Understanding Gross Versus Net Horsepower Ratings > Ate Up With Motor (2023)

There are a lot of misunderstandings among car enthusiasts and historians about vintage horsepower ratings. It’s easy to assume from a casual glance at ads or spec sheets that even quite ordinary American family sedans of the sixties were overwhelmingly powerful, with 300 horsepower or more, and yet by 1975, many of those same cars were down to 150 hp or less. When asked the reason for the huge difference, gearheads tend to shake their heads and mutter about emissions controls and anemic, low-octane unleaded gasoline — which is true, but only partly.

What complicates the issue and makes apples-to-apples comparisons difficult is the fact that those pre-smog horsepower ratings were not calculated in the same way as modern engines. “A horsepower is a horsepower, right?” you say. While a horsepower, pre-smog or post, remains 746 watts (or 736, for metric horsepower), the way that output was measured has changed quite a bit. Let’s explain:


Over the years, the Society of Automotive Engineers (SAE) and similar standards-setting bodies in other countries have developed various methodologies for measuring the output of an automotive engine. These standards fall into two basic categories: gross and net output.

Gross output, which in the U.S. is typically measured using the methodology laid out in SAE standards J245 and J1996, is the output of a ‘bare’ engine running on a test stand with no external engine-driven accessories (e.g., alternators or water pumps), free-flowing exhaust headers with no mufflers, and optimal ignition timing. Gross ratings are also mathematically corrected for standard atmospheric conditions. In other words, gross output represents a particular engine’s maximum output under ideal conditions.

In the real world, automotive engines very rarely operate in ideal conditions. The engines of most cars are burdened with various engine-driven accessories, including the engine’s own water pump and generator/alternator and add-ons like the power steering pump and air conditioning compressor. Engines intended for on-road use typically also have restrictive air cleaners and exhaust systems, sound-deadening mufflers, and emissions-control add-ons like catalytic converters and thermal reactors. Engine tuning is further compromised in the interests of reduced noise, better drivability, improved cold-weather performance, and lower exhaust emissions. All of these factors reduce the engine’s maximum output in ways that the gross rating methodology does not reflect.

For that reason, the SAE and similar bodies have also established standards for measuring net output. Net ratings, such as the ones defined by SAE standards J1349 and J2723, are still taken with the engine on a test stand, but reflect stock ignition timing, carburetion/fuel delivery, exhaust systems, and accessories. The specific methodology varies depending on the specific standard being used, but the gist is that a net rating is a closer approximation of an engine’s output as actually installed in a car or truck.

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Naturally, the net output of a given engine is somewhat lower than the gross output. For example, the 217 cu. in. (3,547 cc) “Stovebolt” six in a 1950 Chevrolet had a gross output of 92 hp (69 kW), but a net output of only 85 hp (63 kW). Chevrolet’s 1955-vintage 265 cu. in. (4,344 cc) small block V8, meanwhile, had a gross output of 162 hp (121 kW) with 8.0 compression and a two-barrel carburetor, but a net output in the same form of 137 hp (102 kW).


Net ratings have existed for many years, but before 1971, most U.S. automakers preferred to quote the more generous gross figures. Net figures might appear in shop manuals, technical papers, or other factory literature, but rarely showed up in advertising.

Until the mid-fifties, the gap between gross horsepower and as-installed output was seldom vast. However, as it became apparent that impressive horsepower numbers sold more cars, manufacturers’ advertised gross output figures began to climb. While automakers didn’t necessarily publish net ratings for their hot engines, the performance of cars so equipped suggested that the advertised figures were now substantially higher than the engines’ as-installed outputs — sometimes by 25% or more.

