As title indicates, anybody know what activates the duty solenoid to bleed off the boost back to the air intake?
Just a little confused as the wastegate diaphram test is 10 psi, but the S5's drop boost at upper end of the rpm's, so curious if the bleeding is due to the duty solenoid being activated. Mine will run 10/11 then drop to 7/8 by 6500.
If a manual boost controller were installed into the rubber line, after the T to the solenoid, I can't see why the boost wouldn't still bleed off as long as the solenoid is being utilized. This is providing the intake and exhaust are not restrictive.
Is my thinking straight? Any thoughts???????

 

Maybe the turbo is tired?

 

I think they drop boost up high because the stock turbo is too small and runs out of breath up there, not because the solenoid is kicking in.

 

Well, from all I have read about the S5 TII, is that it's built into the ecu to drop the boost at the higher RPM's (Jason-NZConvertible). I've also read that some guys have run 17 lbs on the stock turbo. The only way it can drop boost is to bleed off, assuming all else is in proper working order, so that is why I raised the question. What logic is formulated by the ecu to activate the Duty Solenoid? That solenoid is there to control the boost and must have a value to operate.
We'll keep trying.
Thanks

 

Probably the electrical output of the boost sensor to the ECU. Then from the ECU to the Duty Solenoid.

 

I'm fairly certain it must see a value from the boost pressure sensor as one of the inputs, but what is that value? Also is that the only value, or is there a multitude of info that is sorted before the solenoid is activated?
I realize this is a nuisance, but just trying to collect some data. Can't locate the info in the FSM, or at least I couldn't find it.

 

Go to the RELATIONSHIP CHART in the 89 manual and you will see five things that effect the Duty Solenoid. I forget them all. Cas, knock sensor, boost sensor, intake thermo sensor, narrow range tps, milage sensor (I bet its not a player after twenty thousand miles or a similar figure). That's about it.

 

Hailers, thanks again. I did see that chart and you are right on the money, plus a few not listed, but no values. I'm calling it quits as I guess we really don't know what causes that solenoid to operate. Might just hook up some test equipment and give it a go and try and get some feedback, or just plug it up and take a test run.
As usual, thanks again.
Don

 

Don't forget, if you have a FCD installed it tricks the ECU into thinking the boost is lower than it really is.

 

I thought the wastegate opened at ~6 psi and the solenoid just bled off some pressure so the wastegate wouldn't open until 9. If the spring on the wastegate opened at 10 I don't see the solenoid alone venting enough pressure to regulate boost. Maybe I misunderstood what you were saying...

 

I'm just going by the FSM which states to test the WG adjust compressed air to 10lbs and verify that the rod moves. So I'm assuming that the rod is to open the WG at 10psi. I was trying to figure out when the duty solenoid opened to allow boost to bleed off. Could the solenoid open first to bleed boost, then the wastegate to ensure no overboost? I don't know, that's the question.
Thanks

 

I'm just going by the FSM which states to test the WG adjust compressed air to 10lbs and verify that the rod moves. So I'm assuming that the rod is to open the WG at 10psi. I was trying to figure out when the duty solenoid opened to allow boost to bleed off. Could the solenoid open first to bleed boost, then the wastegate to ensure no overboost? I don't know, that's the question. Just trying to understand the system in the S5.
Thanks

FYI no FCD.

 

I'm just going by the FSM which states to test the WG adjust compressed air to 10lbs and verify that the rod moves. So I'm assuming that the rod is to open the WG at 10psi. I was trying to figure out when the duty solenoid opened to allow boost to bleed off. Could the solenoid open first to bleed boost, then the wastegate to ensure no overboost? I don't know, that's the question. Just trying to understand the system in the S5.
Thanks

FYI no FCD.

 

DP

 

DITTO

 

Once again, thanks for all the help. Found information elsewhere that described the operation of the S5 Duty Solenoid/Waste Gate system.