall life.
-BKR7E-4644 (nickel/copper plugs), expect 15-25K out of these plugs, with a regap or two required at 5-8k intervals on stock tune.


-FR7BHX-S (ruthenium) - this is the latest recommendation for a combination of long life and drivability.

Set initial gaps @ .028". Higher gaps will start to blow-out as the gaps increase.

So for what it's worth, some of you may remember that I was saying I had hesitation that felt like timing pull, even on 93 octane during winter months. I believe I got that one taken care of with a new stock ECU tune from Chevrolet, as for the most part, it behaved much better after that.

However, with the AC on fan speed 3, and especially 4, on a hot day (85+), and even sometimes just randomly when it's not that hot, I'd feel a strong timing pull from 1850-2750 RPM...jerky acceleration and the car just felt...slow. Pinging right off the knock sensor, about 3-4 times per gear under acceleration. With the AC off, it's fine unless I'm sitting at a light for a while.

I ordered the copper NGK version of the same heat range plug that's in the car (BKR7E) and dropped them in today. Perfect day to test - lots of traffic, lots of stoplights, AC on fan speed 3/4, and 94 F outside.

Once the ECU "adjusted" after a few seconds, I could not get the car to jerk WHATSOEVER. Very happy. Acceleration is smooth from a stop all the way up to 5500 RPM, and the car drives like what I feel like it was made to drive like.

I don't know why this made a difference, other than my experience that turbo cars do not like platinum plugs and perhaps iridium have the same effect on them. The old plugs look like they're burning just fine and are clean.

EDIT:
Many of us have found that the .035" gaps are a little bit optimistic - our cars will start to blow out after not too long as the gaps grow. I'd recommend starting in the .028-.030" range. Check your plugs again after 10,000 miles and readjust.




Old iridiums
 
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#2 ·
How long do you expect the copper plugs to last? I know one of the reasons GM with the iridium plugs was to reduce the frequency of plug changes.
 
#6 ·
Well, spent part of the day hooning around back roads, then part of the day running errands with the AC on in-town.

There is NO bog off the line in 1st gear with the AC on 3 or 4 like there was before, power delivery is smooth in between gear changes as well, and no jerking/apparent heat soak problems (90F outside). I thought that all of this was just characteristic of this car in hot weather, so I'm completely surprised. The midrange torque between 3000-4000 RPM feels great too.


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#7 ·
For $10 will give it try - Sounds like a nice improvement.
 
#8 ·
Actually, copper plugs will probably not need replacing each year. If they are running clean and not fouled, simply closing the gap to compensate for wear could be all that's necessary. I wouldn't hesitate to think you might get 2-3 years out of a set of copper plugs if the gap is maintained properly. The biggest thing would be to make sure they're not getting fouled over time.
 
#9 · (Edited)
Honestly, those of you that are tuned...I'm not sure if this will make a difference. It sounds like Vince (and others) have done pretty well with improving the drivability of these engines on the stock plugs.

Most people I've heard complain about jerky acceleration seemed to be using regular gas. Unless anyone else here has this issue on a stock Cruze, I'm wondering if I have a knock sensor that is just overly sensitive.


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#13 ·
Honestly, those of you that are tuned...I'm not sure if this will make a difference. It sounds like Vince (and others) have done pretty well with improving the drivability of these engines on the stock plugs.
I am tuned and I still get some hesitation on take off with the A/C on. My plugs are schedule to arrive between Aug 13 and 16. I will report on the results.
 
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#14 · (Edited)
Filled with 87 E10 today just out of curiosity and switched on the AC (3-max). 85 F outside.

It actually drove completely fine. No bog from a stoplight, no jerkiness or hesitation. I felt heat soak once after sitting at a light for 5 minutes, but it was just slightly slower acceleration and no jerk-you-around knock retard.

Next weeks supposed to be in the 90s again, so I'll see how it behaves.

I really can't believe all this knock was a result of the plugs themselves. Kinda makes me think Chevy got their programming right and the plugs were just a marketing decision.


