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      03-27-2013, 02:20 PM   #1
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0-62mph time of 125d...how?

All of my previous BMWs had no problem beating the quoted 0-62mph time, but my 125d is struggling to get anywhere near BMWs claim of 6.5 seconds. Using the Dynolicious iPhone app I am getting around 7.5 seconds 0-60mph time. I'm sure with some more aggressive gear changes I could get close to 7 seconds but 6.5 seems an impossibility.

Has anyone else tried to verify BMWs 0-62mph claims with the 125d? Mine is a manual by the way.
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      03-27-2013, 04:32 PM   #2
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Have you tried shifting at 4500rpm? Since you owned petrol engines in the past, I assume you are shifting at redline. That would be my guess.
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      03-27-2013, 04:53 PM   #3
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Even with 116i petrol engine you have to shift before the redline. These modern engines made to save fuel works best at low RPM.
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      03-27-2013, 04:55 PM   #4
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Dynolicious, does this use GPS or is it connected through some OBD adapter? I don't really trust the GPS in my own phone (Samsung S3). It probably doesn't refresh often enough. I did one 0 to 100 km/h test with an app, and I got 6,55 seconds, while BMW claims 7,90s. Also, this was slightly uphill and in the rain with plenty of wheelspin. If I'm going to try to measure this again, I'll just mount a camera pointing at the speedo, check the video and stop the clock at 105 km/h.
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      03-27-2013, 05:15 PM   #5
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As long as you don't have wheelspin when passing 100 km/h, the OBD2-speed should be rather accurate. I used that with RaceChrono to measure the 0-100 time, and beat the factory figures by one tenth of a second.

The more power you have, the more difficult it is to get a good run with manual gear. It depends on what tyres you have. With winter tyres, you need more wheelspin.
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      03-27-2013, 05:46 PM   #6
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I have an OBD2 plug in thingamy coming next week so I should be able to time mine. Might wait for warmer weather and summers back on before writing it off but I have to say I'd be astounded if it was the stated 6.5s as it certainly doesn't feel quick off the mark. Acceleration at rolling speeds is its forte in my opinion.
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      03-27-2013, 05:52 PM   #7
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The way I see it I have several problems:

- The traction when shifting to 2nd gear is poor
- The first two gears have restricted torque (360nm and 420nm respectively I think)
- I am not being too aggressive with the clutch

I have been shifting at 5000rpm, should I be shifting before that even though the 125d has a twin turbo setup?

Dynolicious is a GPS based system.
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      03-27-2013, 06:08 PM   #8
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Even the M50d engine with 3 turbos has to change gear at around 4500rpm, if you want to make a really quick acceleration time.
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      03-27-2013, 06:23 PM   #9
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Don't ever believe that shifting before red line is helping in improving acceleration stats. When it would, BMW would be total crap in setting up a transmission line. Really, I don't believe they have sunk this deep yet, this is pure basic stuff that even LADA could do perfectly fine ages ago!? BMW is still taking driveline set-up sufficiently seriously these days.

On the other hand, you state that torque is limited in first gears... Where did you get this? I understand that none premiums do this to limit strain on the transmission or can't cope with it in their FWD set-up, but the 125d is neither of both. So I'd expect full access to torque as from 1st gear...

Have you disabled DTSC to allow some spin? At this level, figures are made with controlled burning rubber. You'd have to rev to ~2500rpm, when you floor throttle, the rpm settles on this automatically. Also have totally disengaged the DSTC (hold the button a bit longer until it indicates on the dash it's out).

Then you release clutch almost instantly while keeping the accelerator to the floor. Go up until just before limiter in both first gears. When the spin is feeling too excessive, go a bit softer on the accelerator to gain more grip earlier in the process while trying to sustain the controlled spin as long as possible.

