05 LGT "studdering" during low speed acceleration.

[Driver72]

You probably have it too. It's very subtle and you may not even realize it. It's not like the whole car shakes or bucks or anything. It's just a minor couple of "hiccups" almost like the car just sucked in a couple air bubbles in the fuel line. I'm pretty sure it's across the board with all LGT's It's not like some are tuned different than others, or use a different turbo or ECU, the people who are saying they don't have it, probably just accept it as that's how it is suppose to be.

[Deer Killer]

[quote name='Driver72']You probably have it too. It's very subtle and you may not even realize it. It's not like the whole car shakes or bucks or anything. It's just a minor couple of "hiccups" almost like the car just sucked in a couple air bubbles in the fuel line. [/QUOTE] Get 4 passengers, a full tank of gas, and a steep hill. It will be more like getting rear ended. I'd categorize it as being a function of engine load when at < 50% throttle between 2000-3000rpms. It's rare to make the engine work hard at < 50% throttle, unless you are in a tall gear which means it gets mostly subdued, and that's why I think people don't report feeling it. If anyone in the north boston area thinks their GT MT5 doesn't do it, I'd be glad to try and demonstrate.

[Tzar007]

[quote name='Driver72']You probably have it too. It's very subtle and you may not even realize it. It's not like the whole car shakes or bucks or anything. It's just a minor couple of "hiccups" almost like the car just sucked in a couple air bubbles in the fuel line.[/QUOTE] Well, when I read stuttering, hiccups or words like this, it means for me that the car has to vibrate, shake, miss a beat, or do something like that, even if it is only slighty noticeable. Like I said, the only thing I feel when trying some of the things mentioned here is just a reaction time, a delay. It just seems there is a lag between the time I floor the throttle, and the time the car really starts moving. This period of time where I have the throttle floored and the car finally register (or seems to register) that throttle input lasts maybe 1 or 2 seconds depending how low I am on the RPM. But there is no minor hiccups or anything. It just doesn't move for a split moment, that's it. Oh well. I guess I am lucky not to feel it and not to be bothered by it if that thing really happens to my car :)

[Deer Killer]

[quote name='Tzar007']This period of time where I have the throttle floored and the car finally register[/QUOTE] I specifically said it does NOT happen at WOT.. [url]http://www.legacygt.com/forums/showpost.php?p=61101&postcount=15[/url]

[Tzar007]

[quote name='Deer Killer']I specifically said it does NOT happen at WOT.. [url="http://www.legacygt.com/forums/showpost.php?p=61101&postcount=15"]http://www.legacygt.com/forums/showpost.php?p=61101&postcount=15[/url][/QUOTE] Hmmm. OK, I'll try it at half throttle or less then.

[twisted]

taking the risk of sounding like an idiot, but anyone tried STP injector cleaner? see if it helps??? My old 91 legacy wagon had this problem but the harder i drove it the less it happened but when a friend or someone else drove it (they would drive it nice and easy) and then it would return. Constant STP usage eliminated this problem for me. like i said...may be i'm way off but worth a try ? only a buck something NOTE: (and i dont work for STP and am not trying to promote their product...however i swear by it and their sonofagun interior/vinyl cleaner...smells funny but the shine is way better than armor all and other brands)

[BlkLegGt]

[quote name='twisted']taking the risk of sounding like an idiot, but anyone tried STP injector cleaner? see if it helps???[/QUOTE] Thanks for the creative thinking. But...injector cleaner?...on a brand new car?... I really hope that it DOES NOT cure it:eek:

[agctr]

For me it only happens when I jump on the loud pedal really hard, really fast from take off after I have taken my foot off the brake. Its like the car is taking a deep breath before nailing it. Adam.

[Deer Killer]

[quote name='agctr']For me it only happens when I jump on the loud pedal really hard, really fast from take off after I have taken my foot off the brake. Its like the car is taking a deep breath before nailing it. Adam.[/QUOTE] You have a different engine. I'm sure it's a totally different issue. But FYI, that doesn't happen in my car. I'm going to have to make a vid to clear this all up....

[Tzar007]

[quote name='Deer Killer']You have a different engine. I'm sure it's a totally different issue. But FYI, that doesn't happen in my car. I'm going to have to make a vid to clear this all up....[/QUOTE] Indeed, a video would probably be the most useful thing. I would like to see it first hand what it is. I have tried today to put half-throttle and all my senses were trying to decipher any possible hiccups, stuttering, bucking, or whatever, and geez, seriously I did not feel anything special. There is just a delay between the moment I touch the gas pedal and the moment the engine takes the cue and really start accelerating. Whether I am only at half throttle or full throttle does not make a difference.

