Ryokosman Posted November 14, 2007 Share Posted November 14, 2007 Haven't thought about the stutter being knock related. I'm gonna put some 101 in the tank tomm and see what happens. Link to comment Share on other sites More sharing options...
Lothar Posted November 14, 2007 Share Posted November 14, 2007 The following is a quote posted a while back by Codean, on one of the many "stutter" threads on this forum: The issue is caused by poor factory tuning due to subaru trying to meet LEV2 status. 2007 legacy's and STI's have this issue because they share the same "new"ecu. The source of the problem is that the tuning is too lean (14.7 to 1 AFR) while the turbo is making full boost. Any tuner out there will tell you that running full boost @ 14.7 AFR's all the way up to 4000 rpm is insane. The "stutter" you feel is the ecu pulling igntion timing because the engine is knocking. There have been quiet a few 2007 STI's, even stock, that have damaged pistions due to this issue. The only way to fix this issue is to have the car tuned. Link to comment Share on other sites More sharing options...
rudy Posted November 14, 2007 Share Posted November 14, 2007 So... How I am understanding this is Subaru detuned the hardware/engine, and aggressively tuned the computer to get the same and/or slightly more,but not much noticeable, power. Going by Cobb's results from the 2007+ STI: 2004-2006 STIs can see gains of +25 Horsepower and +40 lb-ft Torque 2007 STI can see gains of +37 Horsepower and 50 lb-ft Torque And Codean's information: Originally Posted by Codean The issue is caused by poor factory tuning due to subaru trying to meet LEV2 status. 2007 legacy's and STI's have this issue because they share the same "new"ecu.The underlying engine hardware is the same or improved over previous years and the car can benefit quite a bit from a tune. My guess, and Christian is the expert who can confirm, is that there is an opportunity to run less aggressive timing but higher boost to achieve higher HP numbers. I know with my Miata, I could run the low boost pulley and pull no timing for ~180whp, or a higher boost pulley and pull some timing for ~190whp. Link to comment Share on other sites More sharing options...
psi365 Posted November 14, 2007 Share Posted November 14, 2007 14.7:1 is actually the ideal air/fuel ratio. The car wouldn't be running lean. From Wikopedia A mixture is the working point that modern engine management systems employing fuel injection attempt to achieve in light load cruise situations. For gasoline fuel, the stoichiometric air/fuel mixture is approximately 14.7 times the mass of air to fuel. Any mixture less than 14.7 to 1 is considered to be a rich mixture, any more than 14.7 to 1 is a lean mixture - given perfect (ideal) "test" fuel (gasoline consisting of solely n-heptane and iso-octane. Christian, Since you are already doing dyno runs on LGT could you finally put to rest the rumor of whether or not spec Bs have more hp over a regular LGT (I believe they are the same)? Link to comment Share on other sites More sharing options...
Town Posted November 14, 2007 Share Posted November 14, 2007 Christian, Since you are already doing dyno runs on LGT could you finally put to rest the rumor of whether or not spec Bs have more hp over a regular LGT (I believe they are the same)? They should be exactly the same. Unless the chrome side sills handle airflow better? Link to comment Share on other sites More sharing options...
Neurodancer Posted November 14, 2007 Share Posted November 14, 2007 WOW -- the quality of this thread really picked back up since SEMA! Thanks Christian! Link to comment Share on other sites More sharing options...
psi365 Posted November 14, 2007 Share Posted November 14, 2007 They should be exactly the same. Unless the chrome side sills handle airflow better? I fully know this, however there are some other members/member that believe the magical spec B fairly sprinkled their car with pixie dust and their car has more hp. Instead that magical fairly is some glue sniffing psycho. Building model airplanes he says. I'm not buying it. Next thing you know you are missing money out of you wallet and your daughter is knocked up. I've seen it a hundred times before. Anyways I know it should be the same, but since they are already doing base lines on stock cars this would be the proof to shut them up that they are the same. Link to comment Share on other sites More sharing options...
rudy Posted November 14, 2007 Share Posted November 14, 2007 14.7:1 is actually the ideal air/fuel ratio. The car wouldn't be running lean. Christian again is the expert and can confirm, but I think you want no business with a 14.7:1 A/F ratio under boost at high RPMs. I believe you want to throw a lot of fuel (usually done when an ECU flips to open loop) and run rich, maybe between 10-11:1 in order to cool things down and keep the EGTs from shooting too high. Link to comment Share on other sites More sharing options...
