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Automotive News & Views 0-60 is so yesterday!
154 messages, Last post on Oct 09, 2007 at 10:40 PM
You are in the Automotive News & Views Forum. Your Hosts are steve_ & claires
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HP and TQ curves are no more reliable than 0-60 times. A dyno run printout can tell you a lot about how much power the car is making at the wheels, but what was the temperature, air density, and humidity that day? Was it performed with Mustang or Dynojet equipment? 0-60 testing suffers from the same variables, with the additional problem of different drivers and different roads. Another problem I haven't seen mentioned yet is gearing. Some cars can reach 60 MPH in 2nd gear, and some require an upshift to 3rd in order to reach that "benchmark" - time lost. Gearing also comes into play when looking at acceleration figures of two different cars. Why can a less powerful 4 cylinder CRV accelerate to 60 as quickly as a 6 cylinder Escape? Just look at the final drive ratio for your answer. 4.36:1 for the Honda compared to the Ford's 3.76:1. If you really want a good idea of how quick a car is compared to another, review 4 or 5 different sources and compare the numbers across the board. Look at 0-30, 0-60, 0-100, and 1/4 mile times/speeds. Look at curb weight, gearing, and HP/TQ curves - not just the peaks, but the amount of "space beneath the curves." Interpret all of this, and you can get a pretty accurate picture of not just how fast the car is, but what kind of power delivery it has. Oh yeah, don't forget to drive the car.
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Replying to: bumpy (Jan 18, 2007 12:31 pm) I am guilty of a misprint, the Corvette engine is listed as "OHC" vs the 911's "DOHC". I'm not an engineer, I take it that "OHC" and "SOHC" are not the same? "Unless the Corvette is wheel-hopping badly or suffering from inordinately high drivetrain losses, it should be able to dispatch the Porsche." I think you nailed part of the answer. In spite of massive rear tires on the Corvette, the 911, even in RWD form, is far more effective in putting it's power to the pavement. The pictures show a lot of tire smoking on the Corvette, with the 911 sling-shotting out of the start. Unfortunately, American performance cars are still designed with an approach that over-emphasizes "quantity" - hp, torque, tire size - than "quality" in the form of cutting edge dynamic engineering. Good thing that's not the case with Boeing and airplanes, or they would be the GM of the airplane business instead of the world leader.
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Replying to: habitat1 (Jan 26, 2007 3:22 am) Except for the early-90s ZR-1, Corvettes have always had pushrod engines with a single cam buried down in the block (OHV) instead of one or two cams on top of each head (SOHC or DOHC). |
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Replying to: fedlawman (Jan 25, 2007 8:23 pm) Actually, it can get even more complicated than that. In addition to the axle ratios of 3.76:1 or 4.36:1, you also have to look at the ratios of the various gears. When you floor a car from a standstill, most likely it's only going to use the first and second gears to get to 60. I dunno, maybe these trannies with 5 and 6 gears might use more, but I doubt it. Usually I think those additional gears are just there to cut down highway revs, or to give you more flexibility at high speed passing. So in theory, one car could have a quicker axle but slower first and second gears than another. But in the case of the CRV versus the Escape, that doesn't seem to be the case. BTW, what is a typical first or second gear ratio these days? I've had a lot of old Mopar products over the years, and traditionally the Torqueflite would use a 2.45:1 first gear, although once they started going to ultra-tall 2.26:1 rear ends in 1981, they changed first gear to something like 2.74:1. I have an old '79 New Yorker with a 2.45 axle, which puts the multiplication for first gear at about 6.00:1. I guess with a ratio like that it's a miracle it moves at all, but on the plus side it can almost make it to 60 mph just in first gear!
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Replying to: andre1969 (Jan 26, 2007 5:03 am) Depends on how much of a barge the car is, but a typical 5-speed manual in a compact was something like 3.3, 1.9, 1.3, 1, and 0.85 with a final in the upper 3s. Automatics are usually geared taller. |
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Replying to: fedlawman (Jan 25, 2007 8:23 pm) If I asked a sales person about 0-60 times, framing it as a measure of performance that was of use to me, I'd frankly be put off by a monologue on gear ratios, launch techniques, weather conditions and tire brands. I'd expect to hear a number and credit for having enough common sense to understand that the number could vary somewhat depending on whatever. I once had a boss who liked concise answers. When he started to get too much info he'd cut the person off with, "I asked what time it is. I don't need to know how to build a watch." He'd let people add detail -- AFTER they answered his questions concisely. Maybe a Porsche buyer, tuner or the Schumacher brothers have different assumptions (and I'm sure have far more expertise than I do), but if I sold cars, I'd try to be clear and concise in my responses to customer Qs. |
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Replying to: saabgirl (Jan 26, 2007 9:48 am) If you can find a typical salesperson on any given Wednesday on any average car lot who could even come up with the correct 0-60 time for the model about which you inquire, I'll buy a new hat and eat it!
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Replying to: andre1969 (Jan 26, 2007 5:03 am) Choice of gear ratio is largely dependent on what overall ratio engineers strive to achieve. If I had to take a guess, I would say a typical 5 speed automatic transmission will have an overall drive ratio of about 12.00:1 in the first gear. That can be achieved using a 3.00:1 axle ratio to go with 4.00:1 first gear ratio, or using a 4.00:1 axle ratio to go with 3.00:1 first gear ratio. The second gear is generally 40-45% taller than the first. And, generally, the overall span for a 4 or 5 speed transmission is 4.5-5.0 (overall span = first gear ratio divided by fifth gear ratio). So, a typical 5-speed auto (or manual) may have the following gear ratios to go with 4.00:1 axle ratio - Gear 1- 3.00:1 (overall drive ratio- 12.00:1) Gear 2- 1.80:1 (overall drive ratio- 7.20:1) : Gear 5- 0.65:1 (overall drive ratio- 2.60:1) In a typical 6-speed auto transmission, emphasis has been on increasing that span to about 6.0 or better. This tends to allow shorter low gears and a more relaxed top gear. In fact, many 6ATs have overall ratio in first gear of over 16.00:1 (that is how BMW's generally provide feel of being more powerful from lower rated power). |
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I think this gives the best indication of how powerful a motor is, with the most consistent results. Plus, no one drives 60 MPH anymore, 70 is a better highway freeway speed.
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Replying to: andres3 (Jan 26, 2007 12:00 pm) 
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Automotive News & Views 0-60 is so yesterday!
