MAP Sensors

 I plan to supercharge my BMW M30 engine and need to know the characteristics I can expect from the Bosch D Jetronic MAP sensor when the manifold pressure  goes positive - up to 1.5 bar abs.  I am assured by an ex Jaguar test engineer that the MAP sensor can comfortably tolerate that pressure without damage but I need to know whether the signal going from the MAP sensor to the ECU will continue to have a linear characteristic in the 1 to 1.5 bar abs  pressure range.

Hi Steve,

this Jaguar ex test engineer is wrong. A MAP sensor cannot tolerate 1,5 bar pressure. Especially not type 2 ones as in your BMW. Diaphragm will not withstand that pressure for long. And your MAP sensor has a full-load stop at 0 bar. So full-load curve will not continue on positive pressure. Of course aneroid cells will further shrink. Could also be that they will be damaged.

Summary: Bad idea!

Hi Steve,

sorry if I have to ask again. 1,5 bar means absolute pressure or pressure over environemental? If it is 0,5 over environment: Then I guess diaphragm will not tear as it can also hold -0,5 bar vacuum, But as it has a certain embossment I cannot gurantee. But diaphragm would not further contribute to enriching fuel mixture. On the other hand aneroid cells will be in a higher pressure than specidifed. Never tried that so I cannot say whether t will be linear in 1,0 to 1,5 bar and whether it will not be damaged as cells are compressed beyond spec.

So you have 2 options:

1. Try and take the risk that your MAP sensor will fail. If worst comes to worst I have a 0280100030 here.
2. Forget the idea and avoid the risk

Thanks for picking up on my question. Gives me confidence to be speaking to someone who knows what they're talking about.
I am already running the car supercharged and yes I did mean 1.5bar absolute, in fact I am actually running 0.4 bar of boost. . I have fitted a wideband A/F lambda sensor which reads a comfortable 14.5:1 at idle and 12.5:1 at high revs on full load.
Occasionally the A/F ratio drops to around 11:1 on part throttle (not good) which may be due to the MAP sensor, or worn injectors passing too much fuel or the 75 degC inlet air temp (there's no intercooler) but otherwise the system has been working well for 3 years now.
I remain concerned however it may not be long before the MAP sensor fails due to the positive (over atmospheric) pressures.
I have a spare MAP sensor which came to me in a box of old BMW bits and it would be good know if is working correctly. What would be your charge to test it?

Volker

I should add , for your info, that the spare MAP I have sensor is type 0 280 100030

Hi,

all BMW MAP sensors are 0 280 100 030. BMW / Bosch decided to make subversions by color points. Unfortunate but that's how it is.