SAE vs DIN vs JIS vs CUNA article from Road&Track
08-29-2001, 06:15 PM
#1
Track Day
Thread Starter
Join Date: Jul 2001
Posts: 20
Likes: 0
Received 0 Likes
on
0 Posts
SAE vs DIN vs JIS vs CUNA article from Road&Track
SAE vs DIN vs JIS vs CUNA
From time to time, it’s entertaining to return to fundamentals (and try to get them right). Consider those most basic—though hardly simple—concepts of horsepower and torque. Those with long memories (or this column, April 1996 or August 1990) may recall the following:
Torque is a twisting force, the twist of a crankshaft being a perfect example. In our English units, it’s measured in lb.-ft. Think about an arm 1 ft. long holding a 1-lb. weight at its end; the twisting force at its other end is 1 lb.-ft.
Horsepower, as its name suggests, is power, a measure of work performed over time. In our English units, it’s related directly to torque by the formula:
Brake horsepower = torque x rpm / 5252.
Why “brake” horsepower? Because the gizmo doing the measuring is called a brake dynamometer; this, because it uses a brake of one sort or another to resist the engine’s torque.
This torque is recorded at various rpm while the engine is operated under carefully controlled conditions. The formula then converts each torque reading to bhp at that rpm. Last, what’s typically reported are the peak readings; the current Mazda Miata’s 138 bhp SAE net at 6500 rpm, for example, and 117 lb.-ft. at 5000. And, to emphasize the point, that bhp rating actually came from a dyno torque measurement of around 111.5 lb.-ft. at 6500. Apparently beyond 6500, the engine’s production of torque fell off even more quickly.
This term “SAE net” opens two entirely different cans of worms, but both worth examining.
First, the SAE part. SAE and other engineering groups around the world establish procedures and conditions under which testing is performed. Other standards have been promulgated by DIN (Deutsche Institut für Normung), JIS (Japanese Industrial Standards) and, though rarely seen these days, CUNA (Comitato Unitario Autotransportatori). A rating may appear as 225 bhp DIN or 186 bhp JIS, thus raising the obvious question, how do you convert from one to the other?
In few words, you don’t, precisely. Different engines respond to the differing test conditions in different ways and, in general, there’s no exact conversion factor, say, between bhp SAE and bhp DIN.
There are rough guidelines, however. In general,
95 DIN = 100 SAE net = 105 JIS.
That is, for a given engine, DIN test conditions yield a bit less torque, and JIS yield a bit more than do SAE net.
The second can of worms concerns the word “net.” SAE defines two different standards, J1349 for net power and J1995 for gross power. Net measurement, for instance, requires a full exhaust system, catalytic converter included; for gross, this is “optional,”i.e., not used.
Again, there’s no exact conversion factor. But, generally speaking, our 100 bhp SAE net would equate to around 140 bhp SAE gross.
There’s interesting auto history here as well: Back in the glorious days of the Horsepower Race, the 1950s and ’60s, power was invariably reported in gross terms—though rarely identified as such. Around 1971, the government encouraged automakers to play down their horsepower ratings, and a transition to SAE net was part of this.
Last, all of these engineering terms are in contrast to yet another, the fanciful press-release rating that has been called “bhp ATB,” as in “at the brochure.”
Data Panel labels
Whenever it seems appropriate, the technical gurus of R&T (Kim, Patrick and me) have lapses of literalism and decide that our Road Test Data Panel needs fixing. There are two changes present in this issue (and others that may appear, once we settle on the wisest course).
First, one of our old panel entries is labeled “Maximum engine speed.” However, this invariably reported the tachometer’s indication of redline (as opposed to any rev-limiter behavior, for example). Hereinafter, we will continue to report the tachometer’s recommendation and identify it as such: “Redline.”
The second item is our reporting of actual fuel consumption obtained while a car is in our possession, hitherto labeled “Normal driving.” Not to raise any cheap shots of “abnormal,” but we’re changing this entry to a more prosaic “Our driving.”
GDI in F1?
Renault engineers have been rumored to be working on a Formula 1 powerplant featuring gasoline direct injection, as has Ilmor for the Mercedes engine powering the McLaren. Already seen in production cars (and in “Technology Update: The Last Internal Combustion Engine?,” December 1997), the idea of GDI is to gain better control of the combustion process by injecting fuel directly into the chamber, not just nearby into an intake port.
