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Old 07-20-2021, 08:04 PM   #1
SubiPsy
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Default Bone stock 2019 WRX, frustrating power loss driving through the mountains

Hello all! I drive a totally stock 2019 WRX, sitting right at 25,000 miles. In the nearly 3 years I've owned the car, I've taken 5 or 6 trips into the mountains around the Tail of the Dragon on the border of NC and TN. Each time, I experience frustrating power loss mainly on the highways and mountain passes in the area. In some cases, I will be traveling downhill at 3,000 rpm and lose speed, even while hitting 2 or 3 PSI of boost. This is most noticeable in 5th and 6th gear, where even at 70 to 80 mph, the car just has no power, and I'll have to downshift to 4th or even 3rd just to maintain my speed. During these moments, the engine note also takes on a different character where even at 3,000 rpm on level ground or going downhill it sounds bogged down like I'm driving through molasses. If I let off the gas completely while in gear, the car slows down like I'm dragging an anchor, even in 6th. 1st - 3rd gear generally feel normal, though I notice the car does tend to tip into boost with less throttle than usual. When I am experiencing the power loss, the MFD gauge will register my throttle inputs as normal, and the engine will still build boost, just with no increase in power output.

Now, I understand that air becomes less dense at higher elevations, but this usually gives turbo cars an advantage over NA engines. I should also make it clear that I am not trying to climb steep hills in 6th gear at 2,000 rpm. In fact, I mainly experience this power loss traveling downhill, and it seems to occur most often through rolling hills where I am constantly changing elevation. This only happens in the mountains, and occurs independent of outside temps or climate control settings. The power loss will sometimes last several miles, then may clear up for a time before returning. I experience no issues or loss of power elsewhere.

I was wondering if anybody else has had a similar experience with the FA engine? Is this just normal behavior for the stock tune as it adjusts to changes in elevation? Or am I simply experiencing the effects of thinner air at higher elevations? Any help or input would be very much appreciated!
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Old 07-20-2021, 11:39 PM   #2
jasonwrx86
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I live in Colorado and my 18 is perfectly fine up and down the mountains.
I don't think its a normal behavior but do check your air filter. The opening for the airbox scoop is directly open to front bumper and at 30k miles mine was filled with leaves and bugs. Maybe yours is heavily blocked unable to allow the engine to breath.
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Old 07-21-2021, 12:57 AM   #3
tegxsi
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Without the ability to monitor or data log it's hard to say.
Maybe its getting heat soaked. The intake temperatures are getting high and making the car pull boost and timing. What is the weather like when this happens?
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Old 07-21-2021, 10:13 AM   #4
SubiPsy
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Without the ability to monitor or data log it's hard to say.
Maybe its getting heat soaked. The intake temperatures are getting high and making the car pull boost and timing. What is the weather like when this happens?
Thatís what I thought the first time it happened, as temps were in the mid 90s. However, I have taken trips with outside temps in the mid 50s - 70s with the same result. Additionally, it happens mostly when Iím moving pretty fast on the highway, where there is more airflow and I would think heatsoak would be less of a concern. Canít view intake temps without an A/P, but oil temps are well within normal (205 to 212) and no change on the dummy coolant gauge.
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Old 07-21-2021, 10:14 AM   #5
SubiPsy
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Originally Posted by jasonwrx86 View Post
I live in Colorado and my 18 is perfectly fine up and down the mountains.
I don't think its a normal behavior but do check your air filter. The opening for the airbox scoop is directly open to front bumper and at 30k miles mine was filled with leaves and bugs. Maybe yours is heavily blocked unable to allow the engine to breath.
Thanks for the reply! I thought of this as well. It turns out my air filter was filthy after 20,000 miles and I did change it to a new oem filter before my last trip. Unfortunately there was no change in performance.
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Old 07-21-2021, 12:10 PM   #6
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Thanks for the reply! I thought of this as well. It turns out my air filter was filthy after 20,000 miles and I did change it to a new oem filter before my last trip. Unfortunately there was no change in performance.
When it bogs down like you say with how much throttle input are we talking about, per dash gauge? 25-30%? More? What happens if while this happens you go wot? Does it still continue to bog down or goes back to normal and accelerates?

