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What are your settings when you launch?
What are your settings when you launch?
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Old 04-13-19, 08:10 PM   #1
PNash
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Default What are your settings when you launch?

Diff Auto or Diff -, Traction Control off???? I'm going to go to the track this spring / summer and I have no idea how to launch the car. Walking that back, I have some idea but no execution. I have a 2019, what say you my Subie Brethren?

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Old 04-13-19, 10:30 PM   #2
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Default Re: What are your settings when you launch?

Locked diff for hardest possible launch. Auto will work well too and will give a bit more mechanical sympathy. Traction control off.

If you don't have an Accessport... clutch in, 100% throttle, right about redline step off the clutch like you just stepped in dog poo (seriously, try it right now). Not completely sidestepping it but letting off very fast. Keep the throttle flat to the floor the whole time. You'll break all 4 tires loose for a moment and take off.

If you have an Accessport... similar instructions, but dial in your Launch Control RPM, clutch in, 100% throttle, give it ~2 seconds to build boost, then release the clutch as described above.
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Old 04-15-19, 08:02 PM   #3
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Default Re: What are your settings when you launch?

Quote:
Originally Posted by brapp View Post
Locked diff for hardest possible launch. Auto will work well too and will give a bit more mechanical sympathy. Traction control off.

If you don't have an Accessport... clutch in, 100% throttle, right about redline step off the clutch like you just stepped in dog poo (seriously, try it right now). Not completely sidestepping it but letting off very fast. Keep the throttle flat to the floor the whole time. You'll break all 4 tires loose for a moment and take off.

If you have an Accessport... similar instructions, but dial in your Launch Control RPM, clutch in, 100% throttle, give it ~2 seconds to build boost, then release the clutch as described above.
Seriously? Is this a *'n joke?

Never tell a newbie to lock their diff on a launch. Jesus. And, 100% throttle? you're going to make him kill his engine.

The Accessport advice is on point though.

For new people, I recommend NOT launching at all. The 2s on your end time isn't worth the damage you're doing to your car.

If you really want to launch, 5k RPM, Auto -, Traction Control off, let off the clutch fast, but NEVER dump it full hard.
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Old 04-15-19, 08:05 PM   #4
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Default Re: What are your settings when you launch?

Quote:
And, 100% throttle? you're going to make him kill his engine.

You will get a slightly better launch by flooring it from idle and then coming off the clutch as the engine hits your desired launch RPM rather than holding it at 5k and trying to floor it as you come off the clutch. The turbo will spool faster and the throttle is already all the way open. It's an interesting timing exercise to get it right though.
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Old 04-15-19, 09:59 PM   #5
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Default Re: What are your settings when you launch?

Quote:
Originally Posted by Noximus View Post
Seriously? Is this a *'n joke?

Never tell a newbie to lock their diff on a launch. Jesus. And, 100% throttle? you're going to make him kill his engine.

The Accessport advice is on point though.

For new people, I recommend NOT launching at all. The 2s on your end time isn't worth the damage you're doing to your car.

If you really want to launch, 5k RPM, Auto -, Traction Control off, let off the clutch fast, but NEVER dump it full hard.
Nope.

The harshest thing you can do is baby it off a launch. There is NOTHING friendly to the car about launching it... but the friendliest way you can do it is to go full out.

Think of it like this... you are dumping a huge amount of energy into your drivetrain. Something is going to absorb the brunt of that. Best case -- you break the tires loose for a moment, they catch and you go. But if the tires don't break loose... that energy gets absorbed by your axles, your transmission, and everything in between.

You need enough power to break them loose and not bog. Trust me... the harshest AND slowest way to launch is to bog it. 5k RPM will probably break the tires loose with Launch Control... but might not without. And regardless... if you don't give it full throttle then you have to feed in the throttle EXACTLY right as you let off the clutch. That means full throttle at exactly the right time. Otherwise you might spin for a fraction of a second... and then you'll bog. And you'll smell clutch and sadness as you pull away from the line slower than you would've if you just got started normally.

