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  #1  
Old 12-08-2015, 01:47 PM
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Boost info 35d

Just curious if anyone knows of any way to find/display boost data. I would imagine some computer in this vehicle HAS to be reading the amount of vacuum and boost it is producing. Which also means there HAS to be a way to see that information (I would hope) without having to install a gauge.
Really, I'm just curious how much boost it creates in different scenarios, such as towing. Any info, is appreciated, thanks, cheers!
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  #2  
Old 12-08-2015, 02:39 PM
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Get a Bluetooth dongle and OBD Fusion app, you can see boost and many other parameters live. App was $5 when i got it few months back. Also reads codes, deletes codes, logs data and many other features.
Ill have to check mine but i think i was getting 20lbs when i get on it.
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  #3  
Old 12-08-2015, 02:49 PM
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Max absolute manifold pressure I've seen is right below 3bar. No vacuum on diesels (unless you're idling during regen).

Boost isn't really that meaningful of a variable to assess engine load in a diesel since it generally throttle fuel, not air. Better parameters are rail pressure maybe coupled with EGT (although with the emission systems EGT becomes a bit more tricky).
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Old 12-08-2015, 03:07 PM
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yea the bmw stock DME doesnt target boost, it targets load.
I have a cobb tune and even with that it is the same thing.
i get higher boost if i 3/4 press the throttle than when WOT, but load is not at maximum
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  #5  
Old 12-08-2015, 03:32 PM
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I'm new to diesel engines; it would seem to me the greater the load the more boost the engine will require to maintain a certain power output for a given request?
I don't question the fuel rail would be a good means to assess this, but for ease of information, wouldn't boost be an "easier" way to observe the same outcome?
Fuel Rail psi should be an input and boost would be the outcome?
I'm glad I asked this question...
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  #6  
Old 12-08-2015, 03:37 PM
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Quote:
Originally Posted by G550Mech View Post
I'm new to diesel engines; it would seem to me the greater the load the more boost the engine will require to maintain a certain power output for a given request?
I don't question the fuel rail would be a good means to assess this, but for ease of information, wouldn't boost be an "easier" way to observe the same outcome?
Fuel Rail psi should be an input and boost would be the outcome?
I'm glad I asked this question...
not necessarily true.
the DME decides what the best way to get optimal load.
Depending on where in the power band, and how much throttle, and many other factors, fueling can be used to create more load, hence why i said at WOT my boost is lower even though i have higher load.

Also note that BMWs LOVE to close the throttle body to prevent traction loss and to maintain a smoothness of the power band.
even with traction control off!
my biggest tuning hic-up was to stop the throttle from closing.
this is also a huge issue with using boost pressure to get any sense of load.
when the throttle body closes, the boost pressure is surged inside the chargepipe, so PSI will be greater, but its not getting into the engine, as the throttle body is partially closed, so it is sort of "ballooning" in the Charge pipe.
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Old 12-08-2015, 04:00 PM
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I use this http://www.amazon.com/ELM327-Version...eywords=elm327 along with Android app Torque. BMW Carly is also good and available for iphone (with wifi dongle, does not work with bluetooth) and android.

Watching boost I mostly see 23psi. The diesel is under boost more often than I would have thought.
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Old 12-08-2015, 04:19 PM
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Quote:
Originally Posted by G550Mech View Post
"easier" way to observe the same outcome?
What is it you're trying to observe?

If it is torque requested than you look at throttle position because, well, the throttle is how you request torque

Torque delivered is very tricky because there are a lot of variables to include. To make your life easier the DDE does all the calculation and provides you with a calculated torque figure through one of the PIDs available via OBD.

I go back at say that being a diesel engine, rail pressure is a better indicator of torque delivery since conceptually a diesel engine throttle fuel not air. And rail pressure is the primary way to do that.

HOWEVER it isn't that simple.
1) you have EGR duty cycle (2 of them) affecting it
2) you have pilot injections affecting it
3) you have boost and turbo switch over
4) you have torque management to protect the transmission

Unless you correctly factor those and many other variable in your analysis, you won't get a good sense of the torque output... That's why if that's what you're after, the calculated torque PID that the DDE reports is a better value to observe. It is calculated and by that it means that the DDE has done the math for you given all the parameters it is controlling.

In the old gasoline engine with manifold injection you look at TPS and figure load. Now even gasoline engine with variable valve lift, boost and stratified injection you can't simply look at MAP and asses load...
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  #9  
Old 11-20-2023, 11:18 AM
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Getting a code 4530 but it doesn't make sense

Quote:
Originally Posted by ZetaTre View Post
Max absolute manifold pressure I've seen is right below 3bar. No vacuum on diesels (unless you're idling during regen).

Boost isn't really that meaningful of a variable to assess engine load in a diesel since it generally throttle fuel, not air. Better parameters are rail pressure maybe coupled with EGT (although with the emission systems EGT becomes a bit more tricky).
I have an issue with my 2011 X5 35d.

It keeps going into limp mode.

I bought it wholesale from a mechanic when he and the customer couldn't reconcile.

The issue is it goes into limp mode and gives codes 4530, 3FF0, 4865.

It builds plenty of power but goes into limp mode at about 35mph.

The car has been smoke tested twice and has alot of parts thrown at it. ie. new MAF,MAP, fuel rail and pump, and I replaced all the vacuum lines and pressure converters and swiched the EL valve under the pressure converters.

I did a swirl flap delete and replaced all the intake manifold gaskets and removed the valve cover and replaced the valve cover gasket. It had CBU in the Intake and valve cover but the valves themselves looked fine.

Your quote about the car targeting fuel and trottle positon instead of boost has me curious.

When I put my torque app on and look at the PIDs for BP and BP Commanded it says the following.

It has a BP-A and BP-B which I assume means the large and small tuirbo.

BP-A never moves from 4.6psi but my BP-A commanded goes up and down with as I give it throttle.

BP-B reads -1.2psi and BP-B commanded reads -1.2

Now the interesting thing is my exhaust Temp reads 31degrees F and never changes.

So following your logic since the EGT isn't being read the car thinks that there is no boost but in reality it is building boost which could make it throw the 4530.

Does this make sense?
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  #10  
Old 11-20-2023, 12:45 PM
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Image of PIDs

CACT is charge air I don't have a PID on exhaust but I can see it on my scanner
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