Ryokosman Posted November 14, 2007 Share Posted November 14, 2007 14.7 on a FI motor is def very lean. Most people I know consider 13's lean. Link to comment Share on other sites More sharing options...
psi365 Posted November 14, 2007 Share Posted November 14, 2007 Christian again is the expert and can confirm, but I think you want no business with a 14.7:1 A/F ratio under boost at high RPMs. I believe you want to throw a lot of fuel (usually done when an ECU flips to open loop) and run rich, maybe between 10-11:1 in order to cool things down and keep the EGTs from shooting too high. I'm not an expert on tuning. I've always been taught that 14.7:1 is the ideal air/fuel ratio(see my post where I quoted Wikipedia) at idle or light throttle. When it comes to changing boost levels and air fuel ratios I leave it up to the experts like Christian. Link to comment Share on other sites More sharing options...
Zed 2.0 Posted November 14, 2007 Share Posted November 14, 2007 Originally Posted by Codean The issue is caused by poor factory tuning due to subaru trying to meet LEV2 status. 2007 legacy's and STI's have this issue because they share the same "new"ecu. The source of the problem is that the tuning is too lean (14.7 to 1 AFR) while the turbo is making full boost. Any tuner out there will tell you that running full boost @ 14.7 AFR's all the way up to 4000 rpm is insane. The "stutter" you feel is the ecu pulling igntion timing because the engine is knocking. There have been quiet a few 2007 STI's, even stock, that have damaged pistions due to this issue. The only way to fix this issue is to have the car tuned.: I'm a engine management noob, but when the engine pulls timing due to knock it will do so for more than that one occasion, correct? It doesn't make sense that a "learning" ECU would allow the engine to knock in the same place every time you accelerate. There is also none of the sound that is associated with knock/ping. Link to comment Share on other sites More sharing options...
Christian. Posted November 14, 2007 Author Share Posted November 14, 2007 Christian, Do you think that this newer, more "aggressively efficient" tuning the cause of the "stutter" problem that many people have seen? That the stutter is actually the ECU pulling timing due to knock? One thing I did not notice was the knock sensor signal spiking around the CL/OL transition so I don't believe this particular car was knocking there, although, the power (torque) productions was definitely lower in that area when compared to previous and post RPM points so that lets you know the ECU is pulling back some ignition advance to protect the engine. I believe this is part of the reported stutter, another part of the stutter has to do with the throttle mapping and other ECU settings which we will be addressing in our calibrations. Could this also be what would cause the car to fall flat on its face on some occasions? I am not sure what is causing this on your car, any additional information would be helpful. I am trying to get as much optimization completed with this initial release. Haven't thought about the stutter being knock related. I'm gonna put some 101 in the tank tomm and see what happens. Sometimes higher octane fuels can handle the additional heat produced by a leaner burn and the ECU will not need to remove ignition advance so things may appear better. The underlying engine hardware is the same or improved over previous years and the car can benefit quite a bit from a tune. My guess, and Christian is the expert who can confirm, is that there is an opportunity to run less aggressive timing but higher boost to achieve higher HP numbers. I know with my Miata, I could run the low boost pulley and pull no timing for ~180whp, or a higher boost pulley and pull some timing for ~190whp. Generally speaking, on turbocharged cars you can produce additional VE (Volumetric Efficiency) through increase boost pressure, taking into account heat exchanging capabilities and keeping hardware within it's mechanical limitations. More VE will require less ignition advance, that is the short answer. WOW -- the quality of this thread really picked back up since SEMA! Thanks Christian! Well, I was super busy trying to figure out how to make this We are just a normal small company with limited resources. I was very busy prior to SEMA working on this = http://www.accessecu.com/Christian/IMG_5080%20for%20Blog.jpg Christian, Since you are already doing dyno runs on LGT could you finally put to rest the rumor of whether or not spec Bs have more hp over a regular LGT (I believe they are the same)? The Spec B will most likely have a different power curve due to different gearing (different torque multiplication). 