History Main / OverDrive

* In ''{{GalaxyQuest}}'', the overdrive blows-out after being held down too long, leaving the ship nearly crippled.

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Odd as it may seem, this unexplained increase in speed can have some basis in reality. It can be simplified as a cost vs. benefit decision. If somebody has 'nothing to lose' and ''must'' be somewhere at a certain time then they have to speed up - BUT - if they push their machine too hard it will fail before they get there. If they had backed off slightly, then it could have broken down ''after'' they had arrived. In a race a driver will hold back simply because there's a notable difference between "the fastest they can drive" and "the fastest they can continuously drive without wear and tear [[PhlebotinumBreakdown completely destroying the engine halfway through the race]]". Smart drivers limit themselves to the latter, and use the engine-wrecking speeds in short bursts--or for those desperate final laps. Fuel consumption is also a potential problem. Having to find out where to refuel in the middle of some prairie or ocean is ''not'' a way to get to destination ASAP. Running out of propellant halfway to the next planet and thus being unable to decelerate is not a good idea either. The cost of fuel, oil (or Helium-3, or whatever) and repairs is also a factor. In most cases engines are supposed to work much longer than one or two rides and generally engines aren't so cheap that the cost of damaging one could be disregarded without a really good reason.

YourMileageMayVary regarding how well the in-universe [[JustifiedTrope justification]] for OverDrive is actually explained. If it's explained at all. And of course, there are some instances--say, short drag races--where this trope makes absolutely no sense no matter how you slice it.

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** Considering it was built from scrap parts, it wasn't exactly the most streamlined podracer around, although it was capable of reaching very high speeds (one of the fastest in the film). Once Anakin got ahead of most of the other racers, it is likely that he did not want to strain the engines more than necessary. Plus, many times he tried to overtake, Sebulba actively blocked him. Also keep in mind that Anakin didn't know he would earn his freedom by winning until after the race.
*** The game confirms this by making the engines burst into flames if Overdrive is not turned off after it overheat for long enough, which can result in your engines deteriorating. And unless you pay for the rather expensive repairs, you'll start the next race with a half-broken engine.

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*** In ''The Wounded'', the matter is very urgent, yet they decide to go Warp 4 so that the writers can have them step on the gas later when things [[ItGotWorse go really bad]].

** This is actually explained by a simple application of physics: aerodynamic downforce ''reduces'' the vehicle's speed, since the air resistance of the vehicle is increased (there's more surface area for the wind to hit). What Super Pursuit Mode actually accomplishes is increasing K.I.T.T.'s ''maneuverability'' at such high speeds, thus preventing Michael from wrapping K.I.T.T. around a power pole[[hottip:*:or rather, wrapping a power pole around [[MadeOfIndestructium K.I.T.T.]]]]. The game makes this point, too. Your maximum speed is decreased a bit, but it's much easier to steer.

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* The Space Shuttle's main engines were designed for a certain maximum normal output, rated as 100%, but can run at up to 110% thrust in emergency abort situations. After a few flights it was determined that 104% was actually safe for continuous operation, and it was easier to routinely go to 104% than to rewrite all the documentation to make that the new 100%.

** Many cars have an aerodynamically-limited top speed, creating a situation where the engine looks like it ought to be able to take you faster, but it doesn't have enough torque to actually accelerate you.

** It actually can cause ''hardware'' errors, which manifest as software crashes. (Generally speaking, all software assumes 100% error-free hardware.)

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* The podrace from ''StarWars: Episode I'' is all over this trope. Sometimes Anakin passes other racers with ease, and other times he keeps pace with Sebulba over long straightaways. It also genuinely makes zero sense that he wasn't gong as fast as he could to begin with, considering how he started the race in last place due to engine failure and his freedom was on the line.

** This is actually explained by a simple application of physics: aerodynamic downforce ''reduces'' the vehicle's speed, since the air resistance of the vehicle is increased (there's more surface area for the wind to hit). What Super Pursuit Mode actually accomplishes is increasing K.I.T.T.'s ''maneuverability'' at such high speeds, thus preventing Michael from wrapping K.I.T.T. around a power pole. The game makes this point, too. Your maximum speed is decreased a bit, but it's much easier to steer.