In fact, back in the 1950s the Mercedes-Benz 300SL had direct fuel injection (see “Coppertech X,” elsewhere in this issue), but this was based largely on aviation technology rather than automotive. Today’s GDI developments exploit electronic engine management in the interest of enhanced fuel economy and reduced emissions.
Economy and emissions in F1?? Yes, because the more efficient an F1 powerplant, the farther and faster it can propel its car between fuel stops (and fuel stops cost considerable time).
One advantage of GDI is its precise determination of when and particularly where injection occurs. This is especially important in F1 engines, whose extreme bore/stroke ratios lead to bizarrely shaped combustion volumes essentially lurking in valve recesses. GDI’s biggest challenge is whether it proves compatible with the 19,000-plus rpm of a modern F1 engine.
Early speed demons
Wilkerson Wright, grandnephew of Orville and Wilbur, once revealed a family secret: “There’s no way to gloss over it,” he said somberly, “Orville was a terrible driver. He drove too fast, and the only thing that you could say in way of justification is that he learned to fly an airplane seven or eight years before he learned to drive a car.”
Amazing, isn’t it?
Automotive technology, of course, was already well along when the Wright Brothers made history December 17, 1903, in a stiff wind at Kitty Hawk, North Carolina. In fact, for a long time thereafter, mankind’s fastest means of getting around wasn’t in the air but on land.
The Stanley Rocket steam car did 121.6 mph in 1906. It wasn’t until 1913 that a Deperdussin aeroplane beat this with 126.7 mph at Reims. And two years before, the Blitzen-Benz car had already posted 131.3 mph.
After World War I the two curves crossed, never to converge again. In 1920, a Nieuport 29V took the aeroplane record at 171.3; the quickest car of the era, a 350-bhp Sunbeam, went “only” 150.8 mph.
Van Valkenburgh’s book is available again
In Chevrolet—Racing: Fourteen Years of Raucous Silence, 1957–1970, Contributing Editor Paul Van Valkenburgh wrote one of the most fascinating books in motorsports. Fascinating and, until recently, out-of-print and difficult to find.
Now, I’m happy to report, my old employer, SAE International, has reissued this important book. It’s available for $45 (substantially less than rare secondhand copies were) from SAE, 400 Commonwealth Dr., Warrendale, Pa. 15096-0001; (724) 776-4970; or online at www.sae.org/bookstore. Tell them Dennis sent you.
From time to time, it’s entertaining to return to fundamentals (and try to get them right). Consider those most basic—though hardly simple—concepts of horsepower and torque. Those with long memories (or this column, April 1996 or August 1990) may recall the following:
Torque is a twisting force, the twist of a crankshaft being a perfect example. In our English units, it’s measured in lb.-ft. Think about an arm 1 ft. long holding a 1-lb. weight at its end; the twisting force at its other end is 1 lb.-ft.
Horsepower, as its name suggests, is power, a measure of work performed over time. In our English units, it’s related directly to torque by the formula:
Brake horsepower = torque x rpm / 5252.
Why “brake” horsepower? Because the gizmo doing the measuring is called a brake dynamometer; this, because it uses a brake of one sort or another to resist the engine’s torque.
This torque is recorded at various rpm while the engine is operated under carefully controlled conditions. The formula then converts each torque reading to bhp at that rpm. Last, what’s typically reported are the peak readings; the current Mazda Miata’s 138 bhp SAE net at 6500 rpm, for example, and 117 lb.-ft. at 5000. And, to emphasize the point, that bhp rating actually came from a dyno torque measurement of around 111.5 lb.-ft. at 6500. Apparently beyond 6500, the engine’s production of torque fell off even more quickly.
This term “SAE net” opens two entirely different cans of worms, but both worth examining.
First, the SAE part. SAE and other engineering groups around the world establish procedures and conditions under which testing is performed. Other standards have been promulgated by DIN (Deutsche Institut für Normung), JIS (Japanese Industrial Standards) and, though rarely seen these days, CUNA (Comitato Unitario Autotransportatori). A rating may appear as 225 bhp DIN or 186 bhp JIS, thus raising the obvious question, how do you convert from one to the other?
In few words, you don’t, precisely. Different engines respond to the differing test conditions in different ways and, in general, there’s no exact conversion factor, say, between bhp SAE and bhp DIN.
