SDS and MAP values

[Arif]

Can someone explain the theory of MAP values of the SDS. I made some changes to the stock settings and the engine responded better. I don't want to get too far into changes until I fully understand the relationship between fuel values and the MAP values. Also when I start the engine I get a bad stumble right off idle when I first start it. After it warms up the response is a lot better Any pointers on how I can clear that up

 

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http://communities.msn.com/TurboZ

 

[This message has been edited by Arif (edited December 07, 2000).]

[Guest Anonymous]

For the misfire when cold, set the cold start enrichment higher at those temperatures.

The map values are simply manifold pressure points. Changing the value simply changes the amount of fuel delivered at that manifold pressure.

 

 

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Morgan

http://z31.com/~morgan/s30

http://carfiche.com

[clint78z]

Ok I will give you the little overview on Air / Fuel managment

 

Mass Airflow: uses a hot wire and a temperature probe . When air passes by the wire it cools the wire and changes the resistance . If we know the volume of air and the flow, then the mass of air is calculated.

 

MAP (Manifold Absolute Pressure): This takes the pressure and temp are used . On a stock engine with no changes to exhaust and intake, the mass of air is known using calibration instruments. This is a very educated guess of the mass of air . When you change parts from stock the guess gets further off and ECU must be programmed . The MAP sensor gives a pressure, the pressure is related to how hard the engine is working . High Vacuum means engine is not working that hard, low vacuum means it's working very hard .

 

In order to tune your engine the mass of air must be known . Then to tune it you would use 14.7 lbs air to 1 lb of gas to set for a clean running car on the highway . For power when engine is working hard use 13 to 12:1 ratio .

 

Basically to tune a car with a map sensor what you do is look at the pressure reading and an O2 sensor . For high vacuum reading, adjust fuel to make 02 sensor bounce back and forth . For low vacuum readings make sensor stay on the rich side . 0 bar is high vacuum 1 bar is no vacuum . Math can be used to help guess at what to set fuel at .