New 3 Bar Map showing boost on factory boost guage at idle

[87GNALKY]

So one would think that going from 2 Bar MAP to 3 Bar Map would cause the factory gauge to show less than actual boost. Not the case with this one..
I T'd the vac/boost line to an external gauge and left the factory gauge as is. Now the factory gauge shows boost just above idle and max boost when the aftermarket analog gauge shows about 10-12 pounds. Any info on why this occurs? Both gauges pick up the vac/boost tube right off of the map side of the throttle body metal tube, pretty much where everyone taps the T in.

 

[pacecarta]

because the factory boost gauge sucks

 

[pacecarta]

key on engine off what is your voltage at green map signal wire (pin B)?

 

[87GNALKY]

because the factory boost gauge sucks

But this defies logic.. The factory gauge on a 3 bar should be somewhere around half of actual boost... If I hook the 2 bar back up it goes right back to it's normal inaccurate self but no boost at 1500 RPMs.. I think I may run the 3 Bar for the new gauge and Powerlogger and the old 2 bar just so my factory gauge still works.

 

[pacecarta]

screw logic .. 2bar map should have 2.5v key on engine off , a 3bar should be 1.6v ..what do you have ??

 

[87GNALKY]

key on engine off what is your voltage at green map signal wire (pin B)?

Haven't tried it yet but will. About to run a signal wire into the Power Logger and see what the deal is..

 

[pacecarta]

with the alkycontrol map harness you dont need to disconnect the 2 bar map to have a 3 bar , you just need to supply a vac/boost line to the 3bar

 

[pacecarta]

and since the factory analog boost gauge is supplying the 5v for the factory map sensor and that 5v is usually not what it should be... the 3 bar should not be run from the oe map plug on fender but rather source its 5v from the tps citcuit as the alkycontrol map harness does

 

[87GNALKY]

Yeah, Ima grab the TPS feed behind the glove box and see if that will fix it.

 

[Jerryl]

screw logic .. 2bar map should have 2.5v key on engine off , a 3bar should be 1.6v ..what do you have ??

New MAP may be 1 bar (?)

 

[earlbrown]

It's because the voltages at any given pressure/vacuum don't match between the 2 bar and the 3 bar.


For example 5#s of boost will have a different output between the two sensors. The 3bar isn't just a sensor that 'goes farther'.