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Old 12-14-2022, 04:31 PM   #1
Mort Mortinsen
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Default Stock 2018 WRX Premium Boost Issue

I just bought a Used 2018 WRX premium from a dealer and the first time I tried to pull out into traffic quickly I noticed the boost is all over the place. It goes up to 21 or so then dropped to about 10psi and the loss of power was noticeable. When I went for a test run I could see (and feel) the boost rising and falling, seemingly without rhyme or reason. And the car surges considerably throughout the rpm range.



I took it to the dealer and they have said they diagnosed it and nothing is wrong and that it is running optimally. The problem is that there is obviously something wrong with the car. I told them as much, but they insisted they had done the diagnostics and that all is well.



I have found online where that model has something called overboost where it will boost to 21 for a short period and then return to 15.9 or so. (I would rather have just straight 15.9).


I traded in a strong focus st for this car and I'm extremely disappointed in the wrx's engine if it's running "optimally". Other than the engine the wrx seems superior in almost every way.




I will be picking the car up soon, and haven't spoken to the tech, but I'm certain it will do it again since it did it almost every time I tested it.


Does this seem like a "stock tune" issue that could be fixed with a tune or is there something more going on? Any help would be appreciated. I would hate to have to get rid of the car.
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Old 12-14-2022, 04:35 PM   #2
K3rm1tth3fr0g
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Subaru dealer or random dealer?
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Old 12-14-2022, 09:16 PM   #3
Mort Mortinsen
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I took it to the Subaru Dealer I bough it from. I just got it back and it doesn't seem to be as bad as before, but still definitely noticeable in 2nd gear. They said they couldn't repeat the problem. They want me to take a video and send it to them. Hopefully that'll help.
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Old 12-15-2022, 12:57 PM   #4
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So I drove it again today and it just doesn't seem right. The power delivery is just all over the place and the surging is driving me crazy. Even while driving normally I can feel it wanting to go then not. I'm not sure of the purpose of overboost either, just to make the hp numbers higher for a second or two? Almost useless imho.



I guess an Accessport and a Cobb OTS map would fix this? Hopefully, because the stock tune is almost a dealbreaker for me. If only it had the ST motor in it.
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Old 12-15-2022, 01:11 PM   #5
K3rm1tth3fr0g
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The twin scroll turbo setup has early torque but it shouldn't feel unpleasant to drive. The stock tune does have notable rev hang between shifts though that protunes and OTS maps will get rid of.

If I were you and can't determine if it's normal since you've never driven one, I'd either test drive another VA WRX at a dealership. Or have another dealership or preferably performance shop, drive the car and tell you if it's behaving normally.

Or just say screw it and do what every FA guy does nowadays and throw every bolt on at it and get an flex tune and run E30-E60 and make boat loads of torque with better spool than stool
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Old 12-15-2022, 01:46 PM   #6
rtv900
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Quote:
Originally Posted by Mort Mortinsen View Post
I'm not sure of the purpose of overboost either, just to make the hp numbers higher for a second or two? Almost useless imho.
overboost isn't really a thing.
There's always a tiny boost spike if you go WOT real quick, so it might go 3-4 psi above normal max boost before the wastegate reacts and controls boost properly.
But we're talking a second at most and it only happens when you first hammer the throttle. If you stay WOT the boost will hold dead nuts like the needle is painted on.

Bottom line, everything you are describing is super subjective and every person describes these things differently.
Boost spike, surging, wants to go but doesn't, power not good, etc.

No way to tell what you mean.
You need to take a video and describe EXACTLY how you are using the throttle.
IMO you should pick a high gear so you'll have some time, go WOT from say 2500 or so and film the boost guage for as long as you can before you run out of space.
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Old 12-15-2022, 02:37 PM   #7
tegxsi
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Stock tune has aggressive throttle/requested tq mapping, aggressive wastegate duty cycle tables but conservative boost target. Aggressive WGDC will cause boost to overshoot while boost target will say, "NO" pull the WGDC back down.

A proper tune should make the throttle feel more linear and fix what you are feeling with the boost.

Last edited by tegxsi; 12-15-2022 at 02:43 PM.
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Old 12-15-2022, 11:24 PM   #8
topgunshooter
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I hated my car until I got it e tuned through phatbotti. Stock tune ruins the car. OTS tunes are a lottery roll. Go e tune or dyno tune.
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Old 12-16-2022, 09:23 AM   #9
Mort Mortinsen
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Ok, I will definitely get the video this weekend, maybe later today. I've allocated (begged the wife for) the funds for the accessport etc.



I've been driving the Focus ST for about 5 years and really love that engine. Basically you stomp the gas (wot), the boost builds to max and stays steady, shift at 5500 or so, boost builds again and stays steady and so on. Power and acceleration rise proportionally to rpm until peak hp rpm.


WRX, stomp the gas, boost builds to max (21) for a second or so with great acceleration. Boost drops to around 16 as rpm rises and acceleration drops a little. As it nears 5000 rpm the boost can go as low a 9-10 psi with a considerable drop in acceleration wavering between 10 and 16 until the next shift.


