Does the motor use a MAP sensor? BOV performance question.

[EI]

Hello all,
I am looking to get myself an EcoBoost in the next few weeks, but have not had a chance to really get under the hood of one yet. Do these motors use a MAP sensor? I saw some videos of people removing the intake recirculation for atmospheric blowoff, but am wondering if it will effect performance as it does with MAF setups.

Thanks!
Dan

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[EcoSwag1990]

http://www.mustang6g.com/forums/showthread.php?t=19333

 

[EI]

I saw that thread just after I posted this, but do not see a mention of a MAP. The performance hit I was referring to is barely noticeable, so people may not realize. It simply causes the motor to run rich for a split second after closing the throttle plate because the metered air that the motor thinks it has is lost through the atmospheric venting.

I was just wondering if there was a MAP, as this would then typically negate that issue.

 

[MAPerformance]

You can vent to atmosphere it will not change the cars behavior. To answer your question the car is speed density, so it is MAP based. More than just 1 MAP sensor as well ;).

 

[EI]

Ok, great. Appreciate the reply. That is what I was looking for. So not an open filament at the intake filter location, and then a absolute pressure on the manifold then? It uses two~ absolute pressure sensors?

 

[arghx7]

I need to get a service manual with the right diagrams for the 2.3, but from memory there is a pressure sensor after the turbo plus one in the manifold.

For a more technical answer to your question:

The whole "MAF vs MAP/Speed Density" dichotomy doesn't apply so much to newer cars. In the old days, say a late 80s Ford or GM speed density system, you had simple lookup tables of rpm vs MAP to schedule spark and look up a volumetric efficiency for fuel calculations. Valve timing was fixed and load was controlled by a cable-actuated throttle, so volumetric efficiency was proportional to manifold pressure. On a MAF based system you had some kind of load calculation related to measured airflow divided by engine speed. Oldschool speed density or MAF are basically reactive systems.

Now the accelerator pedal requests an engine torque or a wheel torque/driving force (Bosch diagrams shown below),

rather than the ECU continuously reacting to some measured parameters. Valve timing can be continuously varied and engine load is controlled by this valve timing, the air fuel ratio, the boost, and the electronic throttle. There's a torque model

and a gasflows model (the successor to old simple speed density calculations)

used to calculate mass airflow in the air path, from airbox all the way to the intake port and then out to the exhaust ports for backpressure modeling. Changing the cam phasing changes the volumetric efficiency of the engine, so a few simple lookup tables of VE vs MAP vs Engine speed aren't accurate enough for a modern engine. There's all sorts of elaborate calculations involved.

So on modern controls like the Ecoboost uses, the ECU calculates mass airflow even if it doesn't have a MAF sensor, and if the engine does have a MAF sensor it's mostly used to correct the gasflow/speed density calculation or for some OBD purposes.

 

[Herr_Poopschitz]

arghx7, what reference are you using? Link? Link to book?

 

[EI]

I need to get a service manual with the right diagrams for the 2.3, but from memory there is a pressure sensor after the turbo plus one in the manifold.

I am rather familiar with how MAF systems work, I have owned and tuned give or take 20 240sx's. Sadly though, those are the newest cars I have ever owned as well, lol. I know the premise and over all how MAP based systems work, just never owned one yet. Hopefully soon I will get my EcoBoost though. : )

 

[arghx7]

arghx7, what reference are you using? Link? Link to book?

http://papers.sae.org/980801/

also, for a book you want http://www.amazon.com/Bosch-Automot...823&sr=1-1&keywords=bosch+automotive+handbook

don't get old editions of this book, they become quickly outdated.

 

[dabsevo]

I got a question, why does the WRX community advise against venting out to atmosphere on their cars? Apparently getting a BOV or having the stock one vent out to atmosphere causes weird things to happen and isn't good for the car. What's the difference?

 

[arghx7]

I got a question, why does the WRX community advise against venting out to atmosphere on their cars? Apparently getting a BOV or having the stock one vent out to atmosphere causes weird things to happen and isn't good for the car. What's the difference?

The amount of air entering the engine is measured with a mass airflow sensor on current Subaru engines. When you vent the air, the ECU basically gets confused. On the 2.3 Ecoboost engine, there is no mass airflow sensor. Mass airflow is modeled based on readings from other sensors (temperature, pressure, etc).

 

[MAPerformance]

I got a question, why does the WRX community advise against venting out to atmosphere on their cars? Apparently getting a BOV or having the stock one vent out to atmosphere causes weird things to happen and isn't good for the car. What's the difference?

Because they are too lazy to convert to speed density like I did on my STI ;) haha.

But, in all seriousness it is because they have a MAF that is anticipating the air from the stock bpv (and aftermarket) to re-enter the intake system post MAF. So it adds extra fuel for that air, but it never happens so the car runs rich and cause poor idle.

 

[dabsevo]

Ah makes sense. Sweet!

 

[EI]

I had mentioned why in my 2nd post I did in here, but I guess I wasn't specific, lol.

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