The late-fifties recession temporarily put the brakes on the advertised horsepower race. By the mid-sixties, the advertised outputs of many bread-and-butter engines were still unrealistically high, but the outputs of Detroit’s most powerful engines were now as likely as not to be deliberately understated. For example, in 1965, Chevrolet released the 396 cu. in. (6,488 cc) Turbo-Jet V8 as an option for Corvettes, rated at 425 gross horsepower (317 kW). The following year, the engine was bored to 427 cubic inches (6,996 cc). At first, some Chevrolet promotional material quoted a gross output of 450 hp (336 kW) for the bigger engine, but the division then hastily restated maximum power as 425 hp (317 kW), no more than the 396. Outside observers were incredulous, particularly since the bigger engine was plainly more powerful than the smaller version.

Understanding Gross Versus Net Horsepower Ratings > Ate Up With Motor (1)

Why would a manufacturer underrate their engines? One possible reason was racing. Particularly in drag racing, eligibility for different classes was sometimes based on advertised horsepower and shipping weight, so an engine that produced more power than its advertised gross rating indicated offered an obvious advantage. Racing officials were seldom fooled by such tricks for long, however, and began to handicap or “factor” advertised outputs to place a conservatively rated engine in a more appropriate class based on its actual performance.

Another reason for underrating was political decorum. Particularly at GM, the most conservative of the Detroit automakers, there was real fear of the safety lobby, which already considered the power outputs of existing engines to be irresponsibly high. In that climate, offering a 450 hp (336 kW) or 500 hp (373 kW) Corvette, for instance, might have been asking for trouble. Insurance was also becoming an issue, with a growing number of auto insurance companies levying prohibitive surcharges on very powerful cars, or simply refusing to cover such cars at all.

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For those reasons, GM also had internal rules limiting all of their passenger cars except the Corvette to a maximum of one gross horsepower per 10 pounds (1 kW per 6.1 kg) of curb weight, leading to curious non sequiturs like rating Pontiac’s 3,300 lb (1,500 kg) Firebird at 325 hp (242 kW) while claiming 360 hp (269 kW) for the mostly identical engine in a 3,600 lb (1,635 kg) GTO.

Underrating of this kind was at best an open secret. When Car Life magazine tested a 1969 Pontiac GTO Judge equipped with the $390 Ram Air IV engine, for example, Pontiac executives freely admitted that the engine’s 370 hp (276 kW) gross rating was purely a political fiction.


Between inflation and deliberate underrating, the relationship between advertised gross horsepower and actual net output was becoming increasingly nebulous by 1970. The gross ratings served a variety of useful marketing and political purposes, but as a realistic measure of engine output, they left much to be desired. In particular, the gross ratings seldom reflected the impact of add-on emissions control devices like air injection and exhaust gas recirculation, which were already beginning to have a noticeable impact on engine performance.

The final straw was the passage of a California law requiring that any reference to engine horsepower in advertisements, brochures, owner’s manuals, or sales manuals for 1972 or later gasoline-powered cars and light trucks state only the as-installed SAE net rating. Faced with that reality, manufacturers decided it was time to abandon the gross rating system entirely, at least in the United States. For 1971, many U.S. manufacturers listed both SAE gross and net ratings (providing a sometimes illuminating comparison between the two) and then switched to net ratings exclusively for 1972 and beyond, even in states other than California. (Making the change across the board was probably a prudent move from a liability standpoint, considering that in the U.S., consumers can and periodically do sue manufacturers whose products don’t perform as advertised.)

The move also provided a useful and relatively inexpensive PR gesture. By simply switching from gross to net ratings, automakers sent a message to lobbyists and lawmakers that the horsepower race was over and Detroit was no longer offering outrageously powerful engines. Beyond that, the timing of the switch helped to obfuscate the actual losses caused by added emission control hardware and lower compression ratios, which was presumably very useful for the unfortunate Cadillac salesman trying to rationalize why the 1972 Cadillac the customer is looking at seems to have 40% less power than the 1970 model he’s trading in.