On the other hand, acceleration from stand still is too much dominated by the stand still grip and inertion and doesn't reflect vehicle dynamics sufficiently. It would for low torqued cars, but the 125d is on the other side...
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      03-27-2013, 06:33 PM   #10
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Quote:
Originally Posted by KoenG View Post
Don't ever believe that shifting before red line is helping in improving acceleration stats. When it would, BMW would be total crap in setting up a transmission line.
If shifting at the red line is the optimal, then why does the automatic transmission - even at its most aggressive setting - shift well before it? I have a hard time believing that the transmission is programmed in a manner that it requires you to shift manually to get the best possible straight line acceleration.
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      03-27-2013, 06:35 PM   #11
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Quote:
Originally Posted by KoenG View Post
On the other hand, you state that torque is limited in first gears... Where did you get this? I understand that none premiums do this to limit strain on the transmission or can't cope with it in their FWD set-up, but the 125d is neither of both. So I'd expect full access to torque as from 1st gear...
Yes I was disappointed when I read a forum thread stating that the torque was limited in the lower gears. However, I have the following reasons to believe that this is true:

- The torque feels weaker in the first 2 gears
- The Sport display on my iDrive reports a maximum torque of 360nm in 1st and 420nm in 2nd gear when I floor the accelerator. In all other gears it goes to the full 450nm.
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      03-27-2013, 06:42 PM   #12
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Quote:
Originally Posted by Wositsch View Post
Even the M50d engine with 3 turbos has to change gear at around 4500rpm, if you want to make a really quick acceleration time.
Not true, on slippery surfaces where the extra OOOMMMPH is wasted in black or white smoke, maybe... but not on surfaces that really grip. And grip is what you need to get close to the specs as an absolute prerequisite for these kind of performance cars.

There is really no rocket science required to determine how your transmission line has to be spaced to get the max out of it in acceleration, this is basic setup theory of the early times of the Ford T actually.

Take note, this is only gear 1, 2 and maybe 3 and therefore it is not in contradiction with an efficient, fuel saving drive line set up either. Certainly not when you have 8 gears at hand like an M550d.
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      03-27-2013, 06:57 PM   #13
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Quote:
Originally Posted by Bradbury View Post
If shifting at the red line is the optimal, then why does the automatic transmission - even at its most aggressive setting - shift well before it? I have a hard time believing that the transmission is programmed in a manner that it requires you to shift manually to get the best possible straight line acceleration.
Whow!!? This indicates that BMW is not taking the effort to optimise their transmissions to every individual car set-up to exploit the max out of it and prefers to just change shift up points while using a standard gearing range.

Manual override shift points is not improving acceleration, I follow your point certainly! When it would, this would be completely idiotic I guess?

On the other hand, in an AT set-up BMW accesses the max shift up as a mere and simple parameter in their logic while the driver is leaving it all up to the machine he's riding. In a MT they SHOULD consider that when you want it all, you definitely go for the redline.
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      03-27-2013, 07:05 PM   #14
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Quote:
Originally Posted by KoenG View Post
Not true, on slippery surfaces where the extra OOOMMMPH is wasted in black or white smoke, maybe... but not on surfaces that really grip. And grip is what you need to get close to the specs as an absolute prerequisite for these kind of performance cars.

There is really no rocket science required to determine how your transmission line has to be spaced to get the max out of it in acceleration, this is basic setup theory of the early times of the Ford T actually.

Take note, this is only gear 1, 2 and maybe 3 and therefore it is not in contradiction with an efficient, fuel saving drive line set up either. Certainly not when you have 8 gears at hand like an M550d.
The 125d has maximum power at 4400rpm, then power starts to drop as the revs get higher, thats just the way diesel works. It's the same story with the M50d engine, It has maximum power from 4000 - 4400rpm.
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      03-27-2013, 07:06 PM   #15
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Quote:
Originally Posted by jhbodle View Post
Yes I was disappointed when I read a forum thread stating that the torque was limited in the lower gears. However, I have the following reasons to believe that this is true:

- The torque feels weaker in the first 2 gears
- The Sport display on my iDrive reports a maximum torque of 360nm in 1st and 420nm in 2nd gear when I floor the accelerator. In all other gears it goes to the full 450nm.
WHAT!? So they are using the same cheap trics like any other FWD car manufacturer is using these days?

In this case the acceleration can not be significantly better than the one of a 120d since it will match torque in first gear (but 125d will hold it a bit longer though) and 120d will not fall really short in second gear either!?

I guess that the acceleration has become a theoretical optimum, only attainable in lab conditions then.
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      03-27-2013, 07:38 PM   #16
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Quote:
Originally Posted by Wositsch View Post
The 125d has maximum power at 4400rpm, then power starts to drop as the revs get higher, thats just the way diesel works. It's the same story with the M50d engine, It has maximum power from 4000 - 4400rpm.
Correct, but you have to factor in the reduction of the driveline. The Ooomp you'll have at the wheels is basically the engine torque multiplied with the transmission reduction. Accept for the time being, that actual torque on the wheels == acceleration.

