I saw a mustange this weekend that was twin turbo with a small and big turbo. I talked to the guy and found out that tuning was a nightmare. Anyways I'm wondering if anyone has ever tried anything like this with a Audi. Cincy I know you already said no. So, why not? If tuned it seems like it could be a nasty. Low and High end big boost. Whats not to love? Also, this mustange was scary fast. I'm curious with a stand alone ECU and some more custom work, new internals, why couldn't you do this with an audi?

 

yeah thyre called sequential turbos. I dont know if anyone with a b5 has done it though

 

I would thing one of the bigest problim woul be that that is no room as it is in a B5 were would you put 2 more turbos? But if it were dune and you were able to make it run right [sm=yikesomg.gif]

 

no you only have 2 turbos not 2 additional turbos. Is that what you meant? THe logic is to have one smaller turbo that will spool quickly to provide boost NOW, then a larger turbo that spools more slowly, but it bigger so can offer you more power!

"Sequential twin-turbo refers to a set up in which the motor can utilize only one turbocharger for lower engine speeds, and both turbochargers at higher engine speeds. During low to mid engine speeds, when available spent exhaust energy is minimal, only one turbocharger (the primary turbocharger) is active. During this period, all of the engine's exhaust energy is directed to the primary turbocharger only, lowering the boost threshold, and increasing power output at low engine speeds. Towards the end of this cycle, the secondary turbocharger is partially activated (both compressor and turbine flow) in order to pre-spool the secondary turbocharger prior to its full utilization. Once a preset engine speed or boost pressure is attained, valves controlling compressor and turbine flow through the secondary turbocharger are opened completely. At this point the engine is functioning in a full twin-turbocharger form, providing maximum power output. Sequential twin-turbocharger systems provide a way to decrease turbo lag without compromising ultimate boost output and engine power. Examples of cars with a sequential twin-turbo setup include the 1993-2002 Toyota Supra Turbo (JZA8x), the 1992-2002 Mazda RX-7 Turbo (FD3S), and the 1986-1988 Porsche 959. With recent advancements in turbocharger design, sequential twin turbo systems have fallen out of favor because they are seen as unnecessarily costly and complex."

 

I believe that this line pretty much sums it up. The best modification that you could do to a 3rd gen Rx-7 or Toyota Supra was a single turbo conversion. the only reason that sequential turbos were popular was to eliminate turbo lag and still attain REALLY HIGH BOOST. Let me ask you this, does your S4 have noticable turbo lag? And the most important question, are you willing to do what it takes to handle REALLY HIGH BOOST, ie. lower the compression, stiffer rods, high dollar custom pistons, inconel exhaust valves (these may need to be custom too), and then hours and hours of tuning to make it driveable? The best upgrade for the S4 is a pair of k04 turbos, with larger intercoolers and a chip to add extra fuel. Even then, you really won't be able to get stupid with the boost level, but you still shouldn't have bad lag.

Does this answer your question?

 

sounds killer!

 

Someone wanna kick down some k04's for Christmas....been a good boy!

 

Sorry the was a dumb post!

Hindsight is 20/20

 

i'm doing research and development basically. i was only speaking of two turbos. there is a duramax with 6 though. don't ask the why question, but if you know why, by all means let me know. if i actually go for this i would be doing it right and getting stupid with it. redoing all stock internals with a stand alone. so why are the sequential turbos obsolete? it makes alot of since to me. it still takes K04's a long time to spool, and kO3's don't give amazing high RMP boost.

 

If you wanted to do that with only two turbos, one being small and one being large then you would have to basically make the original twin turbo setup into a single turbo setup with the two turbos hooked up on the same single exhaust and intake pieces. Otherwise they would fight eachother and one bank would have more restriction than the other. on an s4 it would be difficult to find room unless you plumbed everything over to the airbox area and put the turbos there and made the intake work somewhere else. then by all means give it a go.