[chillywings]

Okay maybe this is a stupid question, but please just hear me out. In all seriousness, if I disconnect the hoses from from my diverter valves (that send the air back to the intake), how is that actually different from a BOV? I understand that BOVs make an effort to make pressure release SOUND better, but is there any difference in function?

Cut me some slack, please thanks.

[309xi]

I know nothing, just browsing New Posts, but isn't a valve something that can open and close, where a loose hose is just in the open position?

Seems like being open constantly would mean it doesn't function the same as a valve would with regards to pressure or things like that. Just a thought. Possibly a bad one. Worth what you paid for it.

[jwalker87]

You are correct; functionally, the only difference between a 'blow off' valve and a 'diverter' valve is that the latter ... diverts ... the air back into the intake tract instead of to the open environment. The former have additional protections designed in to prevent debris lodging in them, or should, since they are open to the environment.

One item of note, if you do disconnect the diverter hoses, be sure to plug them, or you will allow unfiltered air into your intake.

[chillywings]

Originally Posted by jwalker87

You are correct; functionally, the only difference between a 'blow off' valve and a 'diverter' valve is that the latter ... diverts ... the air back into the intake tract instead of to the open environment. The former have additional protections designed in to prevent debris lodging in them, or should, since they are open to the environment.

One item of note, if you do disconnect the diverter hoses, be sure to plug them, or you will allow unfiltered air into your intake.

Thanks. I was wondering about this because I want a little more pressure release sound than I currently have, but I worry a BOV would be too obnoxious for me. Probably I'll eventually get a 'quiet' one.. but maybe I'll mess around and try removing my diverter hoses lol. I think I've seen a couple reports of people finding rubber caps for the intakes at local hardware stores

[Emilime75]

I've been running my stock diverter valves venting to air for almost 3 years. No issues with it, they function just the same as with the hoses running back to the inlets. As jwalker said above, make sure you cap your inlets where the hoses connect to prevent unfiltered air getting into your turbos/intake.

[Tunafish]

What part are you all talking about? The pictures i seen of the diverter valve (11657601058) shows no lines going to it just an electric connection?

[Emilime75]

There is no electrical connection to the DVs. There is a vacuum hose, and the 2 hoses from each DV to the front and rear inlet. The hoses from the DVs to the inlets is what he's talking about.

[Tunafish]

Ok this is the diverter valve.. Now what part is being called the diverter valve in this thread? I only ask not to argue but am interested in doing this..

[Emilime75]

OK, I'm stuck in an N54 world, and that's an N55 DV. N54 DVs have no electrical connection. Guess OP needs to let us know what engine he has, I'm assuming N54 since he's talking plural and I believe the N55 has a single.

[Tunafish]

Yeah i might be off here, wasnt aware that the n54 had diverter valves, looks like its an aftermarket item?

[Emilime75]

N54 has 2 diverter valves, one for each inlet/turbo. There are aftermarket DVs, as well, but they also come in pairs.

[chillywings]

Originally Posted by Emilime75

I've been running my stock diverter valves venting to air for almost 3 years. No issues with it, they function just the same as with the hoses running back to the inlets. As jwalker said above, make sure you cap your inlets where the hoses connect to prevent unfiltered air getting into your turbos/intake.

Well how about that... I guess this might actually be a thing lol. Did you remove the hoses completely, or just tie them up somewhere? I was thinking if you keep the opening of the hose facing down nothing should really get in it. Also, how's the sound??

And yes I've got an N54, which has vacuum controlled diverters.

[c0bra]

You may want to consider DCI. You'll get more blow off sound and also make a nice suction noise when on the throttle.

If you do run the stock hoses VTA, a lot of people put little filters on the ends.

[Emilime75]

Originally Posted by chillywings

Well how about that... I guess this might actually be a thing lol. Did you remove the hoses completely, or just tie them up somewhere? I was thinking if you keep the opening of the hose facing down nothing should really get in it. Also, how's the sound??

And yes I've got an N54, which has vacuum controlled diverters.

I removed the hoses. My diverters are in the stock location, I'm just using an aftermarket charge pipe that keeps the DVs instead of a BOV, but that's just because my stock plastic one blew up, otherwise it is the same. Nothing gets in them, the only time they open is when they're releasing pressure, meaning air is blowing out of them. I can definitely hear them and to me it sounds pretty much just like a BOV. I have also deleted my cowl, so it will be louder in my car than one that still has the cowl in place, but you'll still hear it.

[c0bra]

Originally Posted by Emilime75

I can definitely hear them and to me it sounds pretty much just like a BOV. I have also deleted my cowl, so it will be louder in my car than one that still has the cowl in place, but you'll still hear it.

