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-1.25/+3.25 corrections cylinder 4. Worn plugs? Something else?

Clint Beastwood

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#1
2017 Fist, 18k miles, plugs are about 12k old NGK 1 step colder (pregapped from Mr. Ron), Dizzy tune s2, whoosh intercooler, 2j intake, cobb RMM, currently on stock DV because I am too lazy to swap my Turbosmart EM2 back on. My prior boosted cars (grand national, SRT4) got new plugs every 4000-6000 miles, I don't know off the top of my head what the change interval is on FiST plugs.

I've noticed recently that just normal driving around, I'll look down and see (pretty consistently) -1.25/+3.25 corrections cylinder 4, all the other cylinders are at 0.00/+3.25 or +3.5 (don't remember which). It doesn't matter if I do a hard pull or I just drive around, cylinder 4 always looks about the same. OAR is always fine, flat across the board. Any thoughts? Should I disregard? My daily commute is all surface streets, ~12-14 miles. Car's been behaving fine so I haven't really been looking at the access port, but I noticed that every time I do it's either 0.0.0/+3.25 on cyl 4, or -1.25/+3.25 on cylinder 4. Any thoughts appreciated.
 

MRX330

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If you’re getting big neg corrections at wot, yes worry. If you’re just tooling around, no. Could be knock sensors
 
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Clint Beastwood

Clint Beastwood

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Thread Starter #5
You reinstalled it again?
I go back and forth. Got it down to ~30 minutes from stock -> 2j or 2j -> stock :p hardest part is getting the (gosh darned) rubber coupler between the intake and turbo inlet together.

It still worries me a bit because I can't easily see if the filter is still on the end of the tube. With the way the intake flops around and vibrates (annoying vibration!) I'm worried that the filter could slip off the end of the tube because it's not bead rolled, just smooth pipe.

So - What I'd need to make me happy with it is 1) bead rolled for filter-installation security, and 2) something to mitigate the vibration of the cowl. I have high-temp vibration damping mat applied to the cowl and it'll work for a day or two but then things loosen up enough for it to do a loud buzz/hum during deceleration. Also, anyone thinking of a 2j intake should seriously look int a different DV option. With the stock DV it sounds super loose and floppy, but when I have my turbosmart installed it's very crisp and flutter-y.
 
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Clint Beastwood

Clint Beastwood

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Ok I think it was from my exhaust hitting the mid-chassis brace. Never any negative corrections during a pull, mostly at low speed around town. I noticed twice yesterday I had zero corrections, went over a bump where I heard the exhaust hit, then immediately saw cyl4 corrections (-1.something/3.50) and a -.5/3.50 on cylinder 1.

I found my exhaust was hitting the mid chassis brace, and the tailpipe exit slides horizontally a bit and who’ll thump around. I have the mid chassis brace clearance resolved but need to figure out how to control the horizontal movement
 
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Clint Beastwood

Clint Beastwood

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Thread Starter #9
12k for a spark plug?

Don’t get me wrong I’m all for preventative maintenance, but that seems as excessive as a 1k mile OCI.


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If I was stock I'd call it excessive, but since I'm tuned to 26psi of boost, plugs are cheaper than an engine. I do wish the plugs were as cheap as SRT4 ones. Everyone with an intact motor changed their SRT4 plugs at every oil change, but the plugs were only like 8 bucks for a set of 4. My SRT4 always ran best with cheapo champion copper plugs, they just needed to be swapped pretty often. Now that I think of it, spark plugs on that car lasted longer than the duration between dealership visits :| (it was a super fun car, but dealer support was awful. Huge oil consumption and the turbo impeller had play you could feel? Better swap the car's oil pump! Eating 2 quarts of oil in 1000 miles? Oh that's normal! (so fine, I stopped adding oil and the engine ate itself inside of 2200 miles. They replaced the engine under warranty but not the turbo with the shaft play. I didn't add any oil and the second engine lasted 3500 miles). Guess who finally got a new turbo? Not me. )


