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Discussion Starter · #1 ·
Good evening everyone, I have a 2017 Coupe Manual. I bought it in June as a 80-20 car 80% daily 20% track I have had it to 4 track events 3 at Autoclub and 1 at Chuckwalla. first 3 track days I was having a misfire feeling issue, took it in and all said and done had all coilpacks and sparkplugs replaced under warranty.

Yesterday I was a Autoclub 1st session it was awesome, Ran a 1:57 and I was finally giving a sigh of relief. 2nd session while shifting into 5th boom check engine light and no boost. que the aggravation again. Scanned the car and P330 knock sensor code popped. Let me take this second to say the car is on stock tune with drop in filters, RBF 600, Braided Brake lines and Carbotech pads running on NTO5s. I was running in track mode, I cleared the code and went out again in tour mode with the suspension set to track with ESP and Traction control turned off and it ran great, 4th session i started in Tour then half way through put it into track mode and still all was fine, to say I am frustrated is an understatement.

This is my first GM car and No one here in SoCal seems to know anything about these cars, have any of you guys had issues like this? The only reason I had a good day is my friend let me drive his Porsche GT4 on track, I ran a 1:54 in traffic but I can't afford a 100k car.
 

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Some aftermarket "drop in" air filters for these cars, the AFE ones especially, are known to skew the MAF sensor readings to read less air than is actually coming into the engine. The ECM is only commanding enough fuel for the airflow the MAF sensors are measuring, and since the MAF sensors are reporting less airflow with the aftermarket filters this causes the ECM to command even more boost to meet the torque target. Since more air is entering the engine than the MAF sensors are measuring this causes the engine to run very lean since the ECM is only adding enough fuel for the measured airflow, and this creates a ton of detonation and the ECM throws a P330 knock sensor code putting the car into limp mode because it thinks the saturated knock sensor signal means a knock sensor circuit problem.

Another person here had the same issue with the P330 code on multiple track days... he had brought the car back to the dealer multiple times who were unable to duplicate the issue (good luck getting the engine and air temps as hot as you can during a 30 minute track session when driving on the street) and GM agreed to a buyback. Turns out it was just the AFE drop in filters skewing the MAF and causing the car to run lean... and the stock filters were always back in the car when he brought it back to the dealer anyways. The AFE filters never threw a code on the street, but on the track when engine temps get to 230F+ during a 30 minute session and lots of sustained WOT that lean mixture lead to lots of detonation.

I bet if you do a datalog (extra helpful with a wideband) you'll see your car is running on the lean side. Combine that lean mixture with elevated engine temps during track use and it's a recipe for trouble.

Air filters aren't going to make a difference in power anyways with the stock tune... these ECMs are programmed to deliver a specific torque target, and the ECM will vary boost level and throttle blade angle as needed based on ambient conditions to maintain the pedal requested torque target.

If drop in air filters do increase seat of the pants power and boost level compared to the stock filters, that's because they have altered the airflow through the MAF, causing them not to read accurately, and the ECM is now seeing less air than is actually entering the engine-- and things are now running lean. The intakes on these cars are a bit touchy when it comes to accurate MAF readings, and if you make a change even as seemingly benign as non-stock air filters it's a good idea to datalog it and make sure things are working properly.

So, put the stock air filters back in and try again... I bet your issue goes away.

If you had oiled-style filters installed, get some MAF cleaner and clean off both MAF sensors too in case they were contamined by oil (which also causes them to read less airflow than is actually entering the engine.) Wouldn't hurt to inspect the intake while you're in there for any loose clamps or disconnected tubes that might be letting unmetered air in (the little line for the wastegate solenoids that connects to the driver's side of the resonator box in the front center of the engine is an easy one to forget.) If you want to keep running those drop in filters, I'd suggest a tune.
 

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Trackn V, please post back if you do correct your problem with tta 1456 solution.
 

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You can't run an aftermarket intake without a tune. I think the only one that works is the K&N and it offers no power improvement so whats the point.
For that matter, none of the aftermarket intakes offer a power improvement because the factory system is quite good, it doesn't matter if you have a tune or not, power improvements are below the normal variances you would have from dyno pull to dyno pull.
 