For example: engine delivers 200Nm but the transmission line has a reduction of 3 it will bring 600Nms to the ax of the driving wheels. When you shift one gear up, the engine still delivers 200Nm, but the reduction will only be 2,2 (since you need a higher speed range in higher gear, automatically impacting the reduction) bringing only 440Nms to the ax of the wheels. So basically, in this example, engine torque can go down to 146Nm in the first gear before you consider having the shift up to maximize wheel torque. So when you could have 200Nm engine torque of this engine at this speed, you still best conclude to fall down further to 146Nm on engine torque in low gear since the wheel torque is still better!

So don't read a torque/power engine diagram as an indication where you have to shift, always factor in the gear/driveline reductions. But again, no car manufacturer is publishing this, although even LADA already calculated this (really).

Last edited by KoenG; 03-27-2013 at 07:44 PM..
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      03-27-2013, 07:53 PM   #17
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Shift at 4500 rpm! Once you pass that you are losing time. There is no twin turbo on 125d.
Find a nice stretch of road that uses a long strip of high grip asphalt (cream surface) running out of a round about, plan a nice quiet time of day/night use this surface to start on, will make a serious difference.

Sport + mode
Change at 4.5k
Use high grip surface

Second gained easy...
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      03-28-2013, 03:04 AM   #18
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Quote:
Originally Posted by KoenG View Post
So don't read a torque/power engine diagram as an indication where you have to shift, always factor in the gear/driveline reductions. But again, no car manufacturer is publishing this, although even LADA already calculated this (really).
You don't have to involve torque. Looking at the power graph and gear ratios should be enough. When power is higher in next gear, shift up.

According to the specs from BMW, you should shift at the limiter from first to second on the 116i. My dyno graph and real world testing indicates otherwise. The power graph is not flat, but drops off towards the redline. The shift points between the taller gears are even lower.

On all cars I have had before, the shift point was at the limiter between the first gears.
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      03-28-2013, 04:59 AM   #19
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Quote:
Originally Posted by tawia View Post
Shift at 4500 rpm! Once you pass that you are losing time. There is no twin turbo on 125d.
Find a nice stretch of road that uses a long strip of high grip asphalt (cream surface) running out of a round about, plan a nice quiet time of day/night use this surface to start on, will make a serious difference.

Sport + mode
Change at 4.5k
Use high grip surface

Second gained easy...
I believe it has 2 Borg Warner turbos.
http://www.realoem.com/bmw/showparts...78&hg=11&fg=50

Just out of interest OP. Have you been running the car for a while before attempting this? Quite a few of us have noticed that for the first 10 miles or so of a journey the 125d can feel a bit strangled.

Also, no point in all this talk of launch control type stuff and ATs as the OP has a manual.
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      03-28-2013, 06:01 AM   #20
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The engine was warm but the test time was around 10mins after the engine was started (from warm). It was a cold day (zero degrees C). I had a full tank of Shell V-Power diesel and probably around 40kg of stuff in the boot. I launched from 1500rpm because I wanted to care for my clutch.

I will try shifting at 4500rpm tomorrow and report back to see if it makes any difference.
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      03-28-2013, 07:52 AM   #21
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Are you on winter or regular tyres? Either way it sounds less than ideal conditions. Cold weather a dash too much mechanical sympathy and 80kg (an adult male) extra weight. The weight wouldn't affect it massively. i'd say the cold and inaccuracy of the app are probably the biggest issues here.

Be interesting to see how mine fares when i get this OBD2 dongle.
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      03-28-2013, 08:52 AM   #22
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Quote:
Originally Posted by mowflow View Post
Are you on winter or regular tyres? Either way it sounds less than ideal conditions. Cold weather a dash too much mechanical sympathy and 80kg (an adult male) extra weight. The weight wouldn't affect it massively. i'd say the cold and inaccuracy of the app are probably the biggest issues here.
Cold weather is actually an advantage. Winter tires are also nice for 0-100 runs if you know how to abuse them.

The factory figures are also set with people on board. In the old days, it was with two persons (75+75 kg).
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