2011 WRX Shifting Issues Depending on Gas Quality?

[echardcore]

I apologize if my lingo is off as this is my first manual.

I feel like the quality of gas has a lot to do with driveability specifically when referring to shifting. I feel like its very hard to baby the car/clutch and get a smooth shift on certain fills. I always use BP or Shell Premium. Usually, I am able to rev up powerfully, easily, to about 3k, shift, and engage the clutch (pedal up) at about 2k smoothly. I've observed that throughout the use of certain tanks of gas (right now I filled with Sunoco Ultra 94 but its happened with the aforementioned), engaging the clutch seems to require more RPMs, about 2.5k, and more gas to gently slip the clutch without a THUMP of varying intensities. This doesn't makes sense since I used ultra high octane gas. From what I've found it should be more powerful and easier to shift. I dumped a bottle of Techron in at just under half a tank because I wanted to see what would happen and it seemed to make a slight improvement in ease of shifting which leads me to believe that it has to do with quality of gas. I use Techron about every 3rd or 4th oil change usually anyway.

The THUMP is my main reason for this question. Does that have something to do with improper shifting and the diff? I am pretty sure this needs to be avoided.

Does anyone else have any clue what in the F I am talking about? Basically I like to tell people that my car is extremely picky about gas. Is this accurate?

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[scx89]

does it go away as the car warms up?

[dannyngnX]

its the computer, its recommended to run on 93 octane, or 91 for lower performance..
regardless, every time you fill up. The ecu has already adjusted to the fuel octane and has to re-callabrate every time you switch up the fuel type.

shifting and clutch release also play a role in how smoothly the car will run also..

and race gas might make more Hp and Torque, but with a un-tuned ECU... its just a waste of $$

[echardcore]

this does not go away as the car warms up and rather is prevalent the entire tank until I fill.

This issue happens intermittently when using 93 octane normally. I shouldn't have mentioned that I put 94 in. I was testing to see if that would help.


It's completely noticeable to the extent that when I get a bad tank, I dont want to drive the car. When I get a good tank, I never want to get out of the car.

[echardcore]

this has been happening since I bought the car. the only mod is the K&N air filter and it happened before and after swapping it.

is this an issue of maybe running lean (or rich) vs. normal? there is no smoke or smells fom the car.

[purplewrx]

Have someone else drive your car that has been driving manual for long time. Get there take on it. Might just be your driving

[chapstien]

It's not the gas. the gearbox - engine connection is purely mechanical, the rate at which the engine needs to spin is directly proportional to the rate at which the transmission's input shaft is spinning. The only thing that would make you need to rev higher is the speed you are going at the time of the shift.

[echardcore]

Im going to have to wait until I get another "bad" batch of gas. I just filled up with Sunoco 93 and shes running great again. I definitely want to let one expert I know drive it. I should let him drive it now while its running smooth.

[AllYouSeeisBlue]

Originally Posted by echardcore

I apologize if my lingo is off as this is my first manual.

That^, the quality of gas shouldn't affect the the shifting at all. I've always filled either 91 or 93 depending on where I am and noticed no difference in shift points maybe better throttle response from 93. You probably need to practice your manual skills more, the thump(I'm assuming lurch) is most likely from your revs dropping too fast when you granny shift. You need to shift faster and be quicker about getting on the power after the clutch engages.

[echardcore]

Originally Posted by AllYouSeeisBlue

That^, the quality of gas shouldn't affect the the shifting at all. I've always filled either 91 or 93 depending on where I am and noticed no difference in shift points maybe better throttle response from 93. You probably need to practice your manual skills more, the thump(I'm assuming lurch) is most likely from your revs dropping too fast when you granny shift. You need to shift faster and be quicker about getting on the power after the clutch engages.

I just read up on "Lurch." I dont think that is what it happening. I think the RPMs are dropping when I engage lower gears on the ****ty gas as compared to the RPMs increasing with the better gas.

I will take vids of both and post. My main concern is damage to the car. Thanks for the replies.