There are rough guidelines, however. In general,
95 DIN = 100 SAE net = 105 JIS.
That is, for a given engine, DIN test conditions yield a bit less torque, and JIS yield a bit more than do SAE net.
The second can of worms concerns the word “net.” SAE defines two different standards, J1349 for net power and J1995 for gross power. Net measurement, for instance, requires a full exhaust system, catalytic converter included; for gross, this is “optional,”i.e., not used.
Again, there’s no exact conversion factor. But, generally speaking, our 100 bhp SAE net would equate to around 140 bhp SAE gross.
There’s interesting auto history here as well: Back in the glorious days of the Horsepower Race, the 1950s and ’60s, power was invariably reported in gross terms—though rarely identified as such. Around 1971, the government encouraged automakers to play down their horsepower ratings, and a transition to SAE net was part of this.
Last, all of these engineering terms are in contrast to yet another, the fanciful press-release rating that has been called “bhp ATB,” as in “at the brochure.”
Data Panel labels
Whenever it seems appropriate, the technical gurus of R&T (Kim, Patrick and me) have lapses of literalism and decide that our Road Test Data Panel needs fixing. There are two changes present in this issue (and others that may appear, once we settle on the wisest course).
First, one of our old panel entries is labeled “Maximum engine speed.” However, this invariably reported the tachometer’s indication of redline (as opposed to any rev-limiter behavior, for example). Hereinafter, we will continue to report the tachometer’s recommendation and identify it as such: “Redline.”
The second item is our reporting of actual fuel consumption obtained while a car is in our possession, hitherto labeled “Normal driving.” Not to raise any cheap shots of “abnormal,” but we’re changing this entry to a more prosaic “Our driving.”
GDI in F1?
Renault engineers have been rumored to be working on a Formula 1 powerplant featuring gasoline direct injection, as has Ilmor for the Mercedes engine powering the McLaren. Already seen in production cars (and in “Technology Update: The Last Internal Combustion Engine?,” December 1997), the idea of GDI is to gain better control of the combustion process by injecting fuel directly into the chamber, not just nearby into an intake port.
In fact, back in the 1950s the Mercedes-Benz 300SL had direct fuel injection (see “Coppertech X,” elsewhere in this issue), but this was based largely on aviation technology rather than automotive. Today’s GDI developments exploit electronic engine management in the interest of enhanced fuel economy and reduced emissions.
Economy and emissions in F1?? Yes, because the more efficient an F1 powerplant, the farther and faster it can propel its car between fuel stops (and fuel stops cost considerable time).
One advantage of GDI is its precise determination of when and particularly where injection occurs. This is especially important in F1 engines, whose extreme bore/stroke ratios lead to bizarrely shaped combustion volumes essentially lurking in valve recesses. GDI’s biggest challenge is whether it proves compatible with the 19,000-plus rpm of a modern F1 engine.
Early speed demons
Wilkerson Wright, grandnephew of Orville and Wilbur, once revealed a family secret: “There’s no way to gloss over it,” he said somberly, “Orville was a terrible driver. He drove too fast, and the only thing that you could say in way of justification is that he learned to fly an airplane seven or eight years before he learned to drive a car.”
Amazing, isn’t it?
Automotive technology, of course, was already well along when the Wright Brothers made history December 17, 1903, in a stiff wind at Kitty Hawk, North Carolina. In fact, for a long time thereafter, mankind’s fastest means of getting around wasn’t in the air but on land.
The Stanley Rocket steam car did 121.6 mph in 1906. It wasn’t until 1913 that a Deperdussin aeroplane beat this with 126.7 mph at Reims. And two years before, the Blitzen-Benz car had already posted 131.3 mph.
After World War I the two curves crossed, never to converge again. In 1920, a Nieuport 29V took the aeroplane record at 171.3; the quickest car of the era, a 350-bhp Sunbeam, went “only” 150.8 mph.
Van Valkenburgh’s book is available again
In Chevrolet—Racing: Fourteen Years of Raucous Silence, 1957–1970, Contributing Editor Paul Van Valkenburgh wrote one of the most fascinating books in motorsports. Fascinating and, until recently, out-of-print and difficult to find.
Now, I’m happy to report, my old employer, SAE International, has reissued this important book. It’s available for $45 (substantially less than rare secondhand copies were) from SAE, 400 Commonwealth Dr., Warrendale, Pa. 15096-0001; (724) 776-4970; or online at www.sae.org/bookstore. Tell them Dennis sent you.
