Weak STi?
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This is a discussion on Weak STi? within the Motorsports Talk forums, part of the Community - Meet other Enthusiasts category; From looking at a few posts over on NASIOC I began to wonder if I have a weak STi. It ...

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    Registered User RealDealTarheel's Avatar
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    Weak STi?

    From looking at a few posts over on NASIOC I began to wonder if I have a weak STi. It very well could be that I launch at too low an RPM, I don't know. Anyhow I'm seeing that with a Stage 2 STi I should be trapping in the 105-107ish range, I've never trapped higher than 103. So here's my launch technique and shift points. I hold the revs at 5k, slip the clutch and I shift at 6250-6400 rpm every gear(and that's power shifting). Am I shifting too early? Am I launching at too low an RPM? Or do I just have a weak STi? I haven't put it on a dyno yet because I feel that dyno's are best used for tuning and I haven't gotten around to a pro-tune yet. Any thoughts? My best trap sock was 99mph, the above mentioned 103 was stage 2. Any thoughts?
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    Registered User LilJohn's Avatar
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    what kind of engine management are you useing?
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    Registered User RealDealTarheel's Avatar
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    Quote Originally Posted by LilJohn View Post
    what kind of engine management are you useing?
    I'm using the Cobb AP ver 2 with the OTS map.
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    Registered User LilJohn's Avatar
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    Quote Originally Posted by RealDealTarheel View Post
    I'm using the Cobb AP ver 2 with the OTS map.
    well this isn't that surprising, cobb's OTS maps are very conservative and they run very rich. a protune should get you the HP your looking for.
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    Registered User RealDealTarheel's Avatar
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    Quote Originally Posted by LilJohn View Post
    well this isn't that surprising, cobb's OTS maps are very conservative and they run very rich. a protune should get you the HP your looking for.
    Hmm....do you think I'm trapping where I should be with an OTS map? I still think I should be trapping higher. My times aren't that great either but I think I can attribute that to driver error. I'm curious if driver error will affect trap speed as well. I think trap speed tells the story on how strong a car is.
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    Moderator YBNormal07's Avatar
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    Quote Originally Posted by LilJohn View Post
    well this isn't that surprising, cobb's OTS maps are very conservative and they run very rich. a protune should get you the HP your looking for.
    True, the stock cobb maps are conservative, but in comparison to a stock map, the Cobb stage 2 is quite a bit more hp and tq. A protune provides gains, but they are no where near as significant as the stage 2 map against the stock map.

    OP, since it is time/speed you are looking for, you have the car to do so. Have you considered the elevation of the track you are running at? This will have a major impact of your time/traps.

    Also, you are def shifting a bit early imo. To achieve a 12.9/103 on my 04 STOCK STi, I pulsed the throttle at launch to get as much scrolling as possible of the compressor, then nailed the throttle and did a quick lift of the throttle. If all 4 tires aren't breaking loose, you aren't launching correctly.

    When doing this, you need to be ready for 2nd immediately...like right out of the gate. Set your rev alarm for around 6800.....this will keep you out of the rev limiter if you shift fast enough. If you don't, set the alarm even lower to account for the slower reaction time when shifting.

    Slam the gears quickly, put don't power shift as there is just too much shock to the drivetrain on the AWD platform when doing this.

    You should just be shifting into 5th gear at the end of the track...about 100-300 feet from the finish trap lights.

    Have you read all the stickeys on launching, etc?
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    Registered User RealDealTarheel's Avatar
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    Yeah I've read the stickies but I found that I can't get the car to build any boost with the pulsing method. I just feel like I'm reving it sky high and it doesn't come down fast enough. With the slip method I got just a smidge of wheel spin. I'm shifting in 5th at the end of the 1/4. I'll refrain from power shifting in the future though. I think I'm doing an okay job of driving the car, I just really think I have a weak STi. Unless shifting early is really hurting my trap speed that much. I hesitate to take the car to the rev limit and maybe that's what my fault is.
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    Moderator YBNormal07's Avatar
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    It is hard to build boost on a manual car while the clutch is in...no question.

    The boost pressure I am referring to really doesn't amount to much...it can barely be read on a boost guage in fact. What you are actually trying to do is get the compressore wheel spinning prior to launching to prevent bog.

    There is a definite rythm to building boost at the line. It requires very quick pulses to the throttle, but you have to really listen to the engine and if you have a boost guage, watch the guage closely. If you can see you are exiting vacuum and building even a little bit of pressure, then you are on the right track. If you don't have a guage, you should be able to hear the recirc valve lifting whenever you lift the throttle...once even the slightes bit of pressure is provided at the intake from the turbo.

    You have to combine this pulsing with a very closely calibrated foot plant at the end coordinated with a quick realease of the clutch. The goal is to take advantage of the small bit of pressure you have accumulated and have the car immediately into boost upon release of the throttle.

    Alternatively, you can just mash the throttle when you see the 2nd yellow light, releasing the clutch at the same time. This will give you close to the same results. I say do this at the second light as the small fraction of time it takes to go from no throttle to full throttle is about equal to the time between the 2nd yellow and the green.