* The transmissions in most modern cars have a gear called overdrive, but it's fairly unexciting: it's just the gear that drives the wheels faster than the engine. Overdrive gears provide much slower acceleration than other gears, and are usually only used under conditions of steady speed and light load. Push harder on the gas while in overdrive and an automatic transmission will downshift to a lower gear for more acceleration. They're designed to save fuel, not make you go faster.

* Used in the pilot episode of ''TaleSpin''. Up until then, the overdrive existed, and it was clearly stated that you could only use it for so long before the engine overheated and blew up the Sea Duck. Baloo burned it out forever and ever during the episode; it's just as well, so we couldn't complain about him ''not'' using it in future episodes.

A SubTrope of HoldingBackThePhlebotinum. A SisterTrope of TimTaylorTechnology. If it involves the risk of a catastrophic failure, it's ExplosiveOverclocking.

* Military warships in the {{Honor Harrington}} series has a version, though with acceleration rather than top speed. The inertial compensator that allows the crew to survive the hundreds of gravities their drives are capable off is normally only run to 80% of its theoretical maximum capacity to reduce wear and reduce the risk of failure. It ''can'' be run higher in emergency situations but is not recommended because if it fails you only have seconds of warning and then the entire crew is reduced to a red smear.

* In ''{{GalaxyQuest}}'', the overdrive blows-out after being held down too long, leaving the ship nearly crippled

*** The game confirms this by making the engines deteriorate, overheat and burst into flames if Overdrive is used too much. And unless you pay for the rather expensive repairs, you'll start the next race with a half-broken engine.
*** Isn't it suppose to be that the engine burst into flame if you left the overdrive activated after the warning sign flashes long enough? [[{{onyhow}} This troper]] remembers that when he decelerate while in overdrive will not cause any flames.

-->-- '''David Morgan-Mar''' (paraphrasing ''StarTrek''), ''DarthsAndDroids''

** It actually can cause *hardware* errors, which manifest as software crashes. (Generally speaking, all software assumes 100% error-free hardware.)

* Most modern fighter aircraft are equipped with equipment variously known as an afterburner or reheat. This system dumps additional fuel into the exhaust in order to burn any oxygen that was not consumed in the main part of the engine. This can greatly boost the thrust at the cost of extreme fuel consumption; afterburners can empty the multi-ton fuel tanks of a jet fighter in less then 5 minutes. Go really fast if you have to, but do it too long and you'd better be ready to walk home.

* Many World War II-era fighter aircraft featured an engine setting called "War Emergency Power"[[hottip:wp:[[http://en.wikipedia.org/wiki/War_emergency_power also in wikipedia]].]] which is ExactlyWhatItSaysOnTheTin. It was intended for emergency use in combat and normally had a time limit imposed on its use, as it would wear out the engine in a very short time. WEP appeared in many forms; some aircraft engines simply had the capacity to run at power levels that would overstress their own components. In these cases, a piece of tape was inserted to stop the throttle at the maximum safe setting; if the tape was broken, the engine would need to be inspected after the flight.
Other aircraft implemented WEP through the use of consumable additives. Nitrous oxide injection would cool the fuel/air charge (allowing more fuel and air to enter the cylinder on each cycle) as well as providing additional oxygen at high altitude. A few aircraft were designed for the stress of nitro injection, and were limited only by the onboard supply of nitrous. Water or water/methanol injection provided a lesser version of the same effect, but also cooled the engine and allowed it to operate beyond its radiator's normal capacity.

