Thread: TD5 MAP sensor...how high will it read?

It's not reading air density that I can see.

The flow i have traced in the ECU code is:

Sensor -> ADC -> limit checking -> scaling from ADC output to decapascals

The value in decapascals is then used for internal calculations. Air density is used as part of the calculation of cylinder filling but the value is calculated using ambient pressure, ambient temp (eu3), MAF, MAP and IAT and is a significantly different value to what the MAP reading reports.

The MAP on the Td5 has a small vacuum chamber which provides a reference for 0kpa and allows the sensor to determine absolute pressure. The sensors are temperature compensated and should read within 2-3% of actual manifold absolute pressure if they are in good condition.

Do you know what your boost gauge is referencing it's reading to?

Cheers
Paul

Originally Posted by djam1

I have the boost gauge on the small line running to the VNT actuator.
The differences in results were an eye opener when I put it in because I always did things by the Nanocom pressures.
There can be quite significant pressure changes that are barely acknowledged by the Nanocom.

Part of the issue is that the Nanocom updates logged data once a second, so you are only seeing a tiny fraction of what is being processed by the ECU. The ECU seems to hold the 100kpa reading for a second or two after overboost occurs so I use that an indicator of overboost than looking for peaks over 1.42bar.

cheers
Paul