[chetman7]

I read that stock boost pressure for the n55 is anywhere from 7-10psi

On my previous car I was running a td05-16g turbo at 20psi. Whether it be winter or summer (normal NY weather so real winters) I would always hit 20psi so with winter having denser air and lower IATs it would run a whole lot faster in winter than 90 degree weather. This was with a manual spring wastegate

I logged my 435ix via OBD today and did I bunch of WOT runs. Peak boost from 6.8 to 7.4 psi.

Just wondering how are people getting 10psi?

I am wondering with the electronic wastegate and with BMW stock tune that they tuned it for consistent output of power so in winter to hit "300lbs of torque" it only takes 7psi, and in the summer with less dense air and higher IATs that it will take 10psi to reach that output.

Would that be the correct way to reason it, or should I be checking for a boost leak somewhere

[MaxVasc]

As I understand it, you are correct in your understanding. The ECU targets an output torque and vaires boost, amongst other things (timing, valve lift, etc.), to reach that desired load. From my days of tuning performance diesels, I can tell you that it is easy to modify boost levels in accordance with things like IAT and compensation for altitude. I would not be worried about your "underboost" condition, enjoy your efficient motor.

[FC4]

Originally Posted by MaxVasc

As I understand it, you are correct in your understanding. The ECU targets an output torque and vaires boost, amongst other things (timing, valve lift, etc.), to reach that desired load.

LOL. No.

These cars run 7 PSI stock, 9 PSI with MPPK. Altitude, air density, temperature, alignment of the planets...doesn't matter. A set pressure is targeted and so long as you didn't fill the tank with water, that's what it will run. Your car is fine.

[MaxVasc]

Originally Posted by FC4

LOL. No.

These cars run 7 PSI stock, 9 PSI with MPPK. Altitude, air density, temperature, alignment of the planets...doesn't matter. A set pressure is targeted and so long as you didn't fill the tank with water, that's what it will run. Your car is fine.

I agree that his car is fine. But where are you getting this 7 PSI stock and 9 with MPPK? Mike at BurgerMotorsports says it varies, as did the OP and I. Is it unreasonable to think that the motor is smart enough to adjust for "constant" power like my 2001 unadvanced diesel did and like the M5 and M6 does currently?

[Mike@N54Tuning.com]

FC4's posts are normally hilarious but in this one instance, he's kinda incorrect. The BMW DME targets load not boost. Depending on barometric pressure, inlet temperatures, and some other factors, boost can range from 7-10psi for the same normal load target. On top of that the DME will vary its load target based on barometric pressure to make up for pumping losses, trying to keep power level across a wide range of conditions.

Mike

[Dosturbos]

Originally Posted by chetman7

I read that stock boost pressure for the n55 is anywhere from 7-10psi

On my previous car I was running a td05-16g turbo at 20psi. Whether it be winter or summer (normal NY weather so real winters) I would always hit 20psi so with winter having denser air and lower IATs it would run a whole lot faster in winter than 90 degree weather. This was with a manual spring wastegate

I logged my 435ix via OBD today and did I bunch of WOT runs. Peak boost from 6.8 to 7.4 psi.

Just wondering how are people getting 10psi?

I am wondering with the electronic wastegate and with BMW stock tune that they tuned it for consistent output of power so in winter to hit "300lbs of torque" it only takes 7psi, and in the summer with less dense air and higher IATs that it will take 10psi to reach that output.

Would that be the correct way to reason it, or should I be checking for a boost leak somewhere

Put a JB4 in there you will def hit some higher boost. Your car would freak out if you had a legit boost leak. It would go into half power mode and put up CEL right quick.

[F30_335]

I have MPPK. Maximum boost presure was 1.03bar=14.93PSI. Generally boost is 0.9bar=13PSI.

[MaxVasc]

Originally Posted by Mike@N54Tuning.com

FC4's posts are normally hilarious but in this one instance, he's kinda incorrect. The BMW DME targets load not boost. Depending on barometric pressure, inlet temperatures, and some other factors, boost can range from 7-10psi for the same normal load target. On top of that the DME will vary its load target based on barometric pressure to make up for pumping losses, trying to keep power level across a wide range of conditions.

Mike

Thank you for the information. I am always interested in hearing from people "in the know."

[roadcraftatx]

Hi

Im running bm3 stage 2 in my N54, and I am having some issues with the boost target... I´ve been trying to increased it using different tables like boost limit, boost set limit, and boost multiplier with no success. I cannot get more than 8 psi of boost target. Any advice how to fix this? Thanks

[harkes]

Originally Posted by roadcraftatx

Hi

Im running bm3 stage 2 in my N54, and I am having some issues with the boost target... I´ve been trying to increased it using different tables like boost limit, boost set limit, and boost multiplier with no success. I cannot get more than 8 psi of boost target. Any advice how to fix this? Thanks

You are trying to self-tune? Not to discourage you but the N55 DME is hugely complex with +200 tabels. If you dont have extensive experience tuning N54 then......well, good luck. One of THE BEST and most well known tuners in the business has so far spent 30 revisions on my car - food for thought.

[harkes]

Originally Posted by F30_335

I have MPPK. Maximum boost presure was 1.03bar=14.93PSI. Generally boost is 0.9bar=13PSI.

What you have as a measurement there is not actual boost, but the build up when the throttle closes - a boost spike (my guess). Try to see what boost is while WOT before you shift.

[JaredG_F30]

Agree with Harkes. You need to log at WOT to see what your car is targeting for boost.

Originally Posted by harkes

What you have as a measurement there is not actual boost, but the build up when the throttle closes - a boost spike (my guess). Try to see what boost is while WOT before you shift.

[XutvJet]

My stock tune M235 comes with the MPPK as stock. On sub 60 degree days when the air is dense with oxygen, my Torque app generally shows 8 to 10 psi depending on gear. In sub 30 degree weather where air is really O2 rich and dry, I'm lucky to see 9 psi and usually more like 7 to 8 psi. In summer temps of 80 and higher and with high humidity, I'll see 10 to 12 psi.

I have a 6MT and hard shifts can spike boost numbers by 1 to 2 psi. Meaning I've recorded up to 14 psi, but that's not realistic.

A stock tune non-MPPK EWG N55 is setup for around 8 psi in standard conditions. The MPPK EWG is around 10 psi. However, as you can see, the boost numbers are highly variable depending on load and atmospheric conditions.

Although these cars will generally make consistent peak power regardless of conditions, torque lag is far more prevalent as ambient temps and humidity increase. There's no way around it when the air is less dense with O2.