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
      04-09-2013, 09:01 PM   #1
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

Better performance with AC on?

Floridian heat has sapped a butt dyno estimated 20hp from my car, compared to driving it in Philly. Whats odd, is that recently I've been driving it with the air conditioning on, and it feels like I have more torque.

The supercharger kit is very ambient temp sensitive with how the car feels. Its not decreasing in performance with time (heat soak), but feels stronger or weaker with as little as a 10* temperature variance.

I've heard some 911 turbos run faster with the AC on, because of how the AC lines are routed. Could it hold true for the Z4M also, or am I just being crazy?
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
      04-09-2013, 09:59 PM   #2
seank
15
enthusiast
 
seank's Avatar
 
Drives: e30 m3,e90 wagon,sprinter,z4m
Join Date: Dec 2011
Location: sacramento, ca

Posts: 1,521
iTrader: (3)

Sounds crazy but I've heard crazier, so you are probably normal.
seank is offline  
Appreciate 0
Reply With Quote
      04-09-2013, 10:04 PM   #3
mfanatic325
36
///M-fanatic
 
mfanatic325's Avatar
 
Drives: '07 Z4MC, '04 325Ci
Join Date: Oct 2007
Location: Cupertino, CA.

Posts: 3,683
iTrader: (20)

Garage List
Send a message via AIM to mfanatic325
WTF? How does the AC have to be routed in order to actually have performance gain from using it?

We know that:
1) AC runs off of the crank, so it saps a tiny bit of power as-is when in use
2) AC generates heat with all else equal

Please enlighten me on the other variable(s)
__________________
VF570 S/C|TIAL BOV|SetRabCooler|Brembo GT 6/4|TE37s|NT05s|3.91 Gearing|TCK D/A|RPi Induction|SS Race Mufflers/X-pipe|JVT Headers|AS SSK|VibraTechnics Mounts|Sparco Pro2000/6pt.Harness|MS FloorMounts|SE Custom Harness Bar|Tekarbon Angels|M-Tech Pedals|OE Strut Bar|RE RSMs|8000K D2S|CDV DEL|CF Roof Wrap|MB Grills|UUC TrannyMounts/ClutchStop|V1 Mount|P3C Gauge
mfanatic325 is offline   Taiwan
Appreciate 0
Reply With Quote
      04-09-2013, 10:10 PM   #4
Rated M Roadster
6
Captain
 
Rated M Roadster's Avatar
 
Drives: 2011 X5M
Join Date: Jun 2011
Location: ABQ

Posts: 693
iTrader: (7)

The ac compressor turns off during full throttle...
__________________

Z4MR ll VF570 470whp 344wtq ll AA headers
RE X-pipe ll Stromung ll APEX ARC-8 on PSS
Stoptech 6pot Fr ll H&R coilovers ll APEX stud kit
Aero skirts ll Passport SRX
Rated M Roadster is offline  
Appreciate 0
Reply With Quote
      04-09-2013, 11:36 PM   #5
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

MAGIC
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
      04-09-2013, 11:38 PM   #6
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

Quote:
Originally Posted by mfanatic325 View Post
WTF? How does the AC have to be routed in order to actually have performance gain from using it?

We know that:
1) AC runs off of the crank, so it saps a tiny bit of power as-is when in use
2) AC generates heat with all else equal

Please enlighten me on the other variable(s)
On the 911, the engine bay is very tight, and I imagine the cold AC lines might be near the intake manifold. Maybe I'm thinking of another car, but its something my mind recalled.

I've also always felt like the AC took away power, but maybe its helping the supercharger somehow. Very small chance, logically speaking, but I'll definitely try it on/off on my next dyno run
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
      04-10-2013, 01:40 PM   #7
yousefnjr
5
Lieutenant
 
Drives: 2006 Z4MR
Join Date: Dec 2012
Location: Bay Area, CA

Posts: 599
iTrader: (0)

AFAIK the AC compressor is belt driven and has a clutch, which closes when you turn your AC on, otherwise the pulley is free-wheeling. I doubt the lines running the refrigerant have any cooling effect on under-hood temps.

