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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old January 25th, 2011, 06:29   #1
davies1644
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Default n75 valve on a 1z engine help?

right i have a 1z engine and have just fitted a boost gauge to it to find that the boost is spiking at 1.5bar then drops to 0.8 and then about 1.2 and carries on surging, have looked around and have found its the n75 valve. So what should i do? is their one i can get that allows more boost? or what should i go about next??
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Old January 26th, 2011, 04:17   #2
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delete it?
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Old January 26th, 2011, 05:04   #3
davies1644
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just simply remove it all together and place a mechanical boost controller in??
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Old January 26th, 2011, 05:18   #4
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Did the car have any driveability problems prior to your gauge install? The ECU controls the boost, via the N75. If it runs properly, there are no DTCs, chances are it is all normal. Although it really should not vary all that much, so you may have an N75 issue or a leaky/clogged hose somewhere, weak/binding wastegate return spring/linkage, etc.
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Old January 26th, 2011, 06:02   #5
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just put a mechanical controller linked up as suggested so its sort of in series with the n75 valve and the spike has gone now so looks like a faulty n75 valve i did notice when i was instaliing it oily residue in the lines so was probably this, only issue now is how is the boost adjusted?? on the wastegate arm?
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Old January 26th, 2011, 06:13   #6
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<Bull$hit deleted>
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Old January 26th, 2011, 06:26   #7
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Worst advice you could have given!

NEVER delete an N75!

YOU WILL overspeed the turbo and risk destroying the turbo AND engine!

Would you do this on an ALH with a VNT? This engine is no different!

For you newbies you had better learn how these engines are controlled before spouting off Bull$hit like that!
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Old January 26th, 2011, 06:33   #8
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so what iv done is right run it in tandem with the n75 valve? as it has stopped the spikes, how is the boost pressure increased now?? on the wastegate?
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Old January 26th, 2011, 09:46   #9
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As long as you have a functioning N75 and use a bleed to LIMIT the spikes, you are good to go. DO NOT over-ride the control of the N75, assist it but allow it (the bleed) to regulate maximum boost pressure by tricking the systems control.

The 1Z (Garrett) turbo is pretty weak to begin with, it has the lowest TIT threshold being 1550F max sustained temperature. The KKK (AHU) and VNT(ALH) Garrett are all in the 1650F range meaing a better allow and more margin for performance mods.

Also I have seen in person melted turbines on the 1Z Garretts due to retarded timing, make sure you are running above the mid range and ideally at the top of the range to minimize TIT's.
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Old January 26th, 2011, 10:39   #10
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so to adjust the boost pressure is it on the wastegate? and which way do i turn it?
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Old January 26th, 2011, 10:44   #11
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You adjust pressure via the ECU not the turbo.

It's controlled by the ECU and not some dumb mechancal system like older cars.
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Old January 26th, 2011, 14:25   #12
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well that is good to know i am doing it all wrong concidering all the reading I did 6+ years ago on installing and using one.
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Old July 6th, 2018, 03:01   #13
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Quote:
Originally Posted by Drivbiwire View Post
You adjust pressure via the ECU not the turbo.

It's controlled by the ECU and not some dumb mechancal system like older cars.
Sorry for reviving an old thread but I wanna be sure I understood this.
So the intake pressure goes to the N75 which, depending on the ECU mapping, will or will not direct it to the wastegate to open it and prevent overboost. Right?

So to increase the pressure you could either remap the ECU or shorten the rod of the wastegate ?

Last edited by Xtremer; July 6th, 2018 at 03:13.
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Old July 6th, 2018, 05:55   #14
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This is correct - the wastegate in these cars works on manifold pressure (boost).

Adjusting the rod is just fishing for limp mode when the ECU detects it was not able to limit boost per the boost map.

Best to get a tuned ECU - you will need to determine which ECU you have and contact a tuner which can supply the chips with a modified map. Also make sure your ECU is socketed to accept the chips, or learn how to solder either the chips or sockets.
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Old July 6th, 2018, 08:15   #15
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One more curiosity. Would shortening the rod by a small amount (let's say you would up the boost from 1 bar to 1.1) make the car go into limp mode? And most importantly, will the boost be higher just at a specific RPM or would it be equally raised across the whole RPM range? I hope I explained it clear enough
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