Does it rain when this happens? Any constants you notice weatherwise or circumstances-wise while in these up/down mountainous hills?
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Old 07-21-2021, 12:32 PM   #7
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When it bogs down like you say with how much throttle input are we talking about, per dash gauge? 25-30%? More? What happens if while this happens you go wot? Does it still continue to bog down or goes back to normal and accelerates?

Does it rain when this happens? Any constants you notice weatherwise or circumstances-wise while in these up/down mountainous hills?
Hello! In general I try not to exceed 20% ish throttle in 5th/6th gear (which on the stock tune is <1 psi or so). In these circumstances, I can be at 3,000 rpm in 5th gear, going downhill, and hit 1psi or 20-25% throttle and lose speed. The engine sounds bogged down like Iím at 2,000 rpm going uphill. I havenít tried more throttle in the higher gears, but the engine does not seem to ďrespondĒ to boost as it normally does. If I downshift to 4th or even third and go WOT, the car responds as normal. In fact, I have to cruise at like, 4,000 rpm just to make it up some moderate inclines, whereas 3,000 rpm in 5th gear is usually more than sufficient. WOT in the lower gears feels normal as well. Also, this occurs in rain, sun, dry heat, humidity, and any temp. Weather does not seem to play a factor, though the air is generally more moist in the mountains than at my usual elevation.
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Old 07-21-2021, 12:59 PM   #8
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Originally Posted by SubiPsy View Post
Hello! In general I try not to exceed 20% ish throttle in 5th/6th gear (which on the stock tune is <1 psi or so). In these circumstances, I can be at 3,000 rpm in 5th gear, going downhill, and hit 1psi or 20-25% throttle and lose speed. The engine sounds bogged down like Iím at 2,000 rpm going uphill. I havenít tried more throttle in the higher gears, but the engine does not seem to ďrespondĒ to boost as it normally does. If I downshift to 4th or even third and go WOT, the car responds as normal. In fact, I have to cruise at like, 4,000 rpm just to make it up some moderate inclines, whereas 3,000 rpm in 5th gear is usually more than sufficient. WOT in the lower gears feels normal as well. Also, this occurs in rain, sun, dry heat, humidity, and any temp. Weather does not seem to play a factor, though the air is generally more moist in the mountains than at my usual elevation.
Car is fully stock? Owned by you from new, or this has been happening all along and its nothing new you mechanically changed or did that could have started this you think?

No AccessPort? Id monitor tgv and egr operations at those inputs and those ranges when it usually happens but dont know how youd do it if you have no AP. Anyone have suggestions?

My suggestion is dont go downhill in 5th at 2-3000rpm. But that is coming from someone who drives in 3000-5500rpm range 99% of time. I downshift to be at 3000rpm+ at any given moment in time. Going downhill id be in a gear which is somewhat breaking my acceleration so probably 35-4000rpm range, same goes for uphill, id stay 35-4000+ range and the modulate throttle. If nothing else i would try it to see if it is tune related at that rpm and load request.
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Old 07-21-2021, 02:18 PM   #9
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Car is fully stock? Owned by you from new, or this has been happening all along and its nothing new you mechanically changed or did that could have started this you think?

No AccessPort? Id monitor tgv and egr operations at those inputs and those ranges when it usually happens but dont know how youd do it if you have no AP. Anyone have suggestions?

My suggestion is dont go downhill in 5th at 2-3000rpm. But that is coming from someone who drives in 3000-5500rpm range 99% of time. I downshift to be at 3000rpm+ at any given moment in time. Going downhill id be in a gear which is somewhat breaking my acceleration so probably 35-4000rpm range, same goes for uphill, id stay 35-4000+ range and the modulate throttle. If nothing else i would try it to see if it is tune related at that rpm and load request.
Yep, ordered new by me from factory. Only modifications are muffler delete and shift stop. Never been tuned nor had performance mods. Generally I would agree with downshifting on steep hills to maximize engine braking. I am talking about highway driving where I want to maintain say, 75 mph. The car will slow down as if I am dragging an anchor behind me unless I downshift to 4th gear or lower, even with moderate throttle input. Generally at 3,000 rpm in 5th gear the car feels pretty agile, and I get pretty good power even with low throttle input. In these cases, there is quite literally nothing. I will slow down unless I downshift and mash the gas.
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Old 07-21-2021, 03:20 PM   #10
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Yep, ordered new by me from factory. Only modifications are muffler delete and shift stop. Never been tuned nor had performance mods. Generally I would agree with downshifting on steep hills to maximize engine braking. I am talking about highway driving where I want to maintain say, 75 mph. The car will slow down as if I am dragging an anchor behind me unless I downshift to 4th gear or lower, even with moderate throttle input. Generally at 3,000 rpm in 5th gear the car feels pretty agile, and I get pretty good power even with low throttle input. In these cases, there is quite literally nothing. I will slow down unless I downshift and mash the gas.
So what happens if you were to go 50%+ throttle? What if you go more? And what if you start light until symptoms set on and then push thru it to like 65%+ throttle.

