XRT Tune, knock and Spark Plugs

I have been driving the car on the final XRT calibration for about 400 miles. I have to say, Ed made this car into a blast to drive. tons of power between 3k and 5k rpm, and got 24.7 mpg on the hwy damn near what it was getting with the cobb tune.

 

I've been getting a bit of fine knock and a couple DAM adjustments around 2200 rpm and a light throttle. The DAM always bounces right back to 1. I would have thought it would be learned by now and I would stop seeing this.

 

I reached out to Ed and he suggested I change the plugs, possibly the gas I was using (same station it was tuned on). they are NGK Iridiums with 7500 miles on them. Before I drop $50 and spend 2 hours fighting with the rear coils and plugs to come out with my sausage fingers, Is the tuning process really hard on plugs or something?

 

Seems like these 100k plugs I just put in should be fine, no misses or anything and he isn't asking for a different heat range.

 

For you guys that are tuned - is it common to kill a set of plugs that quickly? Is there buildup on them or something from the tuning process?

 

I'm just curious your experiences.

Edited May 31, 2020 by poconoracing

How many miles on the plugs that are in the car now?

 

Is it only under throttle or as you let off the throttle as well?

How many miles on the plugs that are in the car now?

 

Is it only under throttle or as you let off the throttle as well?

 

7500 miles on the plugs. Stock NGK iridium. I replaced them when I had the motor out to fix the clutch. 120236 they went in. Car now has 127640

 

It’s only around 2200 rpm, taller gears and going into light throttle. Like 4th gear staying with traffic at 45 or so mph. Or 6th gear on the highway when you hit a slight uphill with the cruise on. Let off and it’s gone. Hit the accelerator and put it in boost it’s gone. No issues if you keep it up above 3000 rpm

 

Ed wants me to change the plugs. I’ll do it but I just can’t wrap my head around how these lightly used plugs could be bad, unless there is something in the tuning process that causes a problem. The guy knows these cars and has called every issue accurately.

 

do deposits get on the electrode or something that would make a hotspot?

 

My experience is bad plugs would cause a miss at idle or a drivability issue. It idles perfectly, no miss at all. If I didn’t have the accessport up I wouldn’t even know there was an issue. I’m seeing None of the things I would expect from a plug issue.

 

I was just wondering if others who had their car tuned had to replace the plugs afterwards, and what was the issue.

Edited May 31, 2020 by poconoracing

Well, in fairness Ed at XRT seems to know his stuff from the interactions with him you posted.

 

Can you isolate the knock to specific cylinders? Maybe you can swap plugs around and see if the knock follows?

 

But you would still have to go through the PITA of removing and replacing plugs though.

My tuner recommends changing plugs yearly.

Turbo motors are very hard on plugs, and tuning is hard on the engine period. Low rpm high boost and super-rich fueling is nothing to sneeze at.

 

You could ask Ed if a colder plug might help, also did you use the iridium plugs or Laser Iridium plugs?

 

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Turbo motors are very hard on plugs, and tuning is hard on the engine period. Low rpm high boost and super-rich fueling is nothing to sneeze at.

 

You could ask Ed if a colder plug might help, also did you use the iridium plugs or Laser Iridium plugs?

 

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He definitely knows his stuff. This is more curiosity based on others experiences

 

Plug Installed was NGK LFR6AIX. After going back and forth with him he is suggesting 7's. That makes more sense to me, I cant believe these could be worn out after 7500 miles.

 

Ill post some pics when I pull them.

Edited May 31, 2020 by poconoracing

LFR6AIX is rated to 50k by NGK. My manual calls for SILFR6B8 which is rated for 100k bh NGK. Both have Iridium electrodes but B8 has a Platinum ground vs a Nickel ground for the AIX.

 

I dont know if the different ground shape and material affects performance but I doubt the plugs are worn out at 7500 miles.

 

Could you have been given fake plugs? I hear they are rampant so I got mine off an authorized dealer as listed on NGK USA's site.

