Could use some ideas (pics) for IC piping w BOV

[Guest sabum]

I am in central PA around Harrisburg. I run mostly at a small track called Beaver Springs Dragway. http://www.beaversprings.com/ Its in North Central PA area probably 3-4 hours away fro Philly. You can probably see some older pix of my ride in there somewhere. I did not make it much last year due to a little incident at the national Z convention in NH the prior year.

 

I did want to go to a track called Maple Grove sometime. That might be 1 1/2 hour away.

 

Sabum

[akeizm]

Well, There is alot of writing done in this thread and I cant be bothered reading it tonight heh. But I just got my Z back from getting its piping done, it has 2.5" piping and the way I have run the piping goes:

 

With the compressor facing toward the sump, the ic piping goes under the engine mount, up infront of the engine and into the intercooler on the passanger side (for you whacky americans) then out of the drivers side into the throttle body.

 

This was a random late night post from me Hope it kinda helps heh.

[zero]

VinhZXT, I live in newark. The other turbo Z guys in the area are Joe (ragz), who has a mean v8z a very mean turbo z and a stock z, and datsun280zmike who I am helping with an rb26dett swap. I would love to get together and have a cruise or go to a track. Englishtown is my local.

[Jersey]

I'm in Morris County, up near Wayne NJ. I dont know a whole lot but if i can lend some knowlegde, let me know. Getting together at the track sounds good to me. Last year, for the 5-6 times i was there, i was the only Z. Would be nice to have some support I went to Englishtown twice which was 2 times too many. Great prepped track but both times i only got 2 runs for the 6 hours of basically waiting around. Just isn't worth it to me. I go to Island now which doesn't seem much futher from you Zero - 280 to 80w i would guess. It's not as perfect as Englishtown but, on most nights, you can just about run round robin all night long.

[VinhZXT]

I would love to have a meet. Doesn't matter cruise or at the track. I used to go to ATCO race track. Never went up to English town. Would be nice to go there to see what it's like. Please keep my email address on your list and let me know if you guys going to get together. Thanks

 

Also sorry for the none related subject post.

[pjo046]

There is another valve on the intake, I'm not sure the proper name for it but I've heard it refered to here simply as a 'dump valve'... I dont recall what it looks like as I didn't know what it was before I ditched the turbo intake for the 280z intake... only heard about it or what it did after that. Anyways, that valve basically serves a very similiar function as the BOV from what I understand, so that when you snap the throttle shut after boosting (between shifts on hard acceleration) pressure wont build up after the turbo causing the compressor to surge. Someone else here might be able to point it out on one of these pics so you know what it is. I'm thinking you MUST still have it on there or else 15psi and no way to keep surge from occuring would have surely taken a huge toll on the stock turbo by now....

 

This is just plain wrong. You see, if such a dump valve was mounted on the intake manifold, it wouldn't serve it's purpose. As it would then be mounted AFTER the throttlebody, the only pressure it would be relieving is the pressure in the manifold. The pressure that can cause compressor surge is located BEFORE the throttlebody. That is, when you have high boost and then suddenly close the throttlebody, all the air that is being pushed forward from the turbo has nowhere to go, thus it collides with the tb and pressure builds up in the piping(And IC if there is one in the car) between the compressor and the intake. This pressure forces the compressor wheel to a sudden stop and it is this that can hurt the compressor wheel/turbo.

[Jersey]

I believe what 525 is referring to is the VCV (Vacuum Control Valve) pjo046. It is mounted on the intake and is a one way valve allowing air INTO the intake and not out. A hose gets connected to it and routes back to the stock J-pipe. Here's a post about the VCV i made a while ago...click HERE

[VinhZXT]

I've seen many people installing these expensive aftermarket BOV on their cars and I just don't understand why? I would save that money for other meaningful upgrades. All you really need is that VCV valve if you don't want boost build up in the IC. IMO the aftermarket BOV is made to actually keep boost buildup in the IC and only release it over a certain boost level. That way you won't have boost lag in between shifts. Here is a picture of it that I used on my car with the N47 intake. It is that small thingy on that rubber hose from the J pipe to the intake. BTW the VCV is vacuum and boost activated.

[Jersey]

Vin, is that the VCV between the two pieces of hose? That piece was threaded into the 4th intake runner, right? If so, do you think any pressure from your turbo pushes up that hose, causing the VCV to open and allowing boosted air to basically bypass your IC? Then again, when you're boosting, manifold pressure is rising as well which puts more pressure on the back side of that VCV probably keeping it closed. hmm... Another thought - that VCV may not vent too much air considering it's size compared to a BOV. You might be putting more backpressure on your turbo on throttle lifts than you might want. Just my opinions/thoughts.