Does it bog down in all those instances?

I still think you are experiencing an egr and tgv tune related issue with light throttle and no load basically (going downhill) so car goes into egr mode. I am not a tuner but i would suspect it would not go into same mode with higher rpm, like 45-5000+, thus lower gear works.
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Old 07-21-2021, 03:30 PM   #11
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So what happens if you were to go 50%+ throttle? What if you go more? And what if you start light until symptoms set on and then push thru it to like 65%+ throttle.

Does it bog down in all those instances?

I still think you are experiencing an egr and tgv tune related issue with light throttle and no load basically (going downhill) so car goes into egr mode. I am not a tuner but i would suspect it would not go into same mode with higher rpm, like 45-5000+, thus lower gear works.
Thatís a very interesting theory. Iíve heard some people say they think the car is pulling massive timing, but I donít agree with that theory. We all know the stock tune pulls timing all the time, and this does not feel like that. Itís almost like the engine is choking.

What Iím wondering is why this would occur with the stock tune. Surely Subaru has tuned the car to adjust to variances in elevation, air density, temperature, etcÖ I have been too afraid to really lay into the throttle when the car gets sluggish like this, since the engine sounds like itís lugging. This cannot be the case, however, as I donít think the car would lug with light throttle at 3,000 rpm in any gear, especially going downhill. Itís really like the ecu just doesnít know what to do with the changes in elevation, and downshifting to a very high rpm ďwakes the car up,Ē so to speak. At least this is what it feels like from my perspective as a driver.
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Old 07-21-2021, 06:08 PM   #12
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It is the stock mapping. The stock tune loves to pull timing.
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Old 07-22-2021, 08:41 PM   #13
basyager
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i think your secondary turbine stopped spooling or someting
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Old 07-26-2021, 02:47 PM   #14
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Originally Posted by SubiPsy View Post
Now, I understand that air becomes less dense at higher elevations, but this usually gives turbo cars an advantage over NA engines. I should also make it clear that I am not trying to climb steep hills in 6th gear at 2,000 rpm. In fact, I mainly experience this power loss traveling downhill, and it seems to occur most often through rolling hills where I am constantly changing elevation. This only happens in the mountains, and occurs independent of outside temps or climate control settings. The power loss will sometimes last several miles, then may clear up for a time before returning. I experience no issues or loss of power elsewhere.
I wanted to clarify your understanding of the turbo advantage at higher elevations. The advantage comes from boost from the turbo not from simply having one. I moved to Colorado from Missouri a couple years ago and the wrx is very sluggish at altitude when you are not making any boost. The car tries to compensate for the lack of power by bringing on more boost early, so you find yourself getting into boost earlier and more often than you normally would. I will also say that your muffler deletes will make you lose some low end torque causing your car to feel more sluggish out of boost. I can run 70 mph up I70 into the mountains and not hit more than 5psi usually even with the cruise set. Dont be afraid to get into boost. If the car wasnt made to take any boost in high gears they would have tuned it not to from the factory. As long as you are over 2500 rpm or so you are pretty safe from what I understand.
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Old 07-27-2021, 10:50 PM   #15
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Originally Posted by SubiPsy View Post
Hello! In general I try not to exceed 20% ish throttle in 5th/6th gear (which on the stock tune is <1 psi or so). In these circumstances, I can be at 3,000 rpm in 5th gear, going downhill, and hit 1psi or 20-25% throttle and lose speed. The engine sounds bogged down like Iím at 2,000 rpm going uphill. I havenít tried more throttle in the higher gears, but the engine does not seem to ďrespondĒ to boost as it normally does. If I downshift to 4th or even third and go WOT, the car responds as normal. In fact, I have to cruise at like, 4,000 rpm just to make it up some moderate inclines, whereas 3,000 rpm in 5th gear is usually more than sufficient. WOT in the lower gears feels normal as well. Also, this occurs in rain, sun, dry heat, humidity, and any temp. Weather does not seem to play a factor, though the air is generally more moist in the mountains than at my usual elevation.
