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Someone help us understand what's going on here. In the latest episode of Top Gear, Richard Hammon revisits the Ford Shelby GT500 that the British motoring show tested late last year. For comparison's sake, Hammond brings along his own classic Shelby GT390. We're used to Top Gear bashing our U.S. ware at every opportunity, and the GT500 again takes a licking for having a suspension that can't handle the car's power. But when Hammond wheels out a portable chassis dyno to accurately measure the GT500's horsepower, he seems surprised to learn that the car produces 447 horsepower. Of course, that's 447 wheel horsepower, meaning the horsepower is being measured at the wheel where parasitic drivetrain losses are in effect and reduce the manufacturer's flywheel horsepower rating a good 10 to 20%. In fact, if you factor in a 10% drivetrain loss on Ford's flywheel horsepower rating of 500, you get 450 wheel horsepower, which is pretty darn close to the 447 achieved by Hammond's "rolling road". For some inexplicable reason, however, Hammond and his comparitavely giant co-host, Jeremy Clarkson, ding the GT500 for producing 53 less horsepower than advertised. Huh?

You can view the segment after the jump for the time being (until it gets yanked off YouTube) and make your own judgment, but from our perspective the segment appears highly misleading to viewers who don't know the difference between horsepower ratings at the wheel and the flywheel. What's up, Hamster?

[Source: Dubspeed Driven]

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    • 1 Second Ago
      • 8 Years Ago
      "You'd see rednecks cry when their LS1 made less than 290whp in their heavy ass 5000 lb cars with shitty suspension."

      Umm... My 2002 Z28 SS made 332WHP right off the showroom floor. That's considerably more than the 325HP flywheel rating.

      Next you'll tell me Grand Nationals were overrated at 245hp.

      One more thing, there's nothing... NOTHING old about the mustang's suspension. It is absolutely the best solid-axle rear ever designed. OH, you don't like solid axles? Well too bad! Mustang racers demanded them. They're an absolute necessity for serious drag racing. Ford understood that, and made sure the car had the best possible suspension characteristics the solid axle could provide. Based on sales, this was obviously a huge mistake.

      Put down the NAWZ bottle and try being a little more open minded.
      • 8 Years Ago
      murciealgo142... I don't see how them strapping the car to a dyno and reporting the actual numbers is false reporting.

      Them making up a number out of the sky would be false reporting. Actually dynoing the car on the show seems pretty real-world to me.

      Unless you can think of a different way to measure real world horsepower.
      • 8 Years Ago
      Does this lot know nothing about horsepower ratings? In America cars are no longer rated at the engine, they are rated at the wheel. The Shelby GT500 is supposed to get 500hp at the wheels not at the engine. Therefore what Top Gear did was absolutely correct. Learn before you comment.
      • 8 Years Ago
      Look BOB101,

      I'm not from the UK so I don't know how they rate HP. If it is at the wheels, fantastic, great for you.

      As for those of us in the US, the manufacturers rate at the flywheel. Including any European brands. The GT500 is rated at 500 HP here in the states. It does share the block design and heads with the Ford GT but has a less efficient supercharger (roots style as opposed to twin screw) thus the 50 HP defecit. Anyone doing an ounce of homework would know that, so Hammond's claim that it is the same engine is incorrect and I am sure on purpose as they obvioulsy don't care about details, just to ensure their audience is entertained, that is understood.

      Point is, the car is built for us in the US, you can have your low output/great handling cars there, we don't care. As I said before, I roadrace, so I like a well balanced car- handling, brakes, power. But most people here want to go fast in a straight line and that is the Mustang and GT500 demographic. If you want a handler, the Cobra R and the upcoming rehash of the Bullitt Mustang (less power than GT500, less weight, better suspension) will be your cup of tea, so to speak.
      • 8 Years Ago

      BHP stands for 'brake horsepower', which, despite the odd name, is just another name to describe crank horsepower. I think you meant 'WHP'
      • 8 Years Ago
      First off, yes the 500 advertised HP is at the crank, just as with every other car sold in the U.S. So please shut up, Ford does underrate these vehicles slightly and have talked with many GT500 owners who are making at least their 500 crank horses.

      Second, the slap at solid rear axles just shows how ignorant most people are. I road race a Mustang with a solid axle setup much like the new Mustangs. A panhard bar and torque arm make up an excellent rear suspension.

      IRS' only advantage is adjustability for camber and independent movement of the wheels. Most race tracks are really smooth and negate the need for that indepedent movement of the wheels. As for camber adjustments, unless you plan to seriously race (i.e. proffesionally), you don't need it as the rear tires usually only grip on exits and not in the beginning of turns like the front. I rarely see a car at an event set up with rear negative camber.

