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      12-01-2008, 01:37 PM   #1
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Boost leak?!? NEED HELP!

hey everyone
this weekend i got my springs installed and after they were done i drove it around the block for the springs to adapt. but one thing i noticed was i wasn't boosting at 15 psi anymore(jbx) i was only peaking at 11 so i unswitched the X and i was only getting 8psi. today i decided to uninstall the jbx after i was done i drove around and now im only boosting at 5 psi..does anyone know what the problem is? im guessing my DC's are leaking...am i right? i had no CEL no errors no nothing what can be wrong?
thanks
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      12-01-2008, 01:52 PM   #2
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is it really cold outside?
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      12-01-2008, 01:56 PM   #3
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Quote:
Originally Posted by Sniz View Post
is it really cold outside?
like 34 F
your probably thinking i should warm up the car (i know i know) even when the engine temp is normal im still getting low boost
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      12-01-2008, 01:57 PM   #4
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doesnt the dme cut boost when its super cold?
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      12-01-2008, 02:35 PM   #5
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Quote:
Originally Posted by Crimson92 View Post
doesnt the dme cut boost when its super cold?
well i dont know about that and if that its true im sure its with temps under 20 F...and ive been running the car when its been colder out and this never happened
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      12-01-2008, 05:17 PM   #6
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its been under 40oF here for the past few weeks and i cant get my car past 6psi either. i am completely stock and i used to see 8psi+ sustained all the time. the only thing i can think of would be maybe my boost gauge needs to be recalibrated for cold temps? it is really bugging me, i have no clue what this could be but it just started happening.
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      12-01-2008, 05:31 PM   #7
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How's your mpg? That's a clear sign of a boost leak. If your running through gas faster than before, you probably have a leak.
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      12-01-2008, 05:37 PM   #8
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i really doubt the cold weather is causing it...wouldnt that be better for the turbos
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      12-01-2008, 05:43 PM   #9
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Quote:
Originally Posted by 335i82108 View Post
i really doubt the cold weather is causing it...wouldnt that be better for the turbos
thats what i was thinking also. my Mpg's have remained the same from when i had more boost so i dont think its a leak. maybe this will be a good excuse for me to get the new progman because i am pretty sure i have 29.2. also i want to let the dealer know about this boost shit before i put on my exhaust so they cant try and relate it to that.
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      12-01-2008, 07:51 PM   #10
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Quote:
Originally Posted by branabolic View Post
thats what i was thinking also. my Mpg's have remained the same from when i had more boost so i dont think its a leak. maybe this will be a good excuse for me to get the new progman because i am pretty sure i have 29.2. also i want to let the dealer know about this boost shit before i put on my exhaust so they cant try and relate it to that.
i think i might of found the problem...i posted the same thread on n54tech and terry and others said that cold air=dense air which has less oxygen which causes the turbos not to boost as much
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      12-01-2008, 08:07 PM   #11
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Quote:
Originally Posted by 335i82108 View Post
i think i might of found the problem...i posted the same thread on n54tech and terry and others said that cold air=dense air which has less oxygen which causes the turbos not to boost as much
Wow, that signifies the idiocy I often see there or maybe this was a typo. The denser the air, the MORE O2 is available. This is very much common sense to anyone that has taken 7th grade physical science.

The reason the DME reduces boost is to provide load compensation; less variation in power from winter to summer. This is most likely the case in what you are seeing. Also, remember, the DME will limit boost until the engine is fully warmed.

BTW, what springs were installed?
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      12-01-2008, 08:20 PM   #12
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Quote:
Originally Posted by scalbert View Post
Wow, that signifies the idiocy I often see there or maybe this was a typo. The denser the air, the MORE O2 is available. This is very much common sense to anyone that has taken 7th grade physical science.

The reason the DME reduces boost is to provide load compensation; less variation in power from winter to summer. This is most likely the case in what you are seeing. Also, remember, the DME will limit boost until the engine is fully warmed.

