Boost Targets and Colder Weather

nj335i · 10-09-2008, 08:39 AM

Here in NY/NJ, we've been seeing 50 degree lows overnight. I find that my car is only hitting 13psi when it is tuned for 15psi (Helix Attache). Not sure if it's my boost gauge that's off because I reset it recently though. I'm seeing -20 after the car is warmed up and idling, and that seems normal. Anyone else seeing lower boost in colder weather?

nj335i · 10-09-2008, 03:56 PM

Bump

darkphantom · 10-09-2008, 04:01 PM

-20 boost? I know NYC's been getting low 50s weather....here in houston, we get it down to about low 70s, high 60s and the car has been pulling strong nowadays

nj335i · 10-09-2008, 05:00 PM

Quote:

Originally Posted by darkphantom

-20 boost? I know NYC's been getting low 50s weather....here in houston, we get it down to about low 70s, high 60s and the car has been pulling strong nowadays

-20 in vacuum

Just wanted to see if other members with tunes are seeing lower peaks due to cooler weather...

Alex@AKMotorwerk · 10-09-2008, 05:00 PM

Quote:

Originally Posted by darkphantom

-20 boost? I know NYC's been getting low 50s weather....here in houston, we get it down to about low 70s, high 60s and the car has been pulling strong nowadays

I think he meant -20 "VACUUM" not boost. He is getting lower boost in the cold, but his vacuum is the same.

ontopofm · 10-09-2008, 05:07 PM

is there anything wrong if i only see -10 vacuum?

nj335i · 10-09-2008, 05:23 PM

Quote:

Originally Posted by nj323ci

I think he meant -20 "VACUUM" not boost. He is getting lower boost in the cold, but his vacuum is the same.

Alex, your car is looking great! It sure came along nicely!

End

ing of my own thread.

E82tt6 · 10-09-2008, 05:27 PM

Seeing the same thing with JB3, though I don't trust my boost gauge. It's been sitting further and further below '0' as time goes on. I have to get around to getting my VEI in.

Honestly, it feels fast enough that I might not be having low boost, and the gauge might just be tricking me.

Alex@AKMotorwerk · 10-09-2008, 05:31 PM

Quote:

Originally Posted by nj335i

Alex, your car is looking great! It sure came along nicely!

End

ing of my own thread.

Thanks bro

cwn23 · 10-09-2008, 07:45 PM

Quote:

Originally Posted by ontopofm

is there anything wrong if i only see -10 vacuum?

I think -19 to -21 is the normal value of vacuum when the car is at idle...Are you seeing these values? If not you may have a crimp in the tube where it reads it pressure from.

e.n335 · 10-09-2008, 11:03 PM

I see -21 vacuum @ idle, boost is about 1-1.5 psi lower on cold days ( 13.5 - 14 psi instead of ~ 15 psi ).

ontopofm · 10-09-2008, 11:07 PM

Quote:

Originally Posted by cwn23

I think -19 to -21 is the normal value of vacuum when the car is at idle...Are you seeing these values? If not you may have a crimp in the tube where it reads it pressure from.

oh shiet, i only see -10 max

scalbert · 10-10-2008, 07:42 AM

Quote:

Originally Posted by ontopofm

oh shiet, i only see -10 max

What is the scaling? -10 PSI or -20 inHG?

You may be reading in negative PSI and not the typical vacuum measurement of inches of mercury. The engineering units need to match.

bdkevoIX · 10-10-2008, 07:55 AM

Could be due to the increased density of the air and ecu compensation.

nj335i · 10-10-2008, 08:26 AM

Quote:

Originally Posted by e.n335

I see -21 vacuum @ idle, boost is about 1-1.5 psi lower on cold days ( 13.5 - 14 psi instead of ~ 15 psi ).

Quote:

Originally Posted by bdkevoIX

Could be due to the increased density of the air and ecu compensation.

So at least I'm not going crazy... But why wouldn't the tune take advantage of the denser air and still target 15psi in the colder weather?

cn555ic · 10-10-2008, 09:28 AM

Quote:

Originally Posted by scalbert

What is the scaling? -10 PSI or -20 inHG?

You may be reading in negative PSI and not the typical vacuum measurement of inches of mercury. The engineering units need to match.

I am pretty sure his guage reads psi...I think there has to be a crimp in his tubing!

ontopofm · 10-10-2008, 09:54 AM

Quote:

Originally Posted by scalbert

What is the scaling? -10 PSI or -20 inHG?

