Originally Posted by mrldcty
So, if you want to stay spooled while braking, wouldn't that be clutch in, h/t rather than LFB? I guess if the brakes are significanly front biased, then you could be slipping the rear brakes enough to stay spooled, but wouldn't clutch in + h/t be less hard on the rear brakes?
You heel-toe to put the engine in the proper gear (i.e. in the power band) without unsettling the car when you downshift. Heel-toe works b/c it allows you to avoid engine braking, which causes the car to lurch forward when you shift into a lower gear and slip the clutch. Most commonly the downshift is done just before corner entry (with the intention of putting the engine in the gear you'll need for corner exit), as cars tend to be more settled when they're in gear in a corner, even if your technique for heel-toe's very good. There are some complexities here that aren't worth going into, but the general point is that cars are less settled when they're not in gear.
But in many corners, you'll continue braking after the downshift as you enter into the corner (i.e., trail-brake) in order to keep weight forward and move traction forward to help the car turn in/rotate. During that phase of corning, you might LFB (with a turbocharged car) in order to keep the turbo spooled. By staying on throttle while braking, you're reducing your braking power (in the Elise, given that it's RWD, the reduction happens in the back of the car), but most trail braking is done under light braking anyway. On the track (as opposed to on gravel or dirt, where rallying is done), the point of LFB is *not* to shift the brake bias, but to keep the turbo spooled so when you ease off the brakes the turbo is already producing boost.
In gravel and dirt, the point of LFB is to shift the brake bias backward in order to allow you to lock up the rear tires and rotate the car, but (i) that only works with FWD cars, where the application of throttle reduces the braking done on the front of the car, thereby increasing the braking done on the back of the car, and (ii) it's a technique that's helpful where huge degrees of slip angle are needed (i.e., where you want to get the car completely sideways) in order to drive the car through the corner. Neither applies to the Elise (because it's RWD) on typical road courses (where getting the car completely sideways is rarely faster than keeping the car to reasonable -- under 10 degrees or so -- slip angles).
Hope this helps.
PS: addendum. I've heard that LFB is used in Nascar, but I've never heard any explanation for why that's the case and I don't have any direct confirmation from anyone I know and trust on the issue, so I have to admit that there may be pieces to this puzzle that I don't fully understand.