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      07-14-2011, 10:11 AM   #1
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Turbo Boost PSI

Hello,
I have been reading alot and have not seen any discussion regarding boost pressure? What is the stock psi?
Looking at the dyno charts of tuned 1m's there is no reference to boost psi at specific rpm's? I assume a "tune" also remaps the turbo psi at specific rpm's? - Is the boost psi electronically controlled in the N54?
Thanks - just trying to get educated before I take delivery of my 1m in a couple of months!
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      07-14-2011, 10:53 AM   #2
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I may be talking out of my ass here. But stock boost is around 9 PSI (8 on 135) and overboost cranks that to 12

And yes boost pressure is controlled by the DME


I'm doing this off of memory on a bus to Boston. Haha so forgive me if I'm wrong
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      07-14-2011, 10:55 AM   #3
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that's still an incredibly small amount of boost stock. My 95 3K VR4 was cranking 14 stock. So was my 2005 SRT4.
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      07-14-2011, 11:19 AM   #4
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Also... on a 135i the DME only has tables for boost up too 1bar... so that is why no one goes beyond that level. Other than the piggy backs that trick the DME anyways. As far as I know/heard... only Giac has done the proper DME line coding to make a "flash tune" run higher than 1bar (14.5 psi). I do not know what boost level a 1M runs... but 12 or 13psi is a safe bet.
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      07-14-2011, 11:33 AM   #5
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Quote:
Originally Posted by Daniel135i View Post
that's still an incredibly small amount of boost stock. My 95 3K VR4 was cranking 14 stock. So was my 2005 SRT4.


Boost is just a measure of backpressure. It is dependent also on CR, head flow, intake restriction or lack there of, etc, etc.
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      07-14-2011, 01:40 PM   #6
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Quote:
Originally Posted by Dackelone View Post
Also... on a 135i the DME only has tables for boost up too 1bar... so that is why no one goes beyond that level. Other than the piggy backs that trick the DME anyways. As far as I know/heard... only Giac has done the proper DME line coding to make a "flash tune" run higher than 1bar (14.5 psi). I do not know what boost level a 1M runs... but 12 or 13psi is a safe bet.
Thats why I hate/love new tech in cars... its great to be on the forefront of tech when it helps you, but hindering the tunability of the car like this is a gear heads worst nightmare.

I love the fact that I can wire in a EBC on any of my current cars, dial up the boost and go to town. These new restrictions just suck for us likeminded people.

If BMW wanted to ensure no tuners burnt out the pistons by upping boost and going lean, then they should put logging software into the DME, instead of restriction software. Just my .o2, but that would have been more enjoyable and beneficial on both ends. BMW would get to see the aftermarket stretch the limits with freedom and see where their engineering can go, then again have the backup of denying warranty work off of a retard who cant tune.
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      07-14-2011, 02:39 PM   #7
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I have done only 100km with my 1M so I have not yet done a full throttle but I have seen 105kPa (15.22PSI) with the ScanGaugeII connected to my 1M. That is about 1bar.

The picture is when idle.
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      07-14-2011, 07:48 PM   #8
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So it sounds like most of the "tunes" that are out there are only playing with a/f ratios and timing and available boost below 1bar due to the DME restriction? That seems kind of lame due to the control of "big brother"
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      07-17-2011, 04:50 PM   #9
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I had chance to check again.
There seems to be a limit of 120 KPa (17.4 PSI, 1.2bar) in the system.
No matter how hard I accelerate, it doesn't go over 120 kPa.

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      07-17-2011, 05:07 PM   #10
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I don't think your really seeng 17+ psi of boost.

It is possible that BMW's ecu measures in absolute. Meaning zero boost is 1.0bar. 14.5 psi would be 2.0bar. That was the way all German cars read boost pressure back when we had an analog boost gauge (Porsche's & Audi's).
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      07-17-2011, 05:39 PM   #11
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Thank you for clarifying. Indeed that is the pressure in the intake manifold. Not the boost pressure. So the boost pressure is 0.2bar in this case.

It seems that the system is controlling the intake manifold pressure, not the boost pressure. I also tried on a mountain road and it also displayed 120 kPa.

When not on the gas pedal, it showed 24kPa (3.28PSI, 0.24bar).


Last edited by KIYO; 07-17-2011 at 05:44 PM.
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      07-18-2011, 12:54 PM   #12
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What I remember from BMW is 0.8 Bar max on normal condition and 1 bar with the overboost.
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      07-18-2011, 05:04 PM   #13
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SHIT, SOMEONE JUST WIRE IN AN ELECTRONIC GAUGE ALREADY! Not that hard people. Get some t connectors and line into a vacuum tube, wire that shit hot and mount it.

