Subpage of MembersPage/MarcellGal/PowerAndTraction
Since the precooler and postcooler tubing is done, it's time to connect the boostcontrol parts to get the car ready for tuning upto 210kPa (and than upto 280 kPa with the bigger injectors)
BoostControl is very important on this engine for several reasons
- first we tune with the factory injectors (and FPR), of the 3B engine. These injectors cannot handle the max power of the engine
- it doesn't sound like it makes much sense to tune with small injectors than upgrade and retune, but we want to be have a reasonable starting tables for a near-factory engine ("only" cooler is changed, and K26/27 turbo)
- the engine is still under break-in
- the general rule is to tune safely, go up little at a time
- a reasonably tuned boostcontrol makes the tuning runs much more reproducible. Eg. press throttle fully, and let the boostcontrol make sure the same MAP is maintained. This is nice when comparing runs with slightly different timing.
- boostcontrol makes the car more drivable, by adjusting boosttarget lower as the throttle is released a bit
Wastegate
The factory wastegate is used. It is suitable for much bigger airflow than the limit of the current K26/27 (appr 400 Hp)
We plan to connect
- MAP => bottom of the wastegate
- this means the wastegate is closed quickly when TPS is released (eg. gearshift)
- top chamber of wastegate, via 3-way solenoid
- to athmosphere when boost solenoid is unpowered
- to boost pressure when boost solenoid is powered
This would allow controlling boost in a reasonable range:
- from almost 0 boost (wastegate opening immediately above 104 kPa)
- up to extreme boost, when the exhaust pressure opens the wastegate despite the rather strong springs
- note that with solenoid duty=100%, both sides of the pneumatic actuator get virtually the same pressure (MAP=boost, at least when TPS=100%)
- however, at TPS=90% and below, MAP < boost, which would try to close the wastegate and raise boost => this unintentional positive feedback requires intervention from the boostcontrol electronics
The wastegate has 2 springs (these springs were out during the NA breakin). We'll see if the springs are sufficiently sized for the application.
Boostcontrol solenoid - pneumatic valve
The factory 3-way solenoid is available (greasy, but likely works). We also have boostcontrol solenoid from [webshop Pneumatic valve 3way]
Either should work.
Blow-off valve
A factory [BOV] (also called as "Bosch bypass valve" is installed to protect the tubes, cooler and compressor from pressure spikes when the throttle is suddenly released. Some claims that this valve cannot handle 1.8 bar boost. It's very hard for me to believe this - at least if the MAP hose is connected to the top of the BOV. Anyway, we'll see.
- inlet placed right before the throttle (good)
- out-tube vents to athmosphere. Since we have no MAF (to worry about "wasting metered air") this is allowed
- but it would be nicer to connect it pre-compressor. Will be possible after the airbox is made. With the cone-filter... it's not feasible.