How to avoid blown spark plugs in your tuned Stinger

Thanks to @KLR STINGER for this information:

Any misfires from these piggybacks are 100% due to spark blow out on the transient increase in cylinder pressure during the onset of boost. The 3.3T pistons seem to have a high compression height with small quench area. This could be exacerbating the blow out issue. No matter what the piggyback maker says, you need to use the best quality plug you can with it gapped down to .022-4. This should resolve the misfire conditions that most seem to be having.

In addition you have to consider two things when exploring spark options for FI cars. Effective heat range and Gap.

Heat range denotes how effective the plug is at pulling heat from the ground electrode and shell into the head. Every step colder in heat range, means about 70 degrees cooler electrode. The reason this is important in tuned FI cars, is that the large increases in combustion chamber pressure and heat from tuning (which is what is actually generating more torque and HP) causes the electrodes of the plugs to becoming glowing hot embers. At certain temps, this can lead to pre-ignition (also known as detonation), which can have terrible consequences for the piston ring lands where end gasses accumulate. Running a colder plug is cheap insurance because that 70 degrees colder can mean the difference a cracked ring land, or fused ring, thus saving you engine. General rule of thumb is for every 75-100 hp added, drop to the next colder range. the 3.3T run NGK 7 heat range, so running an NGK or equivalent 8 or 9 is good insurance.

Gap has a direct correlation to spark blow out commonly experienced as misfires. Tuned cars running more than factory boost, need to be gapped down to ensure that the spark plug can do its only real job, which is to consistently fire ignition. Whatever heat range you choose to run, the plugs must be gapped between .022-26. Every car is different, some like alittle more or a little less, and unfortunately its trial and error, but .024 is probably a good starting point. Given the factor plugs have come out gapped at .036 I am not surprised at all at the amount of spark trouble people are having.

Note that in some circumstances, too cold a plug and too tight a gap can have cold idle quality issues, but small price to pay to may consistent power production.

There may also be several options when it comes to plugs. The physical specifications of the OEM plugs are as follows

Hex Size: 16mm
Thread Size 14mm
Thread Reach : 26.5mm
Seat type: Gasket

With those spec you should be able to reverse engineer a number of fitment and heat ranges.

Forgive my ignorance, but does reducing the gap decrease horsepower if the vehicle is running stock boost? Can anyone explain why Kia has such a large gap initially?

No, decreasing gap allows you to make MORE power, due to firing the combustion process more effectively and reliably. Too tight a gap can cause some idle quality issues, but in the range of .022-.026 won't cause any issues.

KLR STINGER said:

No, decreasing gap allows you to make MORE power, due to firing the combustion process more effectively and reliably. Too tight a gap can cause some idle quality issues, but in the range of .022-.026 won't cause any issues.

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Thanks for the reply.. So if what you're saying is true, then why would Kia call for a larger gap from the factory? Emissions?

There is a very good possibility that coil dwell times may be dropping for torque control and/or torque limits. We need to identify what the cause is, because the boxes are not the only thing triggering the missfire.

I mean, it's possible, but Torque limiting strategies in most pcms restrict torque demand/delivery through less intrusive means than causing misfires. Throttle control and spark retard are the common front line controls to manage, and these do not usually cause misfires. I would also expect that to happen in lower gears as a protection for driveline parts, not in higher gears under load.

KLR STINGER said:

I mean, it's possible, but Torque limiting strategies in most pcms restrict torque demand/delivery through less intrusive means than causing misfires. Throttle control and spark retard are the common front line controls to manage, and these do not usually cause misfires. I would also expect that to happen in lower gears as a protection for driveline parts, not in higher gears under load.

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Its not a missfire, its a reduced spark energy later in the crank rotation. Its a new strategy I have seen on newer ECU's/vehicles.

Typically they would close the throttle, reduce boost, retard timing, ect. We are not seeing that anymore, its more about % of ignition efficiency, and a change in crank rotation torque spark based on torque limiters/boost limiters/accelerate limiters.

Lower gears in most newer cars are already limited to reduce wear and tire slip, one of the things we do when we tune is increase or remove those lower gear limits.

The only reason I bring this up is because our shop car had some issues, when we started hitting a particular torque and horsepower points with the off road downpipes/decat on the car. With no tuning box or PNP piggy back.

Interesting. I guess once tuning is online should be easy enough to determine and correct. Magic seems to have the SIM2K-260 cracked, so assuming the definitions are similar to other SIM2k variants, full tuning should be around the corner

I literally understood nothing in this entire thread, lol. I’ll take that as a sign to leave my car stock.

