[Deftronix]

Originally Posted by robnitro

Yes I saw the video and the patent. I get the idea but if you want instantaneous response you could also inject less of that air into the intake to get it to your desired boost...Because you are making more power, your exhaust flow will be much higher which will spool the turbo faster.
My point is that to spool the turbo through exhaust to get that same boost will take a lot more flow than if you fed the engine that air directly. Cold air increases density by cooling the exhaust gases and reduces flow of thosr gases. Turbos are a form of heat energy extraction not just pressure.

But on gas engines it's different because they can have issues running lean too quickly (detonation) so in that case direct intake injection would be hard to manage manage and exhaust side would be easier.

Honesty, a bit dumbfounded by some of the responses here. I'm sure you guys know better than koenigsegg, volvo and the engineers that filed the patent. It's unfortunate this thread is getting completely derailed by people coming in here with "better" theories instead of discussing the actual method posted that has at least some backing from the manufactures already.

[Nadir Point]

You keep talking about Koenigsegg and patents that have absolutely no relevence to a BMW diesel application. Sure the concept sounds interesting - apparently viable in some stage of it's infancy - but... IMHO something like this is liable to behave more like an exhaust brake than a flow magnifier. Think about the physics. Drive preassure is a critical, dynamically managed data point. You're just gonna throw 300 psi on top between the exhaust valves and the turbine. Where is your flow force coming from?

It would be a hybrid air-ex brake. It would do exactly the opposite of what you're trying to accomplish. Fuel is the only way to spool a turbo.

[robnitro]

Let's understand first how intake flows vs exhaust.
Intake air is just air. It gets mixed with fuel and burns, creating a huge expansion as the fuel is turned from liquid to gas by being burned.
Exhaust flow is much bigger than intake flow, even at low loads.

Now from this page: https://www.torquingcars.com/tech-ta...vo-powerpulse/

2-litre tank that holds compressed air at a pressure of 12-bar,
So if it was ideal, 2l x 12x = 24L of air at 1bar. That's not a lot.
In a high spike for power at spool up, exhaust manifold is at 2 to 3 bar.
That tank could do 12L @2bar or 8L @3bar
Not much volume compared to normal exhaust flow.

That same amount of air, 12L@2bar into intake would last much longer as intake flow is much lower than exhaust flow.

And the article explains the issue here:
"
due to the small displacement of the air tank, PowerPulse can only deliver two bursts of pressurised air in quick succession. ‘Quick succession’ is a relative term though, in this case referring to a press, release, and rapid re-application of the throttle"

On a bigger engine like ours it would be even less useful

[Deftronix]

The volvo system was designed for a serial sequential turbo setup which is what ours is. Do you not think the manufactures ran fluid dynamics simulations in solidworks/revit/whatever to see what the best location would be? Think I will listen to what they have to say over these suggestions. The platforms aren't so different. No, it would not act as an air brake.

You are limited on the powerpulse with "quick succession" because they are using a 2 liter tank in that system. My install would have access to 5 gallons because it is there for the air suspension already. I would not be interested in trying this experiment if I had to put in a compressor and tank solely for this reason, I'm not taking my x5 to the track.

This is exhausting - thought posting some legit documentation/media from manufactures that know their stuff would have avoided me being on the constant defense and have all these additional theories come out of the woodwork.

This was more in hopes of finding someone with some actual experience with the method presented. Would be really great for someone taking their 335d to the track to at least try and report back. Since even having a bottle just big enough for one starting spool on the dragstrip would be worth it. By the next time you run the air compressor has refilled the tank. Obviously if the weight added by this equipment removes the time gained then its all for not but again the manufactures probably took that as a factor in initial designs and was still beneficial enough to spend the money and tooling to get it done. I'm a tinkerer at heart so this would be a fun experiment.

[robnitro]

On the track you aren't going to have much lag because of staying in higher rpm. This is for street applications, loafing around 1500 rpm when lag is apparent.
Starting spool on the strip can be done with torque braking.

I wish you luck if you try it.

[nicklockard]

Originally Posted by Deftronix

I was considering that as well but a turbo is designed to use the turbine (hot side) not the compressor to rotate the whole assembly most efficiently. That's why they are different blade designs. If you injected intake side it would just vent to atmosphere since that would be the path of least resistance. There has to be good reason the manufactures and the patent above chose to use the exhaust side.

