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Old 11-18-2012, 11:55 AM   #1
Subiezilla
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I am curious if launch control damages the powertrain(ring lands as many have mentioned) or just the obvious damage caused to the drivetrain from doing launches on our subarus?

Edit: launch control on COBB AP
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Last edited by Subiezilla; 11-18-2012 at 12:46 PM.
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Old 11-18-2012, 12:45 PM   #2
rocketperson7
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if it's a fuel cut launch control, and detonates from going lean, it's a possibility
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Old 11-18-2012, 12:46 PM   #3
Subiezilla
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Quote:
Originally Posted by rocketperson7
if it's a fuel cut launch control, and detonates from going lean, it's a possibility
Specifically LC on the Cobb AP
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Old 11-18-2012, 12:54 PM   #4
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I have never heard of the cobb lc doing this...i have a 12 sti stg 2 and have used lc quite a few times no failure yet ...if anything its worse on every other part of the car rather then the rings
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Old 11-18-2012, 04:56 PM   #5
Subiezilla
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Hopefully COBB can chime in with an official response
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Old 11-18-2012, 06:18 PM   #6
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beating the shyt out of your car, which normally happens when LC is engaged, could, possibly, cause failure of something.
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Old 11-18-2012, 07:54 PM   #7
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Gonna sue Cobb now? lol
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Old 11-18-2012, 11:47 PM   #8
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Quote:
Originally Posted by Nuke209
Gonna sue Cobb now? lol
No one is going to sue Cobb just an honest question
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Old 11-20-2012, 01:59 AM   #9
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Did some google searching and it turns out that cobb's launch control uses fuel cut off, which seems logical that it would creat a lean situation. Lean situations can lead to detonation and piston and ringland damage can occur. Now that's just my logic and correct me if my logic is wrong.
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Old 11-20-2012, 10:17 AM   #10
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Most cars use a fuel cut as the factory rev limiter since ignition cut is much more violent/sudden and also tends to damage cats. Auto manufacturers would not choose to implement fuel cut if it sacrificed reliability and cost them a significant amount of money in warranty claims.

Now how/why is it not an issue to cut fuel while at full tilt? I'm not 100% sure. My only guess is that the lean condition is so short lived rev to rev that theres no problem. When fuel cut is active the injectors are completely shut down and maybe the mix transitions from lean/combustible to uncombustable very quickly and the opposite holds true upon injector reactivation. Just a guess...

And as a BTW...been using AP launch control and flat shifting as needed for months on my stock motor STI. 450+ AWHP on E85. No issues so far (knock on wood).

Last edited by 1QUIKV6; 11-20-2012 at 10:29 AM.
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Old 11-20-2012, 10:22 AM   #11
rocketperson7
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No, it's just better to have detonation for a second than to float a valve

the rev limit is not a miracle worker, people still spin bearings from detonation when you ride the rev limiter (in the 2L)
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Old 11-20-2012, 05:11 PM   #12
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So it can be harmful but only if abused?
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Old 11-29-2012, 07:13 PM   #13
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You're using an aftermarket ROM on your engine computer to artificially increase boost while the car is sitting still so you can launch the car harder. That alone is a good argument for anyone, including the dealer or SoA to categorize as "abuse".

You're modifying the car - don't expect the dealer or SoA to honor warranties related to or caused by your modifications. If you blow a ring land, and the dealership finds out your car has a downpipe and was reflashed, and you've been launching the car you've already dug yourself a ditch. Some dealerships are nicer than others and will try to push to SoA to have it repaired. Others just run it by the book.

When I was playing with Launch Control and beta testing it for Cobb back in 2005 and 2006, and recently as of a few months ago, it would pull a lot of timing in the areas around where you have the launch limit set. This hasn't changed much, and is a persistent problem. I turned off launch control and only use flat foot shifting now, and subsequently have learned to launch the car without the aid of launch control.
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Old 12-03-2012, 10:52 PM   #14
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Quote:
Originally Posted by atomicfire View Post
You're using an aftermarket ROM on your engine computer to artificially increase boost while the car is sitting still so you can launch the car harder. That alone is a good argument for anyone, including the dealer or SoA to categorize as "abuse".

You're modifying the car - don't expect the dealer or SoA to honor warranties related to or caused by your modifications. If you blow a ring land, and the dealership finds out your car has a downpipe and was reflashed, and you've been launching the car you've already dug yourself a ditch. Some dealerships are nicer than others and will try to push to SoA to have it repaired. Others just run it by the book.