KLR STINGER said:

Interesting. I guess once tuning is online should be easy enough to determine and correct. Magic seems to have the SIM2K-260 cracked, so assuming the definitions are similar to other SIM2k variants, full tuning should be around the corner

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Yes, I have several SIM2K definition files, so hopefully... they are similar in how they wrote them.

If not, I have someone who can write a definition file, and give me a proper DAMOS (tuning index) for the ECU.

Just re-gapped the stock plugs to .28, Followed torks video. The car runs absolutely amazing now. tuned with JB4.

Kia Stinger said:

Thanks to @KLR STINGER for this information:

Any misfires from these piggybacks are 100% due to spark blow out on the transient increase in cylinder pressure during the onset of boost. The 3.3T pistons seem to have a high compression height with small quench area. This could be exacerbating the blow out issue. No matter what the piggyback maker says, you need to use the best quality plug you can with it gapped down to .022-4. This should resolve the misfire conditions that most seem to be having.

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@KLR STINGER What aftermarket spark plugs do you recommend.. I noticed that HKS are about $25 a piece.. I've seen NKG for significantly less. Does the brand of spark plug make that big a difference?

ihatecats78 said:

@KLR STINGER What aftermarket spark plugs do you recommend.. I noticed that HKS are about $25 a piece.. I've seen NKG for significantly less. Does the brand of spark plug make that big a difference?

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Re-gap the stock plugs. Colder aftermarket plugs will foul out. read JB4 Review

Kia Stinger said:

Thanks to @KLR STINGER for this information:

Any misfires from these piggybacks are 100% due to spark blow out on the transient increase in cylinder pressure during the onset of boost. The 3.3T pistons seem to have a high compression height with small quench area. This could be exacerbating the blow out issue. No matter what the piggyback maker says, you need to use the best quality plug you can with it gapped down to .022-4. This should resolve the misfire conditions that most seem to be having.

Click to expand...

Thanks Sal for reposting this and great thread of information!

One thing I haven’t seen mentioned is general cost to regap plugs if not inclined or able to change them personally? After reviewing the “install” videos I’m not sure I want to tackle that job. However I could find a experienced Kia mechanic to regap them and curious what the labor cost would be approximately. Would about an hour labor or $50-75 sound fair? Any suggestions are appreciated and thanks in advance all.

StungBlueGT2 said:

Thanks Sal for reposting this and great thread of information!

One thing I haven’t seen mentioned is general cost to regap plugs if not inclined or able to change them personally? After reviewing the “install” videos I’m not sure I want to tackle that job. However I could find a experienced Kia mechanic to regap them and curious what the labor cost would be approximately. Would about an hour labor or $50-75 sound fair? Any suggestions are appreciated and thanks in advance all.

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I wouldn't be surprised if quoted 200 to 400 hundred dollars. it took me about 2 to 3 hours (Took my time) with the how-to video and I'm no stranger to the wrench. If you need a shop to do it, Find a very very very very reputable speed shop or mechanic perform this task. Best of luck

GTB said:

If you need a shop to do it, Find a very very very very reputable speed shop or mechanic perform this task. Best of luck

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Agreed. If I were to pay a shop to do it I would have to trust them a lot. It's too easy for the shop to just say "okay, we did it, give me money please" when in fact they didn't do a thing.

@StungBlueGT2 do you have a friend who knows his way around a wrench that you trust? That may be a good in-between option.

What size spark plug socket is needed to remove the stock plugs?

5/8?

Kamauxx said:

What size spark plug socket is needed to remove the stock plugs?

5/8?

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Yes sir

GTB said:

I wouldn't be surprised if quoted 200 to 400 hundred dollars. it took me about 2 to 3 hours (Took my time) with the how-to video and I'm no stranger to the wrench. If you need a shop to do it, Find a very very very very reputable speed shop or mechanic perform this task. Best of luck

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Thanks for the feedback and that’s closer to what I was expecting.

I was apprehensive when people said they completed the job in an hour, but thought a Kia tech or experienced shop might be able to replicate those times. I guessed 2+ for most and probably 3+ if I tried to tackle it...

I'd prefer not use a shop, however I cannot work on vehicles in my neighborhood and don't have access to a local garage so a tuner shop may be my best option. I appreciate the tip and will heed the advice about "shady" shops. I would only take it somewhere I trust and would let me watch their work.

Kamauxx said:

@StungBlueGT2 do you have a friend who knows his way around a wrench that you trust? That may be a good in-between option.

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Unfortunately I'm the most mechanically inclined of my friends, but will admit that my experience is with rebuilding old school carbureted engines like my Trans-Am. I'm confident I could handle the job, but I'd prefer only having someone familiar with Kia/Hyundai engines and specifically the 3.3T to touch my baby!