Overboost

[blueshark]

Does the hp curve change during overboost?

If there are two torque profiles, wouldn't it stand to reason that there would also be two hp profiles? And, if so, does the quoted 335hp correspond to 450 or 500NM?

[spiderz17]

http://www.automobilemag.com/reviews...bo_engine.html

Dyno tests show the N54is peaking at 293hp. They didn't show any "Overboost vs non-Overboost" curves, but just judging by the peak it doesn't seem like the hp experiences any significant increase during overboost. I'm sure BMW would've bragged about it somewhere if HP did increase. But I'm also curious as to how this is possible. If HP is just a derivation of torque, how is it not affected by the increased torque?

[Dackelone]

Here is the Hp and Tq curves for the 1M. You will notice it doesn't show the overboost +50Nm. So yes, there are two maps. I don't really know why BMW has only shown us this graph - I would have thought the max Hp and T curves would sell more cars.

1M N54

[blueshark]

This begs the question, is the quoted 0-62 time based on the above map, or on the overboost map?

[blueshark]

And, how is overboost activated, anyway? When the throttle is floored? When the M button is on? And how frequently can it be called on?

[blueshark]

What would HP be during overboost?

[MDORPHN]

Originally Posted by blueshark

And, how is overboost activated, anyway? When the throttle is floored? When the M button is on? And how frequently can it be called on?

Overboost is actuated for 7 seconds after an upshift when when full throttle applied.


Neil

[blueshark]

Thanks Neil

[skyphab]

Hi there! Just registered myself, since I'm currently gathering information about the M Coupé

Originally Posted by blueshark

What would HP be during overboost?

HP will increase, but I think you will not exceed the maximum HP output. If you are in overboost mode at 4'500 rpm, you will have 500nm and 235 KW.
If rpm would increase, you would reach and exceed the 250KW maximum output, but since torque is beginning to fall after 4'500 rpm, you won't.

But that's just my theory, dyno runs of a Z4 35IS should show that?

[Dackelone]

Originally Posted by blueshark

And, how is overboost activated, anyway? When the throttle is floored? When the M button is on? And how frequently can it be called on?

By "data mining" some of the old Z4drive35is blogs... it looks like the over boost only works when you go WOT (ie foot to the floor) mode.



http://www.octane.ie/forum/showthread.php?t=44431


Under the bonnet there is a 3 litre twin turbo straight six capable of producing 340bhp and 500nm torque. It is rumoured that this engine is going into the new M1 and it would be a good choice in my opinion.

The speed and power are absolutely phenomenal and unlike anything I have ever driven before. Having floored it and hit the overboost button under the accelerator pedal let's just say I scared myself - wobbly knees afterwards! In hindsight probably not such a good idea in wet conditions.

The noise coming from the back end is a nice low growl. It's very pleasant to listen to and not too much. The flap on the right tail pipe opens at 4.5k revs making it sound like a completely different animal!!


from TopSpeed:

http://www.topspeed.com/cars/bmw/201...s-ar82816.html

The turbocharger system developed for the engine of the new BMW Z4 sDrive35is maintains a high output throughout the entire engine speed range. Nominal peak torque is increased to 332 lb-ft from 1,500 rpm to 4,500 rpm. Maximum output of 335 hp is delivered at 5,900 rpm.


The enhanced engine management system of the BMW Z4 sDrive35is includes an electronically-controlled overboost function to briefly increase torque under full load by another 37 lb-ft. This temporary torque peak of 369 lb-ft gives the car a significant increase in acceleration.


SO... that is a 35 Hp and 32 Ft/lbs increase over the standard Z4 N54 model.

Dackel

[skyphab]

Originally Posted by Dackelone

SO... that is a 35 Hp and 32 Ft/lbs increase over the standard Z4 N54 model.

But not generally, since it's rpm-dependend.
When you are at 4'000 rpm, you'll get a 29 HP gain with +50nm of torque. At 2'000 rpm +50nm means just 14 HP.

But it's still an overall 10-15% increase in horsepower.

[Dackelone]

I did see today (by searching old Z4 threads)... that a Z4 and a Z4is will make the SAME Hp & Tq with a tune.

And btw... did you guys see the AC Schnitzer ACS4 Turbo S article? Seems that AC Schnitzer gets 375 Hp out of the Z4is - so we can assume that the 1M can achieve the same Hp/tune.

http://e89.zpost.com/forums/showthread.php?t=475200


Dackel

[1Mer]

Originally Posted by MDORPHN

Overboost is actuated for 7 seconds after an upshift when when full throttle applied.

Upshift? what about downshifts? Or just flooring it without changing gear?

After the 7 secs is over, does anyone know how long it is before overboost can be activated again?

[heli_ben]

500Nm@1500rpm = 76Kw
500Nm@4500rpm = 231Kw

Peak HP = 250Kw

Thus they quote peak HP & peak torque with & without overboost.

[Impervious]

Any chance of programming it to run overboost constantly? Would this be bad for the car/damage anything?

[blueshark]

... Also wondering if mileage would be affected?

[hwelvaar]

Originally Posted by 1Mer

After the 7 secs is over, does anyone know how long it is before overboost can be activated again?

I thought the 'timer' is reset at every shift.

And even if it's not, after 7 seconds WOT you will be doing 80 Mph anyway

[EA51 LAY]

Originally Posted by MDORPHN

Overboost is actuated for 7 seconds after an upshift when when full throttle applied.


Neil

Thats right = 369ft/lb for that duration + great onramp highway entry

[blueshark]

Originally Posted by hwelvaar

I thought the 'timer' is reset at every shift.

And even if it's not, after 7 seconds WOT you will be doing 80 Mph anyway

So.. it sounds like overboost doesn't require much time to reload?

For discussion purposes, is it reasonable to assume 7 seconds on, 1-2 seconds off, 7 seconds on, 1-2 seconds off, ad infinitum? (I realize this sounds silly, but I'm curious to know of power availability in practice). Does anyone know, from experience in the Z435is?

[JN2009]

Can you beleive if the Overboost give the +50torque and the 340hp annonced by BMW and in normal mode it's the same power of a 135i(306hp).

It's only a bad dream but...

[skyphab]

Originally Posted by JN2009

Can you beleive if the Overboost give the +50torque and the 340hp annonced by BMW and in normal mode it's the same power of a 135i(306hp).

It's only a bad dream but...

Nope, because it says 450NM +50NM Overboost, making 500NM with activated overboost overall.
If you take the HP and TQ curve from the earlier post in this thread and calculate the HP, you will see that the basis is 450NM and this will give you 250KW or 340HP as the peak output.

What is shown is the curve without overboost, not with.

[JN2009]

Originally Posted by skyphab

Nope, because it says 450NM +50NM Overboost, making 500NM with activated overboost overall.
If you take the HP and TQ curve from the earlier post in this thread and calculate the HP, you will see that the basis is 450NM and this will give you 250KW or 340HP as the peak output.

What is shown is the curve without overboost, not with.

ok,ok .I was thinking that's they make like the M5.The annonced a 507hp but in real it's 400hp.507hp is with the M button.