map sensors, diodes and increasing boost? AEB
#1
10-05-2010, 07:15 PM
map sensors, diodes and increasing boost? AEB
Okay so Ive been looking around, I noticed 00 and up can only do this "4.3v 1w zener diode thing on the maf. I have a 97, Is there anyway something like this would work? I really dont wanna spend the money on ECU tuning and/or not being able to have a car if the ecu were to be sent in to get tuned. Im not looking to go past 15 psi either. Please help me understand things. Thanks 
#2
10-16-2010, 10:44 PM
You can't do it because you don't have a MAP (manifold absolute pressure) sensor. On the 2000+ cars, there's a map sensor in the side of the intercooler that measures boost pressure. It sends a rising voltage to the ECU under boost, and at a specific voltage (roughly 5V, which in this car is set to correspond to stock boost level of roughly 9psi), the ECU signals the wastegate to open, limiting boost.
A zener diode is similar to a switch. At its rated voltage, it "turns on" (in the case of the diode mod, the specified 4.3v zener turns on at 4.3v) and splits voltage off, away from the boost-sense signal wire. In that way, the ECU never sees 5v and allows the wastegate to stay closed, so that boost can continue to build indefinitely.
This is good because you can significantly raise boost pressure. It's bad if you use it by itself, because you have no boost cut. In the first couple gears, you go through fast enough to not get into dangerous boost levels, but in the upper gears you can build way too much boost and throw the car into limp mode (best case) or throw the engine into "swiss cheese" mode (holes in the engine parts - worst case). Ideally, you'd run this mod along with a manual boost controller on the wastegate feed line and a boost gauge to set up the MBC around 18psi or so. That way, you defeat the boost cut from the map sensor, but you still have a boost limit due to the MBC opening the wastegate at your set level.
It's a moot point on your car though because you don't have a map sensor to trick.
A zener diode is similar to a switch. At its rated voltage, it "turns on" (in the case of the diode mod, the specified 4.3v zener turns on at 4.3v) and splits voltage off, away from the boost-sense signal wire. In that way, the ECU never sees 5v and allows the wastegate to stay closed, so that boost can continue to build indefinitely.
This is good because you can significantly raise boost pressure. It's bad if you use it by itself, because you have no boost cut. In the first couple gears, you go through fast enough to not get into dangerous boost levels, but in the upper gears you can build way too much boost and throw the car into limp mode (best case) or throw the engine into "swiss cheese" mode (holes in the engine parts - worst case). Ideally, you'd run this mod along with a manual boost controller on the wastegate feed line and a boost gauge to set up the MBC around 18psi or so. That way, you defeat the boost cut from the map sensor, but you still have a boost limit due to the MBC opening the wastegate at your set level.
It's a moot point on your car though because you don't have a map sensor to trick.
^^"
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