Delay box

"Delay Box" is a common slang term used by drag racers to describe an on-board timer which is a Transmission Brake Delay Timer (racers call the transmission brake a trans-brake). A transbrake is a part of a racing automatic transmission used in drag racing, and are not found in manual transmissions. The electronic timer is packaged in a metal enclosure when sold to drag racers, thus the slang term delay box. This timer box is a very accurate type of monostable multivibrator (electrical engineers also call this type of multivibrator a "one shot"). The timer box acts like a time-delay relay. Many delay boxes actually have an internal relay to switch output current, but some models have solid state transistorized output circuits. The transistorized type made today almost always use power MOSFET type output circuitry. Drag racing delay boxes are designed to operate from the vehicles 12 volt DC electrical system. Some drag race cars now use 16 volt DC systems, in such a scenario the delay box has to be capable of working properly from 16 volts DC, as well as 12 volts DC.

The race car driver holds an electrical pushbutton switch depressed with a finger or a thumb of his right or left hand until he sees a specific desired visual cue. That electrical pushbutton switch is monitored by the delay box. As long as the race car driver holds the pushbutton depressed the delay box sends 12 Volts DC (or 16VDC) at many Amperes to the race car's transmission (where an internal electromagnetic solenoid located in or on the transmission energizes, which in turn positions a spool valve that directs hydraulic fluid pressure in the transmission valvebody that locks the transmission in forward and reverse gears at the same time).

When the transbrake is engaged at the drag race track starting line (driver holding the pushbutton depressed), the car is held stationary regardless of how much engine power is applied to the drive line. The driver typically applies full throttle at this time, and the car remains stationary at the starting line under full engine power. When the driver sees the desired visual cue before him (often the top amber lamp illuminating on the Christmas tree, but not always the top amber lamp) the driver promptly releases his finger (or thumb) from the pushbutton. This button release opens the contacts within the pushbutton switch signaling the delay box and the delay box now begins an internal countdown. When the countdown timer reaches zero, the delay box stops current flowing to the solenoid in the transmission and that causes the spool valve to return to its normal position. With the spool valve in its normal position hydraulic fluid pressure in the transmission is removed from the reverse clutch pack (but maintained in the forward clutch pack), this causes the drag race car to "launch" (often with great thrust) from the starting line, accelerating rapidly forward toward the finish line.

Delay boxes began appearing in drag race cars in the 1980s. The early units were timers in a sheet metal box with an analog potentiometer and lock nut to establish a setpoint with no readout or feedback to the driver. These early units used a resistor / capacitor charging scheme to trigger a unijunction transistor to release an electromechanical relay. Such drag racing delay timers are very crude by today's standards. Dennis Reid of Walnut Creek, California (later formed a manufacturing company by the name of Dedenbear, Inc.) is credited with introducing such early devices to drag racing. In the late 1980s units began appearing in the marketplace that were digital in nature rendering the analog design obsolete. The new digital delay box timers used decimal or binary coded decimal thumbwheel switches to set the timer value. The thumbwheels also fed back a numerical value that the driver could use to help him calculate proper settings. A popular early digital unit of this type was designed and produced by Robert Furrow (Bob's Electronics of Weatherford, Oklahoma). Robert Furrow's delay box utilized a quartz crystal for timing accuracy and TTL integrated circuits (what engineers call glue logic). Furrow's digital delay box was a substantial improvement in accuracy and ergonomics but suffered in reliability. Shortly thereafter the first microprocessor based delay box timer was introduced by Richard Beutnagel (Thorn Microsystems in Rochester, NY). Richard Beutnagel's design also used a quartz crystal time base for accuracy but without the glue logic. His design used a single chip microcomputer from Intel, large BCD thumbwheel switches, and a solid state bipolar transistor output circuitry (no electromechanical relay). The single chip design reduced parts count and solder interconnections for enhanced reliability. The firmware embedded within the Intel microcontroller chip did all the timing and control functions the delay box was called upon to perform. Many new TTL and CMOS glue logic designs continued appearing on the market for several more years. Names like Messiere, Terminator, K&R, ATI, Digital Delay (Ike Hamma), Biondo, Davis, D&D (Danny Duberry) and others figure prominently in the history of drag racing delay boxes. Some of the glue logic type designs had large LED ( light emitting diode) readouts to display the timer setting, others featured attractive backlighted LCDs (liquid crystal displays), still others used thumbwheels of varying size and quality. All delay boxes on the market were quartz crystal accurate at this time. Several years elapsed before other delay box designs appeared with embedded microprocessors. Today virtually all drag race delay boxes are microprocessor based with intelligent, backlit LCD readouts. The most popular models feature internal crossover time computation (allowing a driver to pick a visual cue from his opponents side of the Christmas tree, the delay box internally does mathematical computations for the driver), bump up and bump down compensation (allows a driver to easily make small plus or minus timing adjustments quickly and remotely), crossover compensation (an offset time the driver can set when crossing over), safety interlock (prevents delay box from reactivating once the race car is in motion, a nice safety feature), bypass ( a feature where the delay box is deactivated before it is done counting down, thus launching the car immediately), and other features.