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#16 ·
My Plugs arrived late Thursday but did not get a chance to install this weekend. Will try and install tomorrow after work. Expecting mid to upper eighties starting Tuesday.
 
#17 ·
Changed out the plugs - will have to wait till tomorrow to check for hesitation/bog with A/C. It is only in the low 70s now, tomorrow will be mid to upper 80's and humid. However did run it for a few miles in eco mode and after the plug change it has smoother power delivery and pulls a little harder than with old plugs. Old plugs looked fine and was careful and did not break my coil pack.
 
#19 ·
Changed out the plugs - will have to wait till tomorrow to check for hesitation/bog with A/C. It is only in the low 70s now, tomorrow will be mid to upper 80's and humid. However did run it for a few miles in eco mode and after the plug change it has smoother power delivery and pulls a little harder than with old plugs. Old plugs looked fine and was careful and did not break my coil pack.
Looking forward to the update!
 
#20 ·
Went out for lunch but only 82 degrees and 39% humidity (per my weather.com app), however with the A/C on the highest fan setting, I am not getting any bog or hesitation where I usually I get dangerous bog/hesitation pulling across on coming traffic up a slight hill with the A/C on. Results seem very good so far. I would like to see how it does with higher temps and higher humidity and a passenger. So far - very good mod for very little cost.
 
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#21 ·
Well, it still hates 87 when the AC's on (yup, I expected as much, just wanted to test it). Initial throttle bog/tip-in from a stoplight is now instantaneous - no huge lag like before, but it starts jerking a little between 1800-2500 RPM when the turbo picks up.

However, with the last tank of premium in hot weather, it was smooth sailing throughout the entire RPM range.

Blk88verde, what are your impressions?
 
#27 ·
Well, it still hates 87 when the AC's on (yup, I expected as much, just wanted to test it). Initial throttle bog/tip-in from a stoplight is now instantaneous - no huge lag like before, but it starts jerking a little between 1800-2500 RPM when the turbo picks up.

However, with the last tank of premium in hot weather, it was smooth sailing throughout the entire RPM range.
I had to use AC on my way back to Ottawa yesterday. It wasn't too hot (mid-70's) but it was probably clost to 100% humidity a lot of the way. We drove through some pretty crazy downpours.

Anyway, with the AC on and 91 in the tank, even accelerating easily I noticed some "uneven" acceleration starting somewhere around 1700 RPM. Maybe the high humidity had something to do with it (probably did), but I was surprised to feel it none the less. I wonder if the engine mapping changes as soon as the AC is engaged? I've been driving with the same 91 V-Power gas for the last few tanks and felt nothing in the way of hesitation.

For the record I'm not tuned and I have my gaps set to .038" and my plug resistors removed and replaced with all-thread to lower the ignition circuit resistance.

I may just order a set of those coppers and try them out... for $10 it can't hurt.
 
#22 ·
Being on 93 premium (since I am tuned) - all good, zero lag/hesitation with A/C on. I have been away for a few days and took wife's CR-V, so I have not had a chance to further test with more load in the car etc. But like I said on initial impression, these plugs are an excellent improvement over a known route that has previously caused lag/hesitation with A/C on (highest setting) with the stock plugs. As you noted improvement through entire rpm range - my car pulls stronger and smoother up thru 5000 rpms over stock plugs. When I get back home I will be able to further evaluate and report back in.
 
#23 ·
Probably put 150 miles on the new plugs this week end. Still running real good. Zero hesitation /lag w/AC running. Seems to hold speed on long hills better in top gear than with the iridium's. Temps in low to mid 80s and humidity 80 to 90 %.
 
#24 · (Edited)
Probably put 150 miles on the new plugs this week end. Still running real good. Zero hesitation /lag w/AC running. Seems to hold speed on long hills better in top gear than with the iridium's. Temps in low to mid 80s and humidity 80 to 90 %.
Awesome...mods, can we move this to the 1.4 tech section? I think this is a worthy "upgrade" for power delivery with the 1.4 turbo.
 
