BorgWarner R2S Turbo

"Casper" (casperiv) 01/15/2014 at 12:10 • Filed to: None

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I just saw this come through my Facebook feed and thought I would share since there was just a discussion on compound boosting applications. This appears to be BorgWarner's attempt to merge a compound turbo system into a single turbo. This one is designed for BMW's new diesel applications.

Pretty cool if it works. I would try it on my Z.

04sneaky - Boxers. Blowers. Bikes. And bitches. > Casper 01/15/2014 at 12:16

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No way. That'd be extremely inefficient. The second hotside would be severely less pressurized than the second one, therefore making the second coldside also severly under pressured.

The better setup would be something like a T4/T6 flange with sequentials/compounds coming off the single flange. Then they'd each be getting relatively the same pressurized hotside and so an equally relative coldside pressue (aka the actual boost).

Now if this was a sequential design then it might be more understandable as one turbo would be smaller thereby needing less pressure to begin with. But these look equal sized.

HammerheadFistpunch > Casper 01/15/2014 at 12:16

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That's pretty sweet, its just a compound system that's physically joined, but with matched components. Should be a winner.

Casper > 04sneaky - Boxers. Blowers. Bikes. And bitches. 01/15/2014 at 12:25

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What? This is sequential by definition and you can't tell anything about the compounding values without knowing the compressors they are running. Even running like sized turbos will produce increased compression over a single similar sized turbo because you are compressing previously compressed gas.

04sneaky - Boxers. Blowers. Bikes. And bitches. > Casper 01/15/2014 at 12:39

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You're confusing sequential and compounding.

THIS is compounding, in which one turbo creates boost and then sends that boost directly into another turbo to have it pressurized even further.

Sequential is when two turbos are powered through their hotside simultaneously, but yet their cold sides are ran independently. The do not "compound" off each other, one simply is smaller and makes boost at the low RPMs whereas the second is usually larger to carry boost through the high RPMs.

Compound setups share the same manifold, whereas sequentials will have an individual manifold for each turbo, much like the TT Supras.

kanadanmajava > Casper 01/15/2014 at 12:59

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I don't think that this is much different compared to two series mounted separate turbochargers. It should work pretty well if the components are well well chosen and you have need for high boost pressure.

During 80's NASA started a project to an aircraft with a piston engine to really high altitude. They were aiming to get to 90 000 ft (27 km). The fitted 4-cylinder Rotax engine with 3 turbochargers and were able to achieve 1:64 boost ratio when all turbochargers were. The plane took of as N/A and engaged the turbochargers during the climb.

I have lost my source and I'm not sure how high they they did get. But they fell short from the target. The test flights were done in late 90's.

Casper > 04sneaky - Boxers. Blowers. Bikes. And bitches. 01/15/2014 at 13:39

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Ah, gotcha. We call those series systems. It's just a terminology thing. The word series means one thing coming after another in a related nature but not specifically adding to. Sequential implies the reliance upon the prior stage.

Just shop terms, I forgot the old RX-7s and Supras called those systems sequential.

Casper > kanadanmajava 01/15/2014 at 13:42

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The difference is that you aren't assisting spool times via the same lines or gaining the increased compression of gas, if I'm thinking about the same systems you are. In series mount, each turbo takes it's own turn coming online and going off based on RPMs/whatever switch system. The intake air is still only compressed by a single turbo, just which turbo doing the compression changes. Is this the system you are talking about?

You can tell a Finn but you can't tell him much > 04sneaky - Boxers. Blowers. Bikes. And bitches. 01/15/2014 at 13:49

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Looks to be exactly like the schematic of an Opel compounding system from this thread . The only difference is that the two hotsides are integrated into a common housing instead of having piping between them.

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04sneaky - Boxers. Blowers. Bikes. And bitches. > Casper 01/15/2014 at 13:49

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Yeah I would say the internet is largely confused on what to call any of the different setups lol.

Casper > 04sneaky - Boxers. Blowers. Bikes. And bitches. 01/15/2014 at 13:55

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If the internet agrees it means hell has frozen over and there is a good chance of brimstone falling from the sky.

04sneaky - Boxers. Blowers. Bikes. And bitches. > You can tell a Finn but you can't tell him much 01/15/2014 at 14:32

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Which is the only way a compound setup will work efficiently in my mind.

The reason being are the two check valves, and those are essential to keeping the compounds from inhibiting or destroying each other.

The setup in the video above doesn't seem to have any type of check valve, just that wastegate actuator, and it only works on the hotside. The coldside is still allowed to feed into the second (possibly smaller) turbo which would greatly inhibit the efficiency IMO.

kanadanmajava1 > Casper 01/15/2014 at 17:09

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I guess one (smaller probably) would spool up first but both of the wheel-shaft combinations should be pretty small so I don't think that would cause issues. If the goal is to get a bit more boost than a single turbocharger would be able to do both turbochargers could be slightly smaller than the single turbocharger version. That might even make the spooling times shorter.

There seems to be no intercooler placed between the compressors which might hint that this unit isn't aiming for very high boost levels.

I saw one these R2S units mounted in a prototype engine in one offroad engine manufacturer's R&D department several years ago. I haven't seen production version which might hint that there was some issues.

BTW. Did you know that an intercooler should be called as an intercooler only when it is placed between two compressors? Between a compressor and an intake manifold it should called be an aftercooler. Almost the whole industry has forgotten the original meaning of these terms.

Casper > kanadanmajava1 01/15/2014 at 17:41

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I hadn't thought about that, but that's true. Back in the old days they were always called after coolers.

The R2S is actually on the next BMW diesels coming out either next year or the year after. I don't remember when.