What RPM should I be shifting at?

[bmwstve]

Hi,

will it really make your car accelerate faster if you shift at redline?

When I floor the accelerator on S mode on higher gears it always seems that it takes an "uncomfortably long time" to reach the redline (7K rpm) before it shifts to the next gear. Its like the engine is working "extra hard" by revving very high before shifting. and I'm not sure if this is healthy for the engine

So what I usually do is I usually manually shift up at around 6k rpm cause honestly I'm not sure if the car is indeed faster when it shifts at 7k rpm, it just makes alot of noise.

I also found out that if you floor the accelerator, there will be a click on the end and the gear shifts down on its self automatically. Is this normal?

Car is N55 X6

Thanks

[auf Deutsch]

A stock N55 runs out of steam at 6k, so yeah, shifting at that point is most beneficial at enabling the fastest acceleration runs. It won't cause damage revving to redline though.

[overcoil]

Reads like the click you hear on the accelerator at full depression is the 'kick down feature'
and it is supposed to take it down a gear for max acceleration.

About the 7000 or so rpm redline.
I'm just guessing here but an engine will produce maximum horsepower at say 6500 rpm, and maximum torque at let us say 4600 rpm. All those measuring points are useful in racing. For instance out on the track when going after speed you'd never let the tach fall below 4600 rpm. your shift point would be halfway between 4600 @ 6500 rpm. In cornering you would or could use all the way up to 6500 so your not shifting during a high speed turn.
Once you get over 6500 rpm you lose your quickness for accelerating, however if you were on a long straight where your overcoming drag and downforce and you have no more numerically lower gearing to reach a higher speed you can use that 7000 rpm max to strive for maximum speed. That 7000 also allows you to gain in cornering without having to shift in a turn.

The reasaon you may design an engine to have the spread in max rpm, torque and horsepower is complicated, but things like mpg, longevity and spinning a gearbox are all factors.

[///M2-PILOT]

Depends on your cars power curve. Lots of variables!

[GuidoK]

You need to have both the torque curve and the gear ratios of the current and upshift gears to determine the optimal shifting point.
If you have an excel sheet with torque-rpm data you can automate that.

[BMW-330i]

I just let the auto transmission deal with the changes, I have used the redline several times without issue. The 330i rarely get pushed about 5,000 rpm on daily use, however, I'm comfortable to redline on the right road and time. I would try to avoid doing this on a cold engine for obvious reasons.

[ShocknAwe]

Yup, I always shift at redline, even in heavy traffic. Go big or go home. Nothing like sitting parked in bumper to bumper revved to over 7k rpm. The looks I get from the other drivers too, pure jealousy.

[Efthreeoh]

No.

[PureE92]

Nothing like slamming that redline like it owes you some money.

[John_01]

No. For best performance you shouldn't take it to the redline. The power of the N55 is already starting to fall at around 5,500rpm. In second gear you can run it up to 5,800rpm.
If you upgrade the stock intercooler, the N55 can produce a bit more power higher up.

[bmwstve]

Originally Posted by John_01

No. For best performance you shouldn't take it to the redline. The power of the N55 is already starting to fall at around 5,500rpm. In second gear you can run it up to 5,800rpm.
If you upgrade the stock intercooler, the N55 can produce a bit more power higher up.

That's what i've felt actually. For me, flooring it to 7000 didn't make the car "FEEL" faster, the engine just makes alot of noise and the sound is quite harsh.

The engine rating is:
302 hp @ 5800-6000
295 lb·ft @ 1200-5000

So its best to shift at 5800 but the max torque is only still 5000?

[The Wind Breezes]

Yes, every gear, every shift.

Seriously though, it's actually very simple. Since torque at the WHEELS (engine torque multiplied by all gearing) is what actually accelerates you, you want to shift at redline every time for optimum acceleration as long as the torque you get at the wheels by holding on the gear you're in is greater than or equal to the torque at the wheels in the next gear. Since the next gear will have less mechanical advantage over the tire, but presumably more torque from the engine since you will be lower in the revs and more in the meat of the turbo, this is a relationship you can easily figure out with a dyno graph and a table of gear ratios.

For a stock car the dropoff in torque is smooth enough that you will always be faster shifting at redline.

[M.Power]

No.. 2.5-3K RPM normally. But yes, when I feel like having some fun I do.

[swagon]

I cruise at redline.

