NefMoto

Hello, guys! :)
Here I am again with another crazy idea. Please don't judge my sanity and just answer if this is possible on 4cyl.

I've searched google and all I found was usual parallel scheme, where half of exhaust gases go to each turbo. Now with only 4cyl engine exhaust gasses from two cylinders would not be enough to properly spin two k03 turbos, right? So, theoretically, would it be possible to connect them in sequence like in my drawn scheme? Also would the speed of exhaust gasses be enough to spin the second turbo (turbos in question here are k03)? Also, would that double the efficiency islands in combined compressor map of these two turbos?

(http://s4wiki.com/images/thumb/7/75/K03-1870_EXA.png/724px-K03-1870_EXA.png)

Sincerely,
masterj

Nope, for example if both turbos were operating in the peak efficiency part of the compressor map i.e. 73% you'd be operating at 53% (73% x 73%). At that efficiency air charge temperature is going to be pretty high!

If you want to know how a sequential setup with equal sized turbos can look like search for the TT Toyota Supra.
The are also a couple of diesel engines with different sized setups like BMW 123d/125d, Daimler C250 and also engines from Opel and VW which are all 2l 4cyl.
Then there are the 3l 6cyl BMW x35d/x40d/x50d, Audi and Jaguar biturbo diesels all with a different sized setup.

When you do your research you will see it's not as simple as your drawing ;)

Maybe also have a look at compound setups. A few have been done on Mitsubishi 4cly engines. Should be easier on a gasoline engine.

Oh ok, but that would produce around 2.2bar of  boost combined(1.1 each at 73%), right?

I kinda thought that if you have turbo producing 1.1bar of boost at % 73 efficiency i could use two turbos to push same  boost but stress them less (0.55bar each).

BMw run the best setup I think on the 535 diesels

2 turbos, 1 small 1 large and 3 actuators. 1 for each turbo and then 1 to switch flow from the small to large when needed.

It looks like compound setups are very similar in design, except that one turbo is feeding compressed air directly to the other, right? :) Looks simple enough

Nope, if each turbo produces 2.1 bar absolute the second turbo compresses the 2.1 bar absolute pressurised air from the first turbo by a factor of 2.1 to produce 4.41 bar absolute or 3.41 bar of boost.

that is with compound setup, right? I was talking about my idea when both turbos pushes air to intercooler and not turbo->turbo->intercooler->intake mani :)

turbo->intercooler<-turbo
                 v
       intake manifold

both of them share hot exhaust gases one after the other but each of that turbo pushes fresh compressed air directly to intercooler not to one another

Found something similar already on internet :))
http://www.supraforums.com/forum/showthread.php?720625-Kevin-s-Compound-Sequential-Twin-Turbo-Design (http://www.supraforums.com/forum/showthread.php?720625-Kevin-s-Compound-Sequential-Twin-Turbo-Design)

Interesting find. I can't see how this will work properly with equal sized turbos just from looking at the PR over the turbine wheels. Excited to see the outcome  ;D

To address your idea about the twin K03s on a divided exhaust mani, they would probably spool quite well. I've seen some surprisingly large turbos on single cylinder motos and those guys have no issue spooling.

And here's whole article on the said design with twin turbo sequantial setup:
http://mkiv.supras.org.nz/articles/sequential.htm (http://mkiv.supras.org.nz/articles/sequential.htm)

Shall I say, holy sh.? :o

New idea here...
Basically using one small turbo to spinup the huge one.

Let's say we have K04-015 hot side taking all the exhaust gasses. So this K04-015 from cold side will feed boost directly to some HUGE ass turbo hot side (the same would be as exhaust gasses). And this huge turbo cold side would go to engine intake. As I said small turbo will spin up huge turbo and allow minimize it's lag while providing huge benefits of air. Would this theoretically help huge turbo to boost way sooner than it would normally boost from exhaust gasses?

Slightly off-topic, how about something like this: http://www.audiclub.fi/audifinns/showthread.php?t=89474&page=16 (http://www.audiclub.fi/audifinns/showthread.php?t=89474&page=16), one guy here is driving with a turbo-/supercharged AAN. All the text is in finnish but there are lots of pictures of the setup. Twin-charge goodness begins on page 16.

Maybe ElRey will jump in, I would like to see some updates on his project here (http://www.audizine.com/forum/showthread.php/632341-BT-build-with-several-compromises-EXPECT-ONE-gt-stock-like-spool)

Another interesting project here (http://www.audizine.com/forum/showthread.php/554079-Sequential-turbo-setup-Need-Help-Finding-Part) and continued here (http://www.audizine.com/forum/showthread.php/631910-GT25-GT35-Sequential).

I have wanted to twin charge my 1.8t GTI for a long time now. I'm still looking for a decent g60 supercharger for a decent price...dang things are rare nowadays.

Do you mean this ? :


It's daily driven by my wife and me. I'm currently (and slowly) developing custom boost control for the Low Pressure (big) turbo. I will be cloning the existing GGDSAS,LDRPID,LDTVMA functions and adding interaction between the new and existing funcs. I may end-up just using KFTVLDRE control for LP turbo and allowing High Pressure (small) turbo do the acutal PID control.

As it sits now, LP runs off wastegate spring signal from between the two turbos (1st stage). It runs at 6.8psi. The HP turbo adds the difference to target boost. Base boost with 0% duty is 8.9 psi. I run 16-18psi. So, 6.8psi from LP turbo and 9.2-11.2psi from HP turbo. But HP provides all 18psi at low RPM and before LP turbo spools up.



Boost actuated exhaust dump is controlled by N112 with a deleted and rewritten SLS function. SLS relay will control inline fuel pump like it does on my MK4 16vt Jetta Wagon.

Stock bottom-end still, so nothing crazy at the moment. Just enjoying working on the hobby project. Feel free to ask any questions.

elRey Wow... that's great, thanks for sharing.


Would it be possible to control the turbos without the custom coding using the MAP in the stock location?

Are planning on implementing 5120 hack?   

Sure, but not separately. And if you can't control them separately you can't specific at which PR each operates. Thus, you have have to rely on their sizing.
There are a few ways to control them. You can have one N75 control both. Two N75s, one for each but driven by the same ECU PWM allowing different boost signal sources.
MBC on one and N75 on the other. I'm sure there's more. All of which require different KFVPDKS,KFLDRL,KFLDIMX, and PID calibration. However, I want the ability to specify the PR the LP turbo will operate at independent of it's sizing compared to the HP turbo AND retain minimum base boost for drivability without depending on KFVPDKS heavily.


I am planning to. I'm just not looking forward to the work. I have done it for my Jetta Wagon 16vt and it was tedious. I'd rather do the work myself instead of relying on what's out there. I currently have a 4bar in the stock location and a 3bar between LP and HP turbos and wiring in place to support 2nd MAP and N75.

So if I put K04-015 to spin up Holset HX??. Which one I should buy? HX60? HX65? HX70? HX80?