Launch limiter

[Damo]

The missus was out at a friends place tonight and I was determined not to waste the whole night on the www. Can't realy drive the car as its raining and has been for a while, so I decided to try and hook up a crude form of launch control.

Anyone with a 2D programmable rev limit with a couple of coolant temp points can do the same thing.

The basics of it are, using the OE speed switch (normaly closed) in the speedo, a 120ohm resistor and an on/off switch, I am able to fool the ECU into thinking that the coolant temp is above 120c when the switch is 'on' and the car is doing less than 8kmh (where the factory speed switch operates). With that, I am able to have the ECU limit the rpm of the engine to 4000rpm at temperatures above 120c.
So, staged at the timing lights, with the system operating, I should be able to stand on the accelerator and have the engine splutter and hold full boost @ 4000rpm, side step the clutch leave the line with full boost and my 4000rpm limit until I reach 8kmh, then my preset normal rpm limit comes back into play.

I'll have to do a bit of trial and error to see if the system will work as envisiged. Can anyone spell fun!!!


Damo

[Matt]

Can anyone spell fun!!!

'P-h-u-n'

Bloody oath mate that sounds awesome, hope it works to plan.

[tassuperkart]

Damo
A M8 uses one of his analogue inputs vis a switch on the gearstick.

He invokes a 5k rev limit along with about 40 degrees of ignition retard.

This way the engine labours very hard under extreme ignition retard and the turbo spools up to almost full boost even tho the engine is actually free spinning on the limiter.

Also, the limiting becomes very "soft" on the engine as its not "bouncing" on the hard cut. It just kinda missfires, pops an farts, spools up and blows flames out of the pipe until he uncorks it.

This is in a road going R33 4wd and essentially stock, along with a multi-stage boost controller, it will launch from 0 to 100 in under 3 seconds.
Its simply awesome to see!!!!!!!!!!!!!!!!!!!!!!!!!
L8tr
E

[The Renegade]

Damo - You bastard now I'm going to have to figure a way to do this with a Microtech.....

Pretty good thinking mate!

Actually, I'm gonna be trying to figure a way to setup anti-lag for track days! Not even going to try figuring it yet, should be thinking about getting the car finished 1st!

[etking]

i want a launch limiter so i can flame on demand!!! E hook me up lol

[shanec86]

hahah u smart ass damo...sounds like a good idea, i should give it a go

[raddavey]

Damo
A M8 uses one of his analogue inputs vis a switch on the gearstick.

He invokes a 5k rev limit along with about 40 degrees of ignition retard.

This way the engine labours very hard under extreme ignition retard and the turbo spools up to almost full boost even tho the engine is actually free spinning on the limiter.

Also, the limiting becomes very "soft" on the engine as its not "bouncing" on the hard cut. It just kinda missfires, pops an farts, spools up and blows flames out of the pipe until he uncorks it.

This is in a road going R33 4wd and essentially stock, along with a multi-stage boost controller, it will launch from 0 to 100 in under 3 seconds.
Its simply awesome to see!!!!!!!!!!!!!!!!!!!!!!!!!
L8tr
E

It just shortens the turbo life considerably as the unburnt fuel is being ignited in the turbo. The best method to get boost but not that good on the turbo. I'm going to try a plain ignition cut at first and see if thats good enough. I think 7psi would be enough to launch off

[Callumgw]

Just a small point, IF the speed sensor works on the front wheels (ie through the gear box) then if the wheels start to slip, the speedo will exceed 8kph very quickly and unload the rest of the RPM, and your back to doing your own manual launch control. And I would have thought that 4000rpm and a sidestepped clutch would spin the wheels on any well tuned E15T. So I don't see how this work unless you put a speed sensor on the rear wheels...........

or have I missed soimething?

C

[tassuperkart]

It just shortens the turbo life considerably as the unburnt fuel is being ignited in the turbo. The best method to get boost but not that good on the turbo. I'm going to try a plain ignition cut at first and see if thats good enough. I think 7psi would be enough to launch off

Umm Im sorry M8 but I cannt see where the problem lies here.

What unburnt fuel are you talking about?