14.7 on a FI motor is def very lean. Most people I know consider 13's lean. Well......1 Lambda (perfect combustion, equal fuel and air on a molecular level) has an equivalence of 14.68 parts air to 1 part fuel for petrol. Other fuels have other ratios, that is why you should always tune in Lambda...no need to figure out the fuel conversion. All WBO2 sensors measure Lambda and are converted from that value based on the fuel used. That is something that is very difficult for most others to understand. A stoichiometric burn is a combustion which produces the least amount of overall emissions and allows the most efficient processing by modern catalysts. Ideally, you want to have all cars run 1 Lambda under all conditions. It would be ideal if an engine can handle this and it is up to today's automotive engineers to figure this out. Although, by the time they do we will need to stop burning hydro carbons for environmental reasons. Again, thank you all for your patience. Christian. Link to comment Share on other sites More sharing options...
psi365 Posted November 14, 2007 Share Posted November 14, 2007 The Spec B will most likely have a different power curve due to different gearing (different torque multiplication). Christian. THat's what I was guessing was giving people the false sense of more hp in a cB. Link to comment Share on other sites More sharing options...
NateWA Posted November 14, 2007 Share Posted November 14, 2007 That intercooler looks A-Mazing! good thing Im graduating college and getting a job in less than a year!! Link to comment Share on other sites More sharing options...
Zed 2.0 Posted November 14, 2007 Share Posted November 14, 2007 Is that intercooler just a concept design? It looks insane. Link to comment Share on other sites More sharing options...
CapnJack Posted November 15, 2007 Share Posted November 15, 2007 I am not sure what is causing this on your car, any additional information would be helpful. I am trying to get as much optimization completed with this initial release. Christian. Christian, My car is a 2007 LGT with the 5MT, completely stock with about 11K miles on it. I'm not sure who else was having this problem(Carter?), but I have seen it 3-4 times on my car since I purchased it in July of 2007. When accelerating from a complete stop in first gear, the car will have an initial burst of power(just enough to get you in the middle of the intersection) then fall flat on it's face for about half a second, followed immediately by the burst of power that was there when I left the stop. There is no CEL or other indication of problems. I have had the car's ECM reset once already for the studder issue and it went away for about 600 miles(including the total loss of power), but it ultimately returned. I called my dealer and they spoke with Subaru about the new reflash and Subaru told them until the new reflash comes out, the only way to get rid of the studder and loss of power is to reflash it every time the studder returns to basically put the ECM in a constant state of learning. I hope this helps... Maybe others can add to this?? Link to comment Share on other sites More sharing options...
DiscoWagon Posted November 15, 2007 Share Posted November 15, 2007 Mine has the stutter in pretty much any gear during WOT. Link to comment Share on other sites More sharing options...
57ufu Posted November 15, 2007 Share Posted November 15, 2007 Apologies for asking a question that might come across as riduclous. Will the AP work with an Australian Delivered my08 GT spec B. Same engines from what information i have managed to track down but then again who can you really trust on the internet. The only real difference i can think of, outside of the fact you sit on the wrong side of the car, is fuel quality as the US and Aus use different Octane rating systems. eg Your 93 is our 98ish. Link to comment Share on other sites More sharing options...