    Did you check on your elevation? You do have a point in that even with a poor launch, your trap speed should be a least 103...and normally around 105-07 for stage 2. If you aren't at sea level, even 100 feet makes a difference.

    If you still suspect a weak STi, I would look around for a dyno so you can confirm your suspiscions and then go from there. You could have a small vacuum leak, a catching waste gate, or a few other things. I say look at the track elevation first though. 2 mph difference in trap speed can easily be accounted for with 1000 feet of elevation.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
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    Registered User RealDealTarheel's Avatar
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    If I'm not at or about sea level I would be thoroughly shocked. I'm right on the coast here in NC. The track I go to is about 20 minutes inland on what seems to be flat land. I know there's probably some rise between the 20 minutes it takes me to get to the track from my house, but I can't see it making that big of a difference as I'm not climbing any hills or mountains to get there. On the throttle pulse note I have a boost gauge and I do see the vac changing, I definitely see the needle swinging towards boost and away from vac, but not that much. I don't know. I'm thinking I'll just say Eff it and get Ecutek tuned when I drop in what ever turbo I choose to replace the stocker.
    Last edited by RealDealTarheel; 06-20-2007 at 07:12 PM. Reason: My inability to read the gentlemans responce.
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    Moderator YBNormal07's Avatar
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    The track should have a website that lists the elevation. I know of the following tracks in NC:

    Maxton-Laurinburg: 256 ft
    Wilkesboro: 700 ft
    Kinston: 125 ft

    there are about another half dozen or so 1/8th mile tracks too.

    Good luck with your modding.
    tEh PriUs=teH faSTah!@@!
    08 Audi S5 Black Diamond edition
    SOLD: 05 SWP Legacy GT Limited 5MT, 13.3ish@105 (stage 2) crappy stock clutch
    SOLD: 04 MPS/SW WRX Sti. 12.971 @ 103.97 (stock)
    278 AWHP/283 AWT, Catback exhaust
    306 AWHP/341 AWT, Stage 2
    (Scott) Moderator-STi, Drag Racing, Car Purchasing, and Tutorial Forums

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    Registered User rr1911's Avatar
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    Sorry to Hijack but are you using something to cool your intercooler ?
    I think a cooler intercooler might help you a little
    also i would check for a boost leak somewhere ( i zip tied all of my boost lines)
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    Registered User RealDealTarheel's Avatar
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    I use ice water in my intercooler sprayer and I spray the snot out of it before I do my run. I don't think I have any boost leaks because I don't see any wierd spikes or drops in boost and the car boosts the way it's supposed to as far as I know. I only have 2 1/2 weeks left in this country so I won't have a chance to put it on a dyno that I know of and I don't want to drag the car anymore until I get the properly built to withstand it.
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    Registered User rr1911's Avatar
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    how long u gonna spend in the box ?
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    Registered User RealDealTarheel's Avatar
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    Quote Originally Posted by rr1911 View Post
    how long u gonna spend in the box ?
    I'm going to Japan for 3 years. From there hopefully I get put on a Marine Expeditionary Unit so I can go to the sand box or somewhere.
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    Registered User STiDriven's Avatar
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    Quote Originally Posted by YBNormal07 View Post
    It is hard to build boost on a manual car while the clutch is in...no question.

    The boost pressure I am referring to really doesn't amount to much...it can barely be read on a boost guage in fact. What you are actually trying to do is get the compressore wheel spinning prior to launching to prevent bog.

    There is a definite rythm to building boost at the line. It requires very quick pulses to the throttle, but you have to really listen to the engine and if you have a boost guage, watch the guage closely. If you can see you are exiting vacuum and building even a little bit of pressure, then you are on the right track. If you don't have a guage, you should be able to hear the recirc valve lifting whenever you lift the throttle...once even the slightes bit of pressure is provided at the intake from the turbo.

    You have to combine this pulsing with a very closely calibrated foot plant at the end coordinated with a quick realease of the clutch. The goal is to take advantage of the small bit of pressure you have accumulated and have the car immediately into boost upon release of the throttle.

    Alternatively, you can just mash the throttle when you see the 2nd yellow light, releasing the clutch at the same time. This will give you close to the same results. I say do this at the second light as the small fraction of time it takes to go from no throttle to full throttle is about equal to the time between the 2nd yellow and the green.

    Did you check on your elevation? You do have a point in that even with a poor launch, your trap speed should be a least 103...and normally around 105-07 for stage 2. If you aren't at sea level, even 100 feet makes a difference.

    If you still suspect a weak STi, I would look around for a dyno so you can confirm your suspiscions and then go from there. You could have a small vacuum leak, a catching waste gate, or a few other things. I say look at the track elevation first though. 2 mph difference in trap speed can easily be accounted for with 1000 feet of elevation.

    Well thats what it is!!

    I never knew quite what it was, but I always noticed I got the best launch with the two turbo cars i've owned with that method. A Talon TSi FWD and my STi. Both were similar, you blip the throttle a few time up to about 3K, mash the gas and quickly let up the clutch. If I got it right you launch with what feels like max torque. The STi just rips, especially Stg2.

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