#25 ·
I will be doing a 500+ mile road trip starting on Wednesday evening and returning Sunday evening - I will provide another update following my return.
 
#30 ·
So you put in these? Going to pick up a set then. Probably why I get hesitation all the time.

NGK 4644 BKR7E Nickel Spark Plug
SKU: #BKR7E
ITEM: # NGK4644
BRAND: NGK
 
#32 · (Edited)
My old ep civic came with iridiums stock. I swapped them for coppers cuz they were cheaper. The car drove fine but i lost 20whp on the dyno and they fouled out after a few weeks. If anything just swap to 1 heat range cooler iridium than stock. This is what srt4 and terminator cobra owners do, even on a completely stock car.
 
#34 · (Edited)
My old ep civic came with iridiums stock. I swapped them for coppers cuz they were cheaper. The car drove fine but i lost 20whp on the dyno and they fouled out after a few weeks
You were clearly running the wrong gap/heat range for that application. I've run them on a Honda D-series with no problem at all.

Titan, I wouldn't expect more than a 25-30,000 mile lifespan. Thats a year or two of driving for me, which I am fine with. Gap on the low side - the gap will widen with time.



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#42 ·
Ok I went to the parts store tonight and picked up the plugs. They were $2.59/plug from Advance Auto Parts. Just out of curiosity I checked the gaps on them and they are all gapped at 0.35 in the box. I'm going to knock it down to 0.30 before I install them in my Cruze. I am curious to see how this works out also.

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#43 ·
Ok I went to the parts store tonight and picked up the plugs. They were $2.59/plug from Advance Auto Parts. Just out of curiosity I checked the gaps on them and they are all gapped at 0.35 in the box. I'm going to knock it down to 0.30 before I install them in my Cruze. I am curious to see how this works out also.

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Cool - let us know how they work out for you.
 
#45 ·
Searching around for plug info, I found this Amazon listing for an iridium BKR8EIX, basically an iridium tip version of the colder 8 heat range BKR8E-11 plug I referenced above. Check out the first review:

NGK BKR8EIX Iridium IX Spark Plug : Amazon.com : Automotive

That guy had NGK platinum 7's in his naturally aspirated S2000 from the factory, and the only noticeable improvement going to the iridium 8 was no more timing pull at lower RPM. His car is supercharged, and a quick Google search shows that most S2000 superchargers are centrifugal superchargers which make little to no boost at low RPM.

Unless there's some tuning issue where they had to add timing at low RPM when tuning for the blower, it looks to me like even a stock S2000 may have benefitted from this colder plug. This, of course, is all based on reading between the lines of a short Amazon review... not much credibility. But, in an optimistic sense it would look good for trying the colder plug in our boosted 1.4's.

All else remaining equal, a colder plug may foul easier. Still might be worth a try...
 
#46 ·
Searching around for plug info, I found this Amazon listing for an iridium BKR8EIX, basically an iridium tip version of the colder 8 heat range BKR8E-11 plug I referenced above. Check out the first review:

NGK BKR8EIX Iridium IX Spark Plug : Amazon.com : Automotive

That guy had NGK platinum 7's in his naturally aspirated S2000 from the factory, and the only noticeable improvement going to the iridium 8 was no more timing pull at lower RPM. His car is supercharged, and a quick Google search shows that most S2000 superchargers are centrifugal superchargers which make little to no boost at low RPM.

Unless there's some tuning issue where they had to add timing at low RPM when tuning for the blower, it looks to me like even a stock S2000 may have benefitted from this colder plug. This, of course, is all based on reading between the lines of a short Amazon review... not much credibility. But, in an optimistic sense it would look good for trying the colder plug in our boosted 1.4's.

All else remaining equal, a colder plug may foul easier. Still might be worth a try...
I'm actually suprised those who are tuned aren't running 1 step colder plugs... I ran colder coppers in my cobalt, supercharged corolla and built n/a focus.. They would last about 10 k but that meant swapping them once a year at the time.
 
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