[Guest bastaad525]

pjo046 - hey dont' shoot the messenger bud. I really dont know exactly what that valve is, or how it works, as I have never used it myself, having always relied on the 1g DSM BOV I've been using since day one of the turbo swap.

 

 

All i remember is one time a long time ago the subject came up on the board of how the stock zxt deals with built up boost on sudden throttle closure, seeing as how the stock zxt did not have a bov. And I think it WAS Jersey that explained that it is the VCV that serves the function of not letting pressure build up between the turbo and throttle body on sudden throttle closing, and not allowing the compressor to surge, which is deadly to any turbo.

 

But it does stand to reason that if you were to remove the VCV or swap to an earlier intake manifold and did not run a BOV you WILL have compressor surge and will greatly shorten the life of your turbo.

[pjo046]

LOL 8)

bastaad525, okey okey. I just wanted to point that out, as some members might get confused.

 

VinhZXT

"I've seen many people installing these expensive aftermarket BOV on their cars and I just don't understand why? I would save that money for other meaningful upgrades. All you really need is that VCV valve if you don't want boost build up in the IC. IMO the aftermarket BOV is made to actually keep boost buildup in the IC and only release it over a certain boost level. That way you won't have boost lag in between shifts."

 

This it not quite true. The BOV is not activated at a certain pressure from before the TB, but it is being pulled open by the vacuum that is created from the intake when the throttle is shut. Thus the BOV almost always opens when the throttle is suddenly closed, but you only hear the familiar sound from the BOV when the pressure that is released through it is big enoug. So basically, the BOV always let the pressure out of the system between the TB and the compressor. But it keeps the system filled with air and the compressor wheel spinning, so that when you once again hit the throttle, the compressor don't have to start from stillstanding and the IC and plumbing don't have to be filled with air before the boost ocurres. Without a BOV, the air slamming against the throttleplate will reverse and move towards the compressor again, thus causing surge, and also emptying the IC and piping. This means that the IC and piping will have to be filled with air again when you hit the throttle, something which steals time and causes lag. And also as mentioned, the compressor has come to a complete stop and needs more time to build up boost, thus also causing lag.

 

I'm curious as to how your VCV valve system works? Is it a one way valve thing? If so, if the air can only pass from the plumbing and to the intake, then this is a bad idea, as it lets air bypass the intercooler, and also destabilise the airflow. I agree that it would relieve the pressure caused by a shut throttle, but then again, it relieves the pressure in the wrong end of the system, allowing the air to flow FROM the throttleplate TO the compressor before it is released into the manifold. This empties the system for air, and causes lag when hitting the throttle again. Also since this airflow is going in the opposite direction than the air coming from the turbo that causes a disturbance in the airflow when you hit the throttle. If it only works the other way around, then it serves no purpose, as there is only vacuum in the manifold when the tb is shut.

 

If it is so that the valve in your system needs both the boost from the turbo side pushing pluss the vacuum from the intake side(when the throttle is closed) pulling for it to open, then it makes more sense. Then the air bypassing the IC won't be a problem as the valve would only open when there is both pressure upstream of the throttleplate, and vacuum downstream of the throttleplate, a condition that is only present when the throttleplate is suddenly closed. But still, your system would have the error of causing the reversion of the airflow etc. So if so, I would advise you to alter it so that it relieves the pressure from just before the TB, not from the compressor outlet.

 

And I also agree with Jersey in that it might be to small and restrictive to give adequate venting.

[Guest sabum]

Wow Im getting a headache reading all this technical stuff

 

I got got my BOV Greddy S in the mail and the darn thing has the directions in Japanese! The BOV has one big outlet where I assume the main air vents, but, there are 2 more smaller ones. What do I do with them?

 

I am really coming down to the wire here. What do you guys think. Should I try to find a DSM boot quick? Should I just use the stock one and plug all the other hoses? Or go straight with the 2 1/2" It seems using a rubber boot will save a lot of time fabricating the pipe.

 

And I still am not sure what to do with the J pipe, Cut it, or remove it.

 

Thanks in advance.

[VinhZXT]

Sabum,

sorry for hi jacking your post.

Jersey,

Yes that the VCV used to screwed into the 4th runner of the intake. The same boost pressure will be on both sides of the valve so it will not open and allow the air bypass into the intake. You don't need much of an opening to release pressure. Have you check the manual boost controller? a tiny hole about 1/16 or 1/8 of an inch can release a lot of boost from your turbo.