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Discussion Starter · #6 ·
TTA, thanks for the info, I have contacted AFE there located 1.5hrs from where I live. I mainly asked of they have dyno'd their product to see if the product was causing A/F ratio issues, if not I offered to put my car on the dyno and see.

The reply I received was " The main purpose OE filter is not performance but so it will be the last filter you have to buy. You may get up to 57 CFM gain at best which could result in 1-2 hp gain at increase. Rest assured that the AFE OE replacement filters are safe to use on your automobile. The OE replacement filters are designed to meet or exceed the manufactures specifications as far as air flow and filtration goes" in no was my question answered.

I have used several of there products on different vehicles over the years, this is a truly disappointing response.
 

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If AFE only did flowbench testing between the stock air filters and their air filters they could certainly report on pressure drop vs CFM gains, which seems to be what they are saying. If they dyno tested the stock filters vs their filters on a car with a wideband they should have seen the mixture change to the lean side of things, but unless they're experienced in tuning that specific vehicle they probably can't conclude if that mixture change is safe or not.

Honestly, how often is it even a consideration that a simple drop in air filter can throw off the tune by significantly changing how the air flows through the MAF sensors? An entire replacement intake, sure, but just a drop in air filter for the factory intake? I think a lot of it has to do with how close the MAF sensors are to the air filters on the factory intake. If the MAF sensors were located further downstream of the filters, they probably wouldn't be as sensitive to changing to a non-stock air filter.

The AFE filters flowing more on a flowbench isn't the issue, the issue is compared to the stock filters they disturb the air path through the intake near the MAF sensors in such a way it skews the MAFs into read lower than the amount of air actually coming in.

Scott (Tapout) and others have logs from customers showing the MAF skewing and lean issues with the AFE drop ins. Scott may be able to chime in with exact numbers as far as the amount MAF skewing and the actual WOT AFR with the AFE filters vs with stock air filters, but lean and boost are never a good combo.

As I mentioned, one user here had GM buy his car back for the exact problem you are experiencing, a recurring P0330 code during track days when running the AFE drop ins.

The AFE drop ins may run OK and not throw any codes on the street where you are only doing short WOT blasts and the lean issue isn't quite as bad (not a long enough period of sustained knock to trigger the P0330), but on a track sessions where the engine is heatsoaked and running at 230F+, the oil is at 270F+, and intake air temps are high from the sustained hard use, that amount of extra heat lowers the knock threshold, and when the engine is going WOT between every corner for a 20-30 minute session that lean mixture causes lots of detonation and knock retard, and the constant knock sensor activity triggers the P0330 knock sensor circuit failure code and puts the car into limp mode.

If you want to keep your warranty, just stick stock air filters back and and change them when they get dirty. They don't hurt performance on a stock tune because the stock tune works by commanding the engine to output a desired torque target, and the ECM will vary boost and throttle blade angle to meet the requested torque output. The stock tune has quite a bit of of headroom to work with to add both more boost and open the throttle blade more to reach the torque target. The stock tune is very, very consistent in power output over a very wide range of environmental and operating conditions, but that airflow vs torque model the ECM is working to is heavily reliant on accurate readings of incoming air from the MAF sensors.

If you don't care about your warranty and want to keep those filters and also make more power, get the car tuned.
 

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tta above, pretty much provided the answer to your issue and the solution. Its great that you got new spark plugs and coils out of it.
You can have brand new OEM all day long, but if you don't put enough dielectric grease in the boot, it will arc and misfire all day long... ask me how I know.

Here's a great FAQ section that every LF4 owner should review:
 

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Go back to stock filters. The stock calibration is for 93-octane fuel, so in track use, unless it's a really cold day, you're doing to have knock retard, even with the stock filters. Knock retard will raise your ECT. When you go tracking, mix 1:2 100-oct. unleaded racing gas to pump gas. That will bump the octane to 94 and make KR much less of a problem.
 