Just floor it. It's not a big deal. Factory tune is very conservative and will adjust throttle accordingly. Only 20-25% throttle is ridiculous at 3000rpm. I go 100% full throttle from idle and never a problem.
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Old 07-28-2021, 05:12 PM   #16
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With all due respect to our wonderful NASIOC brothers that have graciously offered their time and opinions on your specific issue; I strongly suggest to IGNORE their input due to their obvious overall inexperience with TUNING the FA20DIT motor or any Subaru motor in general. This is NOT to diesrespect their offerings but only to pinpoint the actual cause of the boost "leak" as it has been presented by the owner. I have several additional questions to the SubiPsy (owner) to ask to pinpoint the actual cause of what I believe is a vacuum leak. If you want my input please reply.
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Old 07-29-2021, 05:56 PM   #17
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Probably some sisters on here too.. such a man splainer! Lol .. We need logs to identify if AFR targets are out of wack.. what kind of A/F Learning 1 # do you have ( then we can prove a leak quite easily ) going up a hill in 5th gear 3k or under is not wise! These are not low end torque engines. That is asking for free engine block windows! Btw power can't be measured by "a feeling" my car at 300whp felt way faster because of how boost came on.. my 550whp setup is way faster but is smooth as butter (to ur butt it feels slower) .. my 2 cents, get a data log check the #s .. it could be a variety of things.. but it feels more like a good case of engine lugging, heat soak and bad driver..
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Old 07-29-2021, 06:04 PM   #18
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With all due respect to our wonderful NASIOC brothers that have graciously offered their time and opinions on your specific issue; I strongly suggest to IGNORE their input due to their obvious overall inexperience with TUNING the FA20DIT motor or any Subaru motor in general. This is NOT to diesrespect their offerings but only to pinpoint the actual cause of the boost "leak" as it has been presented by the owner. I have several additional questions to the SubiPsy (owner) to ask to pinpoint the actual cause of what I believe is a vacuum leak. If you want my input please reply.
Boost leak only in the mountains?
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Old 07-29-2021, 08:20 PM   #19
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Boost leak only in the mountains?
Yeah makes no sense to have been happening the last 3 years only in the mountains??? I used my subie for hill climbs.. climbed every mountain in the PNW without a hiccup in 100+ to -35 degrees weather.. My problem is overheating and blowing out rear ends!!
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Old 07-30-2021, 12:31 AM   #20
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Boost leak only in the mountains?
I guess the theory is in the mountains when the air pressure is lower, your turbo works harder more close to it's theoretical limit with less spare pressure to give thus lower max boost.
I do know my WRX has not hit higher than 19 max psi where on flat land I hit more than 21.
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Old 07-30-2021, 10:14 AM   #21
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I guess the theory is in the mountains when the air pressure is lower, your turbo works harder more close to it's theoretical limit with less spare pressure to give thus lower max boost.
I do know my WRX has not hit higher than 19 max psi where on flat land I hit more than 21.
Those arent his problems. His car cant accelerate at all with low throttle demand when cruising in the hills, especially downhill. Downhill is key to me. Dowhill means no load basically so i think emissions activate egr recirc and tgv operation and this results in weird feeling which would result in coasting.
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Old 07-31-2021, 08:50 PM   #22
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Those arent his problems. His car cant accelerate at all with low throttle demand when cruising in the hills, especially downhill. Downhill is key to me. Dowhill means no load basically so i think emissions activate egr recirc and tgv operation and this results in weird feeling which would result in coasting.
Especially RPM being that high. There is just too much pumping loss vs actual making power. I bet if he selects 6th gear at lower rpm, the pumping loss would be a lot less and having enough power to accelerate.
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