Quote:
Originally Posted by vcx
I have a 6MT 340i xdrive, and to be honest, I really doubt the official engine diagram, where peak torque is supposed to arrive at around 1350 rpm already, because I really don't feel so much torque in the low end of rpm, even with a tune. Even my old E90 330i (272 hp) felt more responsive at very low rpm.
Edit: I also don't see the advertised torque value on the torque gauge.
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There's a reason the 'advertised' value is never achieved in the real world:
First, understand how the OEM tests and tunes the engine, (which is also how they achieve that number): They mount the engine to a brake dyno (connected directly to the flywheel, no transmission/driveshafts/wheels/tires/etc), and open the throttle, but tell the dyno to resist changing speed. So the engine loads up, and even if the turbo is BARELY spinning, it will slowly accelerate until it is actually compressing some air, which means more exhaust, which spins the turbo a little more... basically, they can let the engine sit at 1350 RPM very slowly spooling the turbo until the turbo is fully spooled, and then record that number. Then tell the dyno to let it accelerate to 1400, do the same thing, and record the highest number it reaches. They programmatically do this for the entire rev range, and that's how they produce the graph they market.
This is very different from doing a 'dyno pull' at a standard chassis dyno. A typical 'dyno pull' is designed to more closely replicate real-world use: Accelerating as quickly as possible. So, in the real world, at 1350 RPM, the engine doesn't produce enough exhaust to instantly spool the turbo, but it does produce enough power to accelerate pretty well, which lets the RPM go up and more exhaust be produced, spooling the turbo, etc...
So, no, it isn't making peak torque at 1350 RPM when you're accelerating from a stop (or from low-throttle cruise). Personally, in mine, I don't like running it that low unless I am just maintaining cruise speed. It needs to stay above about 1650 for it to feel like it has any real torque.
So, the engine truly can produce that... but not while being used in a real car on a real road, basically. If you somehow had the right incline to go full throttle at 1350 rpm and not speed up any at first... you would find the engine still slowly accelerates as it builds its small amount of boost every second at that rpm.
Side note, I DO wish 6th gear was taller... while I love the passing torque in 6th gear, 70mph is like 2500 rpm, it should be more like 1800, but that would mean you'd have to downshift to pass quickly.... but it would probably be worth it for the mileage gains.