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I feel that an offboard MAP sensor should be the recommended install. I've tried both on-board and offboard. Despite many hours of trying to get acceleration enrichments correct I have found that a MAP sensor mounted close to the vacuum port makes a very noticeable difference in response. The reason for this difference is that the vacuum line adds a delay in the vacuum being sensed. If this adds 20ms then a stab at the throttle (ie rev matching) becomes slugish.
Acceleration enrichment can help this but there is no way to compensate with timing. Transitioning to atmospheric pressure from idle requires less advance. While some engines like to idle at low advance (ie 10-12degrees) others, ie Honda B series prefer 16-18 degrees. You can't keep 18 degrees of timing when you go from 30kpa to 100kpa at 800 RPM. The engine will stumble or die. Moving the map sensor offboard and with 3" of vacuum line corrected this problem. 3 standard sensors are made by GM and are universally used in the standalone ECU market. || GM Part Number || Sensor || || 12223861 || 3 bar || || 16254539 || 2 bar || || 16137039 || 1 bar || I like this MAP sensor because it has proven reliability and universal (in North America) availabilty. If your car breaks down on a road trip where are you or your customer going to find an mpx4250ap? |