Greddy Turbo owners thread
11-07-2010, 10:30 AM
#53
Haven't we already had this discussion? There is supposed to be a pressure increase - that is how we create pressure in the first place.
The neck is part of the volute. The pressure/velocity relationship between the discharge slot and the outlet is the way centrifugal compressors work.
If you made a bend with a higher velocity (which is what you are really talking about), you would just be dropping the velocity elsewhere to make pressure.
All we care about is flow, which is a function of the entire system's velocity.
The neck is part of the volute. The pressure/velocity relationship between the discharge slot and the outlet is the way centrifugal compressors work.
If you made a bend with a higher velocity (which is what you are really talking about), you would just be dropping the velocity elsewhere to make pressure.
All we care about is flow, which is a function of the entire system's velocity.
11-07-2010, 01:31 PM
#54
So even if flow does not change from doing this it could still be beneficial in reducing charge temps at high flow rates .
As an aside : I made the following observation when hooking a boost gauge to the charge tube (pre IC)
At whp below 320 the pressure gauge was steady at maximum flow (and around 14psi)
At 330whp+ the pressure guage started fluctuating rapidly between 14-16psi .
I suspect this fluctuation is to do with the turbo reaching it's maximum flow at that pressure .
Last edited by Brettus; 11-07-2010 at 03:04 PM.
11-07-2010, 04:07 PM
#56
I still think that it is an issue for those wanting to push the limits . You don't see that much restriction as part of any design on any high hp setup .
11-07-2010, 07:15 PM
#60
The volute of a centrifugal pump is the casing that receives the fluid being pumped by the impeller, slowing down the fluid's rate of flow. A volute is a curved funnel that increases in area as it approaches the discharge port.[1] The volute converts kinetic energy into pressure by reducing speed while increasing pressure,
Firstly - there is no increase in area as it turns the 90degrees in the elbow .
Secondly - the fact that the elbow deflects the air 90 degrees to the volute .
After the bend it does start to increase in area but at that point there is no change in direction so that cannot be part of the volute either .
air has to be changing direction AND expanding at the same time to get the effect of a volute .
Last edited by Brettus; 11-07-2010 at 07:44 PM.
11-07-2010, 10:08 PM
#61
Secondly - the fact that the elbow deflects the air 90 degrees to the volute .
After the bend it does start to increase in area but at that point there is no change in direction so that cannot be part of the volute either .
air has to be changing direction AND expanding at the same time to get the effect of a volute .
After the bend it does start to increase in area but at that point there is no change in direction so that cannot be part of the volute either .
air has to be changing direction AND expanding at the same time to get the effect of a volute .
11-07-2010, 11:00 PM
#64
I'll tell you once I get a chance to measure it .
But even if it does expand i'm sure you would agree that it is perhaps the worst volute design you have ever seen , and that it can be improved on .
But even if it does expand i'm sure you would agree that it is perhaps the worst volute design you have ever seen , and that it can be improved on .
Last edited by Brettus; 11-07-2010 at 11:12 PM.
11-18-2010, 08:17 AM
#70
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Alright so just an update..I backed it off to ~12 degrees around peak torque and 20 degrees near redline, with an 11.0 AFR.
Is that better? Or am I still fingering explosion territory
Is that better? Or am I still fingering explosion territory
11-18-2010, 11:36 AM
#71
Play with the ignition timing on the dyno. If backing it down a few degrees (up to 6 or so) at the torque peak (the real torque peak, not the OE torque peak since the turbo moves it down a 1000 RPM or so) doesn't lose power then go with that.
11-20-2010, 07:06 AM
#72
Looking for Sesame Street
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Is there any logical reason I should not revert back to the internal wastegate? The guy I got my kit from welded an external wastegate on and wired the internal shut (I have not seen this to even see how well it was done I am still in Iraq). Anybody willing to do wastegate 101 lesson for me?
11-20-2010, 08:17 AM
#73
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Is there any logical reason I should not revert back to the internal wastegate? The guy I got my kit from welded an external wastegate on and wired the internal shut (I have not seen this to even see how well it was done I am still in Iraq). Anybody willing to do wastegate 101 lesson for me?
11-20-2010, 12:33 PM
#74
Is there any logical reason I should not revert back to the internal wastegate? The guy I got my kit from welded an external wastegate on and wired the internal shut (I have not seen this to even see how well it was done I am still in Iraq). Anybody willing to do wastegate 101 lesson for me?
1/The actuator is very weak and will not support boost at high levels at rpm over 6000 . This in itself is not an issue for the stock turbo as it gets very inefficient above about 6psi at high rpm anyway so you shouldn't be going there.
But if you upgrade the wheel this does become a limiting factor unless you upgrade the actuator or do what I do (jam the WG partially shut) .
2/The WG pivot arm bearing is just steel on cast iron and this can wear leading to the arm sticking . Never been an issue for me but others have reported problems with this . The way mine is set up the WG does not pivot very far anyway so wear is minimised .
3/I strongly suspect that many of the problems (IE boost spike) reported by various people that are blamed on the WG are actually caused by other things in the setup.
