Launch control, can someone explain please.

[hodge]

Hi guys

Would someone mind explaining what launch control does and how it all actually works please. Can get my head around it to be totally honest.

 

Thanks

John

[Scott]

As far as I know it's a rev limiter. If it's clever it will work in conjunction with your traction control at the same time.

 

It basically means you can floor your pedal but the engine will only rev to the pre-set launch limit. On a Supra with road tyres this is generally thought to be around the 4k mark. When you have launch controll and you are sitting on the line, when you floor it the engine will peak at 4k until you drop the clutch and start to accelerate.

[johnny g]

Yep, and the ignition is retarded, then the strategy then rolls on the power and cuts at a preset speed, it uses wheels speed to control the feed from the soft-limit, after the LC has hit the preset RPM/Speed it's disabled and TC takes over on that strategy, I think that's effectively on the 1st -> 2nd gear change.

 

Ryan will set me straight lol

[hodge]

So does this help in pre-spooling the turbo on the line.

[Scott]

So does this help in pre-spooling the turbo on the line.

 

No that's anti-lag

[johnny g]

So does this help in pre-spooling the turbo on the line.

 

If you're bouncing off the soft-limiter, it will pre-spool a little, I believe.

[Scott]

If you're bouncing off the soft-limiter, it will pre-spool a little, I believe.

 

Really? I thought the lack of load, and the load drop from hitting the limit, would actually drop the spool more than raise it.

[johnny g]

Really? I thought the lack of load, and the load drop from hitting the limit, would actually drop the spool more than raise it.

 

The exhaust gases spin the wheel a bit, not into boost I don't think, but certainly get it moving - bear in mind though, this only my understanding of it, and I am usually wrong.

[hodge]

If you're bouncing off the soft-limiter, it will pre-spool a little, I believe.

 

By soft limit do you mean a floating rev limit. By that I mean a preset limit below the engine rev limit???

[johnny g]

By soft limit do you mean a floating rev limit. By that I mean a preset limit below the engine rev limit???

 

Yea, the rev-limit associated with LC - as Scott said, usually somewhere in the region of 4000rpm

[hodge]

Yea, the rev-limit associated with LC - as Scott said, usually somewhere in the region of 4000rpm

 

So what's its advantages other than being able to have your foot flat on the floor at 4K. Isn't it just the same as holding the pedal at 4K.

[hodge]

So where does anti-lag come into all this and how does that work, and what are the pro's and con's.

[johnny g]

So what's its advantages other than being able to have your foot flat on the floor at 4K. Isn't it just the same as holding the pedal at 4K.

 

Well, not really. The LC will also retard the ignition and feed in the power in a consistent way each time - so if you do 0-60 in 4 seconds once, assuming nothing changes with grip or power, you'll always do it. Manually, you won't. I think having your foot flat and popping off the soft-limiter will also pre-spool the turbo more than just holding at 4k manually.

[Scott]

So where does anti-lag come into all this and how does that work, and what are the pro's and con's.

 

Anti-lag generally pulls the spark in one of the cylinders and allows the fuel to hit the hot manifold. When it pops in the manifold the gas from the explosion spools up the turbo. Launch control coupled with anti-lag is a great way to get off the line fast. NOS is another good option

[hodge]

Anti-lag generally pulls the spark in one of the cylinders and allows the fuel to hit the hot manifold. When it pops in the manifold the gas from the explosion spools up the turbo. Launch control coupled with anti-lag is a great way to get off the line fast. NOS is another good option

 

Ahhh, I understand now. Well I know Jamie uses a dry shot of nitrous as a turbo Pre-spool but what would be deemed a better setup, using the anti-lag facility on the Syvecs or a Pre-spool nitrous kit.

 

If the anti-lag works in the way you say Scotty then how does the nitrous Pre-spool work??

[Stephen G]

i think what your thinking about is 2 step launch which you would hear on alot of the us drag supras

[DARETT]

2 step launches all the way.

 

The rev limit is set and the ignition retarded to ensure you get the desired amount of boost on a launch.

this guy must be making around 40psi which is why he's on the 2 step for so long

 

 

Most of the auto transmission guys use Nos from a launch with a trans brake.

[Scott]

Ahhh, I understand now. Well I know Jamie uses a dry shot of nitrous as a turbo Pre-spool but what would be deemed a better setup, using the anti-lag facility on the Syvecs or a Pre-spool nitrous kit.

 

If the anti-lag works in the way you say Scotty then how does the nitrous Pre-spool work??

 

IMO the nitrous would be less detremental to the turbo. Anti-lag will take life out of the tubby.

 

Nitrous works by increasing the "bang" in the engine. The engine needs to have load to make the turbos spool. This is why you won't get a lot out of the engine when you aren't in gear (revving). The harder the engine tries to work the faster the exhaust gas exits and the faster the turbo will spool, creating boost. The nitrous increases the power of the bang in the engine, thus the exhaust flow will be much higher than it would without the NOS.

[Stephen G]

2 step only works taking of the line were as anti-lag would be going every time you take your foot of the throttle to keep the boost up and as you said very sore on turbos.

[hodge]

You've lost me now guys. Would you mind explaining how 2 step works please.

[DARETT]

The revs are limited to say 4k, and instead of a fuel cut an ignition cut is used. The ignition retard allows boost to be built to your desired level. It also causes all the pops and bangs.

You release the clutch when your ready and all hell breaks loose!

[hodge]

The revs are limited to say 4k, and instead of a fuel cut an ignition cut is used. The ignition retard allows boost to be built to your desired level. It also causes all the pops and bangs.

You release the clutch when your ready and all hell breaks loose!

 

So 2 step in hindsight is a combination of Anti-lag and launch control Amir ?

[DARETT]

Yup Antilag for Launching.

 

The antilag system turns off as soon as you launch. Some guys roll it out for a little longer (10mph) but that's the longest I've heard it being run for .

 

Then if you have any lag or bog in between gear shifts or something, a little shot of nos would do the trick to keep the turbo spooling.

Edited November 25, 2011 by DARETT (see edit history)

[hodge]

Yup Antilag for Launching.

 

The antilag system turns off as soon as you launch. Some guys roll it out for a little longer (10mph) but that's the longest I've heard it being run for .

 

Then if you have any lag or bog in between gear shifts or something, a little shot of nos would do the trick to keep the turbo spooling.

 

Won't all this put crazy amount of strain on the engine and turbo??

[DARETT]

On the turbo for sure. However most of the big modern turbo's are pretty durable and can take a fair bit of it.

It's not for very long either, normally it's only held for a few seconds and you can see big boost. The engine's getting a whole load of fuel to keep it happy and with Ryan setting it up you would never have to worry about that.

 

Here's mine when we were testing, in the 2nd short blip of the throttle 30psi was being made which would be more than enough to go from