The immediate result was a dramatic drop in advertised power. For example, the mammoth 500 cu. in. (8,194 cc) engine in the Cadillac Eldorado fell from 400 gross horsepower (298 kW) in 1970 to only 235 net horsepower (175 kW) for 1971. The real decline wasn’t quite as steep as it looked; the 1971 engine did have a lower compression ratio to prepare for the adoption of unleaded gasoline, but the 1971 gross rating was still 365 hp (272 kW), so the actual loss was about 10%, not more than 40%. (Cadillac did not publish net horsepower ratings for the high-compression 1970 engine, but our guess would be that it made 275–285 hp (205–213 kW).)

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Rating methodology notwithstanding, the initial decline in power was relatively modest, but that wouldn’t remain the case for long. For example, the hottest version of Pontiac’s 455 cu. in. (7,481 cc) V8 still managed 310 net horsepower (231 kW) in 1973, but was down to only 200 hp (149 kW) by the time it faded out in 1976. Ford’s familiar 302 cu. in. (4,942 cc) V8, meanwhile, which in the sixties had advertised as much as 306 gross horsepower (228 kW), had plummeted by 1979 to less than 140 net horsepower (104 kW). It was not until the widespread proliferation of electronic fuel injection in the 1980s that net power outputs again began to climb.

U.S. automakers continue to use SAE net ratings, but in 2005, the SAE issued a new standard, J2723, which clarified and amended the existing methodology, among other things requiring that a suitably qualified independent observer be present during the rating procedure. Some engines certified under the new SAE “Certified Power” guidelines ended up with lower ratings than before, while a few others actually ended up with higher ratings. In most cases, the engines were not actually altered in any significant way; the changes were in the test methodology. Most if not all manufacturers now use this methodology for their U.S.-market cars and trucks.


What about cars not built by U.S. automakers? As with many things, the answer is, “It depends.”

German automakers have long rated their engines under the strict DIN (Deustches Institut für Normung, German Institute for Standardization) standards. DIN horsepower and torque figures are metric net ratings, and typically differ somewhat from SAE net ratings due to minor differences in test methodology (such as correction factors for standard atmospheric conditions) and the difference between metric and mechanical units (discussed further below). Some Italian automakers formerly used the Comitato Unitario dell’autotrasporto (CUNA) standards, whose metric net ratings again were similar but not identical to SAE net ratings. Depending on the time period, model, and market, other European automakers might use either DIN or SAE gross figures.

Until the early 1970s, some British automakers quoted SAE gross figures for horsepower and torque, while others listed net figures; some manufacturers listed both. After the U.K. joined the European Economic Community in 1972, the British auto industry switched to DIN ratings.

Japanese automakers rate the outputs of their home-market cars under the Japanese Industrial Standards (JIS), which include methodologies for both gross and net output. The difference between the two was generally around 15% — sometimes a little more, sometimes a little less. Until the mid-eighties, most Japanese automakers quoted JIS gross figures for most if not all products sold in the Japanese domestic market. The switch to JIS net ratings began around 1985, but wasn’t completed until late in the decade. Confusingly, for some model years, manufacturers would quote net ratings for some engines and gross ratings for others, even within a single model line.

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Prior to 1971, most non-U.S. automakers would publish SAE gross figures for all engines exported to the U.S. However, foreign automakers seldom indulged in the kind of gamesmanship Detroit sometimes played with its gross ratings, so the differences between gross and net ratings were typically small and probably fairly realistic. For example, the Triumph TR4 carried a gross rating of 105 hp (78 kW) and a net rating of 100 hp (75 kW), while a 1963 Mercedes-Benz 230SL had a gross rating of 170 hp (127 kW) SAE and a net rating of 150 PS (110 kW) DIN.


There is an additional complication when considering non-U.S. power ratings: the question of units. DIN, JIS, and CUNA standards are typically — but not always — quoted in terms of metric horsepower rather than the mechanical horsepower more familiar to our American readers. One metric horsepower (often abbreviated PS, from the German Pferdestärke) is about 736 watts, while one mechanical horsepower is about 746 watts, so 1 PS equals 0.986 hp. For example, 300 metric horsepower would be about 296 mechanical horsepower, while 150 PS is about 148 hp.

