Okay here's my problem taht was brought up to me the other day by a buddy when we were sitting down discussing how we would setup my car for the launch....

I planned on using a 2 step from MSD. the plan was use the first step for launch RPM at 4000 and the second step for overall Rev limiter set to 8000. I would use the transbrake button as the switcher. transbrake in activates first step, release transbrake activates second step.... okay fine no problem right????

I am using a FAST XFI Standalone setup on my LT1 and plan on running a 2 stage nitrous system. 300 shot direct port thru a single plane Victor Jr manifold, and a Speedtech plate system jetted for 100 hp for the second stage. The XFI box works with TPS % and RPM as it's trigger for the nitrous. So okay good I set it for 95% throttle and 3000 RPM-7600RPM as it's minimum TPS and RPM threshold for nitrous activation. the second stage is time delayed 3 seconds from the start of the 1st stage. If i let off or RPM falls outside of the threshold nitrous quits... fine and dandy.

Now here's the problem on the line with the transbrake in i want to floor the car and have it beaming off the 1st step box at 4K (or whatever I decide to launch at) but if I go WOT with the nitrous on BANG It's gonna fire my 1st stage of juice with me sitting on the line on the limiter. not good....

My only thoughts was to set the RPM threshold in the XFI box like 100RPM's higher than my first step limiter.... so in my case I'd set the n2o threshold at a minimum of 4100 RPM and a max of 7600 RPM and the 1st stage pill in the MSD 2 step would be a 4000 rpm pill..... does this sound right and is it what others are doing to solve this problem????? tia!!!!

 

anyone????

 

You can certainly use either a window switch or a timer for that. The other thing is to wire your window switch into your trans brake button in such a way that you cannot arm/activate your nitrous while on the brake. Second is that you need to make sure that your window switch is set up to cap the nitrous off before the upper 8000 RPM limit regardless if that's the two step or the rev limiter.

I had my transbrake button wired into a timer. That timer had a 0 to 24 second (adjustable in small increments too) range and essentially controlled the arming of the nitrous. Pretty simple after all that's in place. No need to worry about the two step and rev limiter if your window switch keeps you in the right range and off the juice before getting off the trans brake.

 

I would have the transbrake open a relay on the nitrous. That way the nitrous essentially wont arm until the transbrake is released.

 

I would set the nitrous activation 200 rpms lower than converter flash.
Let's say it flashes 4000, set it at 3800.Put the 2step at 3000.
It also allows the tire to plant better also.