Sequential (biturbo ?) turbos on 20vt

[kwlw]

Hi,

How sequential turbo is controlled ?

Because I just come to a another stupid idea (stupid ideas - that's my speciality ) - is it possible to make sequential (?) turbo from let's say diesel turbo (T3 for example) and K26 used in MC.
Let's assume we make exaust manifold somehow, and bolt these two turbos on it. As far I understand then I will need two wastegates - one for "big" turbo, another for small (I don't want it to overspin). If the small turbo has integral wastegate, I suppose it is possible to make adjustments for this small turbo event to pass exaust gases to the "big" when boost is too high.

If someone understood, what I've said above , then there is my question - will I have more torque in low rpm ? Not mentioning exaust making nightmare .

Sau

[S2sedan]

Yes I understood, try to look after BMW Diesel engine, KRAM RS2 already post it before.
They are great in this kind of technology.

[S2sedan]

272 hp on a 3L diesel engine, with 500NM @ 1500 RPM

[quattronutter]

272 hp on a 3L diesel engine, with 500NM @ 1500 RPM

have a look at an rx7 twin turbo,these are sequential with small turbo for better low down torque,i believe it uses a bypass to prevent overspinnig the small turbo once it reaches a certain boost pressure ,there are a few pics floating about on the net of how they operate

[Lee]

What about the Subaru Legacy B4? Isn't that a sequential turbo setup too?
Used for reducing lag and giving a broader power band.

Sequential is an option on the I5 but the plumbing is quite complex. We have looked into this and it is an option. Parallel turbo charging is virtually impossible on the S2 as it is diffult to ensure both turbos are working effectively and to make sure one isn't overspinning. To do that is a difficult balanding act and would be easier if there were 10 exhaust ports on the head....even with this it is still not straight forward. Parallel turbocharging is easy on even number of cylinders.

One ex member...OZzzt RIP... had built a monster manifold for a twin turbo setup but I doubt it will make an appearance. That was not sequential though IIRC.

[kwlw]

Parallel turbo charging is virtually impossible on the S2 as it is diffult to ensure both turbos are working effectively and to make sure one isn't overspinning. To do that is a difficult balanding act and would be easier if there were 10 exhaust ports on the head....even with this it is still not straight forward. Parallel turbocharging is easy on even number of cylinders.

One ex member...OZzzt RIP... had built a monster manifold for a twin turbo setup but I doubt it will make an appearance. That was not sequential though IIRC.

That's the answer I was searching for . Thank you Lee, now things look far more clear

Sau

[karlblues2]

What about the Subaru Legacy B4? Isn't that a sequential turbo setup too?
Used for reducing lag and giving a broader power band.

Yep, I had a B4 and I sold it for the S2!! The lag induced between the two turbos appeared at 3800-4400rpm and became a black hole that you changed up into. Essentially the wastegate for the small turbo 'fed' the spool up for the second turbo, and caused a transition period where the small turbo had consequently dropped boost and the big turbo hadn't spooled up fully. This lag between the turbos was the reason I sold my B4 and the reason Subaru changed to a single 'twin scroll' turbo on the successor named GT after 10 years of trying to perfect the dual stage twin turbo setup.
I wouldn't recommend going that way personally on any car.
HTH
Karl
Oz

[NoNonsense]

@ S2 Sedan: http://www.nononsenseaudi.com/albums...rbos/index.htm

I have been researching something like this with a friend of mine. The way BMW does it is the air is sucked past the large turbo and then into the smaller turbo and then into a single intercooler and manifold. There is a flap in the exhaust which regulates the exhaust gas from one turbo to the other...finally, you'd need two turbos with an internal wastegate...