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STI's can be smooth. A couple years ago I got the best compliment I ever have as a driver. While out on course my passenger said I can't feel when you shift... meaning in and out of corners. It did take a lot to get there though.

First the clutch delay valve causes wandering engagement. It drove me nuts when I first bought my car. It prevents shockload on the drivetrain when doing ham-fisted maneuvers like side-stepping the clutch. Removing it means you accept the liability. For example I got a little over-amped at a driving event and during a launch the combination of too much gas and letting the clutch out too quick obliterated the left rear halfshaft. Of course it was a really high traction surface and the wheel hop wasn't doing me any favors, but I digress.

Second, do not replace the pitch stop without replacing the engine mounts. Reducing the flex in the pitch stop while leaving the soft engine mounts in place will transmit more force to the firewall which could lead to a stress-related failure in the sheet metal.

A one-piece driveshaft will help with jerkiness in low gears. I went another route and took the carrier bearing bushing from open to solid with a DIY two-part urethane kit. Same result, but you don't get the lightness of CF. It may add more NVH (I didn't notice any, but my car is already louder than normal), but the cost-benefit analysis is favorable. $50 vs $1000.

I can't really offer opinion on the shifter. My car came with a Kartboy short shifter. I didn't like it. The throw was too short making it difficult to find the gears, it required too much effort, and it was notchy. I replaced it with a brand new factory STI short-shifter assembly. Then I changed out all the bushings to poly. It's been wonderful, but I think the shifter assemblies have changed since my GD.
 

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That's a really good idea. Frankly everything will be a million times better if the clutch just stays at the same spot.
I find when the car is cold (Australia cold, so like 8-14 degrees C) and on a flat surface the clutch is quite consistent for a while, but after driving for a while and parking, the clutch engagement height seems to change. It could be a bubble.
Ah yeah I am aware of Australian weather.

However, once everything warmed up to operating temperature the clutch should feel consistent.

Try flush out the clutch fluid and dump in 4 dot fluid in there and you can do the goodridge braided line for the clutch also.
 

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STI's can be smooth. A couple years ago I got the best compliment I ever have as a driver. While out on course my passenger said I can't feel when you shift... meaning in and out of corners. It did take a lot to get there though.

First the clutch delay valve causes wandering engagement. It drove me nuts when I first bought my car. It prevents shockload on the drivetrain when doing ham-fisted maneuvers like side-stepping the clutch. Removing it means you accept the liability. For example I got a little over-amped at a driving event and during a launch the combination of too much gas and letting the clutch out too quick obliterated the left rear halfshaft. Of course it was a really high traction surface and the wheel hop wasn't doing me any favors, but I digress.

Second, do not replace the pitch stop without replacing the engine mounts. Reducing the flex in the pitch stop while leaving the soft engine mounts in place will transmit more force to the firewall which could lead to a stress-related failure in the sheet metal.

A one-piece driveshaft will help with jerkiness in low gears. I went another route and took the carrier bearing bushing from open to solid with a DIY two-part urethane kit. Same result, but you don't get the lightness of CF. It may add more NVH (I didn't notice any, but my car is already louder than normal), but the cost-benefit analysis is favorable. $50 vs $1000.

I can't really offer opinion on the shifter. My car came with a Kartboy short shifter. I didn't like it. The throw was too short making it difficult to find the gears, it required too much effort, and it was notchy. I replaced it with a brand new factory STI short-shifter assembly. Then I changed out all the bushings to poly. It's been wonderful, but I think the shifter assemblies have changed since my GD.
Driving it fast around a course is where STI shines. Everything that don't seems to make sense on normal driving on the street made sense around the race track. It is one very smooth car to drive fast. I love the gearbox too as it is easy to shift down back to first gear.

But on daily driving, the lack of engine response at low rpm combined with the all time AWD made the car jerks and buck - if we don't use enough throttle. On race circuit we always apply good amount of throttle and most of the time away from below 3000rpm, hence the STI becomes really smooth.

And this is why I find the standard 2011 WRX STI (to be exact, 2011 UK Type) feels very linear. Sure it don't have the explosive mid-range of say a typical stage 2 tune, but that also means I can use more of the throttle without much thinking of will the car rush forward and ram the car ahead (exaggeration I know, but u get the idea).

So I guess this is where a competent tuner comes in. More power is great, but even better is the ability to have the right amount of power when and where is needed.

And my experience with 3 port boost solenoid on a twinscroll EJ257 led to me to think it is a good idea to use 3 port boost solenoid when boosting up for more power even on stock VF48 turbo. The idea is to have that linear control but with more power so you can have nicer drivability.
 