Thanks for all the replies. I will get that video up soon. I know if I can get this engine sorted I will really love the car.
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Old 12-16-2022, 10:21 AM   #10
lefty o
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there is a dip in the power from approx 4500-5500 with the factory tune.
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Old 12-24-2022, 12:13 PM   #11
Mort Mortinsen
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So I figured I would post how I "resolved" this issue.
After reading a bit more and watching a few Youtube videos, it seemed the way my car was running was actually kinda normal. I had a lot of trouble accepting the fact that a relatively new car in perfect operating condition would run like this. It really was a dealbreaker and I was thinking about getting rid of the car.

I found a few mentions of a Cobb Accessport and tune fixing those type of issues, but I was still worried there was something more wrong with it. How could they sell a car that frankly ran like *****? The dealership sure as hell wasn't going to tell me that it was normal, just that it was running normally and that they couldn't reproduce what I was describing.

I went ahead a got the Accessport and installed the OTS tune a couple of days ago, and I'm extremely happy with the results. It fixed all of my issues with the car. Now the throttle curve is infinitely better, the boost stays steady, and the car is much easier to drive. I did have a problem with a DAM that started at .624 and dropped as low as .4, but I did a reflash with the same tune and now DAM is solid 1 and no knock whatsoever that I saw.

This is how the car should have been from the factory. What is their reasoning for the terrible stock tune? Another thing is I'm surprised at how many reviewers on the internet never even mentioned these issues. I mean, it's the first thing you notice when you drive it little hard. I now really love my WRX. Woohoo! Thanks for all the help!

Last edited by Mort Mortinsen; 12-24-2022 at 12:18 PM.
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Old 12-24-2022, 12:26 PM   #12
K3rm1tth3fr0g
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Quote:
Originally Posted by Mort Mortinsen View Post
So I figured I would post how I "resolved" this issue.
After reading a bit more and watching a few Youtube videos, it seemed the way my car was running was actually kinda normal. I had a lot of trouble accepting the fact that a relatively new car in perfect operating condition would run like this. It really was a dealbreaker and I was thinking about getting rid of the car.

I found a few mentions of a Cobb Accessport and tune fixing those type of issues, but I was still worried there was something more wrong with it. How could they sell a car that frankly ran like *****? The dealership sure as hell wasn't going to tell me that it was normal, just that it was running normally and that they couldn't reproduce what I was describing.

I went ahead a got the Accessport and installed the OTS tune a couple of days ago, and I'm extremely happy with the results. It fixed all of my issues with the car. Now the throttle curve is infinitely better, the boost stays steady, and the car is much easier to drive. I did have a problem with a DAM that started at .624 and dropped as low as .4, but I did a reflash with the same tune and now DAM is solid 1 and no knock whatsoever that I saw.

This is how the car should have been from the factory. What is their reasoning for the terrible stock tune? Another thing is I'm surprised at how many reviewers on the internet never even mentioned these issues. I mean, it's the first thing you notice when you drive it little hard. I now really love my WRX. Woohoo! Thanks for all the help!
Everyone and their mother hates the stock FA tune. You're just late to the party

The FA DAM is much more variable than the EJ DAM. What does reflashing the same tune do for your safety aside from deleting your learned fuel trims?

Research the DAM on the FA and stop reflashing the map when it drops.

https://www.cobbtuning.com/subaru-kn...logic-changes/
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Old 12-24-2022, 01:18 PM   #13
Mort Mortinsen
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I'm always the late one. I just couldn't accept that the stock tune was really that bad.

As for the DAM it didn't drop from 1 it started at .625 (well, within a couple miles of initial flash when i did the first log). and the reflash was 1 day later so the learned fuel trims were minimal. Nothing changed in the car from the first flash and the reflash so maybe something in the initialization process?



I am still learning so thanks for the link. I will check that out.

Last edited by Mort Mortinsen; 12-24-2022 at 01:26 PM.
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Old 12-24-2022, 01:36 PM   #14
BigMotor18
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I agree 100%. I would not have bought my car if I didn’t know I was gonna modify it.
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Old 12-25-2022, 12:22 PM   #15
Mort Mortinsen
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Quote:
Originally Posted by BigMotor18 View Post
I agree 100%. I would not have bought my car if I didn’t know I was gonna modify it.

My problem is I didn't want another Focus St and none of the other cars in the 20-30k used car price range piqued my interest. Now that this problem is resolved I wouldn't change my decision.


The '18 WRX is most definitely handles better, launches better, is more comfortable, has less vibration, the interior seems a bit higher quality, and it has more room.



My '14 ST had great torque, better sound system, better exhaust note (resonator delete), and was a hatch.
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Old 12-26-2022, 12:27 PM   #16
BigMotor18
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Awd was a big factor for me for practicality. It’s not necessarily a daily driver but still need to have the ability to be. Also didn’t want to have high go fwd. I did consider a bmw briefly but didn’t want an older German car to maintain. Wrx was really the only choice that fit want/need. I had a little experience working on a couple Sti also but there are only similarities and not much direct correlation to these FA cars
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