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Link G4+ Latched Launch RPM Mode - rolling race starts

Launch Control

Discussion and questions related to the course Launch Control


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Was just reading the new link g4+ firmware updates and saw this Latched Launch RPM Mode - rolling race starts.

Sounds pretty interesting and handy, considering most street races are rolling starts these days.

Would like to get a better insight as to how it works exactly.

As soon as our 350Z is here we will be adding a worked example using the G4+. While the Z is not turbocharged we will cover rolling launch control and this may end up being added as a separate module in the theory section of the course.

is it added already or still to come the latched launch control ?

Sorry Gojira, this had totally slipped my mind. I'll see what I can do, although obviously we won't be able to generate much boost using our 350Z :)

the course boost control you had a turbo engine?

In the boost control course we used our Toyota 86 :)

can GT86 be used for the latched launch ?

It can, but only because I've written my own rolling launch control function in M1 Build. This means it wouldn't be very relevant to anyone else since this is a custom feature only I have.

this is my latched launch for 1bar boost.

But it's not always as consitent as this log.

sometime it only gets 0.8bar boost, or sometimes it gets 1bar and drops 0.2bar

Attached Files

With your current configuration you're going to see the boost tend to increase as the retard is relatively stable. You normally find that once the boost begins to climb you need less ignition retard to keep it there. If you're targeting say 1.0 bar boost on your rolling launch, I'd set the retard table with MAP as the load axis. Below your target boost you can aggressively retard the timing to build boost quickly. As the boost reaches target you can reduce the retard to stop the boost climbing or overshooting.

Try that and see if the results are a little more consistent. In the drag cars I tuned we often incorporated a wastegate on the charge pipe and used that to maintain very consistent and stable boost during launch by bleeding off excess pressure.

I will post some screenshots tomorrow

a little late because busy, here are the settings and a piece of latched launch control from me.

Any input about adjustments always welcome.

Attached Files

Hi Gojira

To be honnest your settings seems to be way off.

First you only have hard cut limiting. You must enter a limit control range in the advanced limiter settings. I suggest to start with a high limit control range like 500-800rpm. That makes the RPM limiter smoother.

I also suggest to view the Rev limiter webinar for this topic.

What I have in my mind, the launch fuel table is percentage additive to the main fuel map. So zero or very low enrichment numbers should work out fine.

Lastly the idea behind your launch ignition table is right. But you have to be very carfully with to much retard. Your EGT can skyrocking very fast with that much retard. Usually not more than -20deg is necessary.

Allready -20deg introduces alot of heat! I recommend to logg and watch your EGT's very carefully. Keep in mind that EGT sensors respond slowly.

did you also see my logging while latched launching ?

@ Andre : is it a good thing with added fuel to keep the AFR/lambda @ 0.8Lambda while launch activated ?

what are your tauchts about my latched launch ?

I'll agree with Adrian - your limiter settings are going to really hamper the effectiveness of your launch control when your limit range is 0. This provides a hard cut at your rpm limit set point. You want to provide a range here to smooth the cut and make it less abrupt. I'd suggest starting with around 200 rpm which is the default value.

I seldom use fuel enrichment during launch control as you are passing unburnt fuel through the engine on an ignition cut anyway and this tends to do an adequate job of controlling combustion chamber temps. The amount of fuel you're adding is quite excessive as well which will again hamper the effectiveness of your launch control. If I do feel the need to add fuel it would be in the region of perhaps 5-10%.

You can't take any notice of the lambda reading during the launch limiting as unburnt fuel and air is passing across the sensor which typically will have the sensor reading very lean - This is detailed in the course. So trying to maintain a target lambda with the fuel trim table is a little futile during launch control. The only viable option here would be to monitor EGT as this can climb due to the ignition retard and hence some fuel may be used to control this.

This leads me to your ignition retard which on the face of it seems quite excessive. Even with the serious drag cars I have tuned we seldom see the ignition retard past about 10-15 degrees ATDC where as you're using 30-37 ATDC. Of course I have no idea what turbo and engine capacity you're dealing with but on the face of it from pure experience this doesn't add up.

Here's what I'd try:

1. Set your limit range to 200 rpm

2. Set your fuel trim table to 5% above 0 kPa MGP and zero everywhere else

3. I don't personally like the 'absolute degrees' option for ignition retard as it is very abrupt when the retard becomes active. I'd suggest using degrees, where the table will retard from your base table values instead. In this case I'd leave your retard table at zero up to 0-5 kPa MGP and then aggressively retard the timing until you're seeing -10 to -15 degrees actual ignition timing being delivered. As you come up to your boost target you can reduce the retard so you don't overshoot the boost aim.

Try that and let us know if it's effective.

will try, keep you posted

setted it like you said andre, using "degrees" instead of absolute degree's, and 0° retard on 0MGP, and whent to -15° when boost target reached of 1bar. so timing is on 1.25bar boost around 11°, so retard there is -23° and i get 0.2 bar boost, but it is much smoother and as long i keep the latched launch activated, the boost is extremly stable at 0.2bar boost.

Fuel i did also like you said.

so now i start to give small degrees extra to achieve little more boost until i reach my desired boost target.

Attached Files

first i had -8° retarding, effective of 11.5° and boost of 0.16 bar

now i have -14° retard, effective of 6.1° and boost of 0.20 bar boost.

now i made 10° more reatrding and then testing again with logging.

Attached Files

got 1 bar boost with latched launch now

https://www.youtube.com/watch?v=kuEFetdD044

here using it against a Evo with exact the same Hp as me :

https://www.youtube.com/watch?v=yOxpn_i3b3g