Reply With QuoteYes.It is a general concensus that the Pyro thermocouple should be pre turbo?
Wizard
Gday all.
Can I have some feedback on the VNT turbo set up for a '04 TD5 Disco manual. Even after all the mods I have done to my vehicle, I still have turbo lag. Not as much but it is still there and now we have the van (2300Kg's) even more so. I am also at the moment worried sick about high EGT's with the van in tow on severe hills. Can you tell me if these problems will be lessened with a VNT setup. Also, what sort of cost is involved. It is a general concensus that the Pyro thermocouple should be pre turbo? Mine is about 40mm below the turbo (post).
Regards
Robbo
Master
SupporterYes.It is a general concensus that the Pyro thermocouple should be pre turbo?
OldBushie
Higher efficient boost and broader across the rev range, it'll help egts, but by how much I don't know
Make it breathe and it will run cooler.
Get some extra boost from VNT for bottom end.
Larger IC will improve EGTs as well.
Simply: it all helps.
RoverLord
VNT's only help with keeping the EGT's down at the bottom end of engine performance where a normal turbo is still not producing full boost.
once you have full boost wound on from either turbo it all comes down to how well you can cool things....
off max fueling tho more psi in = lower EGT's....
I wouldnt go installing a VNT just in the attempt to lower EGT's at full power settings, short of going to exotic internals changing your driving technique is the only real answer to keeping full power EGT's in check.
Dave
"In a Landrover the other vehicle is your crumple zone."
For spelling call Rogets, for mechanicing call me.
Fozzy, 2.25D SIII Ex DCA Ute
TdiautoManual d1 (gave it to the Mupion)
Archaeoptersix 1990 6x6 dual cab(This things staying)
If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
If you think you're in front on the deal, pay it forwards.
OldBushie
Higher boost with more efficiency would lead to less egts at full loadOriginally Posted by Blknight.aus
RoverLord
correct.... BUT...
if the normal turbo only produces say 22psi of boost and the VNT only produces 22 psi of boost.....
the advantage of the VNT is that its pretty much on full boost from the bottom of the rev range.
Dave
"In a Landrover the other vehicle is your crumple zone."
For spelling call Rogets, for mechanicing call me.
Fozzy, 2.25D SIII Ex DCA Ute
TdiautoManual d1 (gave it to the Mupion)
Archaeoptersix 1990 6x6 dual cab(This things staying)
If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
If you think you're in front on the deal, pay it forwards.
YarnMaster
But with the vanes open the exhaust manifold pressure (EMP) will be lower and VE and airflow will improve - the ratio of boost pressure / drive pressure (or EMP) can make a big difference.
ChatterBox
No point worrying sick about it.
You are in control of your EGT's. A std ECU map and std boost wont get above 630 (pre turbo). My TRS (non flashable) ECU map can exceed 900 on std boost and intercooler.
If you dont want to be mindful of temps, maybe a return to std map is the go?.
I have just fitted the TD5 Alive inter-cooler and boost box.
It has dropped EGT's by 15% average.
With the biggest difference noted at the top end (obviously)
Just got the EGT and boost numbers together for std map and the TRS map, with std and bigger I.C. also some intercooler specs for another post. (follow on from twrC7x post on i.c) Which I will get up shortly. These numbers may or may not help.
cheers
RoverLord
the vanes dont "open" as such they just direct and restrict the flow at low exhaust volumes. Think of it like putting your thumb on the end of the hose if you have the tap only just on you can make the water go the same distance by restricting the flow and directing it where you want it as you can by opening the tap more (within certain limits).
in very specific situations you will get better performance from a "normal" type turbo charger than you will from a VNT type turbo. Typically a normal turbo is setup to be most effecient at a fairly specific set of gas flows, engine rpms and yada yada yada... This however (the numbers here are purely fictional to make the point) is kind of like saying that a 2lturbo (representing an old school turbo) is better than a 4bd1-t (representing a vnt type turbo) because the 2l makes 2nm more torque over a 200rpm section of the torque band than the 4bd1-t but then not going on to say that the 4bd1-t's usable torque band is 800-2400rpm whereas the 2l usable torque band is 2100-2800rpm.
‪VNT turbocharger cutaway animation‬‏ - YouTube
that tube illustrates how the VNT does its magic.
you can see that at lower exhaust flows the vanes turn the gas flow to the outer lip of the turbine at the same time as giving the the exhaust gasses a restriction to cause them to speed up thus giving more torque to the turbine wheel which then does the turbo thing to make more charge air pressure.
Given that a VNT is pretty much making full boost from basically the very bottom of the rev range where you dont have the flow rate to get a normal turbo wound up using a traditional style waste gate actuator thats driven off of the charge air pressure is kind of pointless so you need to goto more exotic control methods to shape the boost you're getting (typically electrical manipulation of air pressure/vacuum or an electric servo control)
‪Turbo Geometría Variable Nueva Hilux‬‏ - YouTube
that tube shows you more or less what happens at the various engine rev ranges
‪Diesel Variable Geometry Turbo Introduction‬‏ - YouTube
that one does it slightly better but with a crappy AI voice.
http://www.youtube.com/watch?v=i8R8r...eature=related
and that one shows what happens on a VNT for a given exhaust flow volume under varying vane positions.
now the killer question... (and this relates to the only REAL downside to VNT turbos and its a failure mode condition, points for the correct answer to the question below, bonus points if you can work out the next question and head of the class if you can then answer it)
what happens to the EGT in a diesel IF you apply a restriction to the exhaust while its trying to make power?
Last edited by Blknight.aus; 1st August 2011 at 12:05 PM. Reason: fixed typos, added a tube and added the questiony bits
Dave
"In a Landrover the other vehicle is your crumple zone."
For spelling call Rogets, for mechanicing call me.
Fozzy, 2.25D SIII Ex DCA Ute
TdiautoManual d1 (gave it to the Mupion)
Archaeoptersix 1990 6x6 dual cab(This things staying)
If you've benefited from one or more of my posts please remember, your taxes paid for my skill sets, I'm just trying to make sure you get your monies worth.
If you think you're in front on the deal, pay it forwards.
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