question about recirculating BOV into turbo
 

I have a Synapse Synchronic BOV that I picked up for a deal and decided to recirculate it back into the turbo inlet.
http://i44.photobucket.com/albums/f9...3/DSC03464.jpg

My question is do I need to ensure that it hits the center of the turbo or does it matter if it's off-center? Would that imbalance the wheel? Would it be better to angle it so it's putting the air more in the direction the wheel will be spinning? (not sure if that makes sense haha) Here is how I'm going to have it run...
http://i44.photobucket.com/albums/f9...3/DSC03465.jpg

...through the front of this filter...
http://i44.photobucket.com/albums/f9...3/DSC03467.jpg


I also have a question about vacuum routing for this. It needs to read off of the IC piping near the turbo, would it be OK to split it off the line going to the boost controller solenoid (which I currently am doing but I'd rather not do to be honest) or do they need to have dedicated lines?
http://i44.photobucket.com/albums/f9...3/DSC03466.jpg

What exactly are you trying to achieve by doing this? I would give it dedicated vacuum source.

Recirculating and shooting the air on the wheel aids in keeping it spooled while you're off-throttle. afgmoto1978 has his recirculated like this too, and he's probably not the only one.

Place it where ever you want before the turbo. It will not make a difference.

Most turbo cars come factory like this, including the TII...

Works very well however you need to CUSTOM pipe a hole/grove into the turbo fin direction otherwise your just blowing air into the turbo and not doing anything.

peace

Why don't you run it before the intercooler? Would save routing mess.

thewird

https://www.rx7club.com/showpost.php...&postcount=719

https://www.rx7club.com/attachment.p...8&d=1204133584

You really think this will do something for you, performance wise? It won't. Why don't you spend some time thinking about how to mount an air filter on the turbo inlet, to keep foreign objects from damaging the impeller, causing you decreased performance and internal engine damage. Just a thought.

Well I was planning on having it just like that except through the filter, and I wanted to get it as close as possible to the impeller so it would have more force, that's my line of thinking anyway.

What do you mean? Are you talking about angling the pipe to a certain part of the impeller? That's what I was asking about, not sure if that's what you're talking about though. Basically what I was wondering is if it needs to shoot straight onto the impeller or if it needs to be angled to push the blades in the right direction. Is that what you're talking about?

I was thinking about that, and that I figure I'm losing some pressure over the length of the hose, but this is where my last BOV was mounted and I figure with this air already cooled it might help in cooling the intake air too. As far as routing in concerned though, I agree with you, it would be much better on the other side.

Another thing I wondered about is pressure loss comparison between the different sides of the IC. Which side is better you think? Or is there no difference? I was thinking it might help keep the IC pressurized a bit more with it on the cold side but I could be totally wrong on this.

Thanks! I saw that post (actually it's what got me thinking about recirculating a while back already) but I couldn't really tell if he had it angled or not. I sent him a PM before I started this thread but I haven't heard back from him, and I'm finished with the rest of my current projects and I'm ready to start on this and get it back on the road, as soon as the snow melts anyway haha.

Why don't you spend some time actually reading my original post before you post up a smart ass remark? I said in the original post that it will go through the filter in the picture, and I've had that filter on there this whole time with my Tial BOV. It would be kinda hard to show you guys how it's going to shoot onto the turbo with the filter on there don't you think? Not to mention I'm trying to get info before I hack a hole into the filter and then can't use it.

Oh I forgot to mention before that I'll probably try to give it it's own vacuum source, I'd much rather do that anyway. It just doesn't seem right teeing it off like this.

Yea i dont like teeing anything. To the guys with experience doing this, is there really a noticeable difference in spool by doing this? It just seems to me that the exhaust pressure would be alot more than the boost pressure coming out of the bov?

Oh I'm not saying it's making a HUGE difference, but to me it's kinda like using exhaust pressure to spin the turbo, it's free so why not use it? LOL

There is going to be more pressure before the IC and the shorter pipe length would mean it loses less speed getting there. Also, post intercooler the air has already been cooled by the IC so why waste it and have to cool it again.

thewird

I definitely get what you're saying about the air pressure and speed on the hotside, but for the cooler air...I wouldn't really be losing the cool air, and I would be cooling it again and cooling the pre-turbo air even more. That's what I would think anyway.

I've felt the air coming out when I rev the engine and it's still pretty substantial. Now I'm just curious if it would be better to angle the pipe or run it straight on. I'm leaning more towards angling it. I also wonder if I should cut it down some to make sure it doesn't sag or if it will be OK at this length.

to me it makes more sense to have it point straight at the blades, they are designed to pull the air in so it wouldn't matter to much, plus it will already be in boost where this would have any kind of affect so i imagine the angle wouldn't matter again, it would get sucked in however the turbo sucks it in.

also, it makes more sense to suck in colder air to me, but i wonder how much less pressure there would be, depends on your i/c efficency i suppose....my .02

Well while the air is blowing onto the turbo, even though the impeller will be spinning a bit from exhaust pressure, this is to help it spin so it needs to push the impeller. Not sure though. I wondered if pushing straight on might be just as good.