[David70]

Originally Posted by The Wind Breezes

Yes, every gear, every shift.

Seriously though, it's actually very simple. Since torque at the WHEELS (engine torque multiplied by all gearing) is what actually accelerates you, you want to shift at redline every time for optimum acceleration as long as the torque you get at the wheels by holding on the gear you're in is greater than or equal to the torque at the wheels in the next gear. Since the next gear will have less mechanical advantage over the tire, but presumably more torque from the engine since you will be lower in the revs and more in the meat of the turbo, this is a relationship you can easily figure out with a dyno graph and a table of gear ratios.

For a stock car the dropoff in torque is smooth enough that you will always be faster shifting at redline.

I agree with this.

Also would say that the percentage of time I am trying for maximum acceleration and shifting at redline is pretty low. The title of this thread had me wondering what was going on and hoping that no one always shifts at redline.

[Delta0311]

Shifting at redline or as I like to call it, the quickest way to warm up your car..

[wdb]

Redline = maximum RPMs an engine can routinely withstand, according to the manufacturer

What does that have to do with how fast you're going?

[Delta0311]

I don't always shift at redline but when I do I drink Dos Equis and rack up DWIs. Stay thirsty my friend..

[Wolf 335]

Some poor soul is going to end up buying your car after you're done molesting it.

Then they will come here and complain how Bmw is junk and that they had to replace the transmission and so on...

Don't redline your engine you fool.

[Delta0311]

Originally Posted by Wolf 335

Some poor soul is going to end up buying your car after you're done molesting it.

Then they will come here and complain how Bmw is junk and that they had to replace the transmission and so on...

Don't redline your engine you fool.

I can understand having some fun here and there but always shifting at redline is retarded.. Hope OP is either leasing, has a good extended warranty, or is BFF with a really good mechanic. No your car won't exploded if you redline but but constantly pushing it to the edge will greatly increase wear and tear, especially on the motor and tranny. And I hope to God OP is at least doing it when the car is properly warmed up (210F).

[bmwstve]

I should've re-phrased the title. Sorry wrong choice of words.

TITLE should be: Do you always shift at red line, WHEN TRYING TO ACHIEVE FULL SPEED/MAX ACCELERATION .

When you try to go fast on the highway/overtaking. "will shifting at redline really make the car accelerate any faster" as compared to shifting at 5500-6000 RPM.

Obviously, I didn't mean to literally shift at redline all the time. That would be stupid and will definitely shorten the life of the car

Only shifting at redline when trying to achieve QUICKER acceleration, is it really faster when you shift at redline?

Cause sometimes I have some friends who drag our cars for fun. Just want to know which is faster, S Mode (car automatically shifts at redline) or shift the gears myself M mode (I usually shift around 5500-6000 rpm)

Some say leave it at S mode and let the car shift itself at 7k rpm, while others say the HP / Torque drops after 5800k so which means car will go faster if you shift earlier and not on redline.

I personally feel that shifting manually at 5500-6000 makes the car "FEEL" faster and engine sounds less harsh.

What do you guys think?

[42pilot]

Originally Posted by bmwstve

That's what i've felt actually. For me, flooring it to 7000 didn't make the car "FEEL" faster, the engine just makes alot of noise and the sound is quite harsh.

The engine rating is:
302 hp @ 5800-6000
295 lb·ft @ 1200-5000

So its best to shift at 5800 but the max torque is only still 5000?

If the engine is rated for full power at 6,000 (which means power drops from there - look at the HP dyno curve), why shift at any higher?

So, referring to the above engine ratings, don't let the RPM get below 1200 (beginning of peak torque) and shift at or just before 6000 rpm (end of peak HP). Any more RPM is a waste of time and RPM. The reason HP falls off is most likely because of fueling, head porting, exhaust porting, turbo air flow, intake airflow, etc.

When I tuned engines, I would set the rev limiter at 400 rpm past peak HP - this allowed for over-revving during shifting before cutting the engine spark. Even though the engine was rated to 7,500 rpm, if peak HP was 6500, I would cut the spark at 6900 and kill the engine completely at 7200 to save valves, rods, valve springs, etc. No need to go any higher.

As for these cars, I would bet the auto transmission shifts at the right place in sport mode, keeping you in the sweet spot and keeping you from damaging the engine. Even though the engine is rated for more RPM than peak HP, you will wear it out faster at high rpm - rings, bearings, valve springs, etc. But it's your car - drive it like you want.