Whats in my cars:

http://www.defi-shop.com/product/rg/rg_top.html
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      07-30-2011, 04:43 PM   #14
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Quote:
Originally Posted by Daniel135i View Post
SHIT, SOMEONE JUST WIRE IN AN ELECTRONIC GAUGE ALREADY! Not that hard people. Get some t connectors and line into a vacuum tube, wire that shit hot and mount it.

Whats in my cars:

http://www.defi-shop.com/product/rg/rg_top.html
The above picture was taken before my first service. I doubt the 120 kPa (1.2 bar) is not over boosted. Because I can get 120 kPa whenever I want.

I like the Defi gauges too.
After my first service, I will fit a Defi BF boost gauge and oil pressure gauge.
I have to search the wire for the illumination which has a constant 12V when lights are on. The license plate lights were constant 12V in the former cars but I am not sure if our license plate light has 12V since we have the LED lights. WDS online is not up-to-date.

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      07-31-2011, 03:13 PM   #15
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Personally, BMW should have mounted one in the car as standard... hell, my SRT had one standard lol.
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      07-31-2011, 04:52 PM   #16
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Quote:
Originally Posted by Daniel135i View Post
Personally, BMW should have mounted one in the car as standard... hell, my SRT had one standard lol.
+1000 many of us repeat it to Scott 26 but we haven`t get nothing
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      07-31-2011, 06:15 PM   #17
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I'd prefer have a water temp gauge and oil pressure gauge.

Boost is nice, but not as important as those two.

Neil
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      08-21-2011, 05:17 PM   #18
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Does anyone know how to initiate the over boost?
My understanding was it will be in the over boost status only for the first seven seconds after shifting with the gas pedal depressed all the way.

The pressure of the intake manifold of my 1M does not go above 1.2 bar (17.4 PSI) in the above situation. I can get 1.2 bar anytime when I depress the gas pedal.

It says in the manual that with the over boost function, it will get 0.8 bar (11.6 PSI) of boost. So my display should show 180kPa (1.8bar).

Page 13 of this manual.
http://www.1addicts.com/goodiesforyou/n54-2.pdf

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      08-21-2011, 05:30 PM   #19
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Quote:
Originally Posted by KIYO View Post
Does anyone know how to initiate the over boost?
My understanding was it will be in the over boost status only for the first seven seconds after shifting with the gas pedal depressed all the way.

The pressure of the intake manifold of my 1M does not go above 1.2 bar (17.4 PSI) in the above situation. I can get 1.2 bar anytime when I depress the gas pedal.

It says in the manual that with the over boost function, it will get 0.8 bar (11.6 PSI) of boost. So my display should show 180kPa (1.8bar).

Page 13 of this manual.
http://www.1addicts.com/goodiesforyou/n54-2.pdf


KIYO what kind of boost gauge are you using and where is it Tee'd into the engine?

From what I remember reading the over boost function only works when the engine is fully warmed up and in the low rev range. I think from 2K roms until 4.5K rpms. It doesn't work bellow or above those rpms - from what I remember. I have never seen any boost level quoted. Just a few psi more has been hinted.

0.8 Bar max sounds about right to me.
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      08-21-2011, 06:06 PM   #20
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Thank you for the input.
I did not check with the variety of RPMs so I will check again in a different RPMs.

It is a ScanGaugeII from Linear Logic which is connected to the OBDII port.
http://www.scangauge.com/products/scangaugeii/
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      08-21-2011, 06:27 PM   #21
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Quote:
Originally Posted by JHOOPS2 View Post
Boost is just a measure of backpressure. It is dependent also on CR, head flow, intake restriction or lack there of, etc, etc.
Incorrect. Boost is a measure of air compression, inside the engine's cylinders by the pistons. Backpressure has nothing to do with it, in fact, in turbo-charged applications we like to reduce backpressure in exchange of exhaust flow, in order to make the system more efficient and less restrictive.
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      08-21-2011, 06:34 PM   #22
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Quote:
Originally Posted by KIYO View Post
Thank you for the input.
I did not check with the variety of RPMs so I will check again in a different RPMs.

It is a ScanGaugeII from Linear Logic which is connected to the OBDII port.
http://www.scangauge.com/products/scangaugeii/

Ahhh... I kind of thought you might be using something like this. These OBD-II scan tools will not give you an accurate boost reading (from what I have read here). The (boost)numbers it shows are not 100% correct.

I think the only real way to figure out how much boost the engine is making is to Tee in a old fashtioned mechanical boost/vacuum gauge.

I am really curious as to how much boost a 1M runs. I know my engine tuner told me that the 135i's only have the line code (tables) to run 1bar of boost. That is why most engine tuners run 0.95 or 0.98 bar of boost. I think only GIAC has gone thru teh trouble of R&D-ing higher boost tables using the DME. of course the piggy tuners run way more boost but that is bc they are tricking teh ECU into running more boost pressure.

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