PeachParts Mercedes-Benz Forum - View Single Post - Bosch air flow meter potentiometer N.L.A.....

dpetryk · #12 05-08-2007, 10:59 AM

I have tossed this one around in my head for a while now. Here are my thoughts.

The MB pot arrangement from what I can understand measures the position of the air mass flow device. The signals are processed by the computer to determine the rate of change in airflow. As you stomp on the accelerator, air flow increases, computer translates this into a shot of fuel to get things moving. It is analogous to the way carbs shoot fuel directly into the manifold when you stomp on the accelerator. Under normal driving conditions where the accelerator moves slowly, the POT does not really have much effect.

A Manifold Absolute Pressure (MAP) sensor measures manifold pressure. Modern computerized engines monitor RPM and MAP then using these values as an index into a "fuel map" the computer determines how much fuel should be injected.

If we replace the MB pot with a MAP and do the appropriate electrical interface so that the MB computer "sees" the same input I don't think it would work like it does now. Take the scenario where the engine is at idle and you floor it. Now the engine is at wide open throttle (WOT) but at very low RPM there is very little air flow and there is NO manifold pressure. Initially the signal would jump up as the manifold pressure is lost but then it stays there as the engine begins to wind up. There would be a initial short shot of fuel then nothing. I think the engine would stall or hesitate or not have much power.

I think a better solution would be to make a module that monitored RPM and MAP then fed a signal to the MB computer. It would be more involved but could provide a customized response to the MB computer and could be tuned as needed. Using a microprocessor you could "map" the response and make it totally programmable.

If there is a market for such a device I could design and build them. Any ideas on how many could be sold? Is seems to me that in the grand scheme of things the market segment would be to guys like yourself who like to tinker with their cars.

Any thoughts?