As for diff modes... you'll always break the rear end loose first on these cars. They send more power to the rear than front, plus the rear weighs a lot less. Auto- will let the rears keep spinning before sending power to the front wheels. Which will make you slower off the line.

Again... if you're going to launch... you are, by definition, doing something abusive to the car in search of getting off the line faster. If you're going to do it, might as well accomplish that goal. As I said... locked will give you the hardest launch, Auto will give you a good one too and be easier on the car. I see no real point in going any more open than Auto as you'll start to defeat the purpose of what you are doing in the first place.

Quote:
Originally Posted by clapanese
You will get a slightly better launch by flooring it from idle and then coming off the clutch as the engine hits your desired launch RPM rather than holding it at 5k and trying to floor it as you come off the clutch. The turbo will spool faster and the throttle is already all the way open. It's an interesting timing exercise to get it right though.
Yup. Lots easier to time just one foot (clutch) than two at the same time (clutch and gas). Kill the engine??

FWIW... my car has probably close to 100 launches on stock engine/drivetrain/everything. If you're launching it... know that it's an abusive thing. But these cars can take it. Every now and again... I wouldn't worry for a second. Do it regularly and be prepared to replace things.
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Old 04-16-19, 02:20 AM   #6
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Default Re: What are your settings when you launch?

Skip over just about everything Brapp has said.
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Old 04-16-19, 10:06 AM   #7
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Default Re: What are your settings when you launch?

Quote:
Originally Posted by brapp View Post
As for diff modes... you'll always break the rear end loose first on these cars. They send more power to the rear than front, plus the rear weighs a lot less. Auto- will let the rears keep spinning before sending power to the front wheels. Which will make you slower off the line.
The rear end weighs less, but it's under more load than the front under a hard launch due to the weight transfer. The 59/41 split is probably about right, honestly, based on weight transfer numbers I've seen for other front engine sedans. There's a reason front engine/rwd launches harder than front engine/fwd despite nearly all front engine cars having a front weight bias. You probably won't gain much performance by locking the diff other than just being much harder on the center diff than you need to be.
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Old 04-16-19, 05:42 PM   #8
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Default Re: What are your settings when you launch?

I ran a 13.6 in my bone stock 2005 STi by holding revs around 5K rpm, leave DCCD in Auto, and releasing clutch as quick as I could lift my foot (not sidestepping clutch).

Car broke traction for a split second in 1st gear before hooking up right before I grabbed 2nd gear.

Quote:
Originally Posted by brapp View Post
Nope.

The harshest thing you can do is baby it off a launch.
I disagree. Babying the car on launch will sacrifice the clutch but PRESERVE the rest of the drivetrain. The harshest launch you can do in any AWD car is a full clutch dump, at redline, with slicks, on an uphill.

Last edited by uberdank; 04-16-19 at 05:47 PM.
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Old 04-17-19, 08:54 AM   #9
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Default Re: What are your settings when you launch?

Honestly, I might even leave it in manual full open for a launch. It'll be a tiny bit slower than auto (or manual locked), but it'll be way easier on the clutches in your center diff.
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Old 04-20-19, 02:01 PM   #10
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Default Re: What are your settings when you launch?

Quote:
Originally Posted by brapp View Post
Locked diff for hardest possible launch. Auto will work well too and will give a bit more mechanical sympathy. Traction control off.

If you don't have an Accessport... clutch in, 100% throttle, right about redline step off the clutch like you just stepped in dog poo (seriously, try it right now). Not completely sidestepping it but letting off very fast. Keep the throttle flat to the floor the whole time. You'll break all 4 tires loose for a moment and take off.

If you have an Accessport... similar instructions, but dial in your Launch Control RPM, clutch in, 100% throttle, give it ~2 seconds to build boost, then release the clutch as described above.

Just my opinion,
donot use Locked diff for launching, I prefer auto or manual (rolled to the rear)

launch rpm depends on vehicle power output , try different rpms starting at 3k

clutch like you stepped in dog poo
Accessport launch control is best
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