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Originally posted by Activ8
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3 turns on an M6 - that would be the 3mm then
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Pilfered the below from that other forum... It was posted by Penbryn, who seemed to know his shit! I remember reading it when I was researching my TDI conversion years ago, and re-reading during the process to make sure everything was bob on. Now, because I never tweaked my ABL, I just thought all was good - no need to make any actuator adjustments (yes I used the ABL turbo etc, I wasn't confident enough to be clocking turbos...).
Dave your conversion is running the original Seat turbo and actuator? But we've both changed to larger volume intercoolers?
On the TDI motor the level of boost is set by the ECU, so once the MAP (Manifold Absolute Pressure) sensor detects that the boost is about to reach the preset threshold it opens the N75 solenoid (actually N75 is modulated - switched on and off quickly) but we'll ignore that for the sake of explanation). This means that there is now a direct link between the actuator and the compressor housing of the turbo so that it can open the wastegate and reduce boost.
Obviously the step response of the 'actual boost' will never follow the commanded boost exactly (blue in the diagram). This due to the latency (delay) of the mechanical components etc. However, the ECU s/w has been designed to essentially ignore the spike or overshoot in boost under normal conditions (plus there is also some hysteresis built-in to the control loop to prevent oscillation). However if this is 'overshoot' exceeds the boost limit for more than a predefined time window then the ECU will enter limp mode.
The problem with the wastegate on the TDI motor is that the more tension that is on the actuator rod the harder it is for the compressed air from the turbo to open it (meanwhile remember that the boost is still climbing - as illustrated by the yellow trace in the diagram above). If the boost gets to the maximum allowable threshold before the wastegate is opened fully you get limp mode or an oscillation ('hunting') of the control loop . By reducing the tension on the rod, boost is regulated more quickly as the peak boost required to open the wastegate is lower. A badly adjusted rod can also cause a sort of pulsating of the boost as the control loop oscillates.
How to set-up the wastegate actuator for the TDI motor:
a) Remove the circlip from the wastegate (A).
b) Open the locknut on the actuator rod (B)
c) Remove the actuator from the wastegate (C)
d) Loosen off the rod until the 'hole' fits easily over the (closed) wastegate lever (C)
e) Remove the rod from wastegate again and turn it 8 turns clockwise.
f) Refit the rod to the wastegate, tighten the locknut, and refit the circlip.
I hope this maybe of some help, to this thread and others who may read it....'00 1.9TDI LWB, '87 Mk2 Golf 16v
Wheel or tyre question? Just ask, it's what i do!Comment
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Finding all of this fascinating.Comment
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Fascinating it is even though I haven't got a clue what they're talking about 😃Comment
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Too much pre-load on the actuator will reduce the effectiveness of the standard N75 and map, (but you could remap it accordingly), the down side is feeding the guessed higher torque through the clutch and gearbox as the range of control is now being physically limited. Keep the actuator at standard and map ALL the controls and performance factors. Saves a lot of time, energy and heartache messing around "fixing" problems.
KISS (Keep it Simple Stupid principle) Over sizing an IC looses pressure fractionally better to calculate the sizing to the realistic bhp target to keep the speed to engine flow constant. You do not need a monster IC at our T4 bhp's. The shiny IC might look better etc but location, bends, tubing sizes & type, the joints all add up to slowing the airflow as well as affecting the final cost. Your only looking to cool the air flow but at these bhp's and pressures it really needs next to nothing.
Sent from my SM-G901F using Just T4sComment
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It's all over my head... Just what I read.
I'm fighting a similar battle to Dave with a sudden drop and then limp at what I assume is peak boost.
Sent from my Moto G (4) using Just T4s'00 1.9TDI LWB, '87 Mk2 Golf 16v
Wheel or tyre question? Just ask, it's what i do!Comment
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Exact same symptoms as mine. AcvOriginally posted by Adventure Van View PostMe cago en la madre que te parió!Comment
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Just had a chat with a mate about these AHU engines and the problems being experienced. So, we've come up with some ideas.
1.Check if you have engine oil in pressure pipe which feeds the inlet pressure to sensor inside the ecu. Replace pipe to be 100%.
Looked up the ECU and its fitted with a 2.5bar MAP sensor and possibly spiking over this during acceleration & load. If the actuator load has been increased this could easily happen. Proposed solution is to upgrade the MAP sensor to 3 bar. This involves removing the ECU's internal MAP sensor and replacing it. Or remove the old one and solder in a new external cable and connect to an externally mounted 3 bar MAP sensor.
A VCDS WOT (nail-it) logrun in 3rd to 4500rpm would identify the spike to prove the above.
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Oh and one last idea, check your vacuum and pressure pipes. Make sure the pipes are sized both length and ID correctly and of the right material. If they deform under vac or pressure toss them away, check they're connected properly / in the right order to the N75 solenoid valves.
This can cause signal delays affecting the ECU response and limp mode.
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We did the clutching at straws stuff ages ago, well I let sausages do it and then was smug when it did sweet f a.
(or were you referring to spedwing and adventure van?)
The RR session compared the MAP reading versus actual and they said it was fine.Comment
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Yeh it feels like that.... clutching at straws - sometimes, but it also shows that T4 ownership solidarity, an interest and a willingness to help?Originally posted by regcheeseman View Post
I find its easy to overlook stuff myself.
The thread's shared with others who have "similar" problems and this thread is a long mash-up of build, support, ideas and woes...
What pressure was the van running up to? Any readouts that can be shared?
Did you try and read the new ECU map?
I might be able to remove or broaden the limp mode tolerances?
Sent from my SM-G901F using Just T4sLast edited by Activ8; 11 December 2017, 06:09 PM.Comment
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Will try with a shot little device we have. Get back to you, thanks.Originally posted by Activ8 View PostMe cago en la madre que te parió!Comment
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