There's also a chance it's "normal" EJ255 stuff- I have a bit of a stumble around 2200 RPM, although it's generally only noticeable when the car is warming up (Cobb OTS Stage 1 91 tune). There's a pretty lengthy thread about this over in the tuning subforum, and I want to say it has been brought up in the 5th-gen forum at some point as well. I moved my fuel pressure regulator vacuum reference from the nipple on the cylinder 4 intake runner to something off the back of the plenum, and while I'd like to say that helped, I don't notice the phenomenon often enough to know for sure. Sounds like putting a few extra feet of fuel line in there helps a little by damping out some of the pulses in fuel pressure, but I haven't gone that far with it.

I believe the plugs listed by scubaboo are the correct oem plug. Fuel stumble would be easy enough to spot in the datalog. I dont recall if it shows up as knock on the AP gauge monitor.

 

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LFR6AIX is rated to 50k by NGK. My manual calls for SILFR6B8 which is rated for 100k bh NGK. Both have Iridium electrodes but B8 has a Platinum ground vs a Nickel ground for the AIX.

 

I dont know if the different ground shape and material affects performance but I doubt the plugs are worn out at 7500 miles.

 

Could you have been given fake plugs? I hear they are rampant so I got mine off an authorized dealer as listed on NGK USA's site.

 

Plugs came from autozone over the counter. I doubt they are fakes.

 

NGK on their website doesn't list a SILFR7B8. Interestingly when you search by Year/Make/Model it doesn't show SILFR6B8 as an option for our cars, yet parts.subaru.com says its the OE plug. Odd

 

I'm going to order the LFR7AIX - same plug I have and one level colder as Ed requested.

 

I'll keep you all posted.

 

Edit - some interesting info on the NGK website -- https://www.ngk.com/learning-center/article/207/what-is-a-spark-plugs-heat-range

Edited May 31, 2020 by poconoracing

IIRC Autozone is in the authorized dealer list so should be GTG.

 

Thanks for keeping us posted!

Many parts sites dont update information but rather copy and paste it from previous years. The plugs you got will work they just may need to be changed more often.

 

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That's weird that on the NGK website it doesn't show the SILFR6B8 as the factory plug - it does show that for other cars with the EJ25 turbocharged engine, though (WRX and STi of same vintage) - the main difference with the LFR6AIX is the ground electrode, which is a platinum pad for the SILFR6B8 and nickel on the other (so it will wear faster) - if the center electrode is showing wear after only 7500 miles, I wonder if the ruthenium plugs would be better? (weird that they are cheaper than the laser iridium ones!)

That's weird that on the NGK website it doesn't show the SILFR6B8 as the factory plug - it does show that for other cars with the EJ25 turbocharged engine, though (WRX and STi of same vintage) - the main difference with the LFR6AIX is the ground electrode, which is a platinum pad for the SILFR6B8 and nickel on the other (so it will wear faster) - if the center electrode is showing wear after only 7500 miles, I wonder if the ruthenium plugs would be better? (weird that they are cheaper than the laser iridium ones!)

 

 

I thought it was odd too. Maybe a flaw In their dB or something.

 

Ed wants a colder plug in the car after the tuning, and the only “7” I could find was the one I ordered. I’ll try them and see if if solves that fine knock issue on light throttle. They were pretty cheap on rock auto, only $30 to my door for the set.

 

If it does solve it ... I’ll run them a while and look for a longer lasting plug in that heat range for the next set.

Apparently there is a ILFR7B8 whose only application is the Lotus Evora.

 

I've found the NGK website isnt updated. Lots of cars that use certain plugs I've looked at arent listed. I'd definitely defer to the car manufacturer recommendations over the NGK website.

 

I have SILFR6B8 listed in my manual, and that's also what I pulled out when I changed plugs recently.

 

 

 

 

Hope the cooler plugs fix your problem!