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Driving it fast around a course is where STI shines. Everything that don't seems to make sense on normal driving on the street made sense around the race track. It is one very smooth car to drive fast. I love the gearbox too as it is easy to shift down back to first gear.

But on daily driving, the lack of engine response at low rpm combined with the all time AWD made the car jerks and buck - if we don't use enough throttle. On race circuit we always apply good amount of throttle and most of the time away from below 3000rpm, hence the STI becomes really smooth.

And this is why I find the standard 2011 WRX STI (to be exact, 2011 UK Type) feels very linear. Sure it don't have the explosive mid-range of say a typical stage 2 tune, but that also means I can use more of the throttle without much thinking of will the car rush forward and ram the car ahead (exaggeration I know, but u get the idea).

So I guess this is where a competent tuner comes in. More power is great, but even better is the ability to have the right amount of power when and where is needed.

And my experience with 3 port boost solenoid on a twinscroll EJ257 led to me to think it is a good idea to use 3 port boost solenoid when boosting up for more power even on stock VF48 turbo. The idea is to have that linear control but with more power so you can have nicer drivability.
True enough. My car is a stage 2+, but HP is second to response and linear power delivery. The mods I've done have been to dig out of low speed corners in autocross. I know what you mean though. If I take off briskly the car is smooth. If I take off slowly the car is smooth. However there is an in between where it just is not smooth no matter how I finesse the clutch. It's right at the cusp of boost coming on and the car does not like to be shifted at that RPM. This is the reason my car will never see big HP numbers. I won't sacrifice response and drivability for HP. I'm not a fan of peaky engines.

That said modifying the bushing that holds the carrier bearing made a huge difference with bucking at low speeds in my car especially during hard launches. At autocrosses before the car would oscillate so bad I would have to temporarily get off the gas sometimes to settle the car. It was frustrating. I have not had that issue since.
 

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i think that if you take your sti to the BMW dealer give it to them and return with a bmw it will be smooth! jk lol ya with work, take out drivetrain slop with bushings, you can do solid mounts with rubber between the contact points. doing research on which suspension combination would be best for your wants/needs, due to personal problems eg migraines, carpal tunnel, leg issues etc, so modding mine has been in similar interest so that it doesn't exacerbate any issues...have done later model shocks/struts/swaybars, whiteline alk, elh, downpipe but retain oe catback, carbonfiber driveshaft, prothane bushing kit, kartboy short shifter, pitchstop, ra intake, egr delete w/protune, soon going on will be 20g, pump and injectors, could also add smaller rims with more rubber, cobb stumble fix...nice an quiet and super fun!
 

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i think that if you take your sti to the BMW dealer give it to them and return with a bmw it will be smooth! jk lol ya with work, take out drivetrain slop with bushings, you can do solid mounts with rubber between the contact points. doing research on which suspension combination would be best for your wants/needs, due to personal problems eg migraines, carpal tunnel, leg issues etc, so modding mine has been in similar interest so that it doesn't exacerbate any issues...have done later model shocks/struts/swaybars, whiteline alk, elh, downpipe but retain oe catback, carbonfiber driveshaft, prothane bushing kit, kartboy short shifter, pitchstop, ra intake, egr delete w/protune, soon going on will be 20g, pump and injectors, could also add smaller rims with more rubber, cobb stumble fix...nice an quiet and super fun!
Can we please see how the RA intake is fitted to your 09? :D
 

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True enough. My car is a stage 2+, but HP is second to response and linear power delivery. The mods I've done have been to dig out of low speed corners in autocross. I know what you mean though. If I take off briskly the car is smooth. If I take off slowly the car is smooth. However there is an in between where it just is not smooth no matter how I finesse the clutch. It's right at the cusp of boost coming on and the car does not like to be shifted at that RPM.
Yeah there is that zone around 3500 rpm where it felt like you either sail pass it or don't be there at all. When I was still on standard VF48 turbo stage 2 tune, due to the lazyness of the turbo below 3000rpm, I never thought it may be boost spike that adds to this jerk when I wasn't really going for it. And afterwards the CF driveshaft masked it quite well to be honest.

Then the jerk and bucking came back with a vengeance when I switched to VF56 twinscroll. On intelligent mode is not an issue as the throttle mapping is backed off, and on sport sharp is not an issue either because whenever I am on that mode I will surely stay above 4000rpm. But on Sport Mode as daily driving mode - the jerk is so violent it felt like engine braking.