You may be reading in negative PSI and not the typical vacuum measurement of inches of mercury. The engineering units need to match.

mine is digital and it's only show the numbers, it's said on their website the reading range is -14 inHg ~ 45 PSI, so i guess the number is correct?

just got an answer from the Rep, it reads -psi during idle

scalbert · 10-10-2008, 12:04 PM

Quote:

Originally Posted by ontopofm

mine is digital and it's only show the numbers, it's said on their website the reading range is -14 inHg ~ 45 PSI, so i guess the number is correct?

just got an answer from the Rep, it reads -psi during idle

Just FYI, -10 PSI is about the same as 20 inHg vacuum so everythign is fine.

scalbert · 10-10-2008, 12:07 PM

Quote:

Originally Posted by nj335i

So at least I'm not going crazy... But why wouldn't the tune take advantage of the denser air and still target 15psi in the colder weather?

Consistency in power; it is really a preference thing. Some enthusiasts would want to extract ever bit of power out of it. Whereas most want it to run the same from summer to winter. Large swings in power output often make people feel something is wrong with the car so the manufacturers try and keep the relative output equal in all weather conditions.

ontopofm · 10-10-2008, 12:10 PM

Quote:

Originally Posted by scalbert

Just FYI, -10 PSI is about the same as 20 inHg vacuum so everythign is fine.

thanks

JOe335i · 10-10-2008, 02:56 PM

i thought boost goes up in colder weather? cooler air?

so boost drops in colder weather? rises in hotter weather?

rooster3.0 · 10-10-2008, 03:44 PM

I think any tune referencing AIT will have lower boost in cold weather. I could be wrong though.

10-09-2008, 08:39 AM	#1
nj335i Modaholic 88 Rep 1,705 Posts Drives: with 3 pedals Join Date: Jan 2007 Location: East Coast iTrader: (7)	Boost Targets and Colder Weather Here in NY/NJ, we've been seeing 50 degree lows overnight. I find that my car is only hitting 13psi when it is tuned for 15psi (Helix Attache). Not sure if it's my boost gauge that's off because I reset it recently though. I'm seeing -20 after the car is warmed up and idling, and that seems normal. Anyone else seeing lower boost in colder weather? __________________ Euro Delivery - April 2007
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10-09-2008, 03:56 PM	#2
nj335i Modaholic 88 Rep 1,705 Posts Drives: with 3 pedals Join Date: Jan 2007 Location: East Coast iTrader: (7)	Bump __________________ Euro Delivery - April 2007
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10-09-2008, 04:01 PM	#3
darkphantom Banned 595 Rep 5,946 Posts Drives: E93 335i Join Date: Aug 2007 Location: The place for Bimmers iTrader: (4)	-20 boost? I know NYC's been getting low 50s weather....here in houston, we get it down to about low 70s, high 60s and the car has been pulling strong nowadays
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10-09-2008, 05:07 PM	#6
ontopofm Lieutenant Colonel 76 Rep 1,548 Posts Drives: stock Join Date: Jun 2007 Location: CA iTrader: (4)	is there anything wrong if i only see -10 vacuum?
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10-09-2008, 05:27 PM	#8
E82tt6 Colonel 103 Rep 2,626 Posts Drives: '08 Black Saphire Z4 MC Join Date: Oct 2007 Location: New Jersey iTrader: (0)	Seeing the same thing with JB3, though I don't trust my boost gauge. It's been sitting further and further below '0' as time goes on. I have to get around to getting my VEI in. Honestly, it feels fast enough that I might not be having low boost, and the gauge might just be tricking me. __________________ '08 Black Saphire/Black Z4 M Coupe RIP Gretta: Blue Water/Lemon 135i. Died to save me. -ChuckV
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10-09-2008, 11:03 PM	#11
e.n335 Moderator 270 Rep 4,481 Posts Drives: e93 ///M3 DCT, 07/2009 Join Date: Feb 2007 Location: Switzerland, ZH iTrader: (0)	I see -21 vacuum @ idle, boost is about 1-1.5 psi lower on cold days ( 13.5 - 14 psi instead of ~ 15 psi ).
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10-10-2008, 07:55 AM	#14
bdkevoIX Captain 18 Rep 739 Posts Drives: 06 Evo IX Mr Join Date: Mar 2008 Location: Maryland iTrader: (0)	Could be due to the increased density of the air and ecu compensation. __________________ 03 Golf TDI w/ r32 conversion - 120bph/40mpg ftw for now.. 06 Evo IX MR - 500whp,,,sold.....
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10-10-2008, 02:56 PM	#21
JOe335i Lieutenant 28 Rep 525 Posts Drives: R32-08STI-e92335i Join Date: Feb 2007 Location: AUSTRIA iTrader: (0)	i thought boost goes up in colder weather? cooler air? so boost drops in colder weather? rises in hotter weather?
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10-10-2008, 03:44 PM	#22
rooster3.0 Major 27 Rep 1,306 Posts Drives: E92 335i Join Date: Nov 2006 Location: Jersey iTrader: (4)	I think any tune referencing AIT will have lower boost in cold weather. I could be wrong though.
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