krazydbiker
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« Reply #15 on: August 20, 2013, 05:02:18 PM »
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interesting post, i recently upgraded my wastegate to just an 8 PSI preload because my exhaust pressure kept pushing the old 3 psi spring open
regardless of having a 20 psi wastegate spring, if your outflowing the turbo whats the point?
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aysix
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« Reply #16 on: August 20, 2013, 05:10:09 PM »
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Notorious, what was the wastegate spring rating of your old 605's? According to MRC they are 1 bar actuators adjusted to 20 PSI by TiAL themselves.
EPL Sets the 605 gates to 16-17 psi on an application that runs 24-30 lbs.
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« Last Edit: August 20, 2013, 05:45:13 PM by aysix »
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Silly Rabbit 6 speed A6
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elRey
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« Reply #17 on: August 20, 2013, 06:54:31 PM »
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It's not an issue of exhuast pressure prematurely openning valve. It's a precision issue.
It's like taking a long range gun shot verse a short range shot. The larger the difference from spring rating to target pressure the less precise control will be. At some point, the slightest gate adjustment by controller will great affect pressure so much that it's to hard to hold target.
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krazydbiker
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« Reply #18 on: August 20, 2013, 07:41:24 PM »
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very true, boost control was very much a pain with that 3 psi spring trying to get a steady 19 psi it was all over the place which put me on the path of fabricating up a bracket and rod to fit a universal wastegate. but elray, i was hearing the wastegate open at higher RPM's which i do not hear now? no clue but i'm satisfied with how everythings been working with my vehicle.... just need a better turbo some day  |
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nyet
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« Reply #19 on: August 20, 2013, 08:22:50 PM »
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It's not an issue of exhuast pressure prematurely openning valve. It's a precision issue.
It's like taking a long range gun shot verse a short range shot. The larger the difference from spring rating to target pressure the less precise control will be. At some point, the slightest gate adjustment by controller will great affect pressure so much that it's to hard to hold target.
Excellent point. And that is precisely the problem with messing with the preload; you progressively lose more and more useful wastegate range. |
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littco
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« Reply #20 on: August 21, 2013, 05:13:10 AM »
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I can only speak from experience and testing in the k03 and k04 turbos but fitting an up rated actuator to these turbos does make a huge difference. Firstly the majority of original stock actuators are old and worn, this leads to waste gates being blown open and n75 dc running at max. Secondly you can get a more linear boost control with a better stronger actuator than some OEM ones, that do a lot at the beggining, then not much then stop.
The ideal rating for a k03 and k04 is 12-14 psi, as previously stated double this and you get a max pressure of boost which is well within k03 and k04 hybrid territory.
Also the correct way of knowing what an actuator rating is is by running actuator pressure only, this will give you the running pressure of the actuator, not by preloading it and pumping it, that only gives the cracking pressure which is very different to running.
You also need to make sure you actuator has enough travel to fully open.
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julex
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« Reply #21 on: August 21, 2013, 07:03:28 AM »
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A word on tuning, which is also covered in a thread on this very forum: http://nefariousmotorsports.com/forum/index.php?topic=4381.0title=With high wastegate cracking pressure, it is very important to properly tune the car so that it knows when the turbos' wastegates open. It is covered in KFVPDKSD / KFVPDKSE maps which tells the ECU how to operate throttle for a given desired boost level. Stock set up is tuned to about 1.4 pressure ratio which is roughly 6psi - k03/k04 actuator spring pressure. Put a different spring on wastegate and car gets all confused and drives like crap in part throttle. I have tials with ~20psi spring pressure (I adjusted them to lowest possible tension while still staying solid closed) and after I massaged these tables and made other changes for flow (RS4 modified mani with 80mm hemi throttle here), my car is now butter smooth and can reach any boost from 0 - 30psi+ accurately and without any hiccups. Boost levels between 0psi to about 22psi (where DC is still 0) are attained via throttling. |
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Matt@GTS
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« Reply #22 on: August 21, 2013, 08:32:38 AM »
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I can only speak from experience and testing in the k03 and k04 turbos but fitting an up rated actuator to these turbos does make a huge difference. Firstly the majority of original stock actuators are old and worn, this leads to waste gates being blown open and n75 dc running at max. Secondly you can get a more linear boost control with a better stronger actuator than some OEM ones, that do a lot at the beggining, then not much then stop.