Last edited by yousefnjr; 04-10-2013 at 02:49 PM. Reason: Typo
yousefnjr is offline  
Appreciate 0
Reply With Quote
      04-10-2013, 02:19 PM   #8
Beedub
40
Brigadier General
 
Drives: 2007 Z4 M roadster vt2-500
Join Date: Sep 2007
Location: UK

Posts: 4,027
iTrader: (0)

Quote:
Originally Posted by yousefnjr View Post
AKAIK the AC compressor is belt driven and has a clutch, which closes when you turn your AC on, otherwise the pulley is free-wheeling. I doubt the lines running the refrigerant have any cooling effect on under-hood temps.
+1
__________________
Pristine Bi-colour Ti /Bsm...z4m roadster Ess vt2-500....Perfection on wheels.
Beedub is online now   United Kingdom
Appreciate 0
Reply With Quote
      04-10-2013, 03:18 PM   #9
GuidoK
4
Some say...
 
GuidoK's Avatar
 
Drives: Z4 3.0i ESS TS2+
Join Date: Jul 2012
Location: Netherlands

Posts: 403
iTrader: (0)

Quote:
Originally Posted by yousefnjr View Post
I doubt the lines running the refrigerant have any cooling effect on under-hood temps.
The lines only get cold after the expansion valve/evaporator (which is located in the cabin heating unit). Before that they are ambient.
Only the lines after the evaporator might be coldish. The evaporator tries to absorb as much heat as possible though.
Everything else is hot in the ac system, and judging form the size of the average condensor there's a fair amount of heat to be dissipated (and gets both under the hood and directly heats the radiator (which is usually placed behind the condensor).

I think the only better performance with ac on is coming from the driver who can keep a cool head
__________________
Z4 3.0i | ESS TS2+ | Quaife ATB LSD | Custom Brembo BBK front/rear | Schrick cams | Schmiedmann headers/cats | Powerflex/strongflex PU bushings | Vibra-technics engine mounts | H&R anti rollbars | KW V3 coilovers
GuidoK is offline   Netherlands
Appreciate 0
Reply With Quote
      04-10-2013, 03:29 PM   #10
GriffBrew
2
Second Lieutenant
 
Drives: 2006 M Roadster
Join Date: Jul 2012
Location: Orlando, FL

Posts: 229
iTrader: (0)

Maybe gas without ethanol? I've seen mileage increases in other cars after leaving Florida, not sure if there are performance increases too.
GriffBrew is offline   United_States
Appreciate 0
Reply With Quote
      04-10-2013, 04:16 PM   #11
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

Quote:
Originally Posted by GuidoK View Post
The lines only get cold after the expansion valve/evaporator (which is located in the cabin heating unit). Before that they are ambient.
Only the lines after the evaporator might be coldish. The evaporator tries to absorb as much heat as possible though.
Everything else is hot in the ac system, and judging form the size of the average condensor there's a fair amount of heat to be dissipated (and gets both under the hood and directly heats the radiator (which is usually placed behind the condensor).
Thanks for breaking it down for me, my mind must be playing tricks on me
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
      04-10-2013, 06:24 PM   #12
3002 tii
88
Major General
 
3002 tii's Avatar
 
Drives: flat out
Join Date: Apr 2008
Location: NNJ

Posts: 8,477
iTrader: (49)

Garage List
I route the AC back to the intake
__________________

Recaro | Volk | AST | Vorshlag | Quaife | Stoptech | Active Autowerke | BMW Performance

Click here for my track videos
3002 tii is offline   United_States
Appreciate 0
Reply With Quote
      04-11-2013, 09:18 PM   #13
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

Quote:
Originally Posted by DSC_OFF View Post
I route the AC back to the intake
sweeeet
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
      04-11-2013, 09:22 PM   #14
gtMc
7
Captain
 
gtMc's Avatar
 
Drives: '08 MC
Join Date: Nov 2011
Location: NNJ

Posts: 703
iTrader: (1)

Garage List
'03 e39 m sport  [0.00]
'08 mc  [0.00]
Quote:
Originally Posted by DSC_OFF View Post
I route the AC back to the intake
really. ? i want to see it.
__________________
ZHP/Zeck CDV/VT engine mounts/RE trans mounts;clutch stop/Stubby
gtMc is offline  
Appreciate 0
Reply With Quote
      05-29-2013, 07:59 PM   #15
Gallardo Rosso
0
Enlisted Member
 
