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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Explanation of boost?



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      11-04-2012, 11:19 AM   #1
E93Blackhawk
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Explanation of boost?

Okay I'm going to get some flaming for this probably. Don't get me wrong, I absolutely am a car enthusiast and love the n54s design.

what I don't get is the concept of boost increase. I know it's measured in psi of course. And i know the n54s stock boost figures roughly.

But how does one 'increase boost'? Is it facilitated by an increase in bolt ons? Such as DPs, FMIC, DCI meth etc? Or how else do you increase boost?

I know you can have boost leaks? Which I presume is by something to do piping being loose letting pressure decrease?

Final question is how do you measure boost? I see everyone saying boost at x psi but how is that measured?

Thanks guys big help if you can answer the above
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      11-04-2012, 11:30 AM   #2
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-Wastegate Duty Cycle (WGDC) directly controls the amount of boost we produce on our wastegated turbo's. It is controlled via vacuum lines, which electronically controlled through the DME. What the bolt on's do (DCI and DP specifically) is reduce the amount of WGDC needed to produce the same amount of boost. This is because the turbo's are working less to achieve target boost, and won't need as high of a value of WGDC.

-You don't increase boost through bolt on's, it's increased through a tune. The factory DME will actually increase boost on it's own at higher altitudes, in order to reach the factory load target.

-If you have a major boost leak, the DME will throw an underboost code because it can't reach it's target. You have the right idea regarding boost leaks: Loose clamps/broken piping/pinholes/bad FMIC welds/and more can all cause a leak in boost, because pressurized air is escaping (Like a small hole in a balloon)

-The DME itself measures the boost pressure. You can install a boost gauge, install a supporting tune with logging capabilities/gauge hijacking, etc to monitor boost.

Hope this helps. Put the suit on, you will need it
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      11-04-2012, 11:51 AM   #3
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Per your question about boost measurements, PSI is the most common number used, pounds per square inch. 14.7 PSI is the amount of weight, or force that a one by one inch column of air from sea level to the end of the atmosphere exerts on a scale. For boost, that = 0, so anything more than that baseline is higher than the atmospheric pressure.
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      11-04-2012, 12:18 PM   #4
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You shouldn't be driving a car, honestly.
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      11-04-2012, 12:42 PM   #5
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Quote:
Originally Posted by cstavaru View Post
You shouldn't be driving a car, honestly.
Great response thanks.. what a waste of a post....

if you havent got anything positive or helpful to contribute with, then please dont make a comment.
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      11-04-2012, 12:46 PM   #6
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Quote:
Originally Posted by cstavaru View Post
You shouldn't be driving a car, honestly.
Also... you must be a complete degenerate, or have just not realised the point of a forum, is to ask questions, post up stories and generally make conversation without the need for those kinds of inflammatory pointless statements.

I posted it up to ask because i was unsure on the subject, i suggest you really think about what the concept of a forum is and think before you post your pointless stuff.

Im sure a several years ago you had similar questions to ask, so don't shunt people down for being inexperienced in areas that they are trying to learn about - hence why i joined the forum.

what a total fool you are.
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      11-04-2012, 12:46 PM   #7
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Quote:
Originally Posted by E90Company View Post
-Wastegate Duty Cycle (WGDC) directly controls the amount of boost we produce on our wastegated turbo's. It is controlled via vacuum lines, which electronically controlled through the DME. What the bolt on's do (DCI and DP specifically) is reduce the amount of WGDC needed to produce the same amount of boost. This is because the turbo's are working less to achieve target boost, and won't need as high of a value of WGDC.

-You don't increase boost through bolt on's, it's increased through a tune. The factory DME will actually increase boost on it's own at higher altitudes, in order to reach the factory load target.

-If you have a major boost leak, the DME will throw an underboost code because it can't reach it's target. You have the right idea regarding boost leaks: Loose clamps/broken piping/pinholes/bad FMIC welds/and more can all cause a leak in boost, because pressurized air is escaping (Like a small hole in a balloon)

-The DME itself measures the boost pressure. You can install a boost gauge, install a supporting tune with logging capabilities/gauge hijacking, etc to monitor boost.

Hope this helps. Put the suit on, you will need it

Thanks for the reply buddy, clarified it much more for me honestly.

Appreciate your time thanks.
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      11-04-2012, 12:54 PM   #8
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Boost = pressurized air,
Its measured by a pressure sensor which translates it into an electrical signal for the ECU to understand.
Bolt-ons increase the overall efficiency of the motor, either by cooling the pressurized air, reducing restrictions on the intake side or exhaust side.
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Originally Posted by E90Company View Post
-You don't increase boost through bolt on's, it's increased through a tune. The factory DME will actually increase boost on it's own at higher altitudes, in order to reach the factory load target.
Boost isn’t increased, the wastegates stay closed longer, to reach the same psi number, so you still get the same amount of boost but the engine has to work harder to get there.
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      11-04-2012, 01:01 PM   #9
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The term PSI is a bit misleading the way we colloquially use it. When we use the term "PSI" we're actually talking "PSIG"(manifold/charge pipe pressure with "0" being atmospheric pressure.)

Unless it is the Cobb guys talking in relation to Boost mean abs and Boost mean act, that's PSI. That's something I see people get confused about when looking at Cobb logs. They think 28psi means 28psig and that's not the case.
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      11-04-2012, 03:10 PM   #10
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+1 Great explanation.

OP next time try WIKI first.


Quote:
Originally Posted by Ænema View Post
The term PSI is a bit misleading the way we colloquially use it. When we use the term "PSI" we're actually talking "PSIG"(manifold/charge pipe pressure with "0" being atmospheric pressure.)