The ideal rating for a k03 and k04 is 12-14 psi, as previously stated double this and you get a max pressure of boost which is well within k03 and k04 hybrid territory.
Also the correct way of knowing what an actuator rating is is by running actuator pressure only, this will give you the running pressure of the actuator, not by preloading it and pumping it, that only gives the cracking pressure which is very different to running.
You also need to make sure you actuator has enough travel to fully open.
Lots of unawares in this thread but this guy knows what's up |
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littco
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« Reply #23 on: August 21, 2013, 08:40:25 AM »
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A word on tuning, which is also covered in a thread on this very forum: http://nefariousmotorsports.com/forum/index.php?topic=4381.0title=With high wastegate cracking pressure, it is very important to properly tune the car so that it knows when the turbos' wastegates open. It is covered in KFVPDKSD / KFVPDKSE maps which tells the ECU how to operate throttle for a given desired boost level. Stock set up is tuned to about 1.4 pressure ratio which is roughly 6psi - k03/k04 actuator spring pressure. Put a different spring on wastegate and car gets all confused and drives like crap in part throttle. I have tials with ~20psi spring pressure (I adjusted them to lowest possible tension while still staying solid closed) and after I massaged these tables and made other changes for flow (RS4 modified mani with 80mm hemi throttle here), my car is now butter smooth and can reach any boost from 0 - 30psi+ accurately and without any hiccups. Boost levels between 0psi to about 22psi (where DC is still 0) are attained via throttling. Interesting stuff will look at those maps, but do they need massaging up or down? I assume down .. |
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julex
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« Reply #25 on: August 21, 2013, 10:30:57 AM »
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X axis for these two tables is vpssplg_w (which is a desired compression ratio) variable. Find a column (for a given RPMs, I chose to hone on it at 4k and 5k) where cell value starts exceeding value from PSPVDKUG table as you move towards right. If you look at the X-value (column header) for that cell, it will tell you the pressure ratio, this value (minus one unit, so about 0.4bar for stock) is your current wastegate cracking pressure. Goal is to redefine vpssplg_w axis to something that would make sense for your wastegates. So in my case, I took 20psi (that's what mine are cracking open at), converted to bars (roughly 1.36) and added 1 to it which gave me the compresion ratio. Then I redefined X axis, which I defined as a table so that I can edit it, by multiplying all cells by result of new compression ratio 2.36 divided by old one 1.36 = 1.75x (rounded up). Old stock and new Tial770 20spi gates attached. |
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nyet
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« Reply #26 on: August 21, 2013, 10:39:47 AM »
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Have you checked to make sure that axis data isn't shared by other maps?
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julex
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« Reply #27 on: August 21, 2013, 10:58:19 AM »
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Have you checked to make sure that axis data isn't shared by other maps?
As far as I can tell, by searching several OLS/XDFs for map address, it is only used for these two maps. Anyway, by now it would be super obvious to me if somehting important shared it since my own car would tell me that. I have no time/energy to dive into assembly so I can't tell if something else is fetching this address. |
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phila_dot
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« Reply #28 on: August 21, 2013, 11:08:12 AM »
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Both axis' are shared only between the two maps SE and SD
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NOTORIOUS VR
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« Reply #29 on: August 21, 2013, 11:22:19 AM »
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Notorious, what was the wastegate spring rating of your old 605's? According to MRC they are 1 bar actuators adjusted to 20 PSI by TiAL themselves.
EPL Sets the 605 gates to 16-17 psi on an application that runs 24-30 lbs.
From what I understand by reading the installation instructions is the cracking pressure on the Tial gates is ~18.5 psi, and that is what you are suppose to verify and set it to using a dial indicator and a pressure tester (which is what I did before installing them). With it setup like that I saw a base boost of approx 22 psi w/ 0% WGDC on the N75. I think most people here are still getting confused about WG cracking pressure and preload.... changing the preload (shortening the stroke) doesn't actually change the cracking pressure on the WG as much as effectively shorten the WG arm travel and possibly causing higher EGTs due to a half open WG flap. |
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