ZPOST
BMW Garage BMW Meets Register Search Today's Posts Mark Forums Read


Go Back   ZPOST > BMW Z4 Technical Talk > Engine, Exhaust, Drivetrain Modifications
  TireRack

SUPPORT ZPOST BY DOING YOUR TIRERACK SHOPPING FROM THIS BANNER, THANKS!
Post Reply
 
Thread Tools Search this Thread
      04-22-2013, 01:09 AM   #1
intoflatlines
Lieutenant
intoflatlines's Avatar
United_States
67
Rep
501
Posts

Drives: Z4MR, E34, E30
Join Date: Mar 2013
Location: Chicago

iTrader: (0)

8000RPM Redline for Z4M?

Probably dumb/weird questions, but here it goes:

When accelerating hard it seems like there's a big loss of power before the 8000RPM redline (maybe around 7800RPM or so). Is this normal?

The last orange/amber LED on the tachometer never turns off. Is this normal?

What RPM do you recommend shifting at for maximum acceleration (stock)?
Appreciate 0
      04-22-2013, 01:30 AM   #2
mfanatic325
///M-fanatic
mfanatic325's Avatar
Taiwan
192
Rep
3,885
Posts

Drives: '01 911 Turbo
Join Date: Oct 2007
Location: Cupertino, CA.

iTrader: (23)

Our fuel cuts out at 7900 RPM, so what you felt was probably the fuel cut. Shift at or just before fuel cut for best performance.

And obviously don't rev high for extended periods at a time.
Appreciate 0
      04-22-2013, 02:25 AM   #3
zubydafa
tosser
Isle of Man
31
Rep
988
Posts

Drives: '07 Z4MC
Join Date: Jul 2011
Location: Allentown, PA

iTrader: (0)

Yup you'll feel that serious loss in power around there...where the fuel cuts out.

My tune is for 8250 max and the motor is still running strong. Unfortunately I'm down on power due to a solenoid (alleged solenoid) but that's a whole other subject.
__________________
'07 MCoupe
lots of mods
Appreciate 0
      04-22-2013, 03:22 AM   #4
ga41
Lieutenant
ga41's Avatar
Cyprus
30
Rep
503
Posts

Drives: Z4 M Coupe
Join Date: Jun 2009
Location: Paphos

iTrader: (0)

Garage List
2006 Z4 M Coupe  [0.00]
Quote:
Originally Posted by intoflatlines View Post
The last orange/amber LED on the tachometer never turns off. Is this normal?
This is normal.
__________________
Appreciate 0
      04-23-2013, 09:52 PM   #5
seank
enthusiast
seank's Avatar
48
Rep
1,695
Posts

Drives: e30 m3,e90 wagon,sprinter,z4m
Join Date: Dec 2011
Location: sacramento, ca

iTrader: (4)

You can raise the rev limit a little, but it won't be worth it if you aren't racing.
Appreciate 0
      04-24-2013, 08:00 AM   #6
elwesso
Second Lieutenant
elwesso's Avatar
25
Rep
299
Posts

Drives: Z4 M Coupe
Join Date: Dec 2012
Location: Indiana

iTrader: (1)

I usually shift at around 7500 anyway, I don't think there's a lot of advantage shifting above there, and apparently the high RPM's is what kills the rod bearings.
__________________
- Wes
2007 BMW M Coupe
2016 VW GTI
Appreciate 0
      04-26-2013, 03:51 AM   #7
exdos
Second Lieutenant
England
6
Rep
222
Posts

Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

iTrader: (0)

Quote:
Originally Posted by intoflatlines View Post

When accelerating hard it seems like there's a big loss of power before the 8000RPM redline (maybe around 7800RPM or so). Is this normal?
Here's a graph from datalogging the ECU of my Z4MC during an acceleration in 2nd gear with the accelerator pedal held to the floor and allowing the rev limiter to kick in. I've recorded, Engine RPM, Vehicle Speed, Absolute Throttle Position and Calculated Load.



For some reason, the Absolute Throttle Position on the Z4MC at WOT records as being 76.1% rather than 100%, whilst the Calculated Load records as 100% (I don't understand why this is the case, but some other cars also do this. Can anyone explain why ATP at WOT is less than 100%?). Since the throttle of the Z4MC is "drive by wire" the graph shows that the actual throttle position is reduced from WOT after the revs reach 7631rpm although the accelerator pedal was fully depressed. Therefore, it seems that the software is already commencing to reduce the air ingestion in anticipation of the engine rev limiter cutting out at 8,000rpm.



