where a car will footbrake to wont make a lick of difference in how fast the car will ET.... in most cases, assuming the convertor flashes just past peak torque, where it should.
In other words, i currently have a convertor that flashes 5100.
I can footbrake it( without rolling through the beams comfortably) to around 3200. That is partly because of the convertor, partly how good the brakes are. Both are a factor.
I can leave at 1500, 2000,2500 or 3000, and the car ET’s virtually the same. I use the rpm to adjust my reaction time, nothing else. In all those cases, the convertor is still going to the 5100 flash before it “ hooks”
In fact, every convertor i have ever had, the above is true. Where ever i leave at rpm wise, the ET Doesnt change.
In fact, if the convertor is specced correctly, i havent seen any difference off the foot, or using a brake. If there is a notable difference, i submit the vert is off somewhere.
Some convertors might be “ tighter” to where you cant bring it up off the foot holding your foot on the brake anywhere near the above example. That could be the case and yet the convertor could be correct for the car.
Example a mild combo might like a 3500 flash convertor that will try to creep At maybe 2200 rpm..
Nothing wrong there, just might be what that combo needs to run best.
I have often found not pushing the convertor as far as the brake will hold it is wise. It allows the suspension to be “ relaxed” and not tense. Particularly noticeable with a leaf spring car.
In short, there is seldom any advantage ET wise to push the convertor to the limit the brakes will hold it, before launching the car.
Just my experience..lol