I have a 2003 C5 with a 408CI engine. Stock 6 speed and rear gears.
I have the Bangshift billy clutch controller. Mcleod RXT twin disc.

Im just trying to get some input on how some of you launch your cars. I have only been to the track once on good tires and made a few hits on the street.
Every pass is between 2.0x to 2.2x 60 foot times. I know that as I keep taking it out it will get better. I am just using too much of the loud pedal.
I am Just looking for some additional input and maybe someone else using this clutch controller and the luck they are having.

I see some people on forums with fairly stock cars with 1.5x short times. I will add a few pictures of my car this far.

 

Ideally, you only want enough clutch torque capacity to hold the engine after the shift into high gear. The more excess clutch torque capacity you have beyond what it takes to hold high gear, the narrower and harder to hit the clutch's sweet spot window for a proper launch will be. An RXT is generally good for around 1000hp. I don't know how much power you have, but a 1000hp capable RXT behind 600hp is a recipe for a narrow sweet spot.

The goal of a clutch hit controller is to momentarily pause the throw-out bearing in the clutch's sweet spot for launch. Then after the car achieves enough ground speed to prevent a bog, it then allows the throw-out bearing to fully retract, which in-turn ensures the clutch doesn't slip longer any than it needs to.

The Bangshift Billy tries to hit the clutch's sweet spot window for launch based on timed fluid flow thru an orifice. When you dump the clutch, a switch on the clutch pedal tells the BSB controller to start counting (initial delay) before pausing fluid flow in the sweet spot. At the pause point, that controller then begins counting how long to pause in the sweet spot (hold time) before then allowing the throw-out bearing to fully retract.

There are external variables that affect the precision of the BSB's ability to hit the clutch's sweet spot window, basically how much fluid flows thru the solenoid during the BSB's initial delay setting...
...how fast you release the clutch pedal with your foot (fresh at the beginning of the day or tired/hot in the evening?)
...clutch fluid temp (first pass in the morning vs hot lapping in the heat of the day?)
...varying launch rpm (higher launch rpm or uncontrolled initial flare will push back harder on the throw-out bearing)
...consistency of the pedal stop (does the pedal stop deflect differently depending on how much pressure you apply with your foot?)
...consistency of the clutch pedal switch (can the switch's activation point change due to vibrations?)

There is also the variable of how hot the clutch itself is, which changes coefficient of friction, which in-turn moves where the clutch's sweet spot during launch will be.

Bottom line is the more excess clutch torque capacity your car has, the more sensitive the BSB will be to external variables.

Grant

 

Thank you for the very good explanation sr530.
I already knew how the controller basically worked but I haven't even thought about the list of variables.

I also did not know the over doing the clutch is what caused my narrow "sweet spot", but I understand why it does. My pedal is fairly high, Delay is set at .055 sec. and the gap between bite point and fully released is very small.
I come off the clutch by basically side stepping it so it should be consistent and I never make back to back runs without approximately a half hour break.

I plan to add more power to the car later with either a centri blower or nitrous but just haven't made it to that point yet.

The car is still stock from the clutch backwards so after my trip with the 28s I really expected to break something and be forced to upgrade but unfortunately it just wanted to spin.
I guess because of my very narrow window on the clutch, I may have to really fine tune the delay, .054 may work better, and just put a little longer hold time.
My settings at the track were Delay: .055 / Hold: .250 / Slip: .750

 

The explanation of how it works was intended for the guys reading this thread that have no idea what a clutch hit controller does or how the BSB works

.250 hold is nowhere near enough time in the sweet spot. When the controller exits hold, a clutch with a narrow sweet spot will almost instantly blow past that sweet spot, which results in either bog or spin...
...a 1.5 60' car is about 8mph @ .25sec, about 875rpm when the clutch exits hold and locks up, huge bog if the tires didn't spin.
...a 1.5 60' car is about 25.5mph @ .80sec hold setting, about 2785rpm. Much better, far less likely to knock the tires loose.

I wouldn't be afraid to go 1.0sec hold setting with an RXT at your power level.

On an NA car with proper delay/hold settings, the .750 ramp time won't do anything for you as the clutch is already locked up by that point or very close to it.

With stock gearing I would start out by setting the hold to 1.00sec, ramp to zero, launch @ 4500 and then adjust delay until the tires stick.

Grant

 

I will try that soon, Thanks!

 

Sub for reference.

 

Save money for a wavetrac diff and G-Force axles or focus on half mile speed events and the 60' in the high1.5x.