[Beanboy]

I did numerous highway pulls tonight (gotta keep the load on the engine varied during break in, eehehee) from 60 to 80 mph in both 4th and 5th gear. RPMs wre from 2.8K-4.5K roughly. Noticed when I floored the car right away, there was a pause before the power hit. And when it hit, there was a hiccup or two as the revs climbed, and it didn't feel as powerful as it could be. Rolling on the throttle gave a little push back, an then pulled cleanly through the revs, with a tapering off of the feeling of acceleration. Not sure if it is related, but I was surprised as to the vast difference in perceived (aka butt dyno) power delivery. Electronic throttle? Asking the turbo to do too much with the throttle wide open at 2.9K? Didn't do it too many times, just enough to replicate the results. -B

[Boostjunkie]

I've mentioned it before in another thread, but the stuttering feels alot like a mild case of compressor surge. The conditions when the stuttering occurs matches up well to when compressor surge is most often encountered. For those turbo neophytes out there, compressor surge is when the pressure after the compressor is higher than inside the compressor. This causes the airflow to backup into the compressor wheel, thereby slowing it, or stopping it, at which point it tries to spool back up again etc... Basically it's when a turbo flows more air than the engine can injest, as limited by displacement and VE, typically a low rpm/high load situation. I think that in their desire to have a responsive motor that makes nice power down low, coupled with good top end power, Subaru might have undersized the turbine a touch relative to the compressor. The resultant turbo, while offering good boost response is seemingly more prone to surge than one might like. I think they might have tried to compensate to some degree with the ECU calibration. You can avoid surge by having the ECU instruct the wastegate to regulate boost to a lower level at low rpm/high load conditions. Judging from the fact that many (myself included) are experiencing what might be mild compressor surge, this calibration may be inadequate or not exist. Actually, this would really just be a band-aid solution, as it would just mask the underlying problem. My other thought is that it may be detonation that is forcing the ECU to pull timing, which of course would also give the same sensation. This actually seemed more likely to me. I had originally thought that the crappy 91 octane premium gas in CA was to blame, but seemingly others in states that offer 93 octane are still experiencing the stuttering problem, so who knows. I honestly think that the stuttering is caused by one of the two above mentioned reasons, or perhaps a combination of the two. The drive-by-wire system has nothing to do with it, and I doubt that the fuel system has anything to do with it either. Personally, I'm waiting for either Accessport to be released or for a reputable tuner to come up with a good LGT base map for an Ecutek reflash. From there we'll have a better sense of what is actually going on, especially if in the process of tuning some good datalogging can be done.

[Beanboy]

How about the cat in the uppipe? It really isn't a huge deal for me. I don't race on the streets, and in a passing situation I'd have a moment to roll on the throttle. Just curious why there is such a large difference, and what can be done to minimize it.

[NeedMoreBoost]

I’m experiencing the same problems as everyone else here. If the car is under 2500rpm and I try to accelerate, the car bucks and I’m wondering when Eddie Murphy put bananas in my tailpipes. :confused: I assumed this was turbo lag. The 05’ Legacy is my first turbo car but I’ve driven my friends cars, which include: Twin Turbo Dodge Stealth Tenth Anniversary RX-7 Eagle Talon TSi Gti 1.8T With the cars listed above, I’ve noticed some lag but never a stutter or hesitation as mentioned in all the post in here. In my car, if I want to avoid this “banana in the tailpipe” hesitation, I have to wait till 2750-3000 rpm to shift and then it usually doesn’t happen. Now I know it’s a 4 cylinder but my old car isn’t a real beast (95’ Gti VR6). I think that’s a weird coincidence that Adam from down under has the similar problems with a Liberty. Is this from a result of poor engine maps? Poor engine maps because of a inadequate turbo? BoostJunkie made very good points IMO and was very informative for me being a turbo virgin. For the record, Yes I did follow the 1000Mi break in theory, Yes I always put 93 octane, I own a manual 05' legacy, and do allot of driving. 5000 miles on my car and it always stuttered from day 1.

