Stock boost level?

[mikk]

impressive, i've never seen an oscilloscope used on an airflow meter. seen plenty of people replace their perfectly good meters unnecessarily upon recommendation by their "mechanics".

right on about scanners, they don't have eyes, ears, and a brain.

[lilcrash]

Ok let's add another symptom. Blow off valve only works occasionally. Does the n249 actually do anything useful, can I just remove it? Also anyone gotten a steady boost level by removing the boost control and installing one that works?

[Jmac]

Ecu controls the valve that controls the boost, want anything else then you go non Vw computer and $$$$$$.
I still have your plugs sitting her mate
Jmac

[Jmac]

impressive, i've never seen an oscilloscope used on an airflow meter. seen plenty of people replace their perfectly good meters unnecessarily upon recommendation by their "mechanics".

right on about scanners, they don't have eyes, ears, and a brain.

Pico Scope is the tool of choice mate, and like you say eyes , ears etc, the scanners including VCDS arent quick enough. Great base line diagnostics but for stuff that dont throw codes like Air mass meters and 02 sensors, the scope picks up on it real time. You can pick up stuff at .2 of a second and then go back and open up and widen the picture to check if that makes sense. Scanners like VCDS are great for most jobs we do but diagnostics, well if a sensor still works within a set parameter but is miles away from what it should be at the time then the ECU thinks all is well, like my bad fuel example. The o2 sensors were still working but were REALLY lazy, i can post up a scope pattern if it will make more sense, but with new sensors they were reacting in split seconds like they should be
Cheers
Jmac

[lilcrash]

Well at random intervals the n75 valve doesnt show any Vacuum so time for it to be removed. So watch this space for progress after removing any valves under the bonnet that the ecu controls.

Jmac. I assumed you were at the rally over the weekend thats why I didnt contact you.

[noone]

What are you looking at to see Vac & N75? It's not a sensor, is this at idle or WOT?

[lilcrash]

I may has mis labeled the n249 and n75 backwards in previous posts. Can't remember what one is what. From now on il just say wastegatr valve and boost control valve. I put a t piece into a vac guage in the vac line to the bov and there is only vacuum to open it occasionally so it's back spoiling my turbo probably 90% of the time. This is while driving

[noone]

Sorry mate, not clear. There are 3 components you seem to be playing with: N249, N75 and diverter / bov.

The N75 regulates the wastegate and it sits near the diverter. The diverter is the larger device and it provides a route for the unwanted boost to escape when changing gears, etc. The boosted air is routed post compressor, pre intercooler back into the intake (post map, pre compressor), so it should be maintained as the ECU is expecting this airflow. The N249 can be bypassed by looping the vac in to the diverter line out. A new Vac line should be run from the manifold to the diverter vac in nipple. The intake manifold produces vacum when off throttle, this vacum is used to open the diverter whilst the N75 opens the wastegate.

Make sense? If you are doing anything else, you may be causing the 'limp mode', limiting boost, etc.

If you don't have a N75 at all, how will the wastegate open? If you use a MBC, the ECU may throw a fit as the logged air readings / boost will be outside the expected parameters and MAY throw you into limp.

Does this borrowed pic look about right?


Looks like you saw JMac, what did he say?

[lilcrash]

currently everything is hooked up as per stock except for the atmospheric blow off valve replaceing the diverter valve. There is no vacuum coming out of the n249 about 90% of the time. So n249 = teh poo so going in the bin. I have very in stable boost levels so the n75 will also go in the bin and il install an aftermarket boost control.

And no I haven't seen jmac

[noone]

How are you measuring VAC from N249? Are you logging it using VagCom or something similar? What aftermarket boost control are you going to use and how will it integrate to the stock ECU?

I guess what I'm saying is that I think you MAY be taking the wrong approach.

If it were me, I'd put it back to stock, reset faults (VagCom or disconnect battery for a few min), connect to VagCom and log. If you are not logging, its hard to see whats doing what and you may continue to replace parts that are not faulty.

The initial issue was low boost. Was it ever boosting harder? What sort of spikes are you seeing? If you want more boost, get it chipped (just a ECU flash really).

-EDIT- Just to clarify, if the car was in limp mode, you will get very little boost. The boost you originally reported seems normal. If you add a BOV that is not routing the air back into the intake, you may be CAUSING the issue now. The N75 is there for a reason. The N249 is there for a reason but can be bypassed without major issues (assuming you route a vac line from the intake to the diverter and loop the N249 connections back on eachother so you are not loosing vac.

[lilcrash]

I'm measuring the vacuum with a vacuum guage, to me that looks like the valve is stuffed, the whole time I've had the car it has run like ****, my wife is learning to deal with the utterly redicilous lack of power it's just the excessive fuel usage that is the main issue now. I'm still looking for someone to do a fault code check. Im just hoping that when we do finally get it fixed it actually can move it's fat ass or I'm pretty sure my wife will hit the roof an demand I get her a decent car.

[noone]

Ok mate, good luck.

JMac is a good man, I'm sure he can sort you out and get you more power if that's what you want.

[Blitzen]

If you are running an atmospheric BOV, I think that is what your main concern would be. Either way, I think you need to get down to Jmac ASAP to get the car scanned.

[RolfGolf]

Has the car been scanned at any stage? This saga seems to have dragged on for far too long with no real progress ... If Jmac is not for you then I'm sure there are other places that can scan your car and sort out the issue. Check the recommended repairers and parts suppliers.

[lilcrash]

im hoping some one can help, based on the weight of the car i think we are aiming for about 200 hp. i doubt the bov is doing any damage as it actually has improved the running on the ocasions that it works, with the n249 blocked it actually kept up with my car until i changed into second, something it hasnt done before.