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Automotive News & Views Can GM make Cadillac the standard of the world Again?
6098 messages, Last post on Aug 14, 2009 at 4:43 PM
You are in the Automotive News & Views Forum. Your Hosts are steve_ & claires
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Replying to: bumpy (Jul 31, 2007 6:19 am) This one??? http://www.automobilemag.com/features/news/0705_c+2008_infiniti_g37+dyno_chart.j- pg
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Replying to: rayainsw (Jul 31, 2007 6:29 am)
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Replying to: bumpy (Jul 31, 2007 6:55 am) Remember, despite it having all the power in the world, unless you can get a 6 speed manual gearbox with tight gearing in that "sports sedan" and then keep it in second gear around town(to get it into the 2500-4000rpm range - expect 16-18mpg!), you're stuck with loafing around town. (of course *I* ignore gas mileage and do this - get about 250 miles per tank. 90% of people don't) Mash the pedal - 3-4 seconds - 35-40 mph... torque converter locks up and you... "loaf". It shifts up a gear... you loaf. You want to unlock that torque converter and pass someone? Well, it's "loafing" at a whopping 900-1200rpm and you suffer a 2-3 second lag before it gets into its power band. The GM? Nope - none of that WOT-lag beahvior with this. The BMW is an exception obviously because they use I-6 engines, which develop better torque and power for their displacement.(technically, the I-6 is the closest thing to a perfect engine that's possible from a power, weight, and efficiency standpoint - which is why BMW refuses to change) P.S. Though, you'll note that only TWO of the GM 3.6 applications are geared for low-end torque. The rest are no different from the standard stuff out there. Go drive a CTS with the 3.6. Now, go across the street to the Buick dealer and drive the LaCrosse CXS. Same engine, same suspension, but which one drives better? Surprizing, isn't it? The CTS feels average. The CXS feels like a small block V8 from the 60s. Blip the throttle even a tiny but over idle and presto - maximum torque. The new DI CTS seems to be simmilar - just without sacrificing HP to do it.
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Replying to: plekto (Jul 31, 2007 9:02 am) Who would want to drive at 1200-1600 rpm? As for the rest of it, it sounds like a torque converter is a death sentence for a good engine and a good reason to avoid the slushbox. Now, where's that manual Lacrosse? |
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Replying to: bumpy (Jul 31, 2007 9:34 am) |
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Replying to: bumpy (Jul 31, 2007 9:34 am) Me, for 1. My Corvette, in sixth gear shows 1600 RPM at approx. 73 MPH. A cruising speed I often find comfortable. Returning 30+ MPG. 80 MPH is approx. 1750 RPM. But who’s counting . . . - Ray Happy at low RPM, cruising & happy at high RPM accelerating ( um ) briskly . . .
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Replying to: rayainsw (Jul 31, 2007 10:04 am) But who would want to run a DOHC V6 that slowly? That's like asking a thoroughbred to do a mule's job.
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Replying to: bumpy (Jul 31, 2007 10:20 am) |
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Replying to: bumpy (Jul 31, 2007 10:20 am) |
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Consider the following: take a pushrod engine - lets say this one: http://media.gm.com/us/powertrain/en/product_services/2008/HPT%20Library/HVV6/20- - - 08_39L_LZG_Impala.pdf Would re-engineering the valve train to have a DOHC instead of the single cam in block change anything? What I mean is to keep the two valve per cylinder design, with the same intake manifold and the same valve timing. I think below 6000 RPM's there would be no change in performance, torque or horsepower. Above 6000 RPM's the DOHC might possibly have bit more power, but with the peak horsepower at 5600 RPMs, it is more a question of falling off more slowly, not resulting in more horsepower. The point of course is that with a DOHC design, one would have 4 valve per cylinder and separate VVT on the intake and exhaust valves. Then one gets something like this: http://media.gm.com/us/powertrain/en/product_services/2008/HPT%20Library/HFV6/20- - 08_36L_LY7_CTS.pdf The big difference between these two engines is the extra valves with the intake and exhaust timing variation independant of each other. The pushrods are irrelavant, except that they probably make putting more than two valves per cylinder difficult or of little real value. |
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