Quote:
Originally Posted by intoflatlines View Post
What RPM do you recommend shifting at for maximum acceleration (stock)?
The slope of the plot of engine rpm above 7,631rpm begins to fall away, therefore, I would suggest that the optimum rpm to gear shift is just as the needle reaches the amber zone in the tachometer. At this point you have also reached peak power output.
Appreciate 0
      04-26-2013, 12:20 PM   #8
inTgr8r
Lieutenant General
inTgr8r's Avatar
Canada
2422
Rep
11,665
Posts

Drives: M2 Comp
Join Date: Mar 2006
Location: Toronto

iTrader: (10)

Quote:
Originally Posted by zubydafa View Post
Yup you'll feel that serious loss in power around there...where the fuel cuts out.

My tune is for 8250 max and the motor is still running strong. Unfortunately I'm down on power due to a solenoid (alleged solenoid) but that's a whole other subject.
hmmmm.... might that be related to your previous tune issue?
__________________
'21 M2C Hockenheim Silver
'18 718 Cayman S Lava Orange (sold)
'13 E92 M3 Santorini Blue (sold)
'07 Z4 M Coupe Alpine White (sold)
Appreciate 0
      04-27-2013, 12:12 AM   #9
seank
enthusiast
seank's Avatar
48
Rep
1,695
Posts

Drives: e30 m3,e90 wagon,sprinter,z4m
Join Date: Dec 2011
Location: sacramento, ca

iTrader: (4)

Quote:
Originally Posted by elwesso View Post
I usually shift at around 7500 anyway, I don't think there's a lot of advantage shifting above there, and apparently the high RPM's is what kills the rod bearings.
There are many reasons where it benefits speed to go above 7500 on a track, but if you don't need to.......
Appreciate 0
      04-27-2013, 01:58 PM   #10
kennyfrc
First Lieutenant
kennyfrc's Avatar
18
Rep
376
Posts

Drives: 2008 Z4MC
Join Date: Aug 2010
Location: ATL GA

iTrader: (1)

Very good information that further supports shifting at 8K doesn't help you.

If there were only a way to graph rod bearing wear in the 7500-8000RPM range.....
__________________
Toy: 2008 Silver Z4MC 300WHP/241TQ

Mods: OEM Euro Headers, RPI Scoop

Daily: 2010 Tacoma Double Cab
Appreciate 0
      04-27-2013, 02:35 PM   #11
O-cha
Brigadier General
O-cha's Avatar
218
Rep
4,726
Posts

Drives: Mcoupe
Join Date: Oct 2007
Location: In front of you

iTrader: (2)

Quote:
Originally Posted by exdos View Post
Here's a graph from datalogging the ECU of my Z4MC during an acceleration in 2nd gear with the accelerator pedal held to the floor and allowing the rev limiter to kick in. I've recorded, Engine RPM, Vehicle Speed, Absolute Throttle Position and Calculated Load.
Whatever you used wasn't logging data with anywhere near often enough, it should be 10-20 times a second minimum, not 2.
__________________
Appreciate 0
      04-28-2013, 02:06 AM   #12
seank
enthusiast
seank's Avatar
48
Rep
1,695
Posts

Drives: e30 m3,e90 wagon,sprinter,z4m
Join Date: Dec 2011
Location: sacramento, ca

iTrader: (4)

Quote:
Originally Posted by kennyfrc View Post
Very good information that further supports shifting at 8K doesn't help you.

If there were only a way to graph rod bearing wear in the 7500-8000RPM range.....
It depends on why you would shift at 8k. If it is to go faster, it does help.

Carrol Smith explained this the best, but I will attempt to give an analogy. If you made a graph showing your hp at all the rpms, you will see something like this (just an analogy, not necessarily your hp numbers): 6500 at 240, 6750 at 245, 7000 at 250hp, 7250 at 255, 7500 at 260hp, 7750 at 265, 8000 at 260hp, 8200 at 255hp.

If you were racing, if you shifted at peak power:7750 you would have at least a 1000 rpm drop and that is being very generous. More like a 1500-2000 rpm drop on most cars. Add all those numbers up between 6750 and 7750.