Because the air doesn't necessarily stay cool. Placing the BOV after the IC (and as close to the TB as possible) is a very effective way to reduce the effects of heat-soak in the IC as it allows you to purge the intake tract.

I tested both pre and post IC BOV locations and noted a substantial improvement in the time required to cool off a heat soaked intake tract during high ambient and heat-soaked conditions and a general reduction of IATs. Accordingly, I permanently moved the BOV to the elbow.

^Well there you go lol. Thanks for your input! Thanks to everyone else too! Please keep posting people.

Get rid of the BOV.

You are better off having 1 bar of boost waiting in front of the throttle after a gear change even if it is at 60 degrees C (so ~180% atmospheric density) than atmospheric pressure air at 35 degrees Celsius 95% atmospheric density.

The available power & turbo spool will be much greater than any bullshit shenanigans you try to pull with plumb back BOV shit (which would actually be detrimental to performance both on transients & more importantly on song as it is just something in the way of air flow 99% of the time) & you are eliminating a potential point of failure. I bet none of the clowns talking about the charge air trying to turn the compressor backwards etc or loss or gain of energy to the turbine/compressor couple have any formal engineering training or have ever done gas flow energy calculations ;-)

I hear what you're saying, and I've seen people run without a BOV, but this is more of a daily driver/street driven than track car just yet and I'm not really into compressor surge, so I think I'll keep the BOV haha. Thanks for your input though.

If avoiding attention from the 5-0 is one of your design parameters than that is fair enough, every car is a compromise of competing interests & keeping your pride & joy on the road is a big one :) I would only suggest plumbing it back to the turbo intake if that will assist in convincing an officer that is part of the emissions control system :lol:

I just hate seeing people who think BOVs are actually about a performance benefit or turbo life/wear spreading ignorane about it further & further in the car community. Fair enough if you have some dodgy high flow setup which is actually running in surge under load on spool up (or cruising up a hill on part throttle on the highway) due to miss matched hot & cold sides you would notice a difference in the life of the turbo, but as for gear changes that is irrelevant compared to many other factors.

The only reason they were ever fitted to factory cars, (plumbed back) is to provide less instability in the readings from mass flow meters, so it was easier to tune them on the off throttle/on throttle transient & pass emissions regs due to not throwing too much fuel into the engine & causing a hesitation & massive HC/soot spit out the tailpipe. They are nothing but dead weight (assuming the noise doesn't get you unwanted attention) on a MAP tuned car.

Actually, hiding from the po-po has nothing to do with it. I can see what you're saying, having that pressure there for when you're back on throttle, and that I wouldn't be off throttle for long enough to make a difference. I just don't see how that would be good for the turbo even for a second, over time I mean. And considering they put these on the cars from the factory, I don't see how running without it would be OK.

On a lighter note, don't you guys' turbos down there in the southern hemisphere spool the opposite direction anyway? LOL

Yes, we only get half the efficiency as the blades are facing the wrong way. :lol:

I find it hilarious that the same people who are terrified of running without a BOV often run ignition cut rev limits, 2 steps, antilag etc and have combustion events in the exhaust manifold. I'd say a single combustion event in the exhaust would have the equivalent fatigue effect on the bearings of literally 100,000-1,000,000 (this does not seem logical unless you have actually studied fatigue loading, but the effect on lifecyle with loadings above a materials fatigue limit is proportional to third power of the loading) non bov'd throttle shut boost events @ 45psi boost.

LOL. Too funny.

I gotta be honest, I have no idea what you're talking about with most of that. I'm not doubting what you're saying, I just don't have any experience with all that and I'm lost LOL. I don't have a 2-step and I don't have rev-cut limits unless that's built into the computer lol.

I am not saying your statement is incorrect. I just want to say that I have seen a shaft on a turbo twist and snap on a VW Jetta which has a recerc. valve that was defective.

Up until that point I thought the idea was crap. With your information on emission and the valve on factory cars makes a lot of sence and I can see how that woul help with HC's plasting out of the ail pipe.

With this said what is the down fall of placing the air over the tubo again? Couldn't this be looked at like regeneration on hybrid cars from applying the brakes? jI us the brakes to load the electric motor, which in turn chrages the battery ever so slightly. This is take on action and using it to creat another action. I understay that this in not free energy because the car has already burned the gas to get the car moving.