Turn DOWN Boost

[JamesJr]

Hi everyone.
Is there anyway to turn down the boost by limiting the amount the N75 valve can open in VAGCOM? New turbo installed and I am getting overboost codes now. Not looking forward to trying to adjust the rod length in the car. 2005 Passat TDI

Thanks

 

[oilhammer]

Fix the problem. Why was the original turbocharger replaced? Is the replacement some non-OEM unit?

 

[JamesJr]

Turbo exhaust seal failure. I put in an new center section, I set the actuator using a vacuum pump on the bench but it over boosts climbing long hills. Yes its best to do it properly...... but my knuckles are sore just thinking about the reaching in and around to get it done.

 

[oilhammer]

If you buy a proper OEM turbocharger, you won't have to mess with this. Since you got "part" of a turbocharger, you have to mess with setting it. Sorry, just how it works. I would never do it like that, I'd just install a new Garrett unit and be done.

The boost mapping is in the software. There isn't anything you can "dial back" to mask the improperly adjusted VNT actuator rod.

 

[JamesJr]

We aren't all rich OilHammer, so we do what we can. Thanks for you input.

 

[oilhammer]

I am far from "rich", too, which is why I drive 20 year old Volkswagens. Time = money. And to be honest, if penny pinching is something you have to do for whatever reason, a Volkswagen probably isn't the wisest choice to be your means of transportation. There are cheaper alternatives, even if they use a little more fuel and suck to drive.

 

[Franko6]

Expecting a cartridge to fix your problem is risky business. The cartridge is cheaper than a 'correct' job. But what you aren't understanding is the turbo cartridge needs to be balanced after installation.

Yeah, I know, CHRA's like Mellet show a balance sheet with the cartridge, but unfortunately, that doesn't necessarily mean it stays balanced when installed in your housing. There are companies that balance your turbo after install, and set the boost. Problem is, maybe they would reject your housing and maybe they would reject your cartridge.

But that is where to start. Have you run any program to show the MAF (Mass Air Flow)and MAP (Mass Air Pressure) numbers? It is just as likely your weak, old turbo never got to running properly and maybe... a big maybe... your new turbo is working correctly, but your MAF and MAP readings are now reaching boost numbers that show overboost, even if you really aren't. You need to compare the value of air incoming on the MAF to the pressure on the MAP. A good MAF will read around 255-275 and the 2 bar MAP should not exceed 2500mb. That is about where they usually code overboost and shut down the N75.

If you don't have the equipment to test, then some things are best left to those with the proper equipment.

 

[Hayze]

Been seeing a lot of "Overboost" related posts lately. This leads me to believe people are getting bored sitting at home during Covid-19 crisis so everyone is tweaking on their cars and messing with the Actuators wanting more hp.

 

[compu_85]

That or cars have sat for a while and actuators have gotten gummy.

 

[pedroYUL]

2005 Passat BHW, does the vacuum shortens or lengthens the actuator rod? ...in my BEW vac shortens the rod, if I had overboost I would just extend the rod a bit.

...if your operation is opposite (as for a BRM PD) then you have to shorten the rod a bit, so that the actuator can't possibly open the vanes more than necessary.

No way around adjusting the actuator rod, I don't believe so.