Another N249 Thread

B5TSN

Guest
I have spent 9 hours under my bonnet today, I'd say 4 or 5 of those were spent removing one use clips and I am NOT exaggerating!

I'm gonna to see my local dealer to see what special tool they use cos it does take ages to remove them......
 

rikwheeler

Active Member
Apr 23, 2006
131
0
Lincoln
www.rikwheeler.com
If you take a look at this vac diagram for the LCR you will see that the N249 is completely separate from everything else. I don't actually know what the N112 looks like. :shrug:

LCRvacsysanno.png

Excellent diagram mate.

Have edited it to show how my car now looks:
ModifiedLCRvacsysanno.png



I'm going to redo all the hoses and was wondering if I can connect it like this using a T piece to connect the recirc valve to the top of the intake manifold instead of the bottom of the intake manifold?:

ModifiedLCRvacsysanno2.png



Can someone also tell me where the hose from the fuel pressure regulator goes :p
 

S17EW O

Guest
This diagram blags my head,will have a look tomorow at my car,have alreay done n249 bypass but am not sure how much I can remove! Can I totaly remove n249,even electrically?or just disconect all its hoses and leave it electricaly connected!?have some nice coil packs bolt downs to fit tomorow so need it all out the way :)
 

Cupra Ross

Breaks things............
May 15, 2005
1,380
1
Edinburgh, Scotland
This diagram blags my head,will have a look tomorow at my car,have alreay done n249 bypass but am not sure how much I can remove! Can I totaly remove n249,even electrically?or just disconect all its hoses and leave it electricaly connected!?have some nice coil packs bolt downs to fit tomorow so need it all out the way :)

You need to replace it with resistors or it'll throw a fault code and you'll get the dreaded EML, if you're handy with electrics its not much of a job to make a small resistor pack and mount it somewhere out of sight. You can't just unplug it though.
 
Last edited:
Mar 26, 2007
2,020
0
S.Wales
You need to replace it with resistors or it'll throw a fault code and you'll get the dreaded EML, if you're handy with electrics its not much of a job to make a small resistor pack and mount it somewhere out of sight. You can't just unplug it though.

Actually you can on the LCR at least. Mine has been unplugged for around a year now and although there is a fault code logged I havn't had any warning lights on the dash at all.

I did get some resistors and plugs from INA but as it turned out I bought wrong plugs. :(
 

Cupra Ross

Breaks things............
May 15, 2005
1,380
1
Edinburgh, Scotland
Actually you can on the LCR at least. Mine has been unplugged for around a year now and although there is a fault code logged I havn't had any warning lights on the dash at all.

I did get some resistors and plugs from INA but as it turned out I bought wrong plugs. :(

There ya go, whip it off and jobs a goodun.
 

20v roper

Active Member
Dec 15, 2006
272
1
sorry to jump on this everyone, ill keep it short, my 1st cupra which i sold last year was an AUQ motor, it was completely standard- i didnt even know what the hell an n249 was! basically that car accelerated better and harder in my opinion to my current cupra which the previous owner had done the n249 mod to, also an AUQ motor. can anyone explain in basic terms why the n249 mod is done? many thanks.
 

Cupra Ross

Breaks things............
May 15, 2005
1,380
1
Edinburgh, Scotland
Its done to remove the ECU's control of the dump valve. The ECU on your Leon uses the N75 (boost pressure control valve) and the dump valve in combination to control boost pressure. There is no need for it to do both and you often find that it opens the dump valve for a fraction of a second when it doesn't need to. This robs you of power and it takes longer for the boost to meet what the ECU is actually asking for. The N75 is perfectly capable of doing the job by itself as it does on nearly every other turbocharged car. The AUQ engine has dynamic MAP sensing and overboost fuel cutoff that will stop a dangerous situation if the wastegate were to jam shut or the N75 valve was to fail, there is absolutely no need for the N249.

Bypassing the N249 means that you are running the vacuum feed to the dump valve directly off the intake manifold so that it can't open until you actually lift your foot from the throttle pedal.

If you think you're down on power, I'd be checking all the hoses coming off the manifold for splits and tears, especially the crankcase ventilation hoses on the underside of it. Either that or log the fuel trims and requested vs actual boost on Vag-Com, these will show if you have a boost leak somewhere.

Not exactly basic but its what you need to know to have a proper understanding of the system. In short, the N249 allows the ECU to open the dump valve. Its not required and the ECU isn't very good at it. The boost control setup works better with the N249 bypassed.
 

S17EW O

Guest
So I can totally remove it then. The only thing I'm not 100% about is. Obviously the 2 pipes of the n249 valve get joined together but I'm sure there's other pipes that gi else where....if there is do you follow these pipes and remove then from where they go or do you just remove then off the valve. Also the pipe running from the dump valve to inlet manifold....does it go on the left or the right of the two small connections on the underside of the inlet manifold??
 
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