[Beanboy]

Well, hopefully when a reflash/remap arrives along with an uppipe upgrade (or would it be a downgrade?) it will help. Think Subaru might release a reflash? Did the WRX get one? Going to the dealer tonight for an inspection sticker, will hopefully get to talk shop with a tech and get the car up on a lift just to poke around. Will mention the stuttering issue, curious if they have heard anything from other buyers yet. -B

[ewc]

This may be a long shot, but perhaps a grounding kit would help the stuttering. Jerky acceleration was common with the WRXs. Adding additional grounds seemed to help at least some people. [url]http://forums.nasioc.com/forums/showthread.php?t=156303&highlight=jerky+grounding[/url]

[Driver72]

Heck, I guess it's worth a shot doing that "grounding" thing. Sounds like the WRX guys had the same problem, but there's is a bit higher in the RPM range. Then again, there boost comes on higher in the rpm range too so that might be relative. Now, I'm not genius when it comes to electricity, heck I'm no genius about anything. So, I don't mind being the first to give this a try on the LGT's but I'd want to get this correct. 1. I need basically any gauge grounding wire from a hardware or Circuit City type electronics store. It obviously needs to be heat shielded so it won't melt from the heat under the hood, correct? 2. Then I run a couple of these wires from the negative battery terminal to several different areas of the car. Now, obviously, I think, these areas need to be metal, as it wouldn't ground on rubber or plastic, correct. Some of the WRX guys mentioned going from the negative terminal to the intake manifold. Huh? Where exactly are they tying this cable to on the intake manifold. They also went from the negative battery terminal to the strut tower. Did they just attach it to one of the bolts on top of the strut tower? If someone can make this clear, I'd give it a shot this weekend and see what the results are for the LGT. Thanks

[Deer Killer]

Here's a montage.. The camera shaking in/out during acceleration is not my fault (I'm holding it tight to the wheel), rather that's because of the stuttering. So it gives you some idea of the G forces involved. However it's less than half of how bad it is with a full load of passengers.. I'll try to get some video with a carload of people *This is with less than 50% throttle!* Can someone please mirror this? Thanks. ht tp://davatar.home.comcast.net/t est1.avi (remove the spaces to see)

[autoeng]

[quote name='Driver72'] I'm pretty sure it's across the board with all LGT's It's not like some are tuned different than others, or use a different turbo or ECU, the people who are saying they don't have it, probably just accept it as that's how it is suppose to be.[/QUOTE] Well, yes and no. Of course the ECUs aren't tuned to each specific car, but you'd be surprised as to the range of performance (and problems!) that tolerance stack-ups can give. It's entirely possible that some cars would exhibit this more than others. My take is lag in the intake system. Not turbo lag, but the lag in time between when the throttle opens, when the fueling, cam timing, etc. changes, and when the air actually hits the cylinder in this specific instance. This lag varies highly based on engine speed due to pressure wave effects, and maybe it's even compounded some by compressor surge (as someone mentioned) at this frequency. Perhaps the calibration for the transition from off-boost steady-state to higher load is poor in this instance due to these effects. My whole point is: I doubt that it's some dumb, easy fix. Too much goes into vehicle validation to miss a simple mistake like "Subaru doesn't know how to use electronic throttle." I'm not saying mistakes aren't made, but give us engineers some credit! (No, I don't work for Subaru! :) ) Definitely an annoying problem that I'll try to duplicate on my test drive next week, though! autoeng

[Deer Killer]

[quote name='autoeng']but you'd be surprised as to the range of performance (and problems!) that tolerance stack-ups can give. [/QUOTE] That's WHY they have engineers... The total tolerance should be way above what any new car will do, because obviously as the engine ages you're going to NEED that tolerance.. somebody fvkced up.. Could be as simple as making ECU maps for a clear uppipe and then some tard shoving in pre-cat to sell it in NA (sort of like the bumpers).

[Tzar007]

[quote name='Deer Killer']Here's a montage.. The camera shaking in/out during acceleration is not my fault (I'm holding it tight to the wheel), rather that's because of the stuttering. So it gives you some idea of the G forces involved. However it's less than half of how bad it is with a full load of passengers.. I'll try to get some video with a carload of people Can someone please mirror this? Thanks. ht tp://davatar.home.comcast.net/t est1.avi (remove the spaces to see)[/QUOTE] OK, I understand now with the video. If I get it correctly, this hiccup can be heard in the sound of the engine which goes like "whooo.....whooo....whooo....whooohoouhooouh", the first three "whooo..." being the hiccups (sorry for my bad interpretation, it's the best I could come up with). It's quite subtle, but it's definitely noticeable (even in the video), and I guess being in the car makes it definetely annoying. I'll pay attention again, but honestly I'm pretty sure my car does not exhibit that behavior. Mine seems just sluggish for 1 second or so but the engine never sounds like this.

