DSM T25 on a 2.2L S10
1.5 BAR
Joined: Oct 2009
Posts: 935
From: CHICAGO
no problem. i was confused. internal wastegate makes the build a little easier. make sure you cap off the compressor housing boost nipple and run a vacuum/boost line from the intake manifold to the wastegate. the wastegate will open quicker preventing boost creep. the pistons in these motors are not very forgiving to lean or over boost conditions so preventing the boost creep will help save it.
1.5 BAR
Joined: Oct 2009
Posts: 935
From: CHICAGO
boost builds up from the throttle body and travels down to the turbo housing. if you use a boost reference at the compressor housing there will be a slight psi difference at the intake compared to the compressor housing. since your boost reference is at the compressor housing your wastegate will see 8psi boost but your intake will see 9 or 10 psi(this is just an example not exact numbers). this is known as boost creep. boost creep will always be there but you can try to minimze it. if you move your wastegate boost reference line to the intake manifold then the wastegate will open earleir minimizing boost creep since there is a psi difference from the intake to the turbo compressor housing.
0.0 BAR
Joined: Jun 2010
Posts: 15
boost builds up from the throttle body and travels down to the turbo housing. if you use a boost reference at the compressor housing there will be a slight psi difference at the intake compared to the compressor housing. since your boost reference is at the compressor housing your wastegate will see 8psi boost but your intake will see 9 or 10 psi(this is just an example not exact numbers). this is known as boost creep. boost creep will always be there but you can try to minimze it. if you move your wastegate boost reference line to the intake manifold then the wastegate will open earleir minimizing boost creep since there is a psi difference from the intake to the turbo compressor housing.
There will be a slight difference(from pressure drop after the intercooler and piping) between the compressor outlet(more psi) and throttle body(less psi). It's a little backwards from what you're describing
but same concept.If you have a problem with boost spike(overshooting your target value then immediately settling down), keeping the wastegate source/reference as close to the compressor outlet and with as short of a line as possible is your best bet to combat it. The difference in psi(usually 1-2psi) from running between the two sources can be accounted for by using/adjusting your MBC.
Thread Starter
0.0 BAR
Joined: Jan 2011
Posts: 20
1.5 BAR
Joined: Oct 2009
Posts: 935
From: CHICAGO
[QUOTE=Mr Peepers;1304940]Ah, difference in vocabulary terms. Boost creep is commonly referred to as the wastegate not being able to bypass enough exhaust gas around the turbine and control boost in higher rpms, causing boost to rise with uncontrollably with rpm.
There will be a slight difference(from pressure drop after the intercooler and piping) between the compressor outlet(more psi) and throttle body(less psi). It's a little backwards from what you're describing but same concept.QUOTE]
its not backwards. best wastegate control is from a boost reference signal coming from the intake manifold. boost pressure builds up from intake and travels toward the compressor housing so if you use a boost source at the compressor housing your actually boosting more at the intake manifold than at the compressor housing. your boost gauge will spike above your targeted boost range until the wastegate opens. it is a delay from the time the intake see 8 psi to the time your compressor housing sees 8psi. a smaller than needed wastegate can cause an over boost condition and not really a boost spike.
There will be a slight difference(from pressure drop after the intercooler and piping) between the compressor outlet(more psi) and throttle body(less psi). It's a little backwards from what you're describing
but same concept.QUOTE]its not backwards. best wastegate control is from a boost reference signal coming from the intake manifold. boost pressure builds up from intake and travels toward the compressor housing so if you use a boost source at the compressor housing your actually boosting more at the intake manifold than at the compressor housing. your boost gauge will spike above your targeted boost range until the wastegate opens. it is a delay from the time the intake see 8 psi to the time your compressor housing sees 8psi. a smaller than needed wastegate can cause an over boost condition and not really a boost spike.
