I am thinking to replace my BOV (which in the current setup vents back into the intake tract) to something that will vent to atmosphere. Max. boost is around 4 psi. Is there anything special I need to consider when I am looking at different BOV options? What are other RS-T setups using? I am sure different BOV have differernt spring constants and pressure capacities, what would be logical to use with my setup up? Thanks for any suggestions.
Well a blow off valve that vents to atmospheric is a very bad idea the ECU won't be able to figure out what is going on. I'm not the best person to ask though so hopefully someone will chime in with a more complete answer. All i know is no one does it normally because it simply never ends well.
Well I think with my setup, 99 RS Turbo (Haltech engine mgmt) the ECU gets a pressure load reading from the MAP sensor, so I don't think it will negatively affect the ECU. There will still be a vacuum line running from the BOV, it will just vent the built up air pressure to the atmosphere instead of the intake. Maybe there will still be some issues??? Others??
Haltec eh? So you are running a speed density system then? (MAP based, as opposed to mass airflow, MAF) If you are running a speed density system, venting to atmosphere isn't a problem. The ECU is only using manifold absolute pressure, throttle position, and RPM to calculate how much air is in the cylinder, taking in account volumetric efficiency for a given RPM and throttle position. Venting to atmosphere doesn't do anything the confuse the ECU. If it is running based on mass airflow, thats a completely different story. When shifting under boost, a BOV lets the pressurised air into the atmosphere, as oppsoed to back into the intake track. The problem is, the ECU took account of that air, but its not there. You end up with an extremely rich condition when shifting. Under vaccuum (not on boost) can cause issues as well. Many BPV's (bypass valves, like all factory Subarus), and other aftermarket BOV's, leak under vaccuum. So when off-boost, air is geting sucked through the BPV. If you are venting to atmosphere, this is a problem since under vaccuum, you are sucking in air through the BOV. This causes you to run lean when off boost. Not great either. I'll be venting to atmosphere since I'm gonna run a standalone in speed density. I personally don't like mass airflow systems, but they are easier to tune. Hope this helps.
it sounds like he already knew all that... but here at mnsubaru if anyone says anything about a bov it always goes straight to this conversation... anyways to answer your question... on the manufacturers sites they usually have a max and min psi but on most adjustable bov's you can get away with low boost pressure... i used to have an mx6 gt which only ran about 8-10 psi at stock and when went out and bought a blitz bov it had a min boost that i didn't check into (10psi) so thus i got compressor surge most of the time and eventually had to pull it apart and inch off the spring till it worked properly
hmm... i had a TXS RFL on my LX-T rig. only pushing 5psi,and i had no issues w/ the RFL. i added a few washers to it to firm up the spring and it workled perfectly. i was tuning via maf. so everytime i vented i gto real rich. but it wasnt anything super crazy.