Yes, you'd have to install a flapper type anti-reversion valve, preferably over-sized with low restriction in the flow direction. The point is to provide the mass of air flow (lbs/minute) that the engine's requesting, as soon as possible. By injecting into the intake side, the exhaust side will have that much less back pressure because it doesn't have to do as much shaft work. The work of compression is being augmented over very short spurts (say as little as 0.2 seconds on throttle tip-in) by the bottle of air. Once the initial burst of pressure has been reached, the turbos can take over--because they got their initial angular acceleration for free. Flowing efficiently is not the point, getting the engine more power at lower rpm's (zero lag) is the point, I think.

There is a guy working on just what I'm talking about for gas engines, which is more complicated because you have to preserve stochiometry balance. For diesels it's so much simpler because there's no such thing as 'too lean'.

For the quoted invention, effectively, they're augmenting turbo shaft work by artificially raising EMP.--whilst simultaneously decreasing EGT's. But if you raise EMP too high, the excess pressure overwhelms the spring strengths on the closed exhaust valves of the other cylinders which ultimately harms net mass flow through the engine. I totally understand why they're choosing the exhaust side though--it's because it is a smaller 'bottle' to fill, and they think the benefits of raising EMP with low EGT is optimal for this configuration.

What do I mean by 'smaller bottle to fill'? I mean that the volume they need to pressurize on the exhaust side is less than the voluem that needs to be pressurized on the intake side. The exhaust manifold volume is roughly 1/2 of the intake manifold volume, and their is not long piping. An eyeball guess is that there is 35%-45% of the volume to pressurize. It's clear to me that when the did their design review, they prioritized having lowest compressed air consumption and smallest compressed air bottle. If that drives your design thinking, then what they did is where you end up. But if your priorities are 'how can I haul ass with monster torque with zero lag?' then you end up designing and assessing pressurizing the intake side.

Pressurizing the intake side ALSO reduces EGT's because the compressed air has augmented turbo shaft work that would otherwise have been provided by burning more fuel. Caveat: depends on how you tune for 'on compressed air'...if you decide to always be at max fueling and max smoke for competition tuning, then EGT's are not lower. But if you tune for street, they would be. In my opinion, the anti-lag is ideal for street, not drag. Drag racers only care about peak power. This is about getting power under the curve at lower rpm's mostly.

[robnitro]

Ahh forgot about smaller volume of exhaust side... But you need more volume since the exhaust flow is higher but it balances out. I wonder if this could cause the turbos to surge if they're staying to produce too much boost down low but then tuning takes care of that by opening the wastegate or vanes.

Egt being lower is a moot point because this is happening right before up to the start of making power when egt is just starting to increase.

[nicklockard]

Rob, there is this mass balance:

Air mass + fuel mass = exhaust mass

Never look at it from a volumetric flow rate--always from a mass flow rate, then back-solve the volume issues from that standpoint (you also need approximate densities of the intake side and exhaust side to work it out, but first-guesses are good enough for making comparisons). I think you're already there, so sorry if I sound preachy. Just stating it to be clear.

I think you're right about EGT's here. And I also think you're right that it *could* cause the turbo to surge because by artificially raising EMP, the turbo's drive ratio is 'off map'.

[Deftronix]

What you guys said about it being better for a street application makes sense. Since I would be using it in my daily, making dual use of the compressor/tank setup would be pretty cool.

Thanks for going further into detail Nick, that's what I got from the documentation as well. A quick burst when a certain throttle % is detected that way it can get there faster/ahead of the first initial higher pressure exhaust gases. The cool air from the injection is more dense and will spin the turbine faster/quicker than exhaust gases as an added bonus depending on PSI injected.

If you did it intake side, could possibly control/shut the stock ASV and time an air injection through one of the npt ports+ check valve on an egr race pipe. But just seems unnecessarily complicated, and too much trial & error involved. Especially since we have a perfect spot (egr port) on the exhaust manifold for it and to me it makes the most sense to put the force at the turbine blade that was most efficiently designed to spin the compressor, without the timing of valves to shut the intake that could potentially starve it of oxygen with even the slightest deviation.

[robnitro]

The intake side is tricky because it'll mess up maf readings. Maf will actually read lower because the compressed air is going in post maf. Some tuning only uses the maf for low loads and speed density/o2 for the higher loads.

Nick
Thanks for the correction on mass density... But yeah exhaust has a lot more energy behind it than the intake. I don't know the conversion efficiency from turbine mass flow to compressor mass flow but it's much less than 100% efficient.