Unfortunately, many sources are maddeningly inconsistent in their application and even understanding of these units, and tend to freely interchange them, always writing “hp” or “bhp” even when talking about PS. Occasionally, some sources will attempt to convert one unit to another, sometimes inconsistently — for example, multiplying by 0.986 a rating that was already in mechanical horsepower. (We’ve almost certainly been guilty of that, although we try to avoid it.) The difference is often small, but it does frustrate efforts to be consistent or precise.


Let’s clear up a couple of common misconceptions about gross and net horsepower ratings:

  1. Contrary to some assumptions, net horsepower ratings DO NOT measure horsepower at the drive wheels. Both gross and net ratings are at the flywheel and do not reflect power losses in the drivetrain.
  2. Because of the vagaries of the old gross ratings, the widespread over- and underrating of different engines, and the considerable differences in the amount of power consumed by different intake/exhaust/accessory configurations (even for different applications of the same basic engine), there is NO reliable formula for converting gross horsepower to net horsepower or vice versa. Sometimes, the difference is as little as 5–10%; sometimes, it’s more than 25%. Unless the factory released both gross and net figures for a given engine (which some did, even in the U.S.), the best you can do is make an educated guess based on state of tune and real-world performance testing — keeping in mind that published road tests didn’t necessarily reflect the performance of cars the average consumer could actually buy.
  3. The ambiguity of gross horsepower ratings means that many pre-1971 American cars were actually a lot less powerful than the advertised figures would suggest. While the late sixties were a golden age of horsepower compared to the late seventies or early eighties, the differences weren’t quite as vast as they appear at first blush. Some engines’ advertised gross horsepower probably exceeded their actual as-installed power by 100 hp (75 kW) or more.



