The "Faster" section just became available in "Explore the All-new 3" on www.bmwusa.com :clap:
New section available in preview of E90!
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Since this is BMWUSA, I assume these figures are for the 3.0 liter 325i?jgrgnt said:
I wonder if that has anything to do with the low-end torque. I also wonder if the 2.5 325i in Europe will have that much low-end torque even if they managed to get the same peak numbers.
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"Low end torque" is what pushes you back in your seat.
That's my very basic understanding of it.
That's my very basic understanding of it.
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Torque is a measure of force, a rotational force to be more exact. Basically, it tells you how "hard" the engin turns the crank. "Low end" just refers to the lower end of the rpm range. So, an engin with a lot of "low end torque" will be able to accelerate the car faster at the lower speeds, like, say, when you're getting off the line.
What you want is the torque plot to be nice and wide while achieving a high torque number. So, you have x amount of torque at lower speeds and you accelerate at a rate of y. If that plot is flat, like you see on that plot above, you still have x amount of torque and higher rpm and thus your car will still accelerate at a rate of y. That's why you hear people say "there is lots of torque everywhere".
Certain engines, like a Honda VTEC system has tow different sets of cams: one low rpm one with low torque and good fuel economy and another high rpm one for high power and bad fuel economy. So, there is a step in the torque plot. Thus, when a VTEC engin reves high and the high rpm cam kick in, you will feel that jolt and there is more acceleration. This is because there was a sudden increase in the amoung of torque. This new Valvetronic thingy from BMW does a similar thing to what the Honda does, but not by having a different set of cams. It can continuously vary the timing and the opening of the valves so that you always have lots of torque. That's why that plot is so wide and flat. Since the BMW's system will give you high torque when you need it at any rpm and good fuel economy at any rpm, the valvetronic is the superior system. Also, its is much newer and more expensive...
Hope that helped..
J
What you want is the torque plot to be nice and wide while achieving a high torque number. So, you have x amount of torque at lower speeds and you accelerate at a rate of y. If that plot is flat, like you see on that plot above, you still have x amount of torque and higher rpm and thus your car will still accelerate at a rate of y. That's why you hear people say "there is lots of torque everywhere".
Certain engines, like a Honda VTEC system has tow different sets of cams: one low rpm one with low torque and good fuel economy and another high rpm one for high power and bad fuel economy. So, there is a step in the torque plot. Thus, when a VTEC engin reves high and the high rpm cam kick in, you will feel that jolt and there is more acceleration. This is because there was a sudden increase in the amoung of torque. This new Valvetronic thingy from BMW does a similar thing to what the Honda does, but not by having a different set of cams. It can continuously vary the timing and the opening of the valves so that you always have lots of torque. That's why that plot is so wide and flat. Since the BMW's system will give you high torque when you need it at any rpm and good fuel economy at any rpm, the valvetronic is the superior system. Also, its is much newer and more expensive...
Hope that helped..
J
Not to nitpick, but BMW's answer to VTEC is VANOS, which can infinitely adjust the cam-shaft. BMW also takes it one step further with "double VANOS," which can adjust both the intake and exhaust timing.
Valvetronic eliminates the need for a throttle butterfly and lets the valves themselves do that job.
-MrB
Valvetronic eliminates the need for a throttle butterfly and lets the valves themselves do that job.
-MrB
I guess that explains why some Acura TL owners complain that all the power is above 3500 - 4000 rpm!!DuckofPrey said:Torque is a measure of force, a rotational force to be more exact. Basically, it tells you how "hard" the engin turns the crank. "Low end" just refers to the lower end of the rpm range. So, an engin with a lot of "low end torque" will be able to accelerate the car faster at the lower speeds, like, say, when you're getting off the line.
What you want is the torque plot to be nice and wide while achieving a high torque number. So, you have x amount of torque at lower speeds and you accelerate at a rate of y. If that plot is flat, like you see on that plot above, you still have x amount of torque and higher rpm and thus your car will still accelerate at a rate of y. That's why you hear people say "there is lots of torque everywhere".
Certain engines, like a Honda VTEC system has tow different sets of cams: one low rpm one with low torque and good fuel economy and another high rpm one for high power and bad fuel economy. So, there is a step in the torque plot. Thus, when a VTEC engin reves high and the high rpm cam kick in, you will feel that jolt and there is more acceleration. This is because there was a sudden increase in the amoung of torque. This new Valvetronic thingy from BMW does a similar thing to what the Honda does, but not by having a different set of cams. It can continuously vary the timing and the opening of the valves so that you always have lots of torque. That's why that plot is so wide and flat. Since the BMW's system will give you high torque when you need it at any rpm and good fuel economy at any rpm, the valvetronic is the superior system. Also, its is much newer and more expensive...
Hope that helped..
J
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57 Posts
Actually, Honda and Toyota both have variable valve timing as well as a serperate lift controller. On the Toyota systems, the cam sprockets (intake and exhaust) are electronically adjustable (like double VANOS). By altering intake and exhaust valves "overlap," they are able to get good torque at low rpms and high horspower and high rpms. They are also able to get excellent freeway fuel-economy by allowing both intake and exhaust valves to be open simultaniously. As the piston travels down for it's intake stroke (intake valves open) the exhaust valves are actually left open as well (for a predetermined time). This allows the engine to bring back in hot exhaust gases to mix with the next intake stroke. By doing this the engine can actually lean out it's fuel mixture extremely low, giving the engine excellent freeway mileage. The only catch is that they have to put an extra catalytic converter in the car because this technique does increase emissions.
The second part of the system is the lift controller. This system works on cam lobes themselves (instead of the cam-sprockets). Instead of a traditional one cam lobe-per-valve, there are two cam lobes per valve. One set of lobes is for low-lift, low revving operations. While the other set is for high-lift, high revving. Since an engine needs to breath better at high rpms, the valves actually open wider once the high-lift lobes are actuated (this is what all those VTEC owners talk about being kicked in the pants). These lobes are actuated by hydraulic pins that actually pin the high-lift actuators into place.
Now, I am not sure if BMW has an equivalent lift-controller like Toyota and Honda, but I know the VANOS is only for valve timing and not lift.
The second part of the system is the lift controller. This system works on cam lobes themselves (instead of the cam-sprockets). Instead of a traditional one cam lobe-per-valve, there are two cam lobes per valve. One set of lobes is for low-lift, low revving operations. While the other set is for high-lift, high revving. Since an engine needs to breath better at high rpms, the valves actually open wider once the high-lift lobes are actuated (this is what all those VTEC owners talk about being kicked in the pants). These lobes are actuated by hydraulic pins that actually pin the high-lift actuators into place.
Now, I am not sure if BMW has an equivalent lift-controller like Toyota and Honda, but I know the VANOS is only for valve timing and not lift.
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