[SBT]

It really sounds like the ECU is pulling timing, almost as though you're getting a misfire or, more appropriately, a "non-fire" when a cylinder doesn't fire when it should for that load/range. I've done the grounding mod on all of the Subes and it makes an amazing difference. I'm really of the opinion, in the case of older generation EJs, that the knock sensor was and is the major contributor to rough engine at/above 2000 rpm through to redline if all other things are working properly, e.g., throttle body, IAS, coilpack, wires, plugs and fuel delivery. And I know that Subaru knows in their engineering heart, that this is the case. I really can't believe that they would allow this trend to continue in their most recent EJ variants, particularly in the Legacy since this is their newest line-in-the-sand automobile. But it's sounding more and more like knock sensor, particularly after listening to the video several times at different volumes to try and pick up the auditory nuances. That would mean that the ECU is protecting the engine but, most likely, erroneously so. SBT

[ewc]

Here's a link with pictures of a review I recently did of my wrx grounding kit. You can see where each circled grounding point is. The intake manifolds are points 2 and 3 in the pic below. The legacy engine should be pretty similar. My setup is a "daisy chain," rather than running each point back to the negative battery terminal. While not ideal, it seems to work pretty well in my situation. You can get any thick gauge wire from a stereo shop, and crimps from Radio Shack. The wire doesn't need to be heat resistant, as you can run it so it doesn't come into contact with the really hot parts of the engine. [url]http://forums.nasioc.com/forums/showthread.php?t=653241[/url] [img]http://www.we-todd-did-racing.com/wetoddimage.wtdr/wNjE3MjYxNnM0MTNkZmQzMXk1NDE%3D.jpg[/img] [quote name='Driver72']Heck, I guess it's worth a shot doing that "grounding" thing. Sounds like the WRX guys had the same problem, but there's is a bit higher in the RPM range. Then again, there boost comes on higher in the rpm range too so that might be relative. Now, I'm not genius when it comes to electricity, heck I'm no genius about anything. So, I don't mind being the first to give this a try on the LGT's but I'd want to get this correct. 1. I need basically any gauge grounding wire from a hardware or Circuit City type electronics store. It obviously needs to be heat shielded so it won't melt from the heat under the hood, correct? 2. Then I run a couple of these wires from the negative battery terminal to several different areas of the car. Now, obviously, I think, these areas need to be metal, as it wouldn't ground on rubber or plastic, correct. Some of the WRX guys mentioned going from the negative terminal to the intake manifold. Huh? Where exactly are they tying this cable to on the intake manifold. They also went from the negative battery terminal to the strut tower. Did they just attach it to one of the bolts on top of the strut tower? If someone can make this clear, I'd give it a shot this weekend and see what the results are for the LGT. Thanks[/QUOTE]

[ewc]

If it were a misfire, shouldn't the CEL flash quickly during the occurence? I know that the wrx ecu had this feature. [quote name='Subietonic']It really sounds like the ECU is pulling timing, almost as though you're getting a misfire or, more appropriately, a "non-fire" when a cylinder doesn't fire when it should for that load/range. I've done the grounding mod on all of the Subes and it makes an amazing difference. I'm really of the opinion, in the case of older generation EJs, that the knock sensor was and is the major contributor to rough engine at/above 2000 rpm through to redline if all other things are working properly, e.g., throttle body, IAS, coilpack, wires, plugs and fuel delivery. And I know that Subaru knows in their engineering heart, that this is the case. I really can't believe that they would allow this trend to continue in their most recent EJ variants, particularly in the Legacy since this is their newest line-in-the-sand automobile. But it's sounding more and more like knock sensor, particularly after listening to the video several times at different volumes to try and pick up the auditory nuances. That would mean that the ECU is protecting the engine but, most likely, erroneously so. SBT[/QUOTE]

[SBT]

With the extended learning curve of the ECU, I'd think that it would log the event, but, if it's creating an incorrect timing retard (due to knock sensor faulty reading) vs. "detecting" an actual misfire, I'm not even sure that it would log it. Like I said, it sounded like it was misfiring or that the ECU was retarding the timing. autoeng's comment about compressor surge may have some merit too. Particularly as it pertains to timing, fuel and a/f when the ECU is rapidly trying to balance everything. If the knock sensor is a causal factor, then the addition of, or because of the compressor surge, everything will get skewed while the ECU balances everything at that rpm/load range. I'm going to run this by the local tech rep to see if he's seen it yet or knows what's causing it. SBT