Drives: 2007 Z4M Coupe
Join Date: Apr 2013
Location: Philadelphia

Posts: 46
iTrader: (0)

I noticed a modest boost in highway MPG with the a/c on in 50-60 degree evening temps. Looking to repeat the experiment in 90 degree daytime heat. Also, my thermostat (gauge on dash) reads low around 180 when full warm... Maybe some correlation.
Gallardo Rosso is offline  
Appreciate 0
Reply With Quote
      06-11-2013, 06:45 PM   #16
Punko
2
Second Lieutenant
 
Drives: 07 Z4 M Coupe
Join Date: Feb 2011
Location: Hamilton, ON

Posts: 248
iTrader: (2)

Quote:
Originally Posted by ZStig View Post
MAGIC
I liked that way too much.
Punko is offline  
Appreciate 0
Reply With Quote
      06-11-2013, 08:04 PM   #17
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

Quote:
Originally Posted by Punko View Post
I liked that way too much.
Its funny re-reading it for me now
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
      06-11-2013, 09:07 PM   #18
mfanatic325
36
///M-fanatic
 
mfanatic325's Avatar
 
Drives: '07 Z4MC, '04 325Ci
Join Date: Oct 2007
Location: Cupertino, CA.

Posts: 3,683
iTrader: (20)

Garage List
Send a message via AIM to mfanatic325
I'm sure it was entertaining for everyone
__________________
VF570 S/C|TIAL BOV|SetRabCooler|Brembo GT 6/4|TE37s|NT05s|3.91 Gearing|TCK D/A|RPi Induction|SS Race Mufflers/X-pipe|JVT Headers|AS SSK|VibraTechnics Mounts|Sparco Pro2000/6pt.Harness|MS FloorMounts|SE Custom Harness Bar|Tekarbon Angels|M-Tech Pedals|OE Strut Bar|RE RSMs|8000K D2S|CDV DEL|CF Roof Wrap|MB Grills|UUC TrannyMounts/ClutchStop|V1 Mount|P3C Gauge
mfanatic325 is offline   Taiwan
Appreciate 0
Reply With Quote
      06-12-2013, 12:16 AM   #19
StickMon
17
My other car is on Mars
 
StickMon's Avatar
 
Drives: 2006 MR
Join Date: Feb 2011
Location: Lo-Cal

Posts: 1,452
iTrader: (0)

I notice that my exhaust note sounds a lot better with the air on.
(Because it's working harder to run the compressor)

Maybe it just sounds torquier with the air on.
StickMon is offline   United_States
Appreciate 0
Reply With Quote
      06-13-2013, 03:04 PM   #20
davesz4mc
2
Second Lieutenant
 
Drives: 2007 z4mc
Join Date: Feb 2012
Location: San Antonio, Tx

Posts: 274
iTrader: (0)

Go to the dyno!

Maybe the added load% remaps fuel/vanos to a diffrent map?
__________________
2007 Z4MC, 1" drop H&R Springs, Evolve Tunning, Headers, K&N Filter, RPI scoop, Red top high energy coils, UUC Red Poly mounts (none bolt-through), UUC Lightweight Flywheel with Organic Clutch and a custom exhaust with just one AeroTurbine muffler.
davesz4mc is offline  
Appreciate 0
Reply With Quote
      06-15-2013, 05:07 AM   #21
The__J__Factor
10
Major
 
The__J__Factor's Avatar
 
Drives: ///M Coupe
Join Date: Sep 2008
Location: Gold Coast, Australia

Posts: 1,028
iTrader: (0)

Ac steals power. when I dynoed my m it was only like 2hp difference but still a loss.
The__J__Factor is offline   Australia
Appreciate 0
Reply With Quote
      06-15-2013, 10:02 AM   #22
ZStig
72
Major General
 
Drives: VT2-525 M Roadster
Join Date: Jun 2008
Location: Delray Beach, FL

Posts: 7,227
iTrader: (3)

Quote:
Originally Posted by The__J__Factor View Post
Ac steals power. when I dynoed my m it was only like 2hp difference but still a loss.
thanks for the confirmation
__________________
ZStig is offline  
Appreciate 0
Reply With Quote
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
Forum Jump


All times are GMT -5. The time now is 09:26 AM.




zpost
Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
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