Unless it is the Cobb guys talking in relation to Boost mean abs and Boost mean act, that's PSI. That's something I see people get confused about when looking at Cobb logs. They think 28psi means 28psig and that's not the case.
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      11-04-2012, 03:18 PM   #11
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Think of it like a hairdryer, theres a low setting an a high setting, you control this through the buttons(electronically).
Well the turbos are the same way, through ecu tuning you can allow them to produce more boost( blow more air).
Where the hairdryer uses more electricity on the high setting to produce more air, the n54 will send more exhaust gases into the turbos to spin them faster and produce more boost.
Hope that helps a bit, theres more to it but that should give you an idea.
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      11-08-2012, 09:04 AM   #12
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Ive seen a post saying a member is only making x psi on JB4.

Yes it could have been a boost leak, WG issue etc.

But my question is does different maps on the JB4 create different psi levels?

Last edited by E93Blackhawk; 11-08-2012 at 09:18 AM.
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      11-08-2012, 10:30 AM   #13
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Yes, different maps allow different boost. On map 1 for instance you only have intakes therefore you will have alot of restrictions on the exhaust side (catalytic converters) and even on the intake side (oem fmic) as you take away these restrictions the car will "breath" better allowing you to up your boost to higher levels while "freeing" up the motor and allowing higher boost levels such as map 2 (downpipes, intake) and map 5 (full bolt ons +meth) and map 7 (race gas map)
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      11-08-2012, 10:48 AM   #14
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I'm not going to flame you OP, not everyone knows these things and sometimes the best thing to do is just ask. Since this topic is so general, and no offense, very simple. It probably can't be found by a search on this forum, although a search on google would probably do the trick.

What the above posters have said pretty much sums up the boost questions and how it is increased.

My contribution I wanted to add is that in the most general form, bolt on simply increase the efficiency of the engine. Increasing the efficiency will in turn increase the horsepower. For example a DCI increases the efficiency in which air can enter the engine and DPs do the same for air exiting the engine.

A tune will do more intricate things that you can learn in tuning threads on here. The Internet is a plethora of information on this, just read, it really is pretty fascinating how it works.
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      11-08-2012, 11:00 AM   #15
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Quote:
Originally Posted by zanelefko View Post
Yes, different maps allow different boost. On map 1 for instance you only have intakes therefore you will have alot of restrictions on the exhaust side (catalytic converters) and even on the intake side (oem fmic) as you take away these restrictions the car will "breath" better allowing you to up your boost to higher levels while "freeing" up the motor and allowing higher boost levels such as map 2 (downpipes, intake) and map 5 (full bolt ons +meth) and map 7 (race gas map)
This is not correct, boost level is dependent on turbo and wastegate cycle you can’t magically get more “psi” by adding an intercooler or intake or exhaust, mods allows the engine to operate more efficiently which will make more power at the same boost level but boost is not increased.
Lastly, the amount of boost that you can run is not dependent on mods as much as you the people who make them want you to think. In the N54 motor its all about octane.
Having stock exhaust and cats will make the engine work harder and run hotter, however if you are running 104 octane you will still make a target boost level of ~16psi you just won’t make as much power as someone who is running 16psi but is fully modded.
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      11-08-2012, 11:10 AM   #16
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Originally Posted by CHECKERED View Post
This is not correct, boost level is dependent on turbo and wastegate cycle you can’t magically get more “psi” by adding an intercooler or intake or exhaust, mods allows the engine to operate more efficiently which will make more power at the same boost level but boost is not increased.
Lastly, the amount of boost that you can run is not dependent on mods as much as you the people who make them want you to think. In the N54 motor its all about octane.
Having stock exhaust and cats will make the engine work harder and run hotter, however if you are running 104 octane you will still make a target boost level of ~16psi you just won’t make as much power as someone who is running 16psi but is fully modded.
Great points. Also, the N54 DME is load targeting, so running the same map with less restrictive intake/exhaust may result in running less boost because it can reach load targets easier.
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      11-10-2012, 08:28 AM   #17
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Thanks guys again. I've started to get my head around the tuning side of things also. Thing is that all of this stuff fascinates me, it's just a lot to learn.

One last question promise hehe

How do you measure psi levels of the engine? Stock boost levels are set I guess at a certain level.but how do you measure.

Does a meth kit increase psi levels?
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      11-10-2012, 12:31 PM   #18
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One more thing also, why does BMW, and generally car companies, make a engine, which restricts air flow and power? Obviously cats in place are for emissions, smell etc, but things like the headers, yes they can be catted and still deliver better flow?

FMIC for instance, why is the stock one so small? Surely a turbo motor would run more hot, and cooling would be preferable to a higher level?

The only real reason i think its that technically OEM parts make the engine run at the factory level it should be, for safety, safety of the tranny i guess also.

Sort of answered my question but just wanted your thoughts?
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      11-10-2012, 12:36 PM   #19
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Originally Posted by E93Blackhawk View Post
One more thing also, why does BMW, and generally car companies, make a engine, which restricts air flow and power? Obviously cats in place are for emissions, smell etc, but things like the headers, yes they can be catted and still deliver better flow?

FMIC for instance, why is the stock one so small? Surely a turbo motor would run more hot, and cooling would be preferable to a higher level?

The only real reason i think its that technically OEM parts make the engine run at the factory level it should be, for safety, safety of the tranny i guess also.

Sort of answered my question but just wanted your thoughts?
You've already pointed out one of the major reasons. Cost is the other. From the OEM's perspective why spend the money to develop parts that will outperform the car?
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