Bypassing the N249 Valve

[tnargert]

So I've seen some b6 threads about bypassing the N249 valve when you're replacing your dv. Apparently they get a quicker more performance oriented response as apposed to the delayed, luxury-based stock response. Is this something we can do to our b8's? And if it is does anyone have a guide?

Also side note has anyone ever replaced their dv through the top of the engine? Because I can only find install guides that go from under the car.

Thanks fellas

[AWDLover]

Don't know about bypassing it. I replaced my DV with a GFB DV+ for better performance. Going at it from the top seems like it would be quite difficult.

[tnargert]

Ya I've got the same one, just waiting to have time to install it. And ya that seems to be he general consensus on the dv. I'll probably just go to lowes and get some ramps to install it.

[tnargert]

But regardless if anyone knows about the n249 id appreciate a response

[zokissima]

Look at the Turbo upgrade or K04 upgrade threads here; i don't have the exact thread here with me, but there have been a few members whom have bypassed the valve when installing a manual boost control apparently. Sorry, I can't remember the exact thread, but it's here in the B8 section.

As for the DV, if you remove a lot of the hardware you can reach it from the top (except the bolt underneath. i changed mine from underneath the car. I simply jacked it up on stands, and was able to reach the valve. I'm away from my car now, so if you want to wait a few days, PM me, and I'll snap a pic of the state its in now, as I believe the DV is somewhat accessible from the top as well, once you completely remove the airbox.

[itlnstallion818]

I did the DV from underneath. waaaay easier to get to

[The Infiltrator]

I did the DV from underneath. waaaay easier to get to

+1

[van462]

The N249 is the DV on our cars. if being bypassed a fake load has to be plugged in where the ECU expects to "see" the solenoid of the DV. A DV can be placed anywhere between the turbo and throttle plate. Look at the CTS K04 you will see it located off the turbo with a pipe feeding it pressure. The stock and CTS configuration both vent off the pressure back pre turbo. A blow off valve type vents it to atmosphere and can cause a rich fuel mixture for a brief moment. On a car with a traditional throttle cable that opens the throttle plate a vacuum DV is pretty standard. When the throttle plate is closed intake manifold vacuum goes high and opens the DV to depressurize the intake tract. The wastegate at this time is also opening to spool down the turbo. When you open the throttle plate air rushes in from the intake tract and vacuum lowers and the DV (and usually wastegate) shut to start building boost. In a throttle by wire car the ECU is controlling all these operations using solenoids. So its possible that the DV can be given the close command at the same time as the throttle plate is being told to move . in theory it should be faster responding as it doesn't have the mass of air that has to move first to change vacuum levels. It just has to be strong enough to shut and stay shut thru boost pressure buildup.
If both systems are operating properly I think even a dyno would have a hard time telling the difference. Most of our issues in throttle response are due to us not having a throttle cable and the ECU is left to interrupt our wishes. It is also a learning system that seems to adapt to highway and traffic too quickly vs a performance orientation.

[tnargert]

Look at the Turbo upgrade or K04 upgrade threads here; i don't have the exact thread here with me, but there have been a few members whom have bypassed the valve when installing a manual boost control apparently. Sorry, I can't remember the exact thread, but it's here in the B8 section.

As for the DV, if you remove a lot of the hardware you can reach it from the top (except the bolt underneath. i changed mine from underneath the car. I simply jacked it up on stands, and was able to reach the valve. I'm away from my car now, so if you want to wait a few days, PM me, and I'll snap a pic of the state its in now, as I believe the DV is somewhat accessible from the top as well, once you completely remove the airbox.

I did the DV from underneath. waaaay easier to get to

Sounds like I'll just be going from under, and I'll look for an install guide with pictures but if I cant I'll pm you. Thanks

The N249 is the DV on our cars. if being bypassed a fake load has to be plugged in where the ECU expects to "see" the solenoid of the DV. A DV can be placed anywhere between the turbo and throttle plate. Look at the CTS K04 you will see it located off the turbo with a pipe feeding it pressure. The stock and CTS configuration both vent off the pressure back pre turbo. A blow off valve type vents it to atmosphere and can cause a rich fuel mixture for a brief moment. On a car with a traditional throttle cable that opens the throttle plate a vacuum DV is pretty standard. When the throttle plate is closed intake manifold vacuum goes high and opens the DV to depressurize the intake tract. The wastegate at this time is also opening to spool down the turbo. When you open the throttle plate air rushes in from the intake tract and vacuum lowers and the DV (and usually wastegate) shut to start building boost. In a throttle by wire car the ECU is controlling all these operations using solenoids. So its possible that the DV can be given the close command at the same time as the throttle plate is being told to move . in theory it should be faster responding as it doesn't have the mass of air that has to move first to change vacuum levels. It just has to be strong enough to shut and stay shut thru boost pressure buildup.
If both systems are operating properly I think even a dyno would have a hard time telling the difference. Most of our issues in throttle response are due to us not having a throttle cable and the ECU is left to interrupt our wishes. It is also a learning system that seems to adapt to highway and traffic too quickly vs a performance orientation.

Wow awesome thanks for the in depth explanation!