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Hib has a good point on the stock timing tables that I neglected to mention... even with the car 100% stock, on hot days or under sustained heavy use that heatsoaks the engine, the stock timing tables that were intended for 93 octane will produce a decent amount of knock retard on 91 octane gas. Even if you have 93 octane pump gas in your area, mixing some 100 unleaded in there is a very, very good idea for track use.
 

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Discussion Starter · #11 ·
Ok here's the update, AFE has not put a car on the dyno to verify air/fuel ratio's I am going to do pulls on the dyno and provide data to the AFE and here but the dyno is full where I am going til January. I have a track day at chuckwalla on the 27th stock filters are back on the car and I am still pulling 20 psi in track mode. we shall see how it does on Sunday! Hope everyone has a Merry Christmas and gets some new gear for there whips!
 

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20psi? That's way too high for a 100% stock car with a stock tune. Even if you're at high altitude and the ECM has bumped the boost a bit to meet the desired torque target in the thinner air that's still high... in high altitude conditions 18psi is about the limit for what the stock tune will allow. Down around sea level density altitudes with reasonable humidity the car should only be needing about 13psi to meet the desired torque targets regardless of drive mode. What elevation do you live at?

Any chance the previous owner could have left a tune in it or modified the stock airbox?

A while back people were removing the intake restrictors near the MAF sensors and thought it made the car faster since removing the sleeves lead to increased boost levels. Turns out removing the intake restrictors near the MAF skews the MAF readings since it increases the cross sectional area of the intake by the MAF sensors making them read less air than is actually coming in. This makes the engine run lean, and the ECM increases boost levels thinking it is not meeting the airflow targets based on the MAF data. People with otherwise stock cars were seeing about 19 psi after removing those sleeves from the intake.

Might be a good idea for you to open the airbox and check it out.

Have a look at this thread for pictures. You want to make sure these slotted sleeves near the MAF sensors are still in your intake:


It would also be a good idea to get some MAF cleaner and spray off both MAFs while you have the intake open in case the previous owner ran oiled filters and some of that oil is now contaminating the MAF sensors. Also check everything on the intake to make sure nothing is loose and letting unmetered air in downstream of the MAF sensors.

You might also want to take the car to the dealer you bought it from and have them check the ECM calibration history in GDS2, or reflash the ECM with a known stock tune. There was a recall on the M6 cars for an ECM reflash for a DTC not being able to set, maybe punch in your VIN on GM's webpage and see if that recall has been done. If it hasn't, you can get the reflash for free and then know for sure it's running a stock tune.

20psi with a stock tune on the car and no apparent mods just doesn't seem right, and sounds like it's going to lead to another P0330 filled track day...
 

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As others have mentioned, if you have 20 psi of boost, you don't have a stock tune in the car. Why don't you consider purchasing HP Tuners? It will be the best investment you ever make on this car.


Once you have that, you will be able to easily data scan the car, and I will be happy to review it for you and help to diagnose your issue. Plus, we can confirm exactly what's been edited in your current tune, and fix whatever is wrong, etc.
 

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Discussion Starter · #14 ·
Twinturbo fan, as soon as i did the intercooler bleed project from tapout, my boost jumped from 15-16 psi sustained to 19. When the coil packs and plugs were changed i immediately was pulling 20 psi. From what im gathering from everyone is that its at the pinnacle of stock tuning, does that sound accurate?
 

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Discussion Starter · #16 ·
The main reason I purchased this car is that it's under warranty, I wanted a solid 80-20 car that i could daily and then track without having to do much of anything, what i have done is in my first post. I understand that with purchasing the HP and tuning the car will yield more hp. I honestly don't feel I need more power especially on track. I have already spent $ in the braking and tires, just wishing that i didn't have issues.... with the car.
 

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If you're down in San Diego, you're near sea level like me (I'm at 30' above sea level.) Near sea level with the stock tune and zero mods the car should only need to make about 13psi of boost to meet the torque targets.

The fact your car is making 20psi makes me think something is wrong-- same with the recurring P0330 codes on the track. Both are indicative of either a problem or mods.

