Schuyler

iTrader: (1)

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.

soviet

iTrader: (10)

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

Joe Perez

iTrader: (8)

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:

Reverant

iTrader: (10)

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

Joe Perez

iTrader: (8)

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...

Reverant

iTrader: (10)

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.

Reverant

iTrader: (10)

Reduced backpressure in the exhaust = increased VE.

Schuyler

iTrader: (1)

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

Reverant

iTrader: (10)

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

Schuyler

iTrader: (1)

So you would suggest still adding the cap with MS3X?

Reverant

iTrader: (10)

Yes, definitely.

Joe Perez

iTrader: (8)

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: