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      01-05-2013, 09:48 AM   #1
bdaddylo
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Max Boost in Cold Weather

Winter finally arrived in Texas. We're experiencing temps in the low 40's and I'm only seeing max boost in the 12 psi range.

Looks like the DME is lowering the max boost due to the lower air temp and increased air density. Is everyone else seeing the same max boost levels in cold weather?
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      01-05-2013, 11:14 AM   #2
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I think the better question to ask is if anyone else has a Boost gauge?

Are you measuring these readings at full throttle under full load? My Turbo cars have always performed better in colder weather.
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      01-05-2013, 01:09 PM   #3
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Quote:
Originally Posted by Redadair View Post
I think the better question to ask is if anyone else has a Boost gauge?

Are you measuring these readings at full throttle under full load? My Turbo cars have always performed better in colder weather.
I think it's pretty self explanatory. You can't quantify boost without a measuring device.

I'm taking boost measurements under full throttle/load on my P3. In ambient temps above 80F, I hit the 14.5psi overboost level, but can't in cold weather. Just trying to see if everyone else with boost gauges is getting the same results.
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      01-05-2013, 01:25 PM   #4
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Interesting to note that there is active boost management to help maintain similar power output in different temperatures. Probably nothing new but nice to know from someone's first hand experience. Wonder whether the same thing happens at high altitudes with turbo engines like the 1M's, as I'm aware that turbo engines cope better with decreasing air density than NA engines.
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      01-05-2013, 01:44 PM   #5
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I think you are spot on.

Increased oxygen content per volume of air, so lower boost to reach a targeted oxygen level.
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      01-05-2013, 01:50 PM   #6
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I don't think it's likely you were seeing 14.5 psi stock in the summer, I don't think I've logged 13 with stock tuning during over-boost? I assume something was going on with the way the pressure was being read. I think 12 is closer to the intended over boost? in time ill log what the stock programming targets.
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      01-05-2013, 06:21 PM   #7
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Quote:
Originally Posted by SpencerMH View Post
I don't think it's likely you were seeing 14.5 psi stock in the summer, I don't think I've logged 13 with stock tuning during over-boost? I assume something was going on with the way the pressure was being read. I think 12 is closer to the intended over boost? in time ill log what the stock programming targets.
Overboost varies depending on gear, speed, engine speed, etc., but max is 14.5psi and it's been well documented here.
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      01-06-2013, 09:49 AM   #8
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I wasn't aware it was that high, I run a jb4 so have logging capabilities as well as a boost gauge and I see 13psi as the stock tunings target psi in the mid range so I think you got lucky on something or it's a boost spike but I would think the high boost target would be stagnant and the boost you would see should be higher(closer to the highest programmed boost target) in cold weather due to being further from detonating, theoretically there should be a boost target and the dme would lower it or remove timing if the knock sensors told it too, so your predicament doesn't make sense to me, anybody really know why the op is seeing that? I don't think the denser air is the reason.
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      01-10-2013, 03:39 PM   #9
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I have noticed my max boost levels have been lower on my P3 as well in the colder weather. Max boost (from the recall on the P3 after a WOT 3rd gear pull) has been 2.0 to 2.5 psi lower.
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      01-10-2013, 04:46 PM   #10
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P3 pulls from the obd II right?

Just a suggestion but you may get an accurate answer quickly at www.n54tech.com vs here.
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      01-10-2013, 07:07 PM   #11
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For the N54, P3 pulls actual manifold pressure from a tap in the vacuum line to the diverter valves
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