Dump valve =? blow-off valve
Turbo timer?
Boost control?
EGR?

Could someone please tell me the function of the above things? I know how a turbo works, but apparently not well enough. TIA.

 

Dump Valve=BOV=Blow off valve: This device purges boost in the pressurized portion of the intake ducting when boost levels reach a certain point. What happens is that when the engine is under load making boost, and you go to shift the car, you momentarily close the throttle body. When you do this the boost level spikes between the compressor wheel and the throttle body. If the BOV wasn't present, this would cause some erratic behaviors when the throttle blades were re-opened, as well as being very hard on the compressor wheel in the turbo. On cars with atomosphericaly vented BOVs you will hear that Psst or whistle sound at each shift. That's the BOV purging the excessive boost.

Turbo timer: This is a device that keeps the motor runningn after you exit the vehicle to ensure that oil is circulated through the turbo after shutdown. On some models of turbocharged vehicles, the ambient temperatures in the turbocharger oil passages is are hot enough to "coke" oil if it was left to sit, or basically break it down removing solids from the oil. This "coked" oil will then play hell on the bearing surfaces which as you can imagine are extremely important to a device spining tens of thousands of RPM when under load. The timer basically keeps the motor running (thus cirulating oil) until the temperatures have dropped sufficiently to avoid coking any oil that will be left to sit in the oil passages of the turbo.

Boost controler: Does what it says, regulates the amount of boost that can be left in pressurized side of the intake ducting for a given RPM or load condition

EGR=Exhaust Gas Recirculation: A method of emissions reduction whereby exhaust gases are recirculated through the engine under certain conditions to assist in a cleaner burning engine/lower emissions.

Hope that helps,
Chris

 

Thanks Chris, very helpful. Are the blow-off valves then controlled electronically through a boost controller? Are all blow-off valves like that or are some of them simpy set to a fixed value and cannot be changed?

 

blow off valves are generally mechanical devices with a spring, the user then turns a screw or something similar to change the spring rate and therefore the psi at which the valve opens.

 

Ok, I'm confused... how does the boost controller interface with the blow-off valve?

 

Its all a mechanical system, and manual boost controller bleeds off pressure (before the wastegate sensor, usually, not the BOV) which results in higher actually boost pressure.

This in turn affects the BOV since there is now more pressure in the system, and it will also need to deal with it, how ever it needs to be done.

 

if you turn up the boost with a boost controller, you'd need to adjust the BOV accordingly.