So I'm getting ready to order/build my MS3X setup, and have decided I'd like to have realtime pressure correction, as I plan on doing a fair bit of mountain driving. My question before I place my order is, would just a standard GM MAP sensor from the junk yard with the appropriate resistors work just as well as the MapDaddy expansion at a fraction of the price? Since its MS3, the sensors wouldn't have to be identical. Searched around and couldn't find a definitive answer on this, so sorry if I missed it.

 

yes it should work, but how will you hit 30psi????

 

Yes.

I'm not even sure what you mean by "appropriate resistors." There should be no hardware deviation at all. The software comes with pre-loaded defaults for a few common GM sensors, you can also specify non-standard sensors by selecting "custom" and entering the 0v and 5v pressures:

 

Yes, this even works on the MS2 now, not just the MS3.

 

To be honest, I'm still not entirely clear on what, exactly, baro correction does. I've never looked that deeply into the code, but for an ECU running in speed-density mode, it's never quite made sense to me why you'd care what the ambient atmospheric pressure is...

 

You may still need an RC circuit for the analog input and a 0.1uF for the 5V rail. Definitely so on an MS2 or on a do-it-yourself MS3 if using ADC6 or ADC7.

Not needed if using an MS3x board and the SPARE_ADC, EGO2 or EXT_MAP inputs.

 

Reduced backpressure in the exhaust = increased VE.

 

Awesome, thanks. That's what i wanted to hear. I'm going to order a MPX4250AP from mouser with my Tyco connector and just use that instead of the mapdaddy.

Edit: I'll order the cap just in case. They cost just s few cents, better safe than sorry. I will be using a MS3X board though

 

Add the 0.1 cap between 5V and ground as close as possible to the MAP sensor.

 

So you would suggest still adding the cap with MS3X?

 

Yes, definitely.

 

Hmm.

That seems like an exceedingly trivial correction, inasmuch as the difference in magnitude between atmospheric pressure and the pressure inside the chamber after a combustion event. Like trying to compute how much rudder trim is necessary to correct the yaw orientation of an Airbus A-380 which has one dead mosquito stuck to the leading edge of the left wing.



Yup. And if you're working with a raw MPX4250, it's easy. Here's how I did mine on the MS3Pro: