HKS downpipe
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Joined: Feb 2003
Posts: 488
From: 12.9 / 105+
Car Info: black my03 5mt wrx s/w
Originally posted by BAN SUVS
The wastegate remains closed until after the turbo has fully spooled and boost is reached.
The wastegate remains closed until after the turbo has fully spooled and boost is reached.
ever hear wastegate flutter?
that's the WG opening way before it's "supposed" to.
jm2c
ken
VIP Member
Joined: Feb 2003
Posts: 488
From: 12.9 / 105+
Car Info: black my03 5mt wrx s/w
Originally posted by BAN SUVS
That's a broken or failing part.
That's a broken or failing part.
the wastegate is held closed by a spring, not a solenoid that switches on and off in a binary state.
the spring's tension must be overcome by the gas pressure differential across the wastegate actuator before the wastegate starts to crack open.
the thing is, this does not occur suddenly and completely.. it is a gradual process.
as the pressure starts to rise across the actuator, the spring will start to have less and less effective pressure. at wastegate spring pressure, the two forces have cancelled each other out and the wastegate is free to flap open completely.
as the effective spring tension is reduced, the increased momentary pressure at the turbine inlet caused by exhaust gas pulses tends to blow open the wastegate (it does open "downstream" as you will remember) for short durations. this tends to happen at part throttle, mid rpm range conditions.
this is wastegate flutter. some have reported success at reducing (but not eliminating) the flutter by adjusting the acutuator arm length, essentially increasing spring preload. nevertheless, it is quite normal, and quite ubiquitous on our cars, and does NOT represent something "broken or failing."
unless you have a VERY effective ball/spring type MBC which COMPLETELY prevents pressure from reaching the wastegate actuator until the setpoint is exceeded (and i haven't seen one yet) then it is impossible to prevent this from occuring to some extent.
if you've got another explanation for wastegate flutter, i'd love to hear it.
hth
ken
VIP Member
Joined: Feb 2003
Posts: 488
From: 12.9 / 105+
Car Info: black my03 5mt wrx s/w
Originally posted by krillz
the wastegate on our cars starts to opem at like 7 psi
the wastegate on our cars starts to opem at like 7 psi
the only thing which can prevent that (premature WG opening, wastegate flutter) is a higher rate spring or additional spring preload.
hth
ken
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Posts: n/a
As many probably already know or guess, CEL on when using downpipe that leave not room for O2 sensor means just that. No O2 sensor. Does this hurt the car? No, it will NOT help will the performance . As I have come to believe, the stock ECU will go in to lets just call it "protect myself" mode, because it no longer knows what is going into the engin. So instead of moving along the original fuel map. The ECU sends a worst case sinerio (sorry I don't know how to spell) air fuel. If you have a Digital Data Capture and plenty of time. Disconnect your O2 sensor and drive with the car. You'll see that signal from the ECU does not change very much, compared to when O2 is there. That why HKS advertise this as Off-Road only. Because when you know what you are going to use the car for, then physically set the mixture and be done with it. I believe that was the idea behind the design.
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