Most of this information is based on decades of reading car magazines. Some of our specific references included (but were not limited to) Robert Ackerson, Chrysler 300 ‘America’s Most Powerful Car’ (Godmanstone, England: Veloce Publishing Plc., 1996); “Alfa Super Spider,” Road & Track October 1959, reprinted in Road & Track on Alfa Romeo 1949-1963, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1985), pp. 52–53, 65; the Auto Editors of Consumer Guide, Consumer Guide Car & Truck Test Monthly August 2005 and July 2006 and Encyclopedia of American Cars: Over 65 Years of Automotive History (Lincolnwood, IL: Publications International, 1996); John R. Bond, “Car of the Year: The 1949 Cadillac,” Motor Trend November 1949, reprinted in Cadillac Automobiles 1949-1959, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1985), pp. 8-9; Bernard Cahier, “Road Test/10-63: Mercedes-Benz 230 SL,” Sports Car Graphic May 1963, reprinted in Mercedes 230SL – 250SL – 280SL Ultimate Portfolio 1963-1971, pp. 31-34; California Vehicle Code, Section 9950; “Chevrolet Camaro Z28,” Car and Driver May 1971, reprinted in Camaro Muscle Portfolio 1967-1973, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1992), pp. 118-121; Chevrolet Division of General Motors Corporation, Chevrolet 1950 Engineering Features: Passenger Cars (Detroit: General Motors Corporation, 1949); Lionel Deluy, “Technologue: SAE What?” Motor Trend, 15 October 2005, www.motortrend. com/news/ technologue-34/, last accessed 10 June 2016; Dodge Division of Chrysler Motors Corporation, “Dodge 71” [1971 Dodge full-line catalog 81-205-1041], Aug. 1970; “GM: Cadillac,” Motor Trend Buyers’ Guide 1971, reprinted in Cadillac Eldorado 1967-78 Performance Portfolio, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 2000), pp. 80-83; “GM: Oldsmobile,” Motor Trend Buyers’ Guide 1971, reprinted Oldsmobile Muscle Portfolio 1964-1971, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1999), pp. 138-140; Tony Grey, “Olds 4-4-2,” Road Test May 1971, reprinted in Oldsmobile Muscle Portfolio 1964-1971, pp. 132-137; John Gunnell, ed., Standard Catalog of American Cars 1946-1975, rev. 4th ed. (Iola, WI: Krause Publications, 2002); Roger Huntington, “Chevrolet’s New V-8,” Motor Life December 1954, reprinted in Chevrolet 1955-1957, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1988), pp. 16-17, 31; Jikayousha [Private Car] Buyer’s Guide Spring ’87 Edition, February 1987; Steve Kelly, “Beware the Quiet Fish,” Hot Rod January 1971, reprinted in Plymouth 1964-1971: Muscle Portfolio, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 2003), pp. 120-122; John Lamm, “King of the Hill: Cadillac Eldorado vs. Lincoln Continental Mark IV,” Motor Trend July 1972, reprinted in Cadillac Eldorado 1967-78 Performance Portfolio, pp. 96-103; Brian Long, Celica & Supra: The book of Toyota’s sports coupes (Dorchester, England: Veloce Publishing, 2007); “Road Testing Chrysler’s Power Flite,” Speed Age November 1953, pp. 58-62, reprinted in Chrysler Imperial Gold Portfolio 1951-1975, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 2004): 20-23; Don Sherman, “Pferdestärke and other horsepower secrets revealed!” Car and Driver Vol. 30, No. 12 (June 1985), pp. 26–27; “Technical Highlights,” Car and Driver Vol. 17, No. 4 (October 1971), pp. 57, 101; “The Judge: Car Life Road Rest,” Car Life March 1969, reprinted in GTO Muscle Portfolio 1964-1974, ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1998), pp. 91-95; William K. Toboldt and Larry Johnson, Goodheart-Willcox Automotive Encyclopedia (South Holland, IL: The Goodheart-Willcox Company, Inc., 1975); “Triumph TR4 (Road Test No. 26/62), The Motor 11 July 1962, reprinted in Triumph TR4 – TR5 – TR250 1961-1968 (Brooklands Road Test Series), ed. R.M. Clarke (Cobham, England: Brooklands Books Ltd., ca. 1997), pp. 30-33; and Mark Wan’s AutoZine (www.autozine.org). We also verified a few details per the Wikipedia® entry on horsepower (en.wikipedia.org/wiki/Horsepower).

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What is the difference between net horsepower and gross horsepower? ›

Gross hp figures were so often manipulated by car manufacturers and marketers that the SAE decided to adopt a new standard of power that took accessories into account. The SAE chose to use net hp ratings, which measures engine power at the flywheel, but still not counting drivetrain losses.

What is the difference between gross power and net power? ›

Net power values are taken with exhaust and air cleaner installed whereas gross power values are collected without these attachments. Actual gross engine power will be higher than net engine power and is affected by, among other things, ambient operating conditions and engine to-engine variability.

What does gross horsepower mean? ›

Gross horsepower is a measurement of engine output, taken at the flywheel, without the engine installed in a vehicle. Since the engine has no load on it, all of its energy can be used for making horsepower.

How is net horsepower calculated? ›

The equation to calculate horsepower is simple: Horsepower = Torque x RPM / 5,252.

How much horsepower did the 426 Hemi really have? ›

MoPar 426 Hemi

The 426 street Hemi was rated at 425 horsepower from the factory. This Chrysler dyno sheet from decades ago and this close-to-stock dyno session of a new 426 Hemi both put the gross horsepower rating at about 470 horsepower without full exhausts and other engine-driven accessories.

What is the most powerful muscle car engine? ›


The 2022 Dodge Challenger isn't one to be messed with. Thanks to its Supercharged 6.2L High-Output HEMI® V8 engine, the SRT® Super Stock has the highest horsepower of any production car and is the most powerful muscle car( Disclosure3).

How many horsepower is 190cc Briggs and Stratton? ›

This genuine 190cc Briggs & Stratton single cylinder engine offers dependable power for your equipment needs. With a power rating of 6.75 horsepower, this engine features a recoil starter, and maintenance-free Magnetron electronic ignition.