That's when I realized 3 port boost solenoid will assists in controlling the boost for smooth transition because I saw there is a boost spike just around the area where the engine will jerk if I am being a half ass with the throttle on sport mode.

This is the diagram that sold me on 3 port boost solenoid:


Yeah ok that diagram is 2015 WRX but it made sense to me because the 2015 WRX uses a twinscroll turbo and it looks like the oem boost solenoid cannot control the boost quick enough to prevent it from boost spiking. A quick spooling twinscroll turbo will cause the car to jerk violently. It's like you are rushing quickly and suddenly the anchor dropped without warning.

So I asked Delicious Tune to get me their 3 port boost solenoid and a fine tune to eliminate that nasty boost spike. Problem solved.

Thinking back, maybe if I had 3 port boost solenoid on VF48 stage 2 the car could've been much better too.

This is the 2015 WRX STi, and for this purpose we use Australian model to match OP's inquiry. There is that nasty boost spike curve on OEM tune and it is still there on stage 2 tune but nowhere near as bad graph wise. So maybe someone can share their point of view what is it like when using 3 port boost solenoid on single scroll VF48 and if it did lessen the jerk and bucking.
 

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If I take off briskly the car is smooth. If I take off slowly the car is smooth. However there is an in between where it just is not smooth no matter how I finesse the clutch. It's right at the cusp of boost coming on and the car does not like to be shifted at that RPM. This is the reason my car will never see big HP numbers. I won't sacrifice response and drivability for HP. I'm not a fan of peaky engines.
This is so misguided. Built and tuned properly your car will loose all signs of STI stumble which you just described perfectly (added: a mild case - it can be much worse and may vary day to day); and run far smoother every where, and make more power everywhere.

i'll admit I had some concerns before I did it - which engine wise was one gigantic leap. It's been 4 yrs and almost 50Kmi. Power-wise, drive-ability, and daily reliability have had no issues - IE I've never broken down on the road. I've made other choices, IE suspension and mounts that make my car - Uh, a little more special :)


To dhelman - it's all tune. 3port BC make response to the ecu faster - ie the waste-gate which it controls it will follow changes according to the tune faster. Yes it may well prevent overshoot if assuming that's what you are showing us.
 

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That said modifying the bushing that holds the carrier bearing made a huge difference with bucking at low speeds in my car especially during hard launches. At autocrosses before the car would oscillate so bad I would have to temporarily get off the gas sometimes to settle the car. It was frustrating. I have not had that issue since.
Can you go into more detail about this mod? Did you just fill up the bushing with urethane?
 

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Change the clutch fluid , get it bled properly before anything else.

I have a 2015 (from new) and the clutch had no issues at all - however recently the clutch started to feel bit grabby - the mechanic says that’s a sign that it could be near the end of its life.

If you are experiencing variable clutch engagement point - it’s either the clutch fluids (cheapest) or i wonder if it could be this grabby feeling I get with my worn clutch plate.


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Discussion Starter #31 (Edited)
Thanks for all the advise guys, this thread was really informative. I've put in an order for the cobb shortshift and bushings. I'm gunna work at it one part at a time. The next cab off the rank will be a CF driveshaft, and then I'll do the mounts. I'll probably finish up with a tune.

I had a chat with a STi motorsports guy after getting him to drive it around, and he told me the clutch is probably getting messed up from hill assist. After I had a think about it, I live in an area where the main road is just slightly elevated, and every time I try to dart across from one end to the other the hill assist is probably engaging while I wait for gaps. He said my clutch biting point is also unusually high, but it's probably because it's on the way out. I asked if there was a way to lower the bite point permanently if I replaced the clutch with a heavier one, but he said it's pretty much a fixed stroke thing from the way the master cylinder works, and it can't be changed. Some people have suggested adjusting a nut near the clutch pedal to lower the biting point, but I read on these forums that it could cause problems with the cars computer systems
 

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My shifter doesn't really move around too much, but I struggle with stop starts occasionally due to a rotator cuff injury (RHD; 1st and 2nd can be a bit of a literal pain when the gearbox decides it's gunna be overly stiff and notchy, it's like shifting a truck sometimes). My hope is that I can make the gearbox feel more effortless, being able to flick from gear to gear with 2 fingers instead having to drive them in. Every now and then I can't even put the car into 3rd without double clutching, and this is just driving at normal speed.
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VW products have buttery shifter.
but seriously, if you like your car, i think getting a cobb short throw shifter install it with the lower shaft as long as possible and the top shaft as short as possible. the result will be that the feel is very stiff but the throw will be very short and the shifter being low, you will be able to involve your wrist in to shifting and less arm/shoulder.

ps: i m no physio/ergotherapist/chiro. just and accountant but have had many injuries from sports...
 