When I was playing with Launch Control and beta testing it for Cobb back in 2005 and 2006, and recently as of a few months ago, it would pull a lot of timing in the areas around where you have the launch limit set. This hasn't changed much, and is a persistent problem. I turned off launch control and only use flat foot shifting now, and subsequently have learned to launch the car without the aid of launch control.
Thanks for the feedback I thought as much about the launch control
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Old 12-04-2012, 09:19 AM   #15
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There are a lot of misconceptions about how launch control works. Our launch control uses the factory fuel cut rev limiter to allow you to hold your specified RPM to build boost and allow for harder and more consistent launches. The ability to hold near a specific RPM is accomplished by the factory rev limiter (and specific narrow RPM window in the LC tune) by alternating between fuel cut and no fuel cut. The idea that you are running lean (and potentially causing knock) when this occurring is a misunderstanding of how the system works. Fuel cut means no fuel whatsoever. You cannot have combustion without fuel and you cannot have knock without combustion. So, while it is possible to knock as RPM drops with launch control (i.e. as fueling is resumed to maintain RPM range), this is no different than the basic premise of any other normal engine operation. As RPM increases with launch control, fuel is cut and each cylinder is just pumping air. A lot of the misconceptions about fuel cut launch control come from attempting to monitor fueling via o2 sensor when launch control is active. Any o2 sensor (factory or aftermarket) does not have remotely anything near the level of resolution to discern a single combustion level event. As such, the o2 sensor reports leaner than expected as it is seeing the oxygen content with no combustion when fuel cut is active.

In our test of the latest launch control, we were not able to duplicate any knock issues internally in many tests on different cars. We did, however, see knock from a few of our external testers (and other customers) and have seen reports of the same from other solutions on the market. Typically, the cars that have issues are beyond stage 2. In some cases, it may be possible to mitigate the knock by manipulating the LC or FFS RPM thresholds and/or by tweaking ignition timing and/or fueling. In some other cases (especially with FFS), there seems to be a false knock component. Regardless, if you are regularly using LC and/or FFS, it would be a good idea to monitor via data logging.

That all said, launch control and flat-foot shift can be very abusive to the car. With launch control, for example, the ability to launch the car much harder than you could without it, obviously puts much more stress on the drivetrain. Holding a specific RPM and building a good amount of boost when the car is stationary also greatly increases the chance of intercooler heat soak (and thus potential detonation). Being able to shift with your foot to the floor (FFS) is obviously harder on the transmission. It is important to understand the risks involved when using LC and FFS. We offer it as an option because there are group of individuals who benefit from these features, such as drag racers who are willing to accept the risk in order to make gains on the track.

Bill
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Old 12-04-2012, 09:19 PM   #16
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^^^^^^^boom.
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Old 12-05-2012, 01:01 AM   #17
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Thanks COBB this thread needed that closure
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Old 12-05-2012, 02:39 PM   #18
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Anyway to turn launch control and FFS off completely? I bought this to smooth out my cAr, I don't race it nor do I ever hard launch from a dig.
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Old 12-05-2012, 02:54 PM   #19
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Quote:
Originally Posted by dsn112 View Post
Anyway to turn launch control and FFS off completely? I bought this to smooth out my cAr, I don't race it nor do I ever hard launch from a dig.
Both launch control and flat-foot shift are disabled by default in our maps by using unobtainable RPM thresholds (8000 RPM). The only way they would become active is if the thresholds were lowered via the AccessTUNER software (i.e. editing the map) or you go into the "Tune" -> "Adjustments" menu on AccessPORT and lower the RPM thresholds for both from the disabled value of 8000 RPM. Otherwise, both will remain disabled completely.

Bill
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Old 12-05-2012, 04:18 PM   #20
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Quote:
Originally Posted by Cobb Tuning View Post
Both launch control and flat-foot shift are disabled by default in our maps by using unobtainable RPM thresholds (8000 RPM). The only way they would become active is if the thresholds were lowered via the AccessTUNER software (i.e. editing the map) or you go into the "Tune" -> "Adjustments" menu on AccessPORT and lower the RPM thresholds for both from the disabled value of 8000 RPM. Otherwise, both will remain disabled completely.

Bill
Awesome, thanks Bill! Feature is cool but totally not for me. Just want the nice smooth power
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Old 12-05-2012, 04:31 PM   #21
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I use to auto x with my 06 WRX and did about 25 events (3 runs per event) using LC & FFS in about 2 years I had to replace my rear diff.
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Old 12-24-2012, 02:28 AM   #22
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I wouldn't think of that as bad. 2 years of hard driving and it held up.
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