+1 to running without the cowl.

With DCI on, cowl off, stock CP and DVs still hooked up, it sounds very much like a BOV. Extra sound with the top down too!

I do have aftermarket CP and BOV in the mail though.

[sharaleo]

Note, on cars with MAF sensors, the air in the system is calculated by volume in the intake system (as measured by the MAF). If you change your diverter valve to vent to atmosphere, you will mess up the A/F ratio entering the cylinder as the air now being vented to atmosphere has already been used to calculate fuel ratio. It will mean you are over-fuelling for a brief period.

Probably not going to matter on a stock tuned car, except for maybe one day throwing O2 sensor related faults or failing MOT tests if you have to deal with those.

On a tuned car, depending on how aggressive the tune it, it may matter more, though over fueling is probably still not a huge issue, say as compared to under-fueling and runnig lean.

Not sure about BMW's, but other cars that are going to be tuned and change from diverter to BOV will typically add a MAP (pressure) sensor to the mix for A/F calculation - say if they were using a piggy back or replacement ECU.

[IllSic_Design]

Originally Posted by sharaleo

Note, on cars with MAF sensors, the air in the system is calculated by volume in the intake system (as measured by the MAF). If you change your diverter valve to vent to atmosphere, you will mess up the A/F ratio entering the cylinder as the air now being vented to atmosphere has already been used to calcualte fuel ratio. It will mean you are over-fuelling for a brief period.

Probably not going to matter on a stock tuned car, except for maybe one day throwing O2 sensor related faults or failing MOT tests if you have to deal with those.

On a tuned car, depending on how aggressive the tune it, it may matter more, though over fueling is probably still not a huge issue, say as compared to under-fueling and runnig lean.

Not sure about BMW's, but other cars that are going to be tuned and change from diverter to BOV will typically add a MAP (pressure) sensor to the mix for A/F calculation - say if they were using a piggy back or replacement ECU.

Good info.
Yeah not an issue with our cars, but it is on cars like DSMs(Eclipse/Laser/Talon) where everyone wants to vent to atmosphere.

[c0bra]

Originally Posted by sharaleo

Note, on cars with MAF sensors, the air in the system is calculated by volume in the intake system (as measured by the MAF). If you change your diverter valve to vent to atmosphere, you will mess up the A/F ratio entering the cylinder as the air now being vented to atmosphere has already been used to calculate fuel ratio. It will mean you are over-fuelling for a brief period.

Probably not going to matter on a stock tuned car, except for maybe one day throwing O2 sensor related faults or failing MOT tests if you have to deal with those.

On a tuned car, depending on how aggressive the tune it, it may matter more, though over fueling is probably still not a huge issue, say as compared to under-fueling and runnig lean.

Not sure about BMW's, but other cars that are going to be tuned and change from diverter to BOV will typically add a MAP (pressure) sensor to the mix for A/F calculation - say if they were using a piggy back or replacement ECU.

N54 = MAP

OP has N54 which is totally fine to VTA those DVs or swap to a BOV.

[Vivek.]

Originally Posted by sharaleo

Note, on cars with MAF sensors, the air in the system is calculated by volume in the intake system (as measured by the MAF).

I thought MAF went by the mass of air (Mass Air Flow), no? AFM's measure just the volume

[chillywings]

Originally Posted by c0bra

N54 = MAP

OP has N54 which is totally fine to VTA those DVs or swap to a BOV.

Honestly, I don't really understand MAPs or MAFs. Does this mean that the engine is automatically able to adjust the air/fuel ratio when venting to atmosphere?

[Vivek.]

Originally Posted by chillywings

Honestly, I don't really understand MAPs or MAFs. Does this mean that the engine is automatically able to adjust the air/fuel ratio when venting to atmosphere?

It means the engine adjusts air/fuel ratio according to the actual amount of air entering the engine. Measured by either the mass of the air flow or the manifold air pressure (MAF, MAP). Venting to atmosphere has nothing to do with this measurement though.

[c0bra]

Originally Posted by chillywings

Honestly, I don't really understand MAPs or MAFs. Does this mean that the engine is automatically able to adjust the air/fuel ratio when venting to atmosphere?

Yes, the AFR will adjust on the N54 bc the MAP sensor is located after the BOV, and the MAP measures air pressure vs air flow. On an N55, my limited understanding is that you can't just slap on a BOV without more involved modification. Lots of info on N54 vs N55 out there, just search for it.

Bottom line: It's safe to slap a BOV on an N54! I finally did it this past weekend bc the stock DVs are mostly plastic.