Stock Boost Question

[J-Sud]

I did some searching as I always hate to ask stupid questions.

I installed my P3 Boost guage last night, right now I am stock and my max boost levels have only been 6.5-7.5 PSI. which seems a little low to me for stock. I always heard 8 psi to be the number. FWIW temp is in the 50s, and I just got the car flashed at the dealer about a week or so ago....

Any input?

[Dackelone]

Test/measure it in 4th or higher gear(s). On a cold day you will get more boost than a hot day.

[stevenc]

^You might see less boost on a cold day because the air is denser and therefore it takes less boost to achieve a desired output. I dont know for sure, depends on how smart the BMW ecu is.

[J-Sud]

Originally Posted by stevenc

^You might see less boost on a cold day because the air is denser and therefore it takes less boost to achieve a desired output. I dont know for sure, depends on how smart the BMW ecu is.

That's what I was thinking. I was doing some high gear pulls too....6.8-7psi

[Thaddy]

Cold air plus being at sea level (almost!) are good conditions for a turbo charger. Honestly, I wouldn't worry about .5 psi. There are a lot of variables that can affect that number, one of them being the accuracy of your boost gauge. Unless it was reading 2-3 psi low, I wouldn't worry about it.

[J-Sud]

Originally Posted by Thaddy

Cold air plus being at sea level (almost!) are good conditions for a turbo charger. Honestly, I wouldn't worry about .5 psi. There are a lot of variables that can affect that number, one of them being the accuracy of your boost gauge. Unless it was reading 2-3 psi low, I wouldn't worry about it.

I hear ya. I just thought it was supposed to be around 8.5 psi max...and when in a high gear I'm getting 6.5-7psi it made me a bit worried...then again it may not need to hit as high of a boost target esp being 30ft above sea level

[Jeef Beef]

Like the others have said, those figures fall within the acceptable range so I wouldn't be too concerned.

[SlicktopTTZ]

This ecu decreases/increases boost to try to maintain even output regardless of ambient conditions.

In 50F weather, you can run MAP7 with just DCI (or even stock box) on 93 octane, and the pull over stock is AWESOME!

I pulled about 8 car lengths on a full bolt-on 350Z from 60-150mph with two passengers in my car last night!

[J-Sud]

Originally Posted by SlicktopTTZ

This ecu decreases/increases boost to try to maintain even output regardless of ambient conditions.

In 50F weather, you can run MAP7 with just DCI (or even stock box) on 93 octane, and the pull over stock is AWESOME!

I pulled about 8 car lengths on a full bolt-on 350Z from 60-150mph with two passengers in my car last night!

Just because im stock now doesnt mean i have always been

[RiXst3r]

Those numbers are exactly what you should be seeing.

As a general rule of thumb from all my samples for a stock n54...

Boost is raised and lowered based on temperature (and several other factors) to maintain consistent torque output.... ever notice how you can hear your turbos more on a hot day?

30F = 5-6psi
50F = 6-7psi
60F = 7-8psi
80F = 8-9psi
100F+ = 9-11psi

The more dense the air, the less of it that the turbos have to shove into the engine to get the same power.

-Rick

[Dackelone]

Hey J-Sud,

Are you running that digital vent boost gauge? IF so... I believe there is a calibrate mode for that gauge. You might try that and "retest".

When I ran a VDO analog boost gauge on a old car of mine... on really cold days (2' C or less) I could pull a few extra psi than on a warm or hot day (25' C). About two or three psi more.

[BahamaBart]

Florida 90 degrees using the P3Cars gauge -
stock, I get 9lb reads.
Jb+ @ 100% I get 13.8lb reads

[J-Sud]

Originally Posted by RiXst3r

Those numbers are exactly what you should be seeing.

As a general rule of thumb from all my samples for a stock n54...

Boost is raised and lowered based on temperature (and several other factors) to maintain consistent torque output.... ever notice how you can hear your turbos more on a hot day?

30F = 5-6psi
50F = 6-7psi
60F = 7-8psi
80F = 8-9psi
100F+ = 9-11psi

The more dense the air, the less of it that the turbos have to shove into the engine to get the same power.

-Rick

Thanks for the info Rick, great gauge btw, very well made. Looks completely stock and seems to be very accurate. Definitely recommended.

Originally Posted by Dackelone

Hey J-Sud,

Are you running that digital vent boost gauge? IF so... I believe there is a calibrate mode for that gauge. You might try that and "retest".

When I ran a VDO analog boost gauge on a old car of mine... on really cold days (2' C or less) I could pull a few extra psi than on a warm or hot day (25' C). About two or three psi more.

First thing I did

[jojo135]

Originally Posted by Dackelone

Hey J-Sud,

Are you running that digital vent boost gauge? IF so... I believe there is a calibrate mode for that gauge. You might try that and "retest".

When I ran a VDO analog boost gauge on a old car of mine... on really cold days (2' C or less) I could pull a few extra psi than on a warm or hot day (25' C). About two or three psi more.

The gauge is accurate. It is the car's ecu which is called the dme that makes it lower in the winter/colder weather. They wanted to mimmick a normally aspirated car when they made the n54 and this is how they made the car have very similar power levels in different climate. If it stayed at 9 psi or went to even higher psi in cold weather, the car would be significantly faster in the cold air. This is because the air is more dense in the cold just like rixter(the manufacterer of the gauge this person installed) said.

I have never loved the cold as much as now that I have a boosted car. Now that I have meth on it also, the car is scary fast.