* Many World War II era fighter aircraft featured an engine setting called "War Emergency Power"[[hottip:wp:[[http://en.wikipedia.org/wiki/War_emergency_power also in wikipedia]].]] which is ExactlyWhatItSaysOnTheTin. It was intended for emergency use in combat and normally had a time limit imposed on its use. Any use also normally had to be noted afterwards and intensive engine inspections done and it wore out these engines quite quickly. This could take several forms some aircraft used Nitrous injection which was useful at high altitude as the extra oxygen allowed the engine to generate horsepower like it was a lower level, some used water injection to cool the engine and allow it to be driven to speeds that would normally damage it, and finally some simply opened the throttle to a setting that the engine could ''theoretically'' handle, but only just and for a limited amount of time. Use of this feature though could and did explode or damage many an engine.
* Many vehicles will have two different speed or power ratings. There will be an absolute maximum above which damage is very likely to occur within a short time (often represented by a red line), and maximum continous which is the maximum which can be held continuously without damage occuring, often a yellow line. "Continuous" is usually a comparative term rarther than literal, generally interpeted as being able to be used continuously throughout a normal operating cycle. In many cases there may also be a further lower speed or power which will be maximum efficiency. Of course, even going above the red-line is acceptable in some situations if either for very short times, or if the gain outweighs the consequences (and usually will have some margin built in).
** As an example: the manual for the Turbomeca Arrius 1A (a turbine engine for helicopters) lists a maximum continuous power of 296 kW, an intermediate contingency rating of 357 kW (120% normal) usable for up to 30 minutes, and an emergency maximum for 2.5 minutes of 388 kW (131% normal)
* The Space Shuttle Main Engines are currently designed to operate stably at 104% of their original thrust rating given back when they were built in the '80s. In abort situations, however, engine outputs of 106% and 109% are available, though not for long.
* Most modern combat aircraft are equipped with afterburners, a system that allows raw fuel to be dumped into the jet engines. As an overdrive it kicks ass, giving potently 160% normal maximum power.. but are extremely inefficient and can empty the several ton fuel tanks of a jet fighter in less then 5 minutes. Go really fast if you have to, but do it too long and you'd better be ready to walk home.
** Averted in some planes (like the SR-71 Blackbird) that are made for high efficiency during afterburn; you can have your engines spittin' flame for as long as there's fuel available, and everything will be ok. The downside is that they are horribly inefficient when ''not'' afterburning. Another problem is that the Blackbird burned a special fuel, which combined its the fuel inefficient afterburners as its usual method of propulsion, drove operating costs ridiculously high.
** Also, supersonic planes aren't really supposed to do that without a good reason (i.e. combat), and most supersonic planes also have to use afterburners to go supersonic. What's more, fast planes typically can't reach their maximum speed until they've reached a very high altitude. Because of this, fighters will often not be anywhere near their maximum speed even if they're hurrying.
*** Afterburners also come with a side effect of a massive thermal signature. This negates a stealth aircraft's stealth by making it visible to thermal sensors, and in general makes it much easier for heat seeking munitions to find their mark even with countermeasures.
* Because of how internal combustion engines work pretty much every modern vehicle has two real top speeds. A cruising speed where efficiency is maximized, and a maximum speed where the engine is operating at the inefficient top half of it's power band, gulping fuel and increasing heat and wear geometrically for a linear increase in speed. An ironic exception to this rule? Atomic powered aircraft carriers and submarines can operate at maximum speed for as long is required without risking damage or using excessive fuel.
** Another exception was the original VW Beetle; in TheFifties when it was normal for a 1200cc. small car to have a top speed in the range of 70 MPH the company used this as a selling point.
** A real life inversion of this would be the [[http://en.wikipedia.org/wiki/SR-71_Blackbird SR-71 Blackbird]]. The unique hybrid turbojet-ramjet design of its engines meant that the plane became ''more'' fuel-efficient the faster it went, peaking out at around Mach 3.2 (its top speed was higher, but never fully utilized for a variety of reasons).
** Many cars also have an aerodynamically-limited top speed, creating a situation where the engine looks like it ought to be able to take you faster, but it doesn't have enough torque for the extra revs to actually accelerate you.
* There's also a feature of the transmission in most modern cars called overdrive, but it's fairly unexciting: it's just the gear that drives the wheels faster than the engine's revs.
** Overdrive gears give much slower acceleration than other gears, and are usually only used by automatic transmissions under conditions of steady speed and light load. Push harder on the gas while in overdrive and the car will downshift to a lower gear for more acceleration. They're designed to save fuel, not make you go faster.

** A real life inversion of this would be the [[http://en.wikipedia.org/wiki/SR-71_Blackbird SR-71 Blackbird]]. The unique hybrid turbojet-ramjet design of its engines meant that the plane became ''more'' fuel-efficient the faster it went.

** Averted in some planes (like the SR-71 Blackbird) that are made for high efficiency during afterburn; you can have your engines spittin' flame for as long as there's fuel available, and everything will be ok. The downside is that they are horribly inefficient when ''not'' afterburning...

* ''{{Cars}}'' is a rare subversion of the "more speed always works'' aspect of the trope: Lightning [=McQueen=] gains a whole lap on Chick Hicks and The King by skipping several pit stops--then all four of his tires blow out in the final lap, and the race ends in a three-way tie.