Currently setup with an HKS BOV. Purchased the recirculation BPV conversion kit to increase performance.

What are the pros and cons of plumbing the BPV to recirculate to the turbine (hot side), or the compressor (cool side)?

Plumbed to the hot side intake / header results in combustion of rich fuel that revs the turbine wheel (basically turning the header into a combustion chamber). This reduces turbo lag, but is detrimental to the structural integrity of the header and the turbine side.
Plumbed to the cool side intake also revs up the compressor wheel, resulting in less lag as well.

So what is the advantage to plumbing the BPV to dump onto the hot side, if plumbing to the cool side also works well?

 

Either I got confused reading your post or you may have some things backward.

Your bypass valve should be plumbed into your inlet pre-turbo and post MAF sensor. A BOV will be a better performer but they are illegal where I'm from.

You never plumb a bypass valve into the hot side because the pressure there should always be higher than the inlet and the pressure from the exhaust would hold it closed.

 

BPV doesn't work on the turbine side.

 

Yes, I'm talking about the intake on the cool side. If I was talking about the compressor outlet side, the bypass valve would vent to itself

You can call the valve whatever you want. It's a valve that sends compressed air to the headers and turbine intake side, yes?
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ANTI LAG VALVE......

 

An anti-lag valve is basically a wastegate with optional multiport outlets to feed to the header. Besides that, one other thing that's different is that many anti-lag valves are iron rather than aluminum, to cope with exhaust temperatures. The intake side of the anti-lag valves are often aluminum though. So dependent upon turbo to throttle body placement, the BOV could work as an anti-lag valve if there's a downstream iron or titanium check valve to prevent backflow from the hot exhaust, keeping the aluminum BOV adequately cooled.

 

For those of you who've ran both setups (regardless of the valve type), does dumping compressed air to the header significantly reduce turbo-lag more than dumping compressed air to the compressor intake? If yes, did you find the benefits significant enough considering the the potential for extra wear when dumping to the headers?

 

You probably won't find a lot of setups like this. Making it work is not as easy as just plumbing your bypass air to the exhaust. No such thing as free energy, a turbo can't spool itself.

The diagram you have posted is part of an anti lag system, the system you have pictured must be plumbed in directly at the exhaust port, as closely to the port as possible. By using very late ignition timing the exhaust gasses are not fully expanded when the exhaust valve opens. The configuration you use sends extra air through to the manifolds, the fuel mix hits the fresh air and completes expansion, which sends a rush of energy into the turbo. This is not something you ever see on a street car, it was used on F1 for a short period and on WRC cars in the 90's. You would need some advanced tuning to run it on anything but a pure race engine, because the nature of it is "always on".

 

You're right about the tuning being more challenging with the dump to header method. Though, the compressed air dump placement being as close to the exhaust ports isn't going to result in vastly superior performance (from a fuel enrichment perspective), compared to dumping one inch further down the header for example. The further the dump is placed downstream from the exhaust ports, the further apart the vapor and droplets. That equates to decreased anti-lag performance, but only slightly.

The second reason to dump near the exhaust ports is because after the exhaust valve closes and before it opens at each cylinder, that is the only time the compressed air from the charged side will not have to fight against the high back pressure from the exhaust ports. The further downstream the compressed air is dumped, the more homogenous the exhaust backpressure becomes, making the flow of compressed air from the compressor to the header less feasible.

You mention street-ability. From an emissions standpoint (you many not have an answer to this since people generally prefer to run rich rather than lean, and anti-lag to headers is a rare setup), would running anti-lag to the headers without enriching the exhausted air with fuel result in less emissions (compared to a non-anti-lag arrangement)? Being that there's un-combusted hydrocarbons and NOx, wouldn't there be enough fuel and oxidizer for the anti-lag effect (less of course than enriched), while gaining improved emissions?

 

The first time I ever saw this was on a video the other day, it was on a big dollar Supra being built for drifting. They used a small drive by wire throttle body mounted on the A/A intercooler for a valve and were injecting in to the merge between all six header tubes. They were retarding timing and adding fuel at the same time.

 

That's all in tuning I guess. I don't think cats are going to survive this type of ALS.

 

What makes you think the lean configuration would be any tougher on the catalytic converter than a rich configuration? Lean only runs hotter than normal (14.7:1 A/F) up to ~15.5:1 A/F ratio. After that, the combustion temperatures decrease significantly, running cooler than normal and rich A/F ratios.
Unless you are talking about the street-ability of anti-lag dumping to the headers in general, not working well with the catalytic converters.

 

Previous response deleted to prevent excess smart-assery and keep the OP from damaging himself or his vehicle.

@Civil It is clear to me you don't understand this process. Your snide responses to the long time, knowledgeable members of this forum are very offensive to me. They are trying to help and your letting your ego control your response rather than absorbing what is being put out for you. You are new here, but Disney Lincoln is one of the most experienced and savvy members we have, you should be prodding him for info and reading his posts, then asking questions about what he says, not developing asinine responses and trying to correct him.

You need to develop an actual understanding of what this system does, how and why before you argue for it any more. There is a reason this is race car only tech. If you cannot grasp why it is not used on street legal vehicles you should not be messing with it. Best case scenario you damage your vehicle, turbo or exhaust system. Worst case scenario you torch yourself, and whoever happens to be riding with you. Injecting unburned fuel into the exhaust system is dangerous, it should not be taken lightly or played with. The techs who develop these systems have time, experience, computer simulation, education and huge R&D budgets. Drivers have safety and halon systems, fire suits and training. You cannot safely implement something like this "half way" which it seems you are trying to do.

Study what is going on with modern OEM systems, make sure you understand the tuning, science and metallurgy.

You need to spend more time thinking of the system holistically and stop focusing on this air injection system. As it stands now it would appear you don't even know the difference between a bypass valve and an anti-lag valve. Reading this forum, understanding the terminology and the turbo drive mechanisms will help.

You also need to develop a clearer understanding of what pressures exist where in both the turbocharging system and internal combustion engine. You need to understand what causes turbo lag, and how it effects your combo before you start trying to remedy it.

You also need to justify why. If it is just to make some cool banging noises fireworks are a lot cheaper. If you are building some sort of competition vehicle we need to know so we can help you choose the correct system for the vehicle.

 

Your responce was not expected.

Your responce seems to indicate that you misinterpreted the tone of my question. "What makes you think the lean configuration would be any tougher on the catalytic converter than a rich configuration?" was not a challenge to you, but rather an inquiry. If you felt bullied, that is a fair feeling and misinterpretation, as these forums unfortunately have too much bullying (as evident by you deleting a person's post). Moreover, communication here is typed and non-verbal, so tone can be easily misinterpreted. However, pulling the trigger was excessive.

 

It has nothing to do with the mixture. You are moving combustion into your exhaust. This is going to kill cats, as well as your pipes. This is the lack of understanding I was talking about.

Start looking at how Porsche is doing their anti-lag on current vehicles. That will be your best bet for the street, it is still going to be hard on everything downstream of the heads but nothing like the bang-bang system in this thread.

 

Thank you for clarifying. It initially sounded like you were saying running a lean anti-lag mixture would be significantly worse than running a normal or rich anti-lag mixture. After clarifying, I see you meant that anti-lag to headers in general may damage the catalytic converter/s and exhaust plumbing (you and I are both in agreement about that). As for Porsche's dynamic boost control, it's definitely neat and a less aggressive way to reduce turbo-lag.