tegel

I am not talking about the engines' torque but the torque that you are putting through the wheels, onto the tarmac.

This is at it's maximum when the car reaches it's peak horsepower, normally close to max rev. When you shift close to max rev, the engine will continue acceleration from a good RPM level (close to max engine torque) and this behaviour will continue until you reach VMAX.

If you shift too early, engine RPM will drop too low after upshift and your acceleration will be slower.

/M

nbusbridge

Sorry if this sounds dumb , but I'm new to the world of auto gearboxes. Here in the UK the majority of cars are manual. Certainly all mine have been.

What is "Brake Torquing" - I have an idea, but can someone explain ?
Cheers

colejl

Foot on brake. Other foot on throttle. REV. Release brake.

Kind of equivalent of 'dropping the clutch'.

nbusbridge

Thanks colejl !
Thought it might be that.

Cheers

swajames

I see where you're coming from, but torque is torque, at flywheel or rear wheel, and it typically peaks someway prior to redline. HP is direct product of RPM and torque so max HP will typically also peak before redline too. I agree with your last sentence, but our definition of what would be too early might be a little bit different. In short, shifting at max rpm isn't going to gain you much, but as I said before it's probably not going to make a massive differerence either way and it's tough to know exactly where the optimum shift point might be.

suraj

I am also interested in finding out what is the best time people have got for 0-60 on a 530i. There have been threads regarding 545 and 550 but none for 530. If someone could share their numbers, that would be great.

BMW claims 6.6s with Step but aren't they known to be conservative? So, has anyone got in 6.3 range?

k3nny

Essentially, if you observed your dyno graphs and decided that if you shifted after the torque curve has gone downwards but in the following gear you are able to continue at a rev point where the engine is still producing its max torque, then its fine.

But if you shifted exactly where the torque curve flats out and before it starts heading downhill but in the following gear, the engine is below where it produces its maximum torque, then i still think you'd be better off shifting at the redline.

A couple of friends and i tried this a the motorplex once.

Back to back runs with all variables being the same between runs as far as we can control like temperature, altitude etc.

One was to shift at where the torque curve flattens out and the other was to shift 100rpms before the redline.

Shifting at the redline produced relatively better times.

This was on my previous R33 Nissan Skyline so then again, the characteristics of a force inducted engine, esp one with a bigger turbo and lag is different to N/A BMW's but i still believe that shifting at the peak of the torque curve and having the rev's go too low and the engine not producing its max torque will produce slower times than shifting at the redline and consistently catching the engine in its "sweet spot".. hehe.. when its producing max torque.

My 2 cents i suppose.. hehe

znod

I explore optimal-shifting theory in post #34 of this thread. While what I say is true about the theory, I am not sure that I drew the right conclusion about optimal shifting in a Step 545i. So, I make several more posts about shifting a Step 545i later in the thread at posts #45 and #49--and even later in another thread linked in #49.

jmdhuse

This analysis should show some margin when applied to the 255hp 530i engine, since its torque curve is pretty flat between about 2500rpm and 6000rpm - no real peaks to worry about. It looks like shifting between 5500 and 6000 rpm would be about right.

znod

I suspect that shifting below, say, 6250 to 6450 is likely to be suboptimal. But, I can't really say much without doing the numbers.