BTW, what springs were installed?
yea my fault typo
i got race springs
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      12-01-2008, 08:25 PM   #13
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Quote:
Originally Posted by 335i82108 View Post
yea my fault typo
i got race springs
No problem, happens to us all.

Then suspension springs and not diverter valve springs? If so then what you are seeing is normal and has to do with the load compensation I previously mentioned.
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      12-01-2008, 08:30 PM   #14
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Quote:
Originally Posted by scalbert View Post
No problem, happens to us all.

Then suspension springs and not diverter valve springs? If so then what you are seeing is normal and has to do with the load compensation I previously mentioned.
yea suspension..it has nothing to do with my problem but it was part of my story lol
and im guessing your right because thats what everyone else is saying...kinda sucks i like when i feel 15 psi
does anyone know if the hot pills will work?( i doubt it will) but it does hurt to ask
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      12-01-2008, 08:30 PM   #15
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Quote:
Originally Posted by scalbert View Post
No problem, happens to us all.

Then suspension springs and not diverter valve springs? If so then what you are seeing is normal and has to do with the load compensation I previously mentioned.
+1, that is what I was getting at earlier today. I have found that under 40 or so degrees i'm normally around 1.5 to 2psi below the boost targets. this is not a scientific study, just what I see when i'm actually paying attention.
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      12-01-2008, 08:32 PM   #16
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Its so great in the winter with lower psi making more if not the same power as in the summer months!!!
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      12-01-2008, 08:45 PM   #17
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Quote:
Originally Posted by 335i82108 View Post
kinda sucks i like when i feel 15 psi
does anyone know if the hot pills will work?( i doubt it will) but it does hurt to ask
The fuel demand would be significant to support 15 PSI, in sub-30 degree weather. Yes, you would have tons of power but wouldn't have traction until 3rd gear. Consider it a tire saving feature.
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      12-01-2008, 08:48 PM   #18
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Quote:
Originally Posted by scalbert View Post
The fuel demand would be significant to support 15 PSI, in sub-30 degree weather. Yes, you would have tons of power but wouldn't have traction until 3rd gear. Consider it a tire saving feature.
hahhah alright
3rd set of tires here we gooo lol
kidding
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      12-01-2008, 09:16 PM   #19
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Quote:
Originally Posted by scalbert View Post
The fuel demand would be significant to support 15 PSI, in sub-30 degree weather. Yes, you would have tons of power but wouldn't have traction until 3rd gear. Consider it a tire saving feature.
I can attest to that!!! I was running 15.4psi on a race gas map on 104 octane last weekend at the track, ambient temps were in the low 30's...I was making tons of power, but no traction even on drag radials until middle of 3rd gear . On that same map in 70 degree weather I should have been seeing 17psi or so. I was able to pick up 28mph in the 2nd 1/8th at the track, thats pretty damned good!

If I had been boosting to 17psi in that cold weather, well, I just dont know.
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      12-01-2008, 09:36 PM   #20
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Quote:
Originally Posted by scalbert View Post

The reason the DME reduces boost is to provide load compensation; less variation in power from winter to summer. This is most likely the case in what you are seeing. Also, remember, the DME will limit boost until the engine is fully warmed.
Makes sense that colder air will be denser and therefore require more fuel to maintain a given A/F ratio.

But does the colder air need a lower boost pressure to achieve the same power output as warmer air would?

Is that what you mean by load compensation?
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      12-01-2008, 09:39 PM   #21
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Quote:
Originally Posted by Ilma View Post
Makes sense that colder air will be denser and therefore require more fuel to maintain a given A/F ratio.

But does the colder air need a lower boost pressure to achieve the same power output as warmer air would?

Is that what you mean by load compensation?
yes
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      12-01-2008, 09:44 PM   #22
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i think it is what he means. lesser boost pressure with 30 degree ambient air temps can yield the same if not more power than hotter air temps boosting a few more psi. thanks scalbert for clearing that up, although it would be pretty sweet if i was still boosting the same pressure with this cold dry New Hampshire air!
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