![]() So, I’m probably going to try it the way it is, program the curve in the Launcher to reduce the nitrous shot below, say, 5000 RPM, just to see where I’m at with gearing and converter, and go from there. That all assumes I can get it to hook with an 11.3:1 SLR, of course.Īnd I realise that converter slip and tire growth can throw these numbers off somewhat. So, it may be more important for me to change my first gear to something like a 2.08:1, which reduces the RPM drop percentage to ~28%, since the car is going faster (~77mph) on the shift (again assuming % slip) and the first gear ratio is closer to the second gear ratio. ![]() That load can’t be good for a motor that’s ingesting a sizeable whack of nitrous. That may in and of itself solve the RPM drop problem, depending on how much the converter slips when I make the shift.īUT, if I’m running the typical “tight“ converter (which I will be, unless I change the stator) that will put a lot of load on the motor and drivetrain (“pulling the motor down”, as some folks call it). So, if I’m shifting at, say, 7500 rpm, with a 33” tire and a 4.57 rear gear and a 2.48 first gear, that equates to around 65mph (assuming 0% slip, of course), and when I shift to second, 65mph equates to just under 4500RPM with a 1.48:1 second gear, which will likely drop my RPM below the stall speed of my converter. ![]() Put another way, it don’t matter what the rear gear ratio is, the 2.48 - 1.48 shift is going to produce an RPM drop of around 40%, whether I put a 3.89 or a 5.14 rear gear in it. ![]() I’ve spent some time overnight running the different gear ratio combos through the RPM drop on Shift calculator on Wallace Racing and then I realized the obvious:īased on what little I know, I think the bigger concern on a nitrous car is the RPM drop on the shift, and with a 2.48:1 first gear and 1.48:1 second, it‘s the difference between 1st and 2nd ratios that matters. ![]()
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