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Z4 M Coupe
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Discussion Starter · #1 ·
I have a Z4 M Coupe, and obviously is has the S54 B32. I am wondering as to when the Engine comes into its own and is no longer "green". I have done a few 0-60 and 1/4 mile runs and the times aren't right, shall we say. Since not many Z4 M's have much mileage yet. I was wondering if one of you E46 M3 guys could assist.
 

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england1987 said:
...I am wondering as to when the Engine comes into its own and is no longer "green"...
At 3k miles, you're 90% there, at 5k miles, 95%. Perfection on German cars may be at 30-40k miles.

Bruce

PS - Most of the road-tested cars in the nutbooks are going to have 3k to 5k miles on the clock, if you're using those as a reference. What are your times and speeds, and how are you measuring them?
 

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Z4 M Coupe
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Discussion Starter · #3 ·
Augenstein said:
At 3k miles, you're 90% there, at 5k miles, 95%. Perfection on German cars may be at 30-40k miles.

Bruce

PS - Most of the road-tested cars in the nutbooks are going to have 3k to 5k miles on the clock, if you're using those as a reference. What are your times and speeds, and how are you measuring them?
0-60mph in 5.6 and 1/4 mile in 14.1 @ 101. Tested with G-tech that my friend has.

Thanks, That seems to be the general concensus. I got a similar answer on bimmerforums
 

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england1987 said:
0-60mph in 5.6 and 1/4 mile in 14.1 @ 101. Tested with G-tech that my friend has...
The odds are good that the G-Tech is not showing accurate times and speeds. Every test run I've done (at the drag strip) had the G-Tech well off the actual time slip until I "tuned" the meter to the car. The most recent example was when the time slip said 16.22 @ 84.53 mph for my bride's Honda Pilot, and the G-Tech said 15.78 at 88. In a Vette, the time slip said 13.06 at 108.53, and the G-Tech said 13.66 at 104. With tuning (essentially adjusting for how much the nose of the car leaps skyward under acceleration), you can get within hundredths of a second and tenths of a mile per hour.

I'm betting that, because your car won't launch the nose (due to stiff springs), the G-Tech is reading low.

Bruce
 

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Since I'm the "friend with the G-Tech," I thought I'd chime in here :angel:

As assumed, I have the latest G-Tech Pro RR version, and I am indeed quite familiar with launch pitch-up and the effects that the G-Tech's setting wrt to that phenomenon has on acceleration times. I've done around 250 runs on the newer G-Tech(not to mention the original little gadget :rofl: ) with a wide variety of cars, so I know what to expect. While one can doubt the outright accuracy of the G-tech, it is extremely consistent if you know what you're doing.

I have found a sort of "default" launch pitch-factor setting that works well with the cars I test that have suspensions on the stiffer side. The M Coupe in question seems to have pretty aggressive front damper rebound settings and high front springrates which make for a very harsh small-bump ride, but appears to give excellent weight transfer on launch....something I'm not used to accounting for in a BMW. There is noticeable squat and hood rise(doubly noticeable because of the particularly long and visible hood), and while no one who rides in the car would say that the suspension is anything but stiff---quite, in fact---I may actually have the G-Tech calibrated for slightly less pitch than I ought to, making the car appear marginally faster, if anything.

I feel that most of the descrepancy in the quoted versus "actual" acceleration times can be pinned on a couple factors, in order of importance, IMO:
1.) Weight---2 passengers in test vehicle, and a resultant load quite substantially in excess of the BMW and magazine testing parameters. This is by far the biggest issue, IMO. When you compute the power-to-weight ratio of the tested car and compare it to BMW spec and versus other vehicles I've tested, the results between them correlate surprisingly well.
2.) Launch---All tested launches are sans wheelspin. This creates a momentary bog at launch while the 3.2L engine struggles up from 2-3k rpms to a point where it begins making enough torque to seriously motivate the car. This is offset to an extent by the aggressive gearing which allows the car to still scamper off the line pretty quickly, but a little controlled wheelspin would help quicken things further. Compounding this is the weight issue mentioned above. I can move a laden, mildly modded E36 M3 weighing in at probably <3200lbs(I serve as weight reduction :bigpimp: ) off the line to 30mph about half a second quicker than aforementioned Coupe with taller gearing, 1000 fewer rpms, 70+ less horsepower and similar torque, while launching the exact same way. Why? The loaded E36 weighs less than the Coupe's curb weight, and a lot less than its loaded up, testing weight. That few hundred extra pounds is a few hundred extra pounds the S54 simply doesn't have the lowend torque to easily deal with, which makes it bog even harder on launch. Yet, when you get to third gear and higher, where weight plays a vastly lesser factor, the car starts pulling like the 330hp car it ought to be.
 

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Excellent post - thanks!

Coupla points, though.

With regard to the launch, the results say it's not too bad. The nutbooks are typically getting somewhere around 13.3s at, say, 106+ mph for the car (when adjusted for SAE "Standard Day" ambient conditions), so if you do a quarter mile efficiency number (ET X mph), you come up with a 1410. Your (england1987's) 14.1 @ 101 gets a 1424. Measured against a 1400 target for hot street cars with good, sticky rubber, these numbers are pretty decent, and more importantly, your results are close to the nutbook results in terms of ET vs mph. So the launch, while a bit off the pace, is still pretty good, as you say, and of course the launch has little effect on quarter mile trap speeds, which is the real issue, in my mind.

The implication of a 101 mph trap speed (against a "target" 106+ mph) suggests that either you guys were testing in Las Vegas at high noon, or that you personally weigh over 500 pounds. :)

Seriously, all other things equal, trap speeds vary by the *cube root* of the power to weight delta, so we're looking at around 15% here in terms of power, weight, or both.

So, was it hot that day? Are you guys at sea level or at altitude?

Bruce
 

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Z4 M Coupe
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Discussion Starter · #7 · (Edited)
Augenstein said:
The implication of a 101 mph trap speed (against a "target" 106+ mph) suggests that either you guys were testing in Las Vegas at high noon, or that you personally weigh over 500 pounds. :)

So, was it hot that day?

Bruce
No, I'm pretty big. eagleye is a rake, but I make up for that. :)

And, to show a comparison. We ran my mums Bentley GT, down the same road, and 0-60 in 4.9 and 1/4 mile in 13.3 @ 106. eagleye will correct me if I'm wrong. the best time to 60 was 4.6...down hill and the worst was 5.2 slight uphill
 

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Yep, 30K is right.
I hope you didn't do those runs before 1200 or 2000 miles.... That does permanent damage.
JL
 

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Z4 M Coupe
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Discussion Starter · #9 ·
Jlevi SW said:
Yep, 30K is right.
I hope you didn't do those runs before 1200 or 2000 miles.... That does permanent damage.
JL
Just so I won't panic, I'll ignore this and hope you are joking:eek:
 

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No joke, read your manual about proper break in.
 
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