Where did you plumb your boost controller into ? UIM is no good !
03-17-2009, 10:20 PM
#1
Where did you plumb your boost controller into ? VFAD nipple is no good !
In most of the installations I've heard about on here the boost controller pressure/vac line is plugged into the nipple under the upper intake manifold that used to supply the VFAD.
Having a pressure gauge on the outlet of the turbo enabled me to see what was going on on both sides of the throttle body with this setup.
What happens is that under partial throttle operation you get a major boost spike/surge on the turbo side of the throttle - I observed over 15PSI . Your boost controller will not see this and may even still be seeing a vacuum .
The reason it does this is that the boost controller blocks the pressure going to the actuator until it sees some boost , so the watsegate remains shut .
The solution is simple . Plug your boost controller into the other side of the throttle body .
I noticed that not only did I cure the surge but the spike in the UIM I was getting at gear changes dissappeared as well because the wastegate remains open a little longer with this setup .
This may be common knowledge to some of the more experienced people on here but I know many people are hooking the controller up to the vfad nipple so thought it worth a thread on why not to do that.
Having a pressure gauge on the outlet of the turbo enabled me to see what was going on on both sides of the throttle body with this setup.
What happens is that under partial throttle operation you get a major boost spike/surge on the turbo side of the throttle - I observed over 15PSI . Your boost controller will not see this and may even still be seeing a vacuum .
The reason it does this is that the boost controller blocks the pressure going to the actuator until it sees some boost , so the watsegate remains shut .
The solution is simple . Plug your boost controller into the other side of the throttle body .
I noticed that not only did I cure the surge but the spike in the UIM I was getting at gear changes dissappeared as well because the wastegate remains open a little longer with this setup .
This may be common knowledge to some of the more experienced people on here but I know many people are hooking the controller up to the vfad nipple so thought it worth a thread on why not to do that.
Last edited by Brettus; 03-17-2009 at 10:40 PM.
03-17-2009, 10:24 PM
#2
Metatron
iTrader: (1)
I identified that as one of the design faults of the original Greddy kit - it has no controller, and the wastegate actuator gets it's control signal from the LIM.
You can see that this would simply provide 100% shut signal to the turbine at all inputs, except WOT - producing whatever spikes and peaks the turbo makes without a relevant control signal.
If you used a signal source at the compressor outlet, or even between the intercooler and throttle body, the whole system would get better control.
S
You can see that this would simply provide 100% shut signal to the turbine at all inputs, except WOT - producing whatever spikes and peaks the turbo makes without a relevant control signal.
If you used a signal source at the compressor outlet, or even between the intercooler and throttle body, the whole system would get better control.
S
03-17-2009, 10:41 PM
#5
Metatron
iTrader: (1)
I prefer a location right before the throttle plate - this takes pressure drop across the IC and intermediate piping into the equation.
If you aim is to have a 'safe and controlled 10psi' you will have a very different pressure at high flow and pressure drop though the IC.
Why not control the available boost right where it matters? Who cares if the actual turbo outlet pressure climbs to 13psi to maintain your setpoint of '10psi @ the throttleplate'......
If you aim is to have a 'safe and controlled 10psi' you will have a very different pressure at high flow and pressure drop though the IC.
Why not control the available boost right where it matters? Who cares if the actual turbo outlet pressure climbs to 13psi to maintain your setpoint of '10psi @ the throttleplate'......
03-17-2009, 10:44 PM
#6
I prefer a location right before the throttle plate - this takes pressure drop across the IC into the equation.
If you aim is to have a 'safe and controlled 10psi' you will have a very different pressure at high flow and pressure drop though the IC.
Why not control the available boost right where it matters?
If you aim is to have a 'safe and controlled 10psi' you will have a very different pressure at high flow and pressure drop though the IC.
Why not control the available boost right where it matters?
03-17-2009, 11:02 PM
#12
I have read a few other threads and it is aparent that people are plumbing into the VFAD nipple . That's good because it means i'm not the only one silly enough to do this but bad because it will be affecting turbo life and drivability for a lot of people .
03-18-2009, 12:36 AM
#14
/\ nifty - how does that work exactly - does it mean the duty cycle can increase if boost starts dropping off at the UIM ?
Just looked up profec spec 11 and it says nothing about 2 lines . I think mine is the same as yours in fact & i only have one line ????
we are talking about the signal line BTW .
Just looked up profec spec 11 and it says nothing about 2 lines . I think mine is the same as yours in fact & i only have one line ????
we are talking about the signal line BTW .
Last edited by Brettus; 03-18-2009 at 12:45 AM.
03-18-2009, 01:01 AM
#15
03-18-2009, 02:00 PM
#23
I can tell you this - I originally had the sensor after the throttle body and saw 15PSI before the TB while after the TB was still in vacuum .
Now I have it in the position shown above and see whatever my controller is set at before the TB and vacuum after under partial throttle .
When you think about it - plugging the sensor for the BC AFTER the TB is much the same as plugging the line supplying the WG actuator AFTER the TB . Which was the reason for Greddy fix #2 .
Why ? As i understand it , the sensor tells the boost controller when to start operating the solenoid . If it sees no boost the turbo will keep spooling under partial throttle.
Last edited by Brettus; 03-18-2009 at 02:06 PM.
03-18-2009, 02:09 PM
#24
Because we don't care what the "boost" is before the TB.
The TB is a partial restriction, even when you are WOT.
The "boost" there is not an indication of flow.
Who cares if the pressure before the TB is 5 or 6 PSI above the pressure going into the motor? When you modulate the throttle, the total flow will be controlled there, so you want the turbo to all be working to produce the appropriate maximum flow, regardless of the resultant pressure.
Pressure is NOT flow. How many more times does this need to be pointed out?
The TB is a partial restriction, even when you are WOT.
The "boost" there is not an indication of flow.
Who cares if the pressure before the TB is 5 or 6 PSI above the pressure going into the motor? When you modulate the throttle, the total flow will be controlled there, so you want the turbo to all be working to produce the appropriate maximum flow, regardless of the resultant pressure.
Pressure is NOT flow. How many more times does this need to be pointed out?