[echardcore]

This is exactly what is happening to me.
http://forums.nasioc.com/forums/show....php?t=2135883

[Dailoh]

Out of curiousity, do you have your A/C on when it shifts (reving) crappy?

[AnthonyWang]

Damm i totally for got what that thump was, i remember looking it up couple months ago and finding an answer for that. But i can tell you its nothing severe, i think almost 50% of WRX owners have that same complaint.

[rkjunior]

Sure it's not the diff?

[mollo43]

try an octane booster along with your high octane gasling every now and then, it might be also that you need to change your fuel pump, i know on my 09 WRX the car sputters and doesnt have a kick in it when you put in regular

[BeefCurtains64]

Lol coming from the guy who install an 89 dollar chip and fry your ecu trololololol

This is not euro trash. Its japs. Gtfo dude

[GrumpyPitbull]

LOL ... either that Mollo43 is a dedicated troll, or the dumbest person to ever own a Subaru.

[James1982]

I just saw that you have a K&N filter, don't know if that has anything to do with it but possibly? Is it tuned for the filter? Have you tried the stock filter?

[echardcore]

Hey James. I am pretty sure this happened before the drop-in K&N. It's bone stock otherwise. I am getting really frustrated with the car. Its impossible to drive it normally. Almost every time I shift I am cursing at the results. It feels like I have to slip the clutch way too much to get a smooth upshift. At this rate i'll need a new one in 2 or 3 more years!

I'm thinking about getting rid of it but this is the car I want and I want to keep it for a long time. I am going to try swapping the gear fluid to the Extra-S as soon as possible. I might also want to do the SPT trans mount. I need to do more research and ask around about it and decide what the best upgrade would be to counter this issue.

I am taking the car in for a slow tire leak tomorrow. I am going to have them check the fluid in the diff but I don't really trust this dealer to do much else.

[BeefCurtains64]

try to make subaru open that tranny up let you take some pics. Post it here so knowledge people can chime in ....

Or open it yourself ..... learn something ....

[echardcore]

i usually shift at 3k. today I started shifting under that and the problem seems to go away. I think I was under 2.5k on most. maybe 3k is no good in these cars.

since i do all my DIY in a park there is no way to "learn" and I dont think anything is broken so I dont think the trans needs to be opened.

[DiscoGsus]

Not to be a dick, but it sounds like you don't know how to drive a manual yet.

Two other things:
The drive-by-wire switch did one really annoying thing in these cars, and that is that the ECU holds the revs for a fraction of a second after you let off the gas, making smooth shifts harder. You learn to drive around it.
The other one is that under hard shifting all of the driveline slop can cause the rear-diff to thunk into your undercarriage. This only happens when you are driving hard, not during everyday shifting.

[echardcore]

Originally Posted by DiscoGsus

Not to be a dick, but it sounds like you don't know how to drive a manual yet.

Two other things:
The drive-by-wire switch did one really annoying thing in these cars, and that is that the ECU holds the revs for a fraction of a second after you let off the gas, making smooth shifts harder. You learn to drive around it.
The other one is that under hard shifting all of the driveline slop can cause the rear-diff to thunk into your undercarriage. This only happens when you are driving hard, not during everyday shifting.

not a dick at all. thanks. you are somewhat correct. i learned stick on an old Escort. The majority of my manual driving before this was on an old manual Forrester that i drove around all of the usa. i definitely have some experience but no racing or high performance exp. i need to get it down though so i can extend the life of my clutch.

only 90$ for the SPT trans mounts and not a long job. Wondering if this would be a good decision. Also plan on the swap to Extra_s next oul change. does this sound like a good plan?

[DiscoGsus]

I have the GroupN tranny mounts in both of my cars, and as long as you are ok with increased NVH (Noise, vibration, harshness) then there is no downside.

For fluid, I love the Extra-S in my STi 6-Speed, but have yet to put it into my '11.

[echardcore]

for granny shifting, what RPMs should I drive from 1st to 2? What about for spirited?