Pressure Sensors/Transducers, Plenum Pressure

[P. Jayaraman]

Hi everyone,

I was wondering if anyone had any recommendations on pressure sensors for monitoring plenum pressure while running our engine on the dyno. We thought of using an automotive MAP sensor at first, but we were told by an alumnus that such a sensor likely doesn't have a high-enough frequency for our purposes.

At the moment, I'm leaning towards piezoelectric-type sensors, but I'm having trouble finding a sensor that can accurately measure vacuum pressure.

Thanks!

[Drew Price]

As far as I understood, most OEM MAP sensors are piezoelectric, and I would imagine the sampling rate is dependent more on the driver than on the sensor in the MAP case.

I know that the Bosch sensors I have at work are piezo - you can see the quarts element through the barb, and then can come home with you from the junkyard in a pocket. (I ASSUME NO RESPONSIBILITY FOR YOU GETTING THE SHIT KICKED OUT OF YOU RUNNING OUT OF A WRECKING YARD IN SOUTHERN ILLINOIS)

MAP sensors often also have reduced orifices on the pressure side to damp the response on purpose to get some noise out of the signal.

While on that topic, the pressure signal in the plenum is by definition damped and desired to be steady-ish... it's there for it's stabilizing effect, not just cause you can put your team's sexy logo on them to make lesser teams jealous while you're waiting to get into tech....


What kind of sampling rate do you think you need? Are you going to tap runners to try to monitor the transient chaos that goes on in there? Cause that's totally different than monitoring plenum pressure....

[Hector]

We thought of using an automotive MAP sensor at first, but we were told by an alumnus that such a sensor likely doesn't have a high-enough frequency for our purposes.
What are your purposes?

If you're just trying to capture the average air pressure in your manifold at any given time an OEM solution should be fine. If you're trying to measure the individual pressure waves to capture the resonance frequency, you're going to need something faster. There's a thread on here about using a microphone and some professional engine software to filter our engine noise and capture the resonance.

[P. Jayaraman]

I'm actually continuing the research of our engine guys from last year (I studied abroad while they did part of it and they forgot to leave good documentation), so even I'm a bit confused, but I'll see if I can get my thoughts on it down.

I am aware of the plenum's use as a damper between the pressure waves in the runners and the restrictor; to that end, I could definitely see a standard OEM MAP sensor doing just fine in that we'd want to be reading a constant pressure. I think the goal here was to evaluate the plenum's effectiveness as a damper by measuring pressure fluctuation.

In this regard, it was recommended by an alumnus working at Caterpillar that we use a higher frequency sensor than the OEM. My impression is that we'd need to have data points at a frequency of about 2.2 kHz, or roughly 10 times the frequency of the engine at our redline.

I'll definitely look into the microphone technique in the other thread.

[Jimmy01]

Sounds to me like you have no idea why or what your doing here. Before you waste half of the year it would be worth making some higher level goals and then decide what you need to do/test in order to meet them.

I'm not sure why you need to know how effective a damper the plenum is unless you are trying to validate a simulation or something.
More important factors relating to plenum volume are peak power and throttle response, a high speed pressure transducer won't help you here. By the way- high speed pressure transducers caple of those sampling rates are F expensive.

[P. Jayaraman]

I am actually trying to validate simulations we've been doing in GT-Power and elsewhere. We've been simulating several differently-sized plenums because we completely changed our intake shape. I am aware that larger volume plenums lead to higher power and torque figures, which is why we plan on testing several prototypes on the dyno and attempting to gauge throttle response after installing it in a test car.

And yeah, finally got some word back from my professors here and it looks like it isn't worth it to look into this much more anyway considering cost and efficacy.

Thanks for the insights everyone!

[Steve Works]

You had quite a few interesting goals. How did it turn out?
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Steve Works
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