Carter Posted November 15, 2007 Share Posted November 15, 2007 I dont want to take over a thread, but I dont know if what I am about to say could be helpful. Yes I have the stutter problem, I'm 08 Legacy GT 5EAT. It has taken me a long time to even guess what could be going on here. After I recoreded some data logs of my vehicle and posted them here I got the idea that the "hesitation/stutter" could actually be knock. I am no expert in this area, but I posted on other forums, and from what I have read EVERYWHERE, i.e. LegacyGT, NASIOC, Audizine, and even CobbTuning people have told me that my a/f ratio at max boost is dangerous and that I should get a tune immediately. Subaru couldnt give a shit. My leanest a/f ratio I have recored is 15.04:1 at a peak of 14 lbs of boost. My test was done in 3rd gear, 100% throttle from 20 MPH to redline. My car will stay lean, closed loop from 1500 RPM up to ~4500 RPM before the a/f ratio goes down to 11.14 (The target number from what I hear) One of my logs can be found here. http://cartermarkham.homestead.com/files/logs/enginuitylog_20071110_115028.csv All the dealers I have contacted, in state and even on the west coast cannot tell me the target a/f ratio at max boost levels and when I tell them the numbers I am getting, they are not concered. "if im not getting a CEL, dont worry." SOA will not release the target numbers. Subaru had a technician come up from out of state on behalf of SOA and he found nothing wrong. Unfortunately they will not allow me to see the data he collected. I dont know what to believe, and it doesnt help that I dont know much about a/f ratios and knocking, but I need an answer. Reading that wiki article only confuses me more. I have done google searches for Turbo engines and their target A.F ratios and everyone says something different. If I am indeed running dangerously lean I might consider a Cobb access port or other software if it will fix the problem. Christian I would appreciate it if you could chime in, as I believe you would know more than these other smucks (just kidding) This whole situation has put me on edge since I have owned the car. As it stands now I am trying to collect as much data and member input as I can. I am planning on trying to lemon the vehicle if the reliability has been sacraficed for the sake of emissions. I cant drive around all the time worried im going to blow the engine. Link to comment Share on other sites More sharing options...
Guest heightsgtltd Posted November 15, 2007 Share Posted November 15, 2007 Dude... take it somewhere else Link to comment Share on other sites More sharing options...
Carter Posted November 15, 2007 Share Posted November 15, 2007 Dude... take it somewhere else I have been to 3, there are very few around. All of them have told me not to worry about it. One dealer said the numbers meant nothing. Link to comment Share on other sites More sharing options...
Guest heightsgtltd Posted November 15, 2007 Share Posted November 15, 2007 No, I mean take this somewhere else out of this thread. It's not the place for it. You already have your own whole ******* thread on this Link to comment Share on other sites More sharing options...
Carter Posted November 15, 2007 Share Posted November 15, 2007 No, I mean take this somewhere else out of this thread. It's not the place for it. You already have your own whole ******* thread on this No, I want to know if the access port can address this problem, if it is a problem. And that is an answer Im hoping Christian can answer. Link to comment Share on other sites More sharing options...
CapnJack Posted November 15, 2007 Share Posted November 15, 2007 Mine has the stutter in pretty much any gear during WOT. Mine has the stutter in any gear except for first. It almost always pulls like the perverbal raped ape in first gear. The only time it doesn't is when it does this burst, bog, burst on very rare occations. It's not repeatable at all and seems to only happen in sport and sport # mode. (Although I don't drive in intellegent very often.) It has happened when the car is cold (blue light still on) and when it's completely warm. I don't know much about knock or af ratios either as this is my first turbo car, but I'm finding the posts by Christian and others very interesting. I believe it's helpfull to put as much information in this thread as possible so Christian does not have to search around to find answers. Link to comment Share on other sites More sharing options...
Jon in CT Posted November 15, 2007 Share Posted November 15, 2007 Will the AP work with an Australian Delivered my08 GT spec B.The AP sold in North America is, at the moment, strictly for North American spec ECUs. Link to comment Share on other sites More sharing options...
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