N249 bypass? Pros and cons?

[GrapeBandit]

I feel so dumb reading over this and realizing how little I knew about engines and then knowing what I know now. Crazy what a few years does for ya.

how about them days you wanted to rally jump your audi

good thing for the forums, a lot of useful information and DIY's here.

[GrapeBandit]

N249 Delete

Application Notes:
Only 2000+ has the N249 valve.

A little discussion:
On 2000+ 1.8T's,the diverter valve is not directly connected to the intake manifold like it was on the earlier 1.8T's. It is connected through a solenoid called the N249, which is able to connect it to the manifold (in it's passive state), or connect it to a constant vacuum source (in it's active state). Thus, the ECU is able to open the DV in situations where it would otherwise be closed. It is somewhat controversial to modify this system as solenoid control of the DV does have its advantages. It is able to help with pre-spooling the turbo (opening the DV at part throttle when boost request is low), and opening the DV sooner upon throttle lift. Many owners who have "deleted" the n249 have noted more "crisp" boost and more predictable DV response. In any case, the 97-99 cars did just fine without it, so we can delete it too.

**Here is a thread which discusses the pros and cons of deleting the N249: http://www.audizine.com/forum/showth...-Pros-and-cons

so. . .conflicting statement
not that it matters to me, but I know it will for others.

[Davdraco1]

how about them days you wanted to rally jump your audi

good thing for the forums, a lot of useful information and DIY's here.

Lol. I forgot about that too. Damn kids....

[walky_talky20]

so. . .conflicting statement
not that it matters to me, but I know it will for others.

I'm not sure what is conflicting there.

- It is true that there are benefits to what the N249 does.
- It is also true that the 97-99 cars did not have an N249. Those cars still worked fine.
- In some cases the benefits of the N249 no longer apply and it actually is a disadvantage and makes the car run worse.**


**For example if you install a Forge Splitter valve (or other vent-to-atmosphere type diverter valve), when the N249 activates for pre-spool (or for compressor bypass during light cruise), you get a gaping hole in your charge pipe. This causes moderate to major problems with fuel mixture. Air metering doesn't work properly in that scenario and the N249 is to blame. Deleting the N249 fixes that issue. Vent to atmosphere then only occurs momentarily when fuel injectors are off (or almost off).

It can also affect the sound of the blow-off/recirculation. By having the valve open slightly later, the boost spikes slightly and makes for higher pressure when the valve cracks. This can result in a different sound and may be desirable for some owners.