093 Setting up Flat shift

first of great webinar, i am also looking forward to the nitrous oxide.

quick question you mentioned using a brake light switch, this is what i have done (admittedly using for launch control at the moment).

my question is on the adjustment to suit the bite point of the clutch, my under standing is you have two adjustments in a stock system.

the pedal starting height, this is adjusted using the stop (now replaced with a switch). and free play of the clutch by adjusting the push rod/clevis length in the clutch master.

so how can i adjust the switch so it occurs closer to the bite point of the clutch?

what have people done? at the moment i am finding as i slip the clutch on launch the launch control doesn't kick of until the clutch is full engage by which point the engine has bogged. (AWD low horsepower).

thoughts?

Josh,

What I have usually done in the past to get it correct is mount a micro switch with a lever arm and make it adjustable.

This way you can easily adjust the lever and switch mounting until it switches on the clutch engagement.

This also allows the clutch pedal to continue its travel back to its stopper without reducing free play.

I have attached a photo of the switch I mean (note you can cut down the lever length to what you desire)

I have also had great success with using a brake switch however the down side is, if you rest your foot on the pedal it will engage the switch and also the only way to get it to switch closer to the clutch engagement point is to reduce free play and clutch travel and having the clutch engage closer to the top of the travel. Negative side to this is that if you reduce free play you can get issues with clutch slip if the release bearing isn't fully disengaging, which will alter with rpm, clutch wear and heat.

Other way is mounting the switch at the bottom of the travel, then you need the clutch to engage closer to the floor.

Or a 3rd way is if you can mount it close to the pivot point then you will get better adjustment as the travel is much less near the pivot point of the clutch pedal.

when setting up a shift "cut" using ignition cut and retard timing method. what do you guys notice is a good degree to pull? also what length of time "milliseconds of cut" to use. i'm using aem infinity for management. to little of ignition retard doesn't seem to do much. right now i'm pulling 10 degrees of timing with 120ms time of cut

The cut time needs to be treated very carefully as re-engaging engine power before the next gear is properly selected can very quickly destroy a gearbox. The correct cut length will depend primarily on the type of gearbox - dog engagement or synchro? Sequential or H pattern.

As an example on a sequential dog box I set up, I used a cut length of 60-80 ms depending on which shift was being made. This would almost certainly be too short for a synchromesh H pattern box though where I may start at 200 ms or thereabouts and then test to see what I can get down to. If you are logging gear position then it's really easy to see exactly how long the shift takes and adjust your cut length based on this. With a fixed 'timed cut' it's always best to be a little conservative as not all shifts are going to be lightning quick so you really need to tune for the worst average shift if you don't want to damage the box.

The retard amount depends on how much torque you want to remove as the shift completes, or to put it another way how much you want to soften the shift as engine power is re-engaged. There's no single value you can apply to every application. In a few of the drag cars I tune I've used 20 degrees, but that doesn't mean I'd use that in every application.

thanks Andre. this personally using a dogbox and right now have 80ms setup for 1-2 and 2-4 but 120ms for the 3-4 shift. I only have 10 degrees pulled but thinking of pulling more as it doesn't seem to cut hard enough in my opinion. I'm also using a ramp in time to soften up the initial shock after the shift on aem infinity

If you're using for example a 100% fuel or ignition cut, then the retard function won't actually effect the cut in my own experience. It's effect is more relevant for torque reduction when the cut is removed.

Generally if you're cut is not great enough in the first place, the dogs simply won't disengage due to the back cut in their design and no amount of yanking on the gear lever will result in the gearbox shifting.