Where did you plumb your boost controller into ? UIM is no good !
03-18-2009, 03:17 PM
#28
No. That is where the solenoid (and therefore the WG) signal comes from.
However, the control signal (the one that tells the boost controller what your target boost should be) needs to know the pressure going into the engine.
The problem with the way the GReddy kit was originally set up, there was simply no signal available to the WG at all if you were at partial boost and it would run away.
Plus, the delay of available pressure to crack the WG caused it to react too slowly, causing spikes.
However, the control signal (the one that tells the boost controller what your target boost should be) needs to know the pressure going into the engine.
The problem with the way the GReddy kit was originally set up, there was simply no signal available to the WG at all if you were at partial boost and it would run away.
Plus, the delay of available pressure to crack the WG caused it to react too slowly, causing spikes.
03-18-2009, 05:30 PM
#32
Because in many part-throttle situations, you have positive manifold pressure.
At throttle positions that produce manifold vacuum, the turbo is barely moving, despite the potential for positive pressure before the TB.
It just isn't a concern.
The flow is minuscule.
At throttle positions that produce manifold vacuum, the turbo is barely moving, despite the potential for positive pressure before the TB.
It just isn't a concern.
The flow is minuscule.
03-18-2009, 07:09 PM
#33
OK I accept what you are saying but I still think my setup is better than having the signal post TB .
I see 10psi (controller setting) max whereas before I was seeing 15. I have zero lag coming off a part throttle to full throttle situation and have so far seen no negatives to doing it this way.
15PSI is still more stress on the system than 10 (couplers and throttle plate etc ) wheather there is no flow or full flow so I'm gunna stick with it .
BTW - the situation I was seeing this 15PSI pressure surge was at around 5000 rpm under partial throttle . It seemed to come on very suddenly at approx. that rpm .
I see 10psi (controller setting) max whereas before I was seeing 15. I have zero lag coming off a part throttle to full throttle situation and have so far seen no negatives to doing it this way.
15PSI is still more stress on the system than 10 (couplers and throttle plate etc ) wheather there is no flow or full flow so I'm gunna stick with it .
BTW - the situation I was seeing this 15PSI pressure surge was at around 5000 rpm under partial throttle . It seemed to come on very suddenly at approx. that rpm .
03-18-2009, 07:58 PM
#37
I think Jeff is trying to get you to see that what is important is what the engine is seeing....
So that has to be post throttle body....
Think about it...throttle body closes...engine gets no flow ...Pre-throttle body sensor will still see pressure/flow ( think BOV)
So that has to be post throttle body....
Think about it...throttle body closes...engine gets no flow ...Pre-throttle body sensor will still see pressure/flow ( think BOV)
03-18-2009, 09:30 PM
#38
/\ I would like to know what happens with turbos other than the Greddy in this scenario .
Do you have a boost guage on the turbo side of the TB MMor Dannobre ?Or anyone else that wants to chime in that has the BC hooked into the UIM for that matter. If so can you see what happpens at partial throttle at around 5000 rpm onwards - I'm curious as to weather this is just a Greddy thing or not .
3rd gear seems best to do this as things happen too quick in 2nd .
Do you have a boost guage on the turbo side of the TB MMor Dannobre ?Or anyone else that wants to chime in that has the BC hooked into the UIM for that matter. If so can you see what happpens at partial throttle at around 5000 rpm onwards - I'm curious as to weather this is just a Greddy thing or not .
3rd gear seems best to do this as things happen too quick in 2nd .
03-19-2009, 02:47 AM
#42
/\ I tried it at 1 psi to start then 7 - same result .
At partial throttle the uim is in vacuum and the solenoid valve is closed until the controller sees pressure so the turbo spools up .
At partial throttle the uim is in vacuum and the solenoid valve is closed until the controller sees pressure so the turbo spools up .
Last edited by Brettus; 03-19-2009 at 02:50 AM.
03-19-2009, 02:07 PM
#44
Maybe by some textbooks it is . However in the Greddy vs RX8 debate I'm saying there is a better solution than what you guys have come to accept as "correct" .
I have always had the understanding that if you want to control something , you monitor what it is doing under all circumstances . A boost controller is suposed to control boost IE the turbo .
How can you control the turbo under partial throttle if you have effectively cut off the only link you had with it by plumbing it into somewhere that does not even read what it is doing ?
03-19-2009, 03:14 PM
#46
hmm I would argue that the throttle is more important in that regard .
The boost controller should control the pressure up to the throttle plate - how much of that is seen by the motor should be determined by the throttle plate itself . I know the throttle is all about controlloing flow primarily but it does control the pressure in the manifold as well.
I've recently been playing with the throttle maps to get better cotrol . The stock settings (particularly in 1st and 2nd) are way too much ON/OFF for a turboed car . I've now got it to a point where I can actually modulate the boost in the manifold with the throttle plate and this has made the car 100% more driveable in the lower gears .
The boost controller should control the pressure up to the throttle plate - how much of that is seen by the motor should be determined by the throttle plate itself . I know the throttle is all about controlloing flow primarily but it does control the pressure in the manifold as well.
I've recently been playing with the throttle maps to get better cotrol . The stock settings (particularly in 1st and 2nd) are way too much ON/OFF for a turboed car . I've now got it to a point where I can actually modulate the boost in the manifold with the throttle plate and this has made the car 100% more driveable in the lower gears .
Last edited by Brettus; 03-19-2009 at 03:41 PM.
03-19-2009, 03:58 PM
#49
How about I use your own words from the Greddy Fixes thread .
There are three MAJOR problems with the Greddy system as it is shipped :
Problem #2
Because the wastegate doesn't open at part throttle, the turbo spools up to very high boost levels - possibly beyond 20 PSI. This boost has nowhere to go as the kit is shipped and ends up stalling the compressor. Those with blow-off valves installed find that the valve often opens, causing a rich condition and stumbling as well as idle problems and stalling.
Unchecked, this over-speed condition will eventually destroy the turbo's bearings or worse. It also causes the PCM to retune for the lost air on BOV-equipped vehicles. Furthermore, it may damage the throttle body (some have experienced this, IIRC) and puts a lot of stress on the rest of the cold side of the system.
It also has the side benefit of making the part throttle/off-idle drivability much easier because the throttle isn't always fighting boost. Now you are not forced to spin your wheels every time you leave a stop light (though you still can if you want to).
.
There are three MAJOR problems with the Greddy system as it is shipped :
Problem #2
Because the wastegate doesn't open at part throttle, the turbo spools up to very high boost levels - possibly beyond 20 PSI. This boost has nowhere to go as the kit is shipped and ends up stalling the compressor. Those with blow-off valves installed find that the valve often opens, causing a rich condition and stumbling as well as idle problems and stalling.
Unchecked, this over-speed condition will eventually destroy the turbo's bearings or worse. It also causes the PCM to retune for the lost air on BOV-equipped vehicles. Furthermore, it may damage the throttle body (some have experienced this, IIRC) and puts a lot of stress on the rest of the cold side of the system.
It also has the side benefit of making the part throttle/off-idle drivability much easier because the throttle isn't always fighting boost. Now you are not forced to spin your wheels every time you leave a stop light (though you still can if you want to).
.