If you shifted over the peak at 8200 with a 1000 rpm drop, you will only be at 7200 rpms. Add up all the hp numbers.

The number that is the highest is where you should shift to give the most power.

Also, rod bearings are not damaged by running at 8000 or even 10,000 rpms assuming you have adequate oil pressure at those rpm's. Most race motors have an upgraded oil pump, especially the s54. Upgrading the oil pump can also allow you to run a thinner oil and run cooler than stock and it will increase the power output of the motor to the rear wheels. There are other parts of the motor that won't handle 9000 rpm's well, but I won't get into that here.
Appreciate 0
      04-28-2013, 03:56 AM   #13
exdos
Second Lieutenant
England
6
Rep
222
Posts

Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

iTrader: (0)

Quote:
Originally Posted by O-cha View Post
Whatever you used wasn't logging data with anywhere near often enough, it should be 10-20 times a second minimum, not 2.
I agree it's not ideal but that's the "polling rate" that the ECU yields to an OBDII datalogger using all the cars OEM sensors 4 PIDs at a time. At the end of the day, ECU datalogging gives a series of "time-lapse snapshots" which gives a very good indication of what is happening and this doesn't devalue the information in any way. The Absolute Throttle Position still starts to reduce before the redline, which explains what the OP has observed.

Last edited by exdos; 04-28-2013 at 05:16 AM..
Appreciate 0
      04-28-2013, 04:15 AM   #14
exdos
Second Lieutenant
England
6
Rep
222
Posts

Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

iTrader: (0)

Quote:
Originally Posted by seank View Post

Also, rod bearings are not damaged by running at 8000 or even 10,000 rpms assuming you have adequate oil pressure at those rpm's. Most race motors have an upgraded oil pump, especially the s54. Upgrading the oil pump can also allow you to run a thinner oil and run cooler than stock and it will increase the power output of the motor to the rear wheels. There are other parts of the motor that won't handle 9000 rpm's well, but I won't get into that here.
Here are some mean piston speeds that I've found here: http://www.eng-tips.com/viewthread.cfm?qid=259413
23.4m/sec Honda S2000 84mm stroke @ 8300rpm
24m/sec BMW S54B32 91mm stroke @ 7900rpm
25.1m/sec Formula 1 40mm stroke @ 19000rpm

This gives some idea of the level of performance of the S54 engine.

I've experience catastrophic bearing shell failure in my S54 Z3 M Coupe (redline at 7,600rpm) as in the photo below.


Appreciate 0
      04-28-2013, 08:06 AM   #15
DRedman45
Lieutenant
DRedman45's Avatar
35
Rep
441
Posts

Drives: E86 //M coupe
Join Date: Oct 2012
Location: Northern va

iTrader: (0)

^it's a shame bmw didn't extend the bearing recall to the early s54 z3m's, all the early s54's had that issue

iirc the s54 is the 4th fastest piston speed of any production car....quite impressive engineering
Appreciate 0
      04-28-2013, 08:15 AM   #16
exdos
Second Lieutenant
England
6
Rep
222
Posts

Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

iTrader: (0)

Quote:
Originally Posted by DRedman45 View Post
^it's a shame bmw didn't extend the bearing recall to the early s54 z3m's, all the early s54's had that issue
It was a shame but I got a brand new short engine from BMW FOC as goodwill.
Appreciate 0
      04-28-2013, 08:59 AM   #17
O-cha
Brigadier General
O-cha's Avatar
218
Rep
4,726
Posts

Drives: Mcoupe
Join Date: Oct 2007
Location: In front of you

iTrader: (2)

Quote:
Originally Posted by exdos View Post
I agree it's not ideal but that's the "polling rate" that the ECU yields to an OBDII datalogger using all the cars OEM sensors 4 PIDs at a time. At the end of the day, ECU datalogging gives a series of "time-lapse snapshots" which gives a very good indication of what is happening and this doesn't devalue the information in any way. The Absolute Throttle Position still starts to reduce before the redline, which explains what the OP has observed.
How do you know it's closing? You have one data point before the limiter that says it's fully open, and one at the rev limiter that says it has closed some... That means absolutely nothing.

You are however correct that it closes some in anticipation, but nothing like your graph shows.
__________________
Appreciate 0
      04-28-2013, 09:08 AM   #18
O-cha
Brigadier General
O-cha's Avatar
218
Rep
4,726
Posts

Drives: Mcoupe
Join Date: Oct 2007
Location: In front of you

iTrader: (2)

Quote:
Originally Posted by seank View Post
It depends on why you would shift at 8k. If it is to go faster, it does help.

