intake connections / BOV operation

[Mikernet]

Hey guys,

OK, lets try this again with a descriptive topic title (I'm learning, I'm learning )

I'm trying to figure out how I would use an intake like the Forced Performance once, which doesn't looks like it has any connectors on it besides to recirculate BOV air. I don't need the connection to the BCS (have MBC), and I don't need the PCV valve connector either (I can vent to atmosphere), but I can't figure out where the third one goes or what it is for.

Also, I'm just wondering: the BOV has a "reference" line going into it from the intake, so why would the stock BOV EVER leak boost under WOT (even under high PSI)? The pressure in the intake pipe and the intake manifold should be equal, thus keeping the BOV in equilibrium, no?

Lastly, this isn't really a question, I just found it odd...my coolant bottle is leaking from the PLASTIC about half way up, where the top of the braket it slides into goes. Isn't that sort of odd? I mean, its plastic...its not like it can rust away or something...I've never seen a coolant bottle degenerate .

 

[No_Skillz]

Your PCV does not connect to the intake pipe. It connects to your intake manifold. I suspect you mean your valve cover(VC) breather, in which case you should keep the OEM setup. Neither of these two have anything to do with venting the BOV to atmosphere.

Coolant bottle is just plastic... could have cracked/split over time.

 

[Mikernet]

Arr, yes, that's the VC breather I was referring to. I can't keep the OEM setup if I go with the FP intake because like i said, there's nowhere to connect those lines. Whats wrong with having the VC breather just go into atmosphere instead of intake? My question was really "how the hell can I use the FP intake, since these are the lines I can't connect."

I never said anything about BOV going to atmosphere, I'm not sure what you are talking about. I said I could vent the PCV valve (but meant the VC breather) into atmosphere. I was also inquiring about the operation of a BOV, and why the stock one would ever leak boost under WOT, since it appears to me as though it opens based on the pressure differential between the intake manifold and intake pipe pressure. I searched but I can't find anything explaining what the purpose of the intake manifold air line is, assuming my observation is incorrect.

 

[odormat000]

you can purchase a little breather cap that goes on the end of your VC but that is something you should get your engined tuned to because the MAS factors in the recirculated air that you are no longer using.

 

[Boostjunki84]

Arr, yes, that's the VC breather I was referring to. I can't keep the OEM setup if I go with the FP intake because like i said, there's nowhere to connect those lines. Whats wrong with having the VC breather just go into atmosphere instead of intake? My question was really "how the hell can I use the FP intake, since these are the lines I can't connect."

You can. You just need some sort of catch can. This way any oil blow-by won't get all over your engine bay.

Street Tuned Motorsports.com - Rochester NY

I never said anything about BOV going to atmosphere, I'm not sure what you are talking about. I said I could vent the PCV valve (but meant the VC breather) into atmosphere. I was also inquiring about the operation of a BOV, and why the stock one would ever leak boost under WOT, since it appears to me as though it opens based on the pressure differential between the intake manifold and intake pipe pressure. I searched but I can't find anything explaining what the purpose of the intake manifold air line is, assuming my observation is incorrect.

Where are you seeing this? Are you referring to the recirc-tube?

 

[gregalmighty]

The other line that connects to your intake is for emissions. You can remove the EVAP system completely on 95-97's I believe without any ill effects or just plug the line that goes to the intake. If you live in an area requiring emissions testing you would probably be better off getting an intake that has all of the ports so you can hook everything up. You can still rig up a catch can as mentioned and plug that particular port with any intake.

As far as the stock blow off valve leaking, its made of plastic and has a really weak spring thats why.

 

[Mikernet]

Hi,

There is already a catch can installed, but it still has a line that goes back to the intake ATM. I'm just going to leave the stock intake...I'll do FMIC, exhaust, and intake after the winter...I just want to get this car rolling for now.

I might be misunderstanding what the line going to the BOV is. What is the purpose of the thin hose going to the intake manifold (not the fat recirc tube)?

I made a little boo boo today....I took out the turbo from the car, and I dinged the condenser, and now it has a tiiiiiny leak out of a microscopic little hole. I assume that if I just let it depressurize and I JB weld the ding, I should be fine, right? The condensor looks newerish, so I don't want to get a new one if I don't have to.

EDIT: the condenser is leaking air, not any liquids.

 

[Boostjunki84]

I might be misunderstanding what the line going to the BOV is. What is the purpose of the thin hose going to the intake manifold (not the fat recirc tube)?

It is for your vacuum source. Basically when the pressure in the intake manifold changes due to the throttle body opening and closing, it causes the BOV to open and close accordingly.

The simplist way for me to explain it is to imagine that your at WOT and your turbo is at full boost; the throttle plate will be open to allow all the air to come into the intake manifold and into the engine. Now, imagine you let off the throttle and the throttle plate snaps shut. What happens to all that compressed air? It has to go somewhere; without a BOV the compressed air tries to go back the way it came, into the compressor of the turbo. This is bad and after a short time, will kill your turbo. So what happens is, when the throttle plate closes, the BOV opens releasing the air either back into the intake pipe(before the compressor, like DSMs do stock) or out into the atmosphere.

 

[Mikernet]

Well, thats what I thought.

So, here is what I was getting at before. Lets say you are at WOT and your turbo is pumping out 20psi. The vacuum source is at 20psi and the pressure in the intake pipe is 20psi, so shouldn't the BOV stay closed? What causes it to leak at higher pressure? The net pressure on the BOV is the difference between the two, so it would just cancel out.

 

[snowborder714]

Your bov is closed until you let off the gas. Once the boost changes to vacuum and the throttle plate snaps shut, all that pressurized air is trapped in your upper intercooler pipe. The bov sees that change from boost to vacuum (via the vacuum line running to the intake manifold) and opens up to release all that air that just slammed into the throttle plate. If it didn't, it would have no place to go and something would blow up. The bov has a diaphragm inside and this is usually what causes the leaks I believe. It is just not good enough to hold the pressure.

As far as hook up other things to your intake (other than the bov dump tube), you can just drill, tap, and JB Weld other nipples on as necessary. gregalmighty was correct that the 4th tube that connects to the intake pipe comes from the charcoal canister. I would recommend either removing the whole system (unless you have emissions testing), dumping it to the atmosphere, or hooking it up. I would not recommend plugging it.

I would also recommend leaving the valve cover breather hooked up to the intake pipe with a catch can in the middle.

If you want a 4" intake pipe that has all the nipples, look at an intake pipe from Dejon. They have options to add on whatever you'd like. For the 3 small nipples, it's $25 ($5 for BCS, $10 each for other two). They're very good quality, as I have a 4" pipe with just the valve cover breather.

 

[Mikernet]

Thanks for your comprehensive answer!

I'll have to leave it on there for emissions, so I'll either add the extra nipples or get an intake with them already on there.