Curious: Recirculating BOV Towards Turbine Wheel

[Teflon]

I think heat would be a killer here. Since the BOV is after the IC the tube the BOV is on could become heated from technically being connected to the exhaust therefore kinda defeating the purpose of an IC.

 

[tenn-gsx]

I'm not thinking this will work very well however I don't think the exhaust pressure is the issue here except maybe at idle. The reason I say that is this. Once you lift your foot off the gas the pressure in the cylinder drops as will the exhaust pressure. At the same time that the exhaust pressure drops the BOV is dumping pressure out of the intake tract. I'm pretty sure that the pressure from the BOV will overcome the exhaust pressure since that is the issue that can cause the turbo to stop or even spin backward when you dont run a BOV in the first place. The reason I dont think It will work well enough )to be worth is is this.
1. Your going to cause your Afr readings to go haywire every time you let up off of the gas pedal.
2. Your going to dump cold gasses directly onto a turbine wheel that is somewhere around 1600 deg?! Sounds like a good way to destroy a turbine wheel from excessive thermal expansion and contraction to me.)
3. I Highly doubt that the small amount of airflow from the BOV will do much for maintaining spool.
4. Turbos work off of HEAT and velocity. You cool down the exhaust gasses and you may just end up slowing down the turbo. (this one is a minor concern though)
5. In order to stop the exhaust gasses from flowing into the intake through the BOV you will have to set the spring pressure higher on the BOV or install a check valve. I see both of these slowing the BOV response down.
6. Allot of expense for a likely failed experiment.
7. You will have to find a way to insulate the intake system from the excessive heat exposure from the exhaust.
8. Your introducing ANOTHER turbulence prior to the turbine which will have the inerrant effect of slowing down spool to some degree.

Positives
1. If you solve all these issues you may have the quickest shift recovery spool out of all of us.

Id rather just properly set up my NLTS and not worry about dumping my boost pressure in the first place.

 

[98GSXin]

Something else to remember is that the exhaust leaving the cylinders will always have more pressure, velocity, and energy than the air entering the engine because it's being further compressed by the engine itself...this is proven by exhaust pressure on non-turbo engines as well. It would make me wonder how much turbo pressure on the cold side would be required to overcome the pressure that exists in the exhaust manifold before it would even begin to make a noticeable decrease in spool time.

So then could the recirculation be ported into just a single runner closest to the turbine wheel? Or is the exhaust back pressure distributed equally throughout the manifold?

I think heat would be a killer here. Since the BOV is after the IC the tube the BOV is on could become heated from technically being connected to the exhaust therefore kinda defeating the purpose of an IC.

Sounds like meth injection could help then?

On Heat: The colder air being shot into the manifold would be heated up somewhat by the connection to the exhaust before making it to the turbine wheel. This connection would have to be forged steel or something to take the rapid heating and cooling.

I think before things can be debated much more on heat, we need to know if the ic piping would be more affected by the exhaust gases or if the exhaust manifold/turbine would be more affected by the colder air. Whichever is going to have the worse effect would have to be addressed for this to be successful. Any ideas on how to get comparative numbers?

 

[PieEyedPiper]

I think before things can be debated much more on heat, we need to know if the ic piping would be more affected by the exhaust gases or if the exhaust manifold/turbine would be more affected by the colder air. Whichever is going to have the worse effect would have to be addressed for this to be successful. Any ideas on how to get comparative numbers?

They're both negligible.

I see no reason why the ic piping would spontaneously start to retain more heat than it already does. Just because the bov now discharges into the exhaust manifold does not require the ic piping to start radiating detrimental amounts of heat into the air charge. Say you didn't use a silicone coupler (heat insulator), the air charge doesn't even stay in the piping long enough for pipe temperature to have a significant impact. You guys are losing me fast with things like this.

While I apologize, that I cannot provide any data, I'm also confident that the less-dense and cooler air charge from the bov would just wash in the exhaust stream.

This is still pissing into the ocean or tossing an ice cube into a volcano.

 

[kicker91laser]

I am surprised this discussion is still going on. It has been said multiple times, the exhaust pressure pre-turbine will almost always be greater than the pressure in the charge air plumbing. If you actually did build this AND got the bov/wastegate to open, you would have exhaust gasses blowing into the charge air plumbing. This would slow spool down and act like a huge EGR valve.

I don't fault the OP for thinking outside the box, but I simply see no way this can improve anything other than reduce emissions(due to the egr effect).

 

[98GSXin]

I don't fault the OP for thinking outside the box, but I simply see no way this can improve anything other than reduce emissions(due to the egr effect).

Well if you're not sold on it for performance, maybe someone can fab it up if they just can't seem to pass emissions here in California! haha.

 

[talonDSMerr]

Somebody said it earlier in this thread, but this idea has actually already been put to use in rally cars as an anti-lag system, so it does work. The method was coupled with some very trick actuation methods and tuning. When you let off the throttle, the ECU dumps extra fuel into the combustion chambers and retards timing. When the BOV releases boost into the turbine, this mixes with the extra fuel and ignites once it hit the turbine wheel, creating a mini-explosion and keeping the turbine spooled and ready to make boost off the bat. Downside is, of course, is that it can be catastrophic to the turbine.

 

[PieEyedPiper]

Well if you're not sold on it for performance, maybe someone can fab it up if they just can't seem to pass emissions here in California! haha.

That was actually pretty funny.

Somebody said it earlier in this thread, but this idea has actually already been put to use in rally cars as an anti-lag system, so it does work. The method was coupled with some very trick actuation methods and tuning. When you let off the throttle, the ECU dumps extra fuel into the combustion chambers and retards timing. When the BOV releases boost into the turbine, this mixes with the extra fuel and ignites once it hit the turbine wheel, creating a mini-explosion and keeping the turbine spooled and ready to make boost off the bat. Downside is, of course, is that it can be catastrophic to the turbine.

Actually, this is huge. Thanks for bringing it closer to the light for us. Here we are debating the wrong things. We ought not be debating/trying to discharge the bov into the exhaust stream to reap some sort of spool benefit - that's not even how the system works.

As mentioned above, there is a smaller, continuous burn taking place in the exhaust manifold thanks to the fresh air charge we just received and the rich condition/retarded timing the ECU is creating. The additional combustion process takin place inside the exhaust manifold is what is driving the turbine - NOT the piddly mouse sneeze emitted by the bov.

So, anyone seen this setup on the evo3 in action?

 

[98GSXin]

So it is possible/beneficial! And yet, old news... Never been so excited and disappointed at the same time before.

So then it wouldn't really be practical to add a 5th combustion point right at your turbine for a daily driver or even mild track car because it would eat itself up. But for dedicated track cars, this would work out pretty well. I can live with that conclusion.

 

[tenn-gsx]

the exhaust pressure pre-turbine will almost always be greater than the pressure in the charge air plumbing.

Except when you let off the throttle. Which so happens to be when the bov opens and the turbo slows down. See the first paragraph in my previous post. I still dont think this is a good idea considering the other available options we have for maintaining spool between shifts. NLTS I have also heard of folks injecting notrous directly into the exhaust pre turbine during shifts and while staging to launch.

 

[PieEyedPiper]

Except when you let off the throttle. Which so happens to be when the bov opens and the turbo slows down. See the first paragraph in my previous post. I still dont think this is a good idea considering the other available options we have for maintaining spool between shifts. NLTS I have also heard of folks injecting notrous directly into the exhaust pre turbine during shifts and while staging to launch.

I think I just read a thread about Lucas English doing that.. now wher'd that get off to.