SRT4 gripes aside - aince I re-hung my exhaust to give more mid-chassis brace clearance and reinstalled my Turbosmart EM2 plumb-back I *once* got a -0.75/3.50 correction on cylinder 4 - other than that it's always 0.00/3.50. I have never managed to capture one of the negative corrections on a data log - yesterday I logged while driving around aimlessly for an *hour* (yay audiobooks!) and never captured a correction. I stopped for Jamba juice, started the car, and within 5 minutes had the -0.75/3.50 correction. No hard pulls, just driving around. This morning I data logged for about an hour and all the cylinders stayed at 0.00/3.50. I'm going to guess something somewhere is loose, but as I'm about at 12k miles on the plugs it's probably safe to order another set.

On a side note - the 2j intake is WAY less annoying with the Turbosmart EM2 DV installed. A little flutter here, a little flutter there, but it doesn't waffle open and closed while driving in a straight line at constant throttle.
 
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Clint Beastwood

Clint Beastwood

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Thread Starter #11
If he’s running step colder plugs it’s not



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Yeah I've been a step colder for roughly 12k miles. I've been able to replicate the negative correction by smacking the exhaust with a wrench, but it's weird that it only does it on cylinder 4. I think I remember reading that cylinder 4 is the "problem" cylinder because it gets hottest but I am not 100% sure.
 
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Clint Beastwood

Clint Beastwood

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Thread Starter #12
I have a log file up https://datazap.me/u/clitbeastwood/log-1563925766?log=0&data=4-7

knock at almost no boost. Any thoughts? I've secured the exhaust, nothing is hitting the mid chassis brace.
Ordered new plugs from whoosh as a precautionary measure. Running 91 octane. Any input is appreciated, I don't generally push the car hard, I'm really surprised to see knock in a "driving to the store" duty cycle.
 
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#14
Weird, hope it’s not more serious than plugs.

Can someone explain why 1 step colder plugs have such a short operational life? Is it because the electrodes on the plug are gapped farther apart?


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Can someone explain why 1 step colder plugs have such a short operational life? Is it because the electrodes on the plug are gapped farther apart?
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They may be more prone to fouling. I think it's the other way around, the colder plugs call for a tighter gap. People probably change them more often than necessary because it's an easy job and not terribly costly.




DEss
 

Spork1569

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They may be more prone to fouling. I think it's the other way around, the colder plugs call for a tighter gap. People probably change them more often than necessary because it's an easy job and not terribly costly.




DEss

Maybe I should check my plugs. I have step colder ones and I get random negative corrections usually when it's hotter out. Although for me cylinder 1 seems to be the trouble cylinder as opposed to 4.
 

Spork1569

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#18
Do you get them at part throttle just driving around?
I notice them more when letting off the throttle after higher boost it seems. I haven't datalogged in a while so I can't say exactly when they are happening but I notice the minimum value on the AP after such pulls.

Especially now that it's getting hotter if I let off from full boost to no throttle or half throttle it'll show the negative corrections usually from 0 to -1 but I've seen as low as -2 only once. Never seems to happen when it's colder in the morning.
 
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I notice them more when letting off the throttle after higher boost it seems. I haven't datalogged in a while so I can't say exactly when they are happening but I notice the minimum value on the AP after such pulls.

Especially now that it's getting hotter if I let off from full boost to no throttle or half throttle it'll show the negative corrections usually from 0 to -1 but I've seen as low as -2 only once. Never seems to happen when it's colder in the morning.
Just a general rule for me but in this summer heat I do just about anything I can to stay out of boost of temps are near 95 or higher. Basically I just accept my car drives likes balls in the summer but my mazdaspeed did too.


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Clint Beastwood

Clint Beastwood

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Just a general rule for me but in this summer heat I do just about anything I can to stay out of boost of temps are near 95 or higher. Basically I just accept my car drives likes balls in the summer but my mazdaspeed did too.


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Thats what concerned me, knock and negative corrections decelerating or at 5psi of boost :|

I don't know what the threshold for knock is before its dangerous - as far as I know, any = bad.
 

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