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
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

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?
__________________
Appreciate 0
      04-09-2013, 09:59 PM   #2
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)

Sounds crazy but I've heard crazier, so you are probably normal.
Appreciate 0
      04-09-2013, 10:04 PM   #3
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)

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)
Appreciate 0
      04-09-2013, 10:10 PM   #4
Rated M Roadster
Captain
Rated M Roadster's Avatar
160
Rep
891
Posts

Drives: F10 M5, i3, Z4M
Join Date: Jun 2011
Location: PDX

iTrader: (9)

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

CURRENT ll F10 M5 l E85 Z4MR l I01 i3 REX
SOLD ll E70 X5M l E85 Z4MR VF570 l E36/7 Z3MR l E36 328i
Appreciate 0
      04-09-2013, 11:36 PM   #5
ZStig
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

MAGIC
__________________
Appreciate 0
      04-09-2013, 11:38 PM   #6
ZStig
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

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
__________________
Appreciate 0
      04-10-2013, 01:40 PM   #7
yousefnjr
salty cowboys fan
yousefnjr's Avatar
6112
Rep
3,392
Posts

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

iTrader: (2)

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
Appreciate 0
      04-10-2013, 02:19 PM   #8
Beedub
Major General
United Kingdom
423
Rep
5,327
Posts

Drives: 2007 Z4 M roadster vt2-500
Join Date: Sep 2007
Location: UK

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
__________________
Z4MR VT2 - Clubsport build.
Multi award winning Detailing | Wrap | PPF specialists UK based - www.topwrapz.com
Appreciate 0
      04-10-2013, 03:18 PM   #9
GuidoK
#buildnotbought
GuidoK's Avatar
10473
Rep
4,815
Posts

Drives: Z4 3.0i ESS TS2+
Join Date: Jul 2012
Location: Tinkering in the garage

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+ supercharger | Quaife ATB LSD | Brembo/BMW performance BBK front/rear | Schrick FI cams | Schmiedmann headers+cats | Powerflex/strongflex PU bushings | Vibra-technics engine mounts | H&R anti rollbars | KW V3 coilovers/KW camber plates | Sachs race engineering clutch | tons of custom sh#t
Appreciate 0
      04-10-2013, 03:29 PM   #10
GriffBrew
Second Lieutenant
United_States
5
Rep
234
Posts

Drives: 2006 M Roadster
Join Date: Jul 2012
Location: Orlando, FL

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.
Appreciate 0
      04-10-2013, 04:16 PM   #11
ZStig
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

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
__________________
Appreciate 0
      04-10-2013, 06:24 PM   #12
3002 tii
Lieutenant General
3002 tii's Avatar
2272
Rep
12,559
Posts

Drives: Z4 M, X5, GX460
Join Date: Apr 2008
Location: CT

iTrader: (99)

Garage List
I route the AC back to the intake
__________________
Follow for latest mods
Appreciate 0
      04-11-2013, 09:18 PM   #13
ZStig
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

Quote:
Originally Posted by DSC_OFF View Post
I route the AC back to the intake
sweeeet
__________________
Appreciate 0
      04-11-2013, 09:22 PM   #14
gtMc
Captain
gtMc's Avatar
21
Rep
704
Posts

Drives: '08 MC
Join Date: Nov 2011
Location: NNJ

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
Appreciate 0
      05-29-2013, 07:59 PM   #15
Gallardo Rosso
Enlisted Member
0
Rep
46
Posts

Drives: 2007 Z4M Coupe
Join Date: Apr 2013
Location: Philadelphia

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.
Appreciate 0
      06-11-2013, 06:45 PM   #16
Punko
Second Lieutenant
20
Rep
250
Posts

Drives: 07 Z4 M Coupe
Join Date: Feb 2011
Location: Hamilton, ON

iTrader: (2)

Quote:
Originally Posted by ZStig View Post
MAGIC
I liked that way too much.
Appreciate 0
      06-11-2013, 08:04 PM   #17
ZStig
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

Quote:
Originally Posted by Punko View Post
I liked that way too much.
Its funny re-reading it for me now
__________________
Appreciate 0
      06-11-2013, 09:07 PM   #18
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)

I'm sure it was entertaining for everyone
Appreciate 0
      06-12-2013, 12:16 AM   #19
StickMon
My other car is on Mars
StickMon's Avatar
United_States
635
Rep
3,124
Posts

Drives: 2006 MR
Join Date: Feb 2011
Location: Lo-Cal

iTrader: (1)

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.
Appreciate 0
      06-13-2013, 03:04 PM   #20
davesz4mc
Second Lieutenant
23
Rep
296
Posts

Drives: 2007 z4mc
Join Date: Feb 2012
Location: San Antonio, Tx

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.
Appreciate 0
      06-15-2013, 05:07 AM   #21
The__J__Factor
Major
The__J__Factor's Avatar
Australia
88
Rep
1,090
Posts

Drives: ///M Coupe
Join Date: Sep 2008
Location: Gold Coast, Australia

iTrader: (0)

Ac steals power. when I dynoed my m it was only like 2hp difference but still a loss.
Appreciate 0
      06-15-2013, 10:02 AM   #22
ZStig
instagram 997turbotom
279
Rep
7,376
Posts

Drives: Interlagos Z4MR
Join Date: Jun 2008
Location: Delray Beach, FL

iTrader: (4)

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
__________________
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 01:24 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