 

Poj,

If the BOV works exactly the same way as the VCV then why waste money and time to install it? The VCV is a lot easier to install comparing to the BOV. Also when the VCV sucked open it will only suck the air coming from the compressor. If you take forever to shift then yes it will eventually suck all the air from the IC and pipings. If you shift quick the air still should filled up in the IC near the throttle. As soon as your compressor start spinning again you should not have that much lag. On the other hand if you put the BOV right before the TB then the BOV will release all that cool air that was passed thru the IC. So when you open the throttle the compressor has to do more work to push the air thru the IC again. This topic been talked for awhile and noone is right or wrong. This is just my logical thoughts.

 

Same principle with when people installing the IC and then move the air filter inside the engine compartment. I've talked about that on Zcar.com and I doubt anyone even care about that because it is just too much trouble to put the air filter in front of the radiator after the IC install. I did some local driving in my 280ZXT and after 1/2 an hour the underhood temp. was really high and my IC pipes coming out of the compressor was so hot. To a point it could burn my hand if I leave it on there long enough. My IC pipes are aluminize steel and I was glad I went with that instead of aluminum. Again this is just my logical thinking and I am trying to get people to understand. Cheer... take care.

[pjo046]

Hi again!

Well, I'm not trying to argue or anything, but if you read through Corky Bell's Maximum Boost, you'll see what his opinion is on these matters. Should think he knows what he's talking about. He states that it is way better to have the air-filter in front of the radiator than in the engine compartment, and that the outlet for the BOV(Or in your case the VCV) should be as close to the TB as possible, and certainly after the intercooler. And the air moving around in there moves pretty fast, so I don't think you have to shift gears so very slow for the phenomenon I was talking about earlier to happen. You see yourself how fast the compressor surge occur if you don't have a antisurge-device. No matter how fast you shift, you get compressor surge.

 

But, I guess it doesn't matter THAT much about where the outlet for the BOV(VCV) is, or where the airfilter is located, but it DOES matter.

[pjo046]

Sabum, I would go straight for the 2.5 inch pipe. You say there is one big outlet on the Greddy S. This is where the air wents yes. You either leave this open, or attach this to the intake pipe between the airfilter and turbo.

 

And then there are two more small outlet nipples. One coming straight out from the upper part of the BOV right? and the other one coming out from the lower part? The one from the upper part is used to connect to the intake manifold. It is this that makes the BOV opens when there is a big vacuum in the intake. The lower one you either leave open, or you connect this one to the intercooler-piping. The last option is the best one.

[mobythevan]

You don't need much of an opening to release pressure. Have you check the manual boost controller? a tiny hole about 1/16 or 1/8 of an inch can release a lot of boost from your turbo.

 

So your line going to your MBC is about 3/16" and the tiny hole is 1/16". So if you charge pipe is 2.5" then the BOV hole should be one third of that, a little over 3/4". Sounds about right for the same proportional flow.

 

The only way to solve the size of BOV hole required is to start really small and work up until the lag between shifts is gone. I'm guessing none of us have run that experiment.

 

back to the topic you can see in this pic where my BOV is located and vented to atmosphere

 

[Guest sabum]

pjo046/// thank you.

 

Jersey/// Did you find those pictures from infront of the rad that show the IC mounting and fit? Also what intake boot is that Dsm from? I assume eclipse/talon just want to make sure.

 

Sabum

[mc]

I have been folowing this informative post.Could someone post a picture[close up] of this VCV??I MIGHT WANT TO TRY ON MY 1988 200SX SE remote mount turbo.I need to add a BOV but this VCV sounds easier and CHEAP.

[Jersey]

Sorry Saddam, no pictures found. If i get a chance, i'll snap a few off today/tonight. The boot was actually off of a '90 Laser. MC - i'll snap a pic of the VCV.

[Guest bastaad525]

Jersey - I just ran across some of your pics online that show what Sabum is asking about...

 

here: http://zdriver.com/gallery/showgallery.php?cat=500&ppuser=5226&thumb=1

 

at least there were pics of the IC mounting, no good pics of the boot though.

 

Hope this helps. Jersey your I/C looks to have been a PITA though since it was so much shorter than need be to just run the inlet/outlets thru the holes in the radiator support that were already there, instead it looks like you had to do some cutting of the support to get it to fit. Most guys seem to luck out getting a right sized and shaped I/C that will allow them to just pass the inlet/outlets thru those larger holes that are already there, mine was the PERFECT size for doing that.