How can I tell what horsepower My Briggs & Stratton engine is? ›

You can find the gross horsepower or torque value labeled on your engine. To find an engine's horsepower, look for a number with “HP” or “cc.”

Do power plants run at full capacity? ›

The Capacity Factor

It basically measures how often a plant is running at maximum power. A plant with a capacity factor of 100% means it's producing power all of the time. Nuclear has the highest capacity factor of any other energy source—producing reliable, carbon-free power more than 92% of the time in 2021.

What is net power of engine? ›

Net power: the effective power output by the engine's power output shaft that is measured when engine is equipped with all the parts needed for actual operation conditions and is operated in the regulated rotating speed in the engine laboratory table.

What is horsepower net? ›

SAE “net” horsepower is only crank horsepower that is net of any necessary ancilary devices needed to make the engine run. These devices include the alternator and water pump. Engines rated SAE gross are run without powering the water pump (typically electric driven) and an alternator.

How is horsepower rated? ›

Though we refer to horsepower, the true metric of an engine's power is its torque. Mechanical horsepower (determined on a dynamometer) is determined by multiplying torque by engine rpm and then dividing that sum by 5,252.

Is 1 HP equal to a horse? ›

Power of a horse

Although it may seem safe to assume that one horsepower is the output a horse is capable of creating at any one time, that is incorrect. In fact, the maximum output of a horse can be up to 15 horsepower, and the maximum output of a human is a bit more than a single horsepower.

How is motor power calculated? ›

By taking the voltage and multiplying it by the associated current, the power can be determined. A watt (W) is a unit of power defined as one Joule per second. For a DC source the calculation is simply the voltage times the current: W = V x A.

Is horsepower measured differently now? ›

The original measure of horsepower started off calculated differently than we use now. In fact, up until 1971, the term “gross” horsepower was most common. Now, people calculate horsepower by multiplying torque by maximum speed and dividing by 5252.

What muscle car has the highest horsepower in 1970? ›

The Ultimate Muscle Car – The 1970 LS6 Chevelle Was America's King Of The Streets
  • While the cars were tested with either four-speed or automatic transmissions, they did display similar times. ...
  • The 450 horsepower LS6 was the most powerful engine offered in 1970.
14 Nov 2019

How much horsepower did the 428 Cobra Jet really have? ›

22 Though some claim the 428 CJ actually made in excess of 400 hp, we observed 365.1 hp at 4,800 rpm, almost 10 percent more than advertised. After some break-in miles, we'd likely see 375 hp and, with headers, yes, very likely 400 ponies.

Which is better 426 Hemi or 440? ›

From the factory, the 440 had more power and was faster than the hemi. However, you could get more power out of the Hemi once you started to modify it. Things like different intakes, carburetors, head porting, and forged internals would blow everything else away.

What is the king of all muscle cars? ›

LS6-Powered 1970 Chevy Chevelle SS Is The King Of Muscle Cars.

What is the rarest muscle car of all time? ›

The Shelby Cobra Super Snake and the Shelby Mustang GT500 Super Snake are the rarest muscle cars ever built. Both were launched in 1967, both are made by Shelby, and both carry the Super Snake moniker.

What is the fastest American made muscle car? ›

The 2018 Dodge Challenger SRT Demon is the fastest muscle car ever made with a 0-60 time of 2.3 seconds and reaching a top speed of 211 mph.
1. 2018 Dodge Challenger SRT Demon.
2018 Dodge Challenger SRT DemonSpecs
Torque717 lb-ft regular fuel 770 lb-ft 100 octane fuel
0-60 MPH2.3 seconds
Top Speed211 MPH
3 more rows
30 Apr 2022

What is horsepower net? ›

SAE “net” horsepower is only crank horsepower that is net of any necessary ancilary devices needed to make the engine run. These devices include the alternator and water pump. Engines rated SAE gross are run without powering the water pump (typically electric driven) and an alternator.