Delay box use was very controversial in the 1980s and 1990s, with the peak of controversy occurring around 1993-1994. This continues to this day but the controversy has dropped substantially from its peak. Delay box use became controversial because more experienced racers lost the advantage they had enjoyed over the younger rivals. Many racers who were against the use of delay boxes complained to race track owners and drag racing sanctioning bodies that the delay boxes were unfair. Many old time racers said that their use constituted cheating. The term "cheater boxes" was heard at the drag races for many years. Track owners around the United States actually created races on the same race day at their facility dividing racers into two groups or classes, a box class and no-box class. Racers began hiding the delay box and entering the no-box class. Delay box use by motorcycle drag racers lagged far behind those in use by the car racers. One reason for this was motorcycle drag racers had a wide variety of driveline configurations, the cars almost all had automatic transmissions with transbrakes.

Early delay box use was limited to transbrake equipped cars, but innovative racers quickly adapted the delay box to cars with dual line locks (devices which locked the brakes on all four wheels electrically), and manual transmissions with the use of a hydraulic throw out bearing to hold the clutch plates apart, and dragbikes that used pnuematics or hydraulics to actuate the clutch, or centrifugal dragbike clutches known as "slider clutches" that engage with RPM. When using a delay box on a motorcycle with a slider clutch, the engine RPM was electronically controlled by an electronic rev limiter connected to a delay box. When the delay box timed out the engine was allowed to freely rev-up engaging the clutch and launching the motorcycle downtrack. As you can see, delay boxes can be used on both cars and motorcycles. A transmission brake is not required to use a delay box for drag racing.

Some inventive racers modified delay boxes to do more than delay the release of transmission brakes, and concealed the additional circuitry within the delay box enclosure in a way that did violate some drag racing rules. Electronic closed loop control of a drag race car's Elapsed Time ( E.T.) is not permitted. The illegal circuitry did things that effected the vehicles elapse time making the vehicle much more consistent electronically, more consistent than humanly possible. Things became so wild that in the 1990s the NHRA (National Hot Rod Association) required delay box manufacturers to make the delay boxes harder to modify by end users, and shrink enclosures so there was no room for additional contents. Sealing the delay box enclosure so it would be easy to see if it was tampered with was also part of the process. The NHRA also created rules specifying how a drag racer electrically wired his race car, requiring racers to leave wires unbundled so they could be quickly and easily traced by eye. Rules were also created limiting how many interconnects could attach to the wire between the delay box and the transmission. NHRA track officials were empowered to inspect the wiring to insure it met with the new rules. The NHRA also began requiring delay box manufacturers to pay a fee and submit delay box designs for the NHRA's approval. Think of it as a NHRA tax on delay box manufacturers. Then the NHRA instituted rules which allowed only NHRA approved delay boxes at its race tracks. Once submitted for NHRA approval, and paying the fee, delay box manufactures were not allowed to make any changes in design for any reason without resubmitting to the NHRA for reapproval, and paying another fee. Essentially if you made delay boxes, you were not going to be able to sell them without the blessing of the NHRA and paying the delay box tax. To obtain the NHRA's approval, delay box manufacturers had to accommodate the NHRA by making any design changes the NHRA wanted to see. Essentially the NHRA was now designing delay boxes by proxy. Furthermore, drag racers were prevented from using any delay box they made themselves at home. This is something which changed the face of drag racing in a huge way because grass roots drag racing was where you could build your own chassis, engine, transmission, differential, vehicle plumbing & vehicle wiring, etc. Traditionally if you were very skilled you could build your own race car with your own two hands from parts wherever you acquired them. You were not required to buy anything pre-made if you didn't want to. Those days became history almost overnight. Virtually any racer innovation (electronic or mechanical) now came into question and could cause you to be disqualified from the drag races. An NHRA track could deny you the ability to race at their track if they saw something homemade on your race car, and it didn't matter if you had towed your car on a trailer for 5 days cross country to get to a drag race. The path to racing with the least worry about being disqualified was to buy everything for your car from approved NHRA manufacturers (other sanctioning bodies quickly followed suit, such as the IHRA, NMCA, and others). When it came to delay boxes, the rule was quite clear, you MUST buy a unit from an approved manufacturer, and all delay box manufacturers had to submit each of their designs (which included revealing trade secrets to the NHRA, with the NHRA refusing to enter into Non-Disclosure Agreements with the delay box manufacturers). Drag racers were not allowed to make their own timers, and if you were wise, you would not make any other parts of your race car or motorcycle either.

Only a few delay box manufacturers were willing to pay NHRA delay box approval fees and submit designs for the NHRA's approval without getting a non-discolsure agreement. Nor did many delay box manufacturers wish to be forced to comply with NHRA design change demands. These manufactures promptly went out of business or transitioned into non-racing related markets. As a result, very few companies manufacture delay boxes for drag racing today (the reduced competition allows these few companies to enjoy the entire market to themselves) and each design is close in functionality to the next. Innovation has virtually ceased in the market. The approved manufacturers of delay boxes also enjoy a bonus of reduced competition in the market for their other on-board race timers such as: throttle stop timers, data loggers (data recorders), shifter timers, RPM switches, electronic nitrous oxide injection controllers and other devices. Non-approved delay box manufacturers are basically shut out of the entire drag race electronics market.

Not adjusting for inflation, digital delay box prices have not changed much since they first came onto the drag racing scene two decades ago. A delay box from the late 1980s cost racers between $200 and $300 back then. Today a basic unit costs around $200 and a fancy model with a plethora of features is in the $350 - $450 range.

Early delay boxes were not considered very durable, and some were not sufficiently accurate. Over the past 25+ years, drag racing delay boxes have evolved into very reliable instruments that are used on cars and motorcycles alike.