Carrol Smith explained this the best, but I will attempt to give an analogy. If you made a graph showing your hp at all the rpms, you will see something like this (just an analogy, not necessarily your hp numbers): 6500 at 240, 6750 at 245, 7000 at 250hp, 7250 at 255, 7500 at 260hp, 7750 at 265, 8000 at 260hp, 8200 at 255hp.

If you were racing, if you shifted at peak power:7750 you would have at least a 1000 rpm drop and that is being very generous. More like a 1500-2000 rpm drop on most cars. Add all those numbers up between 6750 and 7750.

If you shifted over the peak at 8200 with a 1000 rpm drop, you will only be at 7200 rpms. Add up all the hp numbers.

The number that is the highest is where you should shift to give the most power.

Also, rod bearings are not damaged by running at 8000 or even 10,000 rpms assuming you have adequate oil pressure at those rpm's. Most race motors have an upgraded oil pump, especially the s54. Upgrading the oil pump can also allow you to run a thinner oil and run cooler than stock and it will increase the power output of the motor to the rear wheels. There are other parts of the motor that won't handle 9000 rpm's well, but I won't get into that here.
This is wrong on many levels, adequate oil pressure doesn't mean rod bearings won't be destroyed by higher RPMS. The OEM bearings are not designed to, and will not live for very long at 10k, even with perfect oil pressure.

As for the shift points, that is a very poor explanation, though it does sort of correlate with the correct. Shift points are wholly determined by thrust at the wheels. Thrust at the wheels is determined by torque and gearing. Essentially what you are looking for is where your wheel thrust in the current gear drops below where it will be in the next, that is the point you shift at. You cannot find this point simply by following your explanation and "adding up" HP numbers.
__________________
Appreciate 0
      04-28-2013, 10:04 AM   #19
exdos
Second Lieutenant
England
6
Rep
222
Posts

Drives: Z3 M Coupe(S54) and Z4 M Coupe
Join Date: Apr 2008
Location: UK

iTrader: (0)

Quote:
Originally Posted by O-cha View Post
How do you know it's closing? You have one data point before the limiter that says it's fully open, and one at the rev limiter that says it has closed some... That means absolutely nothing.

You are however correct that it closes some in anticipation, but nothing like your graph shows.
Please produce for us the appropriate datalog graphs showing us all precisely what happens.
Appreciate 0
      04-28-2013, 10:38 AM   #20
yousefnjr
salty cowboys fan
yousefnjr's Avatar
6115
Rep
3,392
Posts

Drives: ‘06 Z4MR, ‘20 X7, ‘22 M4x
Join Date: Dec 2012
Location: Bay Area, CA

iTrader: (2)

Appreciate 0
      04-28-2013, 02:15 PM   #21
O-cha
Brigadier General
O-cha's Avatar
218
Rep
4,726
Posts

Drives: Mcoupe
Join Date: Oct 2007
Location: In front of you

iTrader: (2)

Quote:
Originally Posted by exdos View Post
Please produce for us the appropriate datalog graphs showing us all precisely what happens.
Anything could have happened between those two data points. Just because I demonstrated to you why your results are invalid doesn't mean I'm going to correct them for you.
__________________

Last edited by O-cha; 04-28-2013 at 02:44 PM..
Appreciate 0
      04-28-2013, 10:38 PM   #22
johanness
Banned
56
Rep
1,739
Posts

Drives: 2008 Z4MC
Join Date: Aug 2010
Location: Seattle, Vancouver

iTrader: (3)

Garage List
Quote:
Originally Posted by O-cha View Post
Whatever you used wasn't logging data with anywhere near often enough, it should be 10-20 times a second minimum, not 2.
It's the same DashDyno unit that is telling him his stock Z4M is now making 370RWHP with the help of his home made intake (or roughly 450hp at the flywheel).
Appreciate 0
Post Reply

Bookmarks

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off



All times are GMT -5. The time now is 08:44 PM.




zpost
Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
1Addicts.com, BIMMERPOST.com, E90Post.com, F30Post.com, M3Post.com, ZPost.com, 5Post.com, 6Post.com, 7Post.com, XBimmers.com logo and trademark are properties of BIMMERPOST