Most ECU rev limiters do not cut ignition for the very reason you are stating, rather they cut fuel, which does nothing more than create a missfire.
This is very kind, or "soft" to the engines.
Any fuel making its way into the engine will be burnt well before the turbo sees it.
The turbo will only see grossly elevated EGT's for the short length of time the engine is sitting on its staging limit and retarded ignition but thats not an issue in the short term.

You are proposing to cut ignition only whilst still pouring in raw fuel at WOT which is the most brutal from of engine rpm limiting there is and has been responsible for broken crankshafts and loading the exhaust and then igniting that wasted fuel is going to be pretty hard on things thats for sure.

You positive you want to go down that path???

L8tr
E

[Panda_ET]

mm flames

[Damo]

Just a small point, IF the speed sensor works on the front wheels (ie through the gear box) then if the wheels start to slip, the speedo will exceed 8kph very quickly and unload the rest of the RPM, and your back to doing your own manual launch control. And I would have thought that 4000rpm and a sidestepped clutch would spin the wheels on any well tuned E15T. So I don't see how this work unless you put a speed sensor on the rear wheels...........

or have I missed soimething?

C

Your right, but I was intending to have it work for launches at the strip on slicks. And rather than have the engine banging off the 7.5k limit I have for day to day, I could lower it on demand and have a happy medium of slip and initial grip.
One of my problems is that I live 3hrs away from the nearest 1/4 (WISD), and had to drive the car home from meets in the past. This shows in the fact that my best 60ft was a miserable 2.1sec. I seem to be a little soft on my launches, so this should give me no excuse.
On the street is a different story though. The system would still work, but I would need to have a micro switch limiting boost in 1st.

The other cool thing that could be done, in the ignition v's coolant map, I could take out all ignition timing above 120c to create anti-lag, this would probably give me max psi at 2grand or so.

Another mix on the whole shooting match would be to use the clutch switch to activate another limiter so you could flat change without fear of spinning the engine to death.

How many gear switches are there on the box? I know there is one for neutral, 4th and 5th, any others?


My ET has been blowing 12inch flames on gear changes for quite some time.
Time to set it up so it can do it while stationary.


Damo

[Callumgw]

So, for what i read your just using the OE speed switch as the input and taking advantage of the "over 120 degreesC" to cause the ecu to apply "safe" or "limp home" modes to limit the RPM? Couldn't you achieve this by placing a frequency activated switch on the rear wheels? I know it's extra cost, but it'd be a little better in the end, I think. You could still tune it.................. ............................ ........................... ......................... ......................... ........................ ............................. .....................

Just did a Dogpile search and it might'n be as easy as I though, best i came up with was:
http://autospeed.drive.com.au/cms/A_2810/article.html

[Damo]

So, for what i read your just using the OE speed switch as the input and taking advantage of the "over 120 degreesC" to cause the ecu to apply "safe" or "limp home" modes to limit the RPM? Couldn't you achieve this by placing a frequency activated switch on the rear wheels? I know it's extra cost, but it'd be a little better in the end, I think. You could still tune it.................. ............................ ........................... ......................... ......................... ........................ ............................. .....................

Just did a Dogpile search and it might'n be as easy as I though, best i came up with was:
http://autospeed.drive.com.au/cms/A_2810/article.html

Yeah, something like that might be the go.

Hooked up my original idea and tried it out..................my bloody speed switch wont frigging work! (Thats what 25YO crap will do) Hit the primer switch at cruze speed, and everything dies in the ass. Oh well, I'll just do something like a remote switch on a coil wire (like a car phone charger cable) and just hold onto it with the left mit whilst doing gear change thing. Or mount a button on the top of the gear nob somehow.


Damo

[tassuperkart]

Bloody hooligan............bwaaaaaaahahahahah!
L8tr
E

[ETEEZA]

Can anyone spell fun!!!

'P-h-u-n'

Bloody oath mate that sounds awesome, hope it works to plan.

this sounds interesting,i hope you get it going right,never heard of it before....sounds abit too hectic for me,but does sound very interesting indeed...so tell me,when you do this double clutching does the GEARBOX hold up,or is this another way to break our GEARBOXES...???