how does the stock boost control work with the ecu? and...

[azn2nr]

how does the stock boost control work with the ecu? and can i fiddle with it as in adjusting the the electrics somehow at the ecu (perfect power) to use is as a ebc?

[azn2nr]

32 views and nothing???

[Binford]

It's up to 42 veiws now, and sorry but I dunno how it could be done.

[vrg3]

The boost control solenoid decides whether pressurized air from the compressor outlet goes to the wastegate actuator or gets sent back to the compressor inlet.

The solenoid is driven at a constant rate with a varying duty cycle. A higher duty cycle means more air is bled off and so more boost is produced.

The ECU constantly etermines a target boost level based on a table indexed by engine speed an throttle position. It selects the duty cycle accordingly. There's some level of feedback in this control but it's not clear to me how the feedback works exactly.

I don't know what exactly you mean by "adjusting the electrics somehow at the ecu (perfect power)."

If the solenoid is electrically not present, the ECU will go into a failsafe mode where it prevents you from going on boost by cutting fuel.

You can trick the ECU into thinking the solenoid is still there by replacing it with a 200-ohm 1-watt resistor.

I would imagine any device designed to drive a duty solenoid to control boost pressure ought to be able to use the stock boost control solenoid.

[THAWA]

If the solenoid is electrically not present, the ECU will go into a failsafe mode where it prevents you from going on boost by cutting fuel.

I've been wondering how it does this. Does it just refernce other inputs and sees a situation where you should be on boost, then cut fuel?

[vrg3]

I don't know exactly how it decides, but it's probably something like when airflow exceeds what a 2212cc four-stroke motor would flow at 100% volumetric efficiency. Or maybe just when the pressure sensor reading goes above the barometric pressure reading the ECU had made earlier.

[azn2nr]

you kinda answered my question but to be more spesfic

The ECU constantly etermines a target boost level based on a table indexed by engine speed an throttle position. It selects the duty cycle accordingly.

this is what i want to focus on. the perfect power or any other piggy back works on adjusting signals from the engine to the ecu, the only problem is that i would probaly find major problems with adjusting what the ecu sees as engine speed and throtle position while fiddling with maf signal and cam sensors. so would it be possible to figure out what duty cycle the control solenoid goes into with each voltage or electric signal its seeing and use that to turn up the boost?

[vrg3]

You'll have a hard time changing boost levels by tweaking inputs into the ECU.

Doesn't the Perfect Power have the ability to drive a duty solenoid according to some kind of user-defined map?

[azn2nr]

im not too sure about if it has the ability to drive a duty solenoid but how if it could how could it do it without the ecu paying attention? the resistor??

also i wasnt talking about imputs to the ecu but from it to the solenoid. adjusting thoes outputs to the solenoid. i think the main problem wiht that is acutaly having to amplify the signal to the solenoid instead of lowering it. then again if it couldnt amplify the signal than how would it be able to drive the solenoid in the first place?

[vrg3]

Yes -- you'd hook the resistor up to the ECU and hook the solenoid up to the piggyback.

The "signal" to the solenoid is like that to the injectors -- the ECU switches the ground to close or open the circuit. It's not something you "amplify" or "lower."

It's possible that a piggyback could lengthen the pulse width, maybe. But then the ECU might just stop pulsing the solenoid altogether as it fails to control boost accurately.

[azn2nr]

i thought piggyback scaled back the maf signal to compensate for larger injectors. or am i wrong in that

[vrg3]

Depends on the piggyback, no?

[free5ty1e]

The 200-ohm resistor (or combination of resistors that results in 200-ohms with over 1 watt of power dissipation) works like a charm to trick the ECU into letting you do what you want with the solenoid. Vikash speaks the truth about the ECU not liking when it sees you mess with the solenoid

What you are asking for is being developed right now in the LegacEBC, which may or may not turn into the LegaCU if the resources for everything are available in one silicon wafer.

[rallysam]

I don't know exactly how it decides, but it's probably something like when airflow exceeds what a 2212cc four-stroke motor would flow at 100% volumetric efficiency. Or maybe just when the pressure sensor reading goes above the barometric pressure reading the ECU had made earlier.

I think it's more complicated than that. When you're in limp mode, it cuts fuel way before you start to get on boost. For example, it'll die at idle if you poke the throttle open more than roughly halfway - before the engine even revs up above idle speed. So, it must cut it based on throttle position among other things.

[vrg3]

You may be right. But realize that engine speed doesn't really factor into what I was saying... If you jab at the throttle you may get close to 1.1 liters of air per revolution even right off idle.

[rallysam]

Oh I see. You're right - the computer can divide the MAF signal by the RPM to see airflow per revolution. I was thinking that if it just looks at the MAF signal alone it would see that hardly any air is going by.