I am somewhat new to turbocharging in general and I wanted to fully understand how the system works on a J-body. As we all know most GM vehicles use a Mass Air Flow Sensor.

Why is the FMU and electronic fuel management still nessesary with a MAF car? Is the ECU not capable of fueling enough by changing pulsewidth of the injector based on the MAF readings? If someone has a good full explination on how the overall system works in general, that would be very appreciated.

Thanks
Nick

I don't know what kinda car you have, but if its a J-body, then you don't have a MAF





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Well, it is not my car it is a buddies...I haven't really looked into it too much but my grand am was a Mass Air I just assumed that GM did the same for the J-body cars.

Nope.





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I didn't think that even any of the grand am motors had MAFs?



Cardomain|Myspace

because why would GM have tuning tables that go as far as they would have to go to account for boost if they're building a 170 hp NA motor? Just to be nice and make it easy on the enthusiast?




Arrival Blue 04 LS Sport
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Megasquirt
'Nuff said

These cars use MAP sensors or Manifold Absolute Pressure sensors. It senses the air pressure going into the engine and together with the IAT and TPS sensors determines how much fuel goes into the engine at any given RPM and engine load. The stock MAP sensor is only a 1 Bar sensor...which means it only sees 1 Bar or 14.7psi of air pressure at the most. 14.7psi happens to also be atmospheric pressure, so anything over atmospheric pressure - AKA boost pressure from any forced induction - it can't read.

Depending on the year of the car and the engine it has, you can get the PCM reflashed with GM's supercharger program which uses a 2 Bar MAP and larger injectors which will give you a starting point and allow the PCM to be able to read boost. Only problem is that the reflash is only good to a certain psi level...5-7 I believe (somebody correct me if I'm wrong). Anything more and you start maxing out those 310cc injectors and then you'll need larger ones and something to control them with.


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450WHP Turbo Ecotec swap in the works...

M I N I O N - Sinbird wrote:I didn't think that even any of the grand am motors had MAFs?

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they do, actually alot of GM's do use maf's...but jbody's obviously don't