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Maybe a better post for the NG900 BB due to it's t-5 application, but this is an update on the MBC+Anticipator setup:
A quick premise for the Anticipator:
The ball-spring MBC opens the wastegate at the last moment as you get on boost. When the MBC starts to flow, it has to pressurize the WGA to the point where the pressure just balances the spring pressure and the WG valve is zero pressure on its seat. So that takes time and the WG has not started to open. Then it takes more time to increase the pressure and move the WG to a stable control point. When boost comes on fast in cool or cold weather, there will be pressure overshoots because the MBC just cannot stroke the WGA fast enough. Using an Air Pressure Regulator in line with the MBC, helps to prepressurize the WG line so when the MBC finally opens, the line to the WG already has pressure in it opening the WG faster reducing the pressure overshoots.
In search of an APR that is sensitive enough to lower pressures is difficult. Most places sell APR's that go from 0-150psi. The problem with these are that it lacks the sensitivity needed for the application. An APR with a range of 0-10psi would be ideal. I have found one place who sells these but an account with the company is required I have found an easier solution. I took apart the APR and replaced the spring inside. The original spring was extremely stiff. The replacement spring is much softer allowing for more incremental changes when adjusting the APR to apply the right amount of pressure to the WG line without opening it up.
Secondly, with Dean's help, I moved the pressure tap of the MBC to the TB between the TB and the IAC. There is a connecting hose there which is fitted with a plastic hose barb attached. The barb is fitted into the hose creating a tee and is held in place with some nylon cording and automotive goop so it won't blow out the fitting.
Tapping the MBC from the TB reduces boost droop at high rpms, but it is also a bad place due to the pressure overshoots from there. Using the anticipator setup and the MBC tapped at the TB eliminates the overshoots and allows for longer boost without any droop.
These two changes are significant to the setup as it now allows for more sensitivity from the APR and being it is a DIY change, any non-relieving APR can be modified to meet the low pressure demands of the application instead of endlessly searching for a low pressure APR which can be difficult. The pressure tap at the TB requires a little work, but easily done.
So current setup is:
TB tap to the MBC
Turbo compressor hose to APR
MBC and APR to Y hose barb connecting them back together to the WG hose.
I haven't reattached the gauge on the APR to know what amount of pressure is being applied to the WG, but inital guess would be around 5-6 psi.
The colder weather no longer affects the MBC as it has done in the past.
I have some pics of the setup if anyone is interested.
Search:
drs_anticipator
for more details
posted by 208.235.174...
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