      I've run on track with the likes of Vettes, Porsches, and BMWs. I can easily keep up and I have less power than many of them.

      Also, in the video, you see that the Roush Mustang with a slightly modified suspension (shorter springs, different rate shocks, bigger sway bars- still solid axle), different brakes (probably similar in size though) gets around the track 2 seconds faster. The GT500 is set up for daily driving, the Roush is setup for handling and with that go the trade offs in ride quality. If you want your GT500 to handle better, simple mods are a few dollars away.
      • 8 Years Ago
      Just found the owner of the Roush that was on the show: http://www.importmyvehicle.com - They seem to sell new Roush Mustangs for £29,995! I think I want one!!!!
      • 8 Years Ago
      I'll bet that it does not make 500hp even when measured the correct way.

      Everybody knows that Ford engines dont make their rated horsepower. Hell, they even got a class action suit for their false claims on the 305 hp Cobra around 1995.
      • 8 Years Ago
      Uhhh....am I missing something or have some of you forgotten the concept of Apples to Apples. First, if you have any doubt Ford is talking about 500 BHP as opposed to WHP ask them. The marketing material I have seen on Ford's website says "HP". Common knowledge within the auto industry is that car companies advertise BHP whether they indicate it or not in a marketing brochure. Take a look at the web specs on BMW's site for the M5 - again no mention of BHP or WHP, just "HP". Welcome to marketing 101 - take the biggest number we can legally support through an accepted measuring standard (in this case SAE) and publish THAT number but not all the fine print.

      But I digress....the real issue is basic apples to apples comparison. If Top Gear is going to go after Ford for mis-representing its advertised horsepower in the GT500 they need to come out and state exactly how they are arriving at that conclusion and provide evidence for their apples to apples comparison that supports their position.

      It even seems to a non-technical person like myself that comparing a "derived" BHP figure from their dyno setup with a computational adjustment for drivetrain loss against a BHP figure taken with an engine dyno (IF IF IF that is in fact what they did and it doesn't sound like this episode explains that) is not necessarily an apples to apples comparison.

      Did they actually state what their HP figure meant in the show? BHP or WHP? I guess my feeling is that we can't get very far as to the accuracy of their claim without a LOT more information as to what their testing protocol was and what they are actually stating. At this point (having not seen the episode however) they are throwing around "HP" as much as the manufacturers do.
      • 8 Years Ago
      this is normal i dyno-ed my car and it has 103 horsepower. in the papers it says 101 hp so the dyno test took that into account, the drivetrain loss. i believe it is so in the episode as well.
      • 8 Years Ago
      Just an fyi from ford website glossary:

      The amount of power needed to lift a 550-lb. object at a rate of one foot in one second. Horsepower is expressed as the torque in lb.-ft. times the number of revolutions per minute divided by the constant 5252:
      HP = Torque x Engine Speed - (T x rpm) 5252
      Gross horsepower is obtained by a dynamometer test of an engine equipped only with the built-in accessories essential to its operation, such as fuel pump, oil pump, coolant pump and built-in emissions control equipment Net horsepower is obtained by a dynamometer test of a complete engine equipped with all the accessories necessary to perform its intended functions unaided, including the air- intake system, exhaust system, cooling system, generator, starter and emissions control equipment.

      Not sure if there's anything posted on the 500hp being net or gross.

      but anyhoo i'm a big mustang fan, and i'm well aware of it's shortcomings. However, it serves it's purpose to haul butt on the cheap (at least usually pretty cheap). I tried looking up new M3 and it's not out yet, but the M5 looks sweet and USA website posts this - "The world-renowned super-sport sedan is now the most sophisticated and powerful 5 Series ever, powered by an incredibly advanced V-10 engine, with a five-liter capacity, 10 cylinders, 500-hp (SAE net) output, 383 lb-ft maximum torque, and engine speeds in excess of 8,000 rpm." however this level of comfort and power comes at a steep price 80k+ us dollars. 2 different cars, 2 different prices, similar power, different handling characteristics. Take them for what they are and move on. SAE net? does that mean at the crank? and if so, I wonder if they put the m5 up on that dyno would they complain about hp discrepancy?
      • 8 Years Ago
      Top Gear is fun and entertainment, that's it. Eye-catching production values, and no substance. Technical expertise on the show hovers somewhere between 'embarrassing' and 'non-existent'.

      This is the show, after all, in which Clarkson repeatedly talks about cars having 'x' quantity of 'torques'.

      Entertainment, not journalism. Fun to watch, unquestionably, but I feel sorry for anyone who takes very much of what they say seriously.
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