What is net power of engine? ›

Net power: the effective power output by the engine's power output shaft that is measured when engine is equipped with all the parts needed for actual operation conditions and is operated in the regulated rotating speed in the engine laboratory table.

Is 275 hp a lot? ›

Right between 200 and 300 is a good amount of horsepower for a car.

When did net horsepower come out? ›

In 1970 California passed a bill that demanded automakers quote “net” horsepower calculated using S.A.E Standard J245 when communicating engine power to customers in advertisements, brochures and manuals starting with the 1972 model year.

How is horsepower rated? ›

Though we refer to horsepower, the true metric of an engine's power is its torque. Mechanical horsepower (determined on a dynamometer) is determined by multiplying torque by engine rpm and then dividing that sum by 5,252.

Is 1 HP equal to a horse? ›

Power of a horse

Although it may seem safe to assume that one horsepower is the output a horse is capable of creating at any one time, that is incorrect. In fact, the maximum output of a horse can be up to 15 horsepower, and the maximum output of a human is a bit more than a single horsepower.

Is horsepower measured differently now? ›

The original measure of horsepower started off calculated differently than we use now. In fact, up until 1971, the term “gross” horsepower was most common. Now, people calculate horsepower by multiplying torque by maximum speed and dividing by 5252.

How is engine power calculated? ›

The answer is simple: horsepower is calculated by multiplying the amount of force (in pounds) by the speed (in feet per second). So, let's say your car's engine can generate 200 pounds of force and move at a speed of 2 feet per second. The engine horsepower would be 400 (200 x 2).

What is the street legal horsepower limit? ›

In the United States, you can have as much horse power as you like; as long as it does not disrupt safety. And, of course meets the criteria of safety and standards to make the car street legal.

What is the gross mechanical power? ›

Pm = VI - I2R

Since V and R are fixed, the power developed by the motor depends upon armature current.

How much horsepower does a cold air intake add? ›

Cold Air Intakes are said to improve your vehicle's performance by 5-20 horsepower. This number will vary depending on the make and model of your vehicle. While this isn't enough power to put you back in your seat, it will give your car or truck a little pep in its step.

Is 400hp enough? ›

Whether 400 hp is a lot depends entirely on the type of car. For a supercar, it isn't much, but for a family sedan, it's more than you'd need. However, for sports and luxury cars, 400 is a solid amount.

Is 180 hp fast? ›

It depends on the vehicle. 180 horsepower in a motorcycle would be very fast. 180 horsepower in a large commercial truck would not be fast. 180 horsepower in a mid-sized sedan would be fast enough i.e. be able to cruise at highway speeds and accelerate safely onto the highway.

What was the fastest muscle car in 1969? ›

To get your wheels turning and interest piqued, below are the top 5 that made their list:
  • Plymouth Roadrunner – 107.65 mph, 13.32 sec.
  • Boss 429 Mustang – 107 mph, 13.34 sec.
  • Charger 500 – 109 mph, 13,48 sec.
  • Corvette L88 – 111.10 mph, 13.56 sec.
  • Mustang Mach 1 – 103.44 mph, 13.69 sec.
16 Dec 2021

Why did horsepower drop in the 70s? ›

Horsepower ratings is the US began to drop in the early seventies for two reasons. One was that advertised horsepower changed from gross to net. The other was the advent of emission controls to reduce tailpipe emissions.

What was the most powerful muscle car in the 70s? ›

Ranking The Most Powerful Classic Muscle Cars Released In The '...
  • 5/10 1970 Oldsmobile 442 - 365 HP.
  • 4/10 1970 Mercury Cyclone Spoiler Boss 429 - 370 HP.
  • 3/10 1971 Plymouth Hemi'Cuda Convertible - 425 HP.
  • 2/10 1970 Dodge Challenger R/T 426 Hemi - 430 HP.
  • 1/10 1970 Chevrolet Chevelle SS454 - 450 HP.
20 Jun 2021


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