Edited June 1, 2020 by Scubaboo

I did 30k on my last set of (stock) plugs on Ed's stage 1 tune and they looked "ok" when they came out. I don't have an AP to monitor the knock parameters but I haven't experienced anything noticeable. He might be suggesting fresh plugs if he was excessively rich or lean during your tuning process. Worth a shot.

Dumb question but are they gapped correctly? When you tune you often gap them differently for the power.

 

The plugs shouldn't go at 7500, but half its normal life is pretty common in a boosted car thats been tuned or had engine modifications.

 

I would swap plugs as others have said to see if its a specific cylinder. Its a headache but best to check on that first.

You can also log cylinder roughness count I believe it's called in the AP, or knocksum.

 

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I did 30k on my last set of (stock) plugs on Ed's stage 1 tune and they looked "ok" when they came out. I don't have an AP to monitor the knock parameters but I haven't experienced anything noticeable. He might be suggesting fresh plugs if he was excessively rich or lean during your tuning process. Worth a shot.

 

I'm going one heat range colder per his guidance. I'll keep you guys posted. Plugs should be here by the weekend to change them and see how it goes.

Dumb question but are they gapped correctly? When you tune you often gap them differently for the power.

 

The plugs shouldn't go at 7500, but half its normal life is pretty common in a boosted car thats been tuned or had engine modifications.

 

I would swap plugs as others have said to see if its a specific cylinder. Its a headache but best to check on that first.

 

They were gapped correctly when they went in, No issues at all with knock during tuning. It really showed up on these last 2 iterations when I started 'normal' driving. Its a very specific situation - light throttle, slight uphill or acceleration to stay with traffic and 4th gear or higher.

 

I'm going through the trouble of pulling them all, I'll just replace them. They are not that expensive.

FWIW I have a similar thing happening sometimes especially in the summer. I sometimes wonder if driving without the monitor on would be better for a few weeks letting the ecm workout the timing tables according to my driving.

 

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FWIW I have a similar thing happening sometimes especially in the summer. I sometimes wonder if driving without the monitor on would be better for a few weeks letting the ecm workout the timing tables according to my driving.

 

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Lol I thought the same thing. Maybe less information is better! Plugs are enroute. I'll let you guys know.

There's also a chance it's "normal" EJ255 stuff- I have a bit of a stumble around 2200 RPM, although it's generally only noticeable when the car is warming up (Cobb OTS Stage 1 91 tune). There's a pretty lengthy thread about this over in the tuning subforum, and I want to say it has been brought up in the 5th-gen forum at some point as well. I moved my fuel pressure regulator vacuum reference from the nipple on the cylinder 4 intake runner to something off the back of the plenum, and while I'd like to say that helped, I don't notice the phenomenon often enough to know for sure. Sounds like putting a few extra feet of fuel line in there helps a little by damping out some of the pulses in fuel pressure, but I haven't gone that far with it.

 

Nick on the FB group was complaining of a stumble issue in his LGT. Apparently Ed smoothed it out though.

 

He's a bit cryptic sometimes with his messages but he's generally spot on. He's called out intake leaks on cars just looking at logs. Buddy of mine turned out he had a pin hole leak in his stock air intake piping.

 

I haven't done any tuning recently sadly. We did a lot of R&D of ROM's for the shifting in the past. That and throttle response. I wish to turbo the 3.6 but it's just so costly.

Nick on the FB group was complaining of a stumble issue in his LGT. Apparently Ed smoothed it out though.

 

 

 

He's a bit cryptic sometimes with his messages but he's generally spot on. He's called out intake leaks on cars just looking at logs. Buddy of mine turned out he had a pin hole leak in his stock air intake piping.

 

 

 

I haven't done any tuning recently sadly. We did a lot of R&D of ROM's for the shifting in the past. That and throttle response. I wish to turbo the 3.6 but it's just so costly.

Buy a tig welder and learn a new skill, that will cut down on the cost, lol.

 

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