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Have you tried a weighted shift knob? I have had the ones from Chris at WC Lathewerks and they make any shifter feel amazingly smooth. 1 lbs steel knob helps with inputs so it requires less force on your end of things.
 

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This is so misguided. Built and tuned properly your car will loose all signs of STI stumble which you just described perfectly (added: a mild case - it can be much worse and may vary day to day); and run far smoother every where, and make more power everywhere.

i'll admit I had some concerns before I did it - which engine wise was one gigantic leap. It's been 4 yrs and almost 50Kmi. Power-wise, drive-ability, and daily reliability have had no issues - IE I've never broken down on the road. I've made other choices, IE suspension and mounts that make my car - Uh, a little more special :)


To dhelman - it's all tune. 3port BC make response to the ecu faster - ie the waste-gate which it controls it will follow changes according to the tune faster. Yes it may well prevent overshoot if assuming that's what you are showing us.

I don't have the STI stumble and that is not what I'm talking about. Also I'm done arguing with you on these forums. You seem to miss the point on most of my posts.
 

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I also got motylgear put in the tranny and shifting is super smooth. With that new oil and GrpN mounts, it’s really way more smooth than stock. Shifts are more precise, smooth, with way less shifter play and jerkiness when letting the clutch go. And power transfer is smoother since it doesnt have to rock the engine/tranny before power gets the wheels moving and it has less rebounding happening too.
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I just wanted to update on the motylgear I mentioned a few pages back. While shifting and overall tranny feel was really smooth and felt so good, I found that I would occasionally get grinding on 5 to 4 downshifts, and also going into 1st on a really slow roll. It would happen pretty much once or twice a day, and I never had grind on the factory fill. Basically, I think that even semi-synth motylgear is too slippery... like it can't get the sychros up to speed fast enough even if its not supposed to be as slippery as Gear300.

I don't know what that would do in the long-run having some grind every day, and I would hate to think of grind happening on the track, so I had it drained and used the standard fill my dealer had as the regular tranny oil -- no more grinding. Shifting isn't as smooth anymore, but at least no grinding. I really think the tranny doesn't like slippery aftermarket fluids. It really needs a certain amount of friction that Subaru-spec oil has. I'll miss that shifting feel, but at least I feel confident in the tranny again.
 

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If I take off briskly the car is smooth. If I take off slowly the car is smooth. However there is an in between where it just is not smooth no matter how I finesse the clutch. It's right at the cusp of boost coming on and the car does not like to be shifted at that RPM.
signs of STI stumble which you just described perfectly (added: a mild case - it can be much worse and may vary day to day);
I don't have the STI stumble and that is not what I'm talking about. . . .
Nah, you didn’t describe on your own the stumbling behavior of an almost stock year/model car in which virtually every one of em intermittently exhibit(s)(ed) stumble – so much so that threads concerning filled sites like this for years and eventually not soon enough the aftermarket began to offer stumble kits for similarly afflicted Subarus when SOA didn’t eliminate it on their own!


You seem to miss the point on most of my posts.
Yes, I’m aware that you were primarily arguing the absolute smoothness of a family of cars known by most of us to be far from smooth. But smooth is a relative term so I’ll just take what you’ve written with a whole shaker of my favorite sea salt and not argue about it.
 

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I just wanted to update on the motylgear I mentioned a few pages back. While shifting and overall tranny feel was really smooth and felt so good, I found that I would occasionally get grinding on 5 to 4 downshifts, and also going into 1st on a really slow roll. It would happen pretty much once or twice a day, and I never had grind on the factory fill. Basically, I think that even semi-synth motylgear is too slippery... like it can't get the sychros up to speed fast enough even if its not supposed to be as slippery as Gear300.



I don't know what that would do in the long-run having some grind every day, and I would hate to think of grind happening on the track, so I had it drained and used the standard fill my dealer had as the regular tranny oil -- no more grinding. Shifting isn't as smooth anymore, but at least no grinding. I really think the tranny doesn't like slippery aftermarket fluids. It really needs a certain amount of friction that Subaru-spec oil has. I'll miss that shifting feel, but at least I feel confident in the tranny again.

Fantastic experiment report!!! Thank you!!



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Interesting, but various shifting complaints have been reported resolved by various oil changes from stock, to return to stock, and to "special" mixtures of more than one type/brand. I've personally run Gear 300 for the last 100K or to 240ish with no shifting issues.
 
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