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Sedans Volkswagen Jetta VW Jetta TDI
3757 messages, Last post on Dec 07, 2009 at 4:45 PM
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Howdy folks, I've recently become interested in the new tdi engines that vw is putting in some of it's new models. I was on car and driver earlier, and I noticed that the 'passing acceleration' for the tdi was astonishingly quick. http://www.caranddriver.com/content/download/126293/1711316/version/1/file/2009+- Volkswagen+Jetta+TDI.pdf "50-70 6 seconds" Now, I understand diesels enjoy an advantage at highway speeds due to the amount of torque they produce at lower rpms. However, this number is faster than a honda fit, gti, a mini cooper s, miata, etc virtually every thing else on my shopping list (in terms of passing power). While I believe it would be reasonibly fast, certainly faster than the honda fit (which did the same test in ~12 seconds), I find it very hard to believe that it is faster than the others. I believe they must have gotten the math wrong. For example, if you look at the test sheet, and you compare the 50mph time with the 70mph time you get 5.1s, not the 6 seconds they claim. Does anyone have any other sources that provide a 40-70 ish number? |
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Replying to: mortal (May 15, 2009 9:34 pm) |
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Replying to: mortal (May 15, 2009 9:34 pm)  altitudes of 3,000 to 7,000 ft. !!!
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Engine power (hp pr kw) to weight ratio is what determines max acceleration whether on level ground or up a hill. The transmission can change torque, but not power. A Jetta TDI can pass a naturally aspirated V8 if the Jetta driver puts the pedal to the floor and the V8 driver doesn't care to contest the matter. Or if the V8 is powered car is relatively heavy. |
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Replying to: mortal (May 15, 2009 9:34 pm) Are you really basing your vehicle-choice on this type of stastistic? Example, I *really* like the fact that VW automaticlly locks all the doors once you are moving. But my Subaru Baja does not do this and I end up driving around with the doors unlocked. Do I like the Subaru less than the VW.... no! I like the 56MPG of my TDI and the accellaration of the turbocharged subaru engine. The VW handles FAR better than Subaru : VW rides better than VW. VW radio and power-windows work with key turned off : Subaru does not do this. VW can lower/raise all windows FROM OUTSIDE CAR : Subaru does not do this Subaru has AWD and excells in the snow : VW is adequate in the snow with ESP, ADR and EDL. VW is more refined with featuers not found in other vehicles. This is one reason we have 3 VWs in the family. If Subaru offered the Baja as a Diesel, I would own one in a hearbeat... but they dont. Every vehicle has its up/down side and it is often difficult to make a choice when they are all considerd. Test drive what you want and chose what you personally like. Good Luck. |
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Replying to: mortal (May 15, 2009 9:34 pm) The passing interval measure includes transition time between steady speed and acceleration. |
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Replying to: mortal (May 15, 2009 9:34 pm) Two thoughts. The TDI was tested with the automatic DSG transmission. I think when passing tests are done they are in auto mode with the transmission downshifting. When testing a car with a manual transmission they use top gear with no downshifting and the time is much, much slower than if they had tested an automatic. Also, the time from from one MPH to another MPH in the acceleration tests from a stop will be less. For example the differential from 50 to 70 MPH from the 0-50 and 0-70 tests will be less than for the 50-70 MPH passing test, even for a automatic, as you start from a steady 50MPH, rather than being already accelerating. I think on the passing times you should compare the TDI only with other tested cars that had automatic.
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Replying to: fgbrault (May 17, 2009 10:34 am) Passing times have always been a measure of the quickest pass possible, else it would make no sense to do the measurement. If it's a stick or tiptronic you would gear down in anticipation of passing and punch it. Without a shiftable auto you would just punch it. The clock is started when the engine is throttled up. It takes time for the turbo and fuel system to ramp up, even a gasser w/o turbo. Extreme engines are built to have very little transition time - TDIs not so much. 
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Replying to: siberia (May 17, 2009 5:29 pm)
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Replying to: gfr1 (May 17, 2009 7:48 pm) http://www.caranddriver.com:80/reviews/hot_lists/high_performance/performance_fi- les_tested_by_c_d/how_does_c_d_test_cars_feature+t-acceleration_and_braking+page- -2.html We also perform two acceleration tests, from 30 to 50 mph and from 50 to 70, in a vehicle's highest gear. In vehicles with manual transmissions, this test measures how well a car's gearing matches the torque curve of its engine. With automatics, the test begins in top gear and then the car downshifts automatically under hard acceleration. This provides information about transmission responsiveness and actual passing times, but any comparison of results between manuals and automatics is meaningless. Just one more in a life-long series of embarrassments. 
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