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      05-18-2016, 08:47 PM   #1
D041987
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BMW 328I vs 428I Power Difference?

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So my car is at the shop and I had the chance to drive another 2013 328I and my friend just got a 2015 428I loaner. 328I is 6 speed manual 428I is the Xdrive Grand Coupe 8AT. Since they are to be the same n20 motor we did back to back runs with launching, 30mph to 100mph and 60mph to 120mph runs.

The 428i launches the same as the 328I but past 20mph the 428I puts on some distance and keeps pulling.

From 30MPH to 100MPH the 428I has once again put car lengths on the 328I

From 60MPH to 120MPH this was closer but 428I put about 4 car lengths on the 328i.

Am I missing something here? The 428 is all wheel drive which should translate to less power at the wheels and its also heavier!!! On the Sport Display the 328I maxes out around 240 and tappers down to about 180HP mark while the 428I in almost every run stayed around the 260HP mark Torque on both was around the 260 in mostly all gears.

Is this just ecu calibration?
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      05-18-2016, 08:55 PM   #2
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Could be tuning. Could be something wrong with that particular 328i.
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      05-18-2016, 09:32 PM   #3
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Transmission makes a huge difference - transmission efficiency/gear ratio and most certainly and significantly it is something related to shifting skill:
1) Timing - Driver 9 times out of 10 shifts earlier or later than optimal RPM, a mistake ZF8 doesn't make.
2) Shifting Time - Say you lose a full sec in total to ZF8 during 5 times' shift to 120MPH, which is more than just reasonable and only possible with a pro driver. Assuming the average MPH difference when you shift = 15MPH, approx. 6.66 m/s, or 22 ft/s for the Americans. That just make a one and half car length deficit.
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      05-19-2016, 10:59 AM   #4
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Quote:
Originally Posted by SeanWRT
Transmission makes a huge difference - transmission efficiency/gear ratio and most certainly and significantly it is something related to shifting skill:
1) Timing - Driver 9 times out of 10 shifts earlier or later than optimal RPM, a mistake ZF8 doesn't make.
2) Shifting Time - Say you lose a full sec in total to ZF8 during 5 times' shift to 120MPH, which is more than just reasonable and only possible with a pro driver. Assuming the average MPH difference when you shift = 15MPH, approx. 6.66 m/s, or 22 ft/s for the Americans. That just make a one and half car length deficit.
+1
What he said.

ZF 8 speed is often compared with dct for its sheer speed.
0-120 is 4 shifts. Each of the ZF up shift at 150ms in sport + is worth about a car length.
Not only that your able to be flat up shifting, throttle stays open thus boost stay constant (unless reduction is needed for spikes) end result is torque stay constant.

Net result is you would need another +30hp to = out that lost consistently.
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      05-19-2016, 01:19 PM   #5
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Quote:
Originally Posted by ShocknAwe View Post
Could be tuning. Could be something wrong with that particular 328i.
Or you'd be surprised what the difference is when one is running high octane and the other has crappy gas.

But is this also verified both are N20's or both N26's.
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      05-19-2016, 02:03 PM   #6
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As mentioned, its probably the transmission
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      05-19-2016, 08:52 PM   #7
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I own a 428 GC and the auto tranny when shifting from 1->2->3 is way faster than any drivers can shift in a manual...Im not kidding first to second gear shift is like 3/4 of a second if not less
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      05-19-2016, 08:53 PM   #8
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Quote:
Originally Posted by CRJdriver
Quote:
Originally Posted by SeanWRT
Transmission makes a huge difference - transmission efficiency/gear ratio and most certainly and significantly it is something related to shifting skill:
1) Timing - Driver 9 times out of 10 shifts earlier or later than optimal RPM, a mistake ZF8 doesn't make.
2) Shifting Time - Say you lose a full sec in total to ZF8 during 5 times' shift to 120MPH, which is more than just reasonable and only possible with a pro driver. Assuming the average MPH difference when you shift = 15MPH, approx. 6.66 m/s, or 22 ft/s for the Americans. That just make a one and half car length deficit.
+1
What he said.

ZF 8 speed is often compared with dct for its sheer speed.
0-120 is 4 shifts. Each of the ZF up shift at 150ms in sport + is worth about a car length.
Not only that your able to be flat up shifting, throttle stays open thus boost stay constant (unless reduction is needed for spikes) end result is torque stay constant.

Net result is you would need another +30hp to = out that lost consistently.
Well said
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      05-25-2016, 01:45 AM   #9
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Well did another run now both 2014 BMW 328I Auto and 2016 428I Auto. 428i still pulled on the 328i by 2 to 3 cars in the same races. So it must be the tune, also noticed that the TRQ on both is the same but HP according to the onscreen display shows 240 to 245 on the 328I and 260 to 270 on the 428i!

So I have to assume the 428I has a different tune in which it is making more HP as the car just feels like a N55 motor where the 328I feels less powerful!
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      05-25-2016, 08:45 AM   #10
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do u have the last 7 of that 428?

For an N20 10:1 compression, you need a FBO car for N55 numbers.
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      05-25-2016, 12:35 PM   #11
tc328
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So you saying the 4 loaner has a tune???
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      05-25-2016, 12:48 PM   #12
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maybe it has a dinan piggyback
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      05-25-2016, 04:33 PM   #13
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Or n20 vs n26??
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      05-30-2016, 01:33 AM   #14
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Not sure on the engine and doubt the loaner will have a aftermarket tune. Do not have the vin but might get it sometime this week.
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