I have install/enable Launch controle and Shift cut on my VW golf running VEMS V3.2 with firmware/MT 1.0.53 using input channel 6 and 7 (mcp3208 + two 10KOhm pullup).
I can not use the original shift-cut function. At least not with the type of gearshift/gearbox that's in my old VW Golf, it is very hard to shift gear from 1 to 2 as fast as from 2-3 and 3-4.
I think a function like the launch controle, with a soft rpm limiter that's on as long as clutch is down, is much better fore shift-cut. It would also make it posible to drive the car easely on road, for every day use or between stages in rallys, without disabling the function.
I am successfully useing the launch controle function fore shift-cut, but is then missing it fore launch.
I find the shift-cut function useless and hope very much it is chanced before spring (race start), but what is others experiences with this function? What do you think of it?
Comments from Emil:
We are using shiftcut and it works very good, clutch doesnt even have to be pressed completely, Function should not ever be changed in my opinion. You must have something wrong in the car, either with first gear traction or broken gear box. We are loosing approx 0.2 bar boost during shifting.
The only problem i had on some cars is that it gets too powerful and tires go up in smoke, or clutch slipping
Re: Tanks fore your comment Emil.
Do you have a contact/switch on the gear shifter or clutch pedal fore the shift-cut? How fast are your gear shift (rpm drop)?
My engine louses rpm fast when ign is cut, so I can't set time to much more then 0,3sek and that is hard always to stay under when running a stage. Maybe if running 1/4 mile, yes.. also when making down-shift it can give "problems", it just runs smoother with the max rpm/soft rpm limiter function.
Swiches mounted on the clutch pedal, pretty early (switch enabled with pedal pressed only a little bit.
i usually configure cut time around 160mS for a good driver, 200mS for a intermediate driver ;)
dragracing / streetracing that is.
If you want to try, you can reconfigure one input to control ALS function instead of shiftcut, and set launch rpm under launch control, fuel based launch control RPM limit, That RPM is activated when pulling the ALS input. This launchcontrol doesnt build boost as fast as the real launchcontrol, but should work with a smaller than huge turbo. Just exaggerate your fuel enrichment setting.
- What is gear switch doing in a clucth pedal ? I mean that gearbox 'does not know' 'when power should be cut' when instrumented from clucth pedal position. Hence switching should be done from gear stick (or linkage if possible) point of view. Spring limited mechanical switch, strain gage or some other gear changing/force sensing method in linkage/stick works. //Bengt R
For sure the VW golf II geargox/shift isn't good very good/fast but thats also why I thing the max rpm/soft rpm limiter function is better, it doesn't use fixed time!
But, I have only been using this on a non-turbo car, so thats all I can relate to.
Old suggestions fore shift-cut:
- a "minimum rpm" (at the moment the clutch is pressed) so the shift-cut function is disabled when your not racing the car.
- I thing the is very much needed if this "time-based" 100% ignition-cutting is going to bee used.
- I haven't tryed using this much because it's very hard to make a smooth shift, most of the time it resulted in hard beaking or acc. Maybe with some training this would work fore 1/4 mile but at least it needs a "minimum rpm"!
- maybe a "max rpm" and "controle range (shared)" (soft rpm limiter) that's on as long as clutch is down, as a alternative to the "time-based" 100% ignition-cutting.
- I tryed using the launch control function as "shift-cut" by setting "launch control max rpm" ~500rpm under shift-point (shift-ligth). This works great with smooth and fast shifts (0,3-4ms) when shifting at shift-ligth.
Two 5-10KOhm resistors (marked with red) must be placed at R85 (ch.6) and at R86 (ch.7), to pull the inputs op to +5V (+5V = off).
- "The schematic is confusing here, R86 is Channel 8 and R85 is channel 7, and they both go to JP11", but in reality mcp3208 pin8 is channel 7, mcp3208 pin7 is channel 6 (and there is no channel 8 at all).
- The schematic counts from channel 1 to 8, and MegaTune (and I) counts from channel 0 to 7. So when I write ch.7 it's ch.8 on the schematic.. confusing, yes.
From the holes (marked with blue, the top one is ch.7) you have to mount wires to some free pins on one of the Econoseal-III connectors.
- A 5.1V zener-diode migth also bee mounted on eatch input fore protection.. http://www.vems.hu/wiki/index.php?page=GenBoard%2FUnderDevelopment%2FDigitalInputs
- "SCL" (old) can also bee used fore launch input, that's JP1 pin 3. Pin 1 is "SDA" used fore ALS, and 2 and 4 is GND.
Here is the external wiring I'm planing.. a contact under the clutch, and one on the steeringwheel (or where i'll find it convenient) to activate launch-controle insted of shift-cut.
The shift-cut function is activated when you press the clutch unless you press the ekstra button while pressing the clutch. When the clutch has been pressed you can release the button and Launch-controle is activ insted of shift-cut until the clutch has been released one time.
I tried that schematic and it did not work. The problem is that when you activate launch while pressing clutch, it switches, but now when you releace the cluch, it does not switch back. I think it's because of the 5V pullup from the ECU. So I added diodes and problem was solved. My schematic looks like that:
The extra switch is for disabling shift-cut circuit.