VW Vortex - Volkswagen Forum banner

Why bypass the N249?

46K views 26 replies 15 participants last post by  rains 
#1 ·
I heard people bypass the n249 but I dont understand why. Could you guys please give me a little briefing and also is it recommended if you want to chip your car with unitronic (or any other company)
 
#2 ·
most people do this to clean up the engine bay and mostly the top of the engine...i removes most of the vacuum line clutter and the big vacuum reservoir on the of the valve cover..

people also say that the DV response is much quicker and stronger as after removing all this junk it is hooked up to a direct vacuum source...

i wouldnt know if there was a difference i removed the n246/SAI/Combi valve/All the EVAP lines and the vacuum hard lines before putting the motor in my mk2..

but its is much cleaner looking!
 
#5 · (Edited)
i took all that ish out my engine bay and its so much easier to work on and you can see whats really going on under the hood without all the extra clutter



 
#8 ·
The N249 is used by the ECU to dump boost through your DV when it senses an overboost situation coming or is in effect.

The main reason in bypassing the N249 is to prevent this from happening, Since most the people in this forum are running elevated boost levels and want more boost/power taking this control away from the computer is a good thing.

In order to accomplish this task your DV is hooked up to a vacuum reservoir along with the N249(this is because you need vacuum to open a DV and if your engine is in boost your obviously not producing vacuum) This reservoir is just another space that has to fill up before the vacuum source actually gets to your DV to open under normal conditions.

So a secondary benefit to bypassing the N249 and this reservoir is a quicker response time(were talking milliseconds here) in the valve opening. not only that but since there is a direct line of boost going to the top without the reservoir the valve is also shut faster when you get back on the throttle between shifts. It gives a more direct feel to the car between shifts and when you get on it from a constant roll(I.E passing someone on the freeway)
 
#9 ·
it's basically a solenoid that the ecu uses to decided whether or not the dv has vac pressure, and therefore can hold boost. If you take it out, the dv will function off of true vacuum pressure in the manifold. The n249 bracket also holds the n112, which controls the SAI pump. If you don't plan on removing the SAI, you should leave the n112 in there.

http://uk-mkivs.net/forums/t/265883.aspx
 
#14 ·
it's basically a solenoid that the ecu uses to decided whether or not the dv has vac pressure, and therefore can hold boost. If you take it out, the dv will function off of true vacuum pressure in the manifold. The n249 bracket also holds the n112, which controls the SAI pump. If you don't plan on removing the SAI, you should leave the n112 in there.

http://uk-mkivs.net/forums/t/265883.aspx
 
#12 ·
LOL VTA? vent to atmosphere im guessing?
 
#19 ·
i had 2 walmart bags full of stuff!
 
#27 ·
My car is quite a bit happier sans N249. My diverter valve is quite a bit more responsive, holds boost properly (as opposed to when-it-felt-like before), and it makes a 'better' noise now.

Now, mind you, half the hoses to my N249 were cracked, so it's not like it was 100% when I pulled it out.

Here's all I pulled out (not just the N249, the SAI, and emissions too)

 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top