A Line-Loc (Hurst's brand) or roll control is a system that can be added to the factory braking system of a car so that the driver can engage only the front brakes to assist in standing burnouts. The system is relatively simple, usually consisting of an electrically activated solenoid valve positioned in the front brake line, often close to the point where it originates at the master cylinder. To use the system, the driver steps on the brakes with a fair amount of pressure and then hits the switch that activates the solenoid valve. This effectively traps the brake fluid between the valve and the front brakes, so when the driver releases the brake pedal, the hydraulic pressure to the front brakes remains. This is how the front brakes are engaged independently of the rears. At this point, the driver can put the transmission in gear and apply throttle to spin the rear wheels without being hindered by the rear brakes while the front brakes hold the car in place. This system is intended for use on a dragstrip, where standing burnouts are a typical part of the tire-heating ritual. If you race often, you may want to invest in one-roll control kits aren't very expensive and are relatively simple to install. However, if you just want to do random burnouts, you ought to be able to modulate the brake and throttle to obtain the desired results ... just don't tell your parents/principal/local cops where you heard this when you get busted.
Overdrive AlternativeI have always wondered why overdrives are used instead of having the same number of gears in the transmission with the top gear being 1:1 and adjusting the rearend ratio to make the engine and road speed the same as in an overdrive application. What about the efficiencies of different ratios and different sizes (designs) of differentials?R.E. Carlsonvia e-mail
Carlson, huh? Sounds German. Or maybe you just think like a German, because the arrangement you propose is actually common practice on many German cars, most notably Mercedes-Benz and Porsche. Many of these cars use four-speed automatics or five-speed manual transmissions that do not feature overdriven gears. Instead, top gear is 1:1, and First gear is extra low. The end results are cruising speeds and rpm ranges that are similar, if not the same, as some overdrive-equipped vehicles. The Germans have likely opted to go this route because they favor high-speed cruising, and technically, overdrives are intended for loafing along the highway to save fuel. Accelerating in overdrive puts a heavy load on the transmission, even though many of the American V-8-powered cars we know and love can accelerate readily in OD if the rearend ratio is low enough.
Overdrives are intended to lower engine rpm at a given cruising speed, rather than as a means of increasing top speed; you may have noticed that many road tests for new vehicles list top speed in High gear, rather than in Overdrive. Having a 1:1 top gear and a numerically lower rear gear is a more durable arrangement if you plan to hold the throttle to the floor in the quest for top speed travel. Since we don't have our own Autobahn, most American performance cars are geared for brisk acceleration with the added bonus of low-rpm highway cruising through an overdrive.
However, if you seek the type of configuration favored by many Europeans for your hot rod, investigate the Richmond five-speed manual trans. It was intended as a bolt-in replacement for many traditional four-speed transmissions, and features a 1:1 Fifth with several available gear spacings, all utilizing a fairly low First gear. We've seen plenty of street cars using this transmission that were running rearend gears in the neighborhood of 3:1 or less while still enjoying strong acceleration.