As I mentioned above the previous owner may have done mods and left them on the car. My first hunches would be either removal of MAF sleeves or they left a tune on the car-- a tune that's too aggressive for a 20-30 minute track session when things heatsoak.

Checking for the MAF sleeves takes 10 minutes tops, do that first. If they're gone, you're going to either need to tune for their absence or get another unmodified intake.

You just mentioned the boost level changed after the coil packs and plugs were changed... that introduces the possibility that the vacuum hoses for the wastegate solenoids were hooked up incorrectly or the nipples on the solenoids were broken or cracked during the coil & plug swap since the lines have to be disconnected and the vacuum tank removed in order to access the coil packs and spark plugs. It would be helpful if you can take the cosmetic cover off the upper intake and get some good pictures of all the solenoids, connectors, blow off valves, and vacuum lines on the vacuum tank. It's a single torx bolt at the passenger side front and then the cover just lifts off. Give all the vacuum lines at the solenoids a gentle wiggle to make sure the nipples on the solenoids aren't cracked or broken. They may have also forgot to reconnect the fresh air vent line for the wastegate solenoids to the resonator box at the front center of the engine... the vent line should plug in on the driver's side of the resonator box. If they forgot to reconnect that line it will create an unmetered air leak on bank 1, although I don't think it would be a large enough leak to lead to 20psi of boost.

If I was down in San Diego I'd plug in with HPtuners or GDS2 for you and see what's going on, but I'm up by Sacramento. Maybe there's another member in the San Diego area with HPtuners that can help.
 

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The main reason I purchased this car is that it's under warranty, I wanted a solid 80-20 car that i could daily and then track without having to do much of anything, what i have done is in my first post. I understand that with purchasing the HP and tuning the car will yield more hp. I honestly don't feel I need more power especially on track. I have already spent $ in the braking and tires, just wishing that i didn't have issues.... with the car.
You don't get HP tuners to get more HP. You get it to see what's going on with your car. If you want more HP you go through a tuner who can use HP to dial in the tune.

Bleeding the intercooler, plugs, coil packs, and any other bolt on will not get you 20psi. If you're lucky you may see 18psi stock. Also, boost doesn't necessarily mean you're getting more power. That could be the car trying to compensate for a weakness elsewhere in order to meet its target torque range.

As far as contacting AFE, most of these companies create a filter that meets the dimensions and size and then quote HP gains on similar vehicles. They aren't going to dyno your car so that you can see the truth. Your filter size, exhaust size, or intake size does not influence stock power. Only your ECU does that. The days when cars ran distributers and adding a new filter suddenly added 15HP were over a long time ago. The stock filter set up on this car is quite good for stock power and even above. The evidence is how even with tuning they show very little gain.

In a nut shell, You're not hitting 20psi stock. I believe the dealership sold you a car and they were unaware it had a prior tune. That's not uncommon. You could get ahead of it and have the dealership check the ECU and reload the stock tune. If they sold it to you that way they can't void your warranty. The better route is to stop buying bolt on and get HP tuners so Scott can look at the tune and see what's going on. Pursuing AFE at this point is a waste of time.

I think if you pull your plugs and properly grease the ceramic, put the factory filters back in, and make sure the sleeves are still there, you'll see things return to somewhat normal.
 

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Discussion Starter · #19 ·
Good Morning, hope everyone had a merry Christmas, as best you could. I pulled the box and put in the stock filters, the sleeves are not there. My friend owns a shop in the area and he is going to dyno and data log the car and send it to Twin Turbo Fan and check everything out. Thanks for all the feedback guys truly, as I stated before I don't think the car needs more power on track just want to make sure everything is good to go.
 

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Good Morning, hope everyone had a merry Christmas, as best you could. I pulled the box and put in the stock filters, the sleeves are not there. My friend owns a shop in the area and he is going to dyno and data log the car and send it to Twin Turbo Fan and check everything out. Thanks for all the feedback guys truly, as I stated before I don't think the car needs more power on track just want to make sure everything is good to go.
You're missing one point, you need the sleeves or else you're wasting time on the dyno.
 
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