sequential twin-turbocharging.

[kotomile]

Okay, so in order to fully understand how this works I've been reading online, but haven't found the right answer. Everything I come across basically says "at low rpm..small turbo, and at high rpm.. big turbo!"

But they don't get into the HOW. Is there a valve in the exhaust somewhere to disallow/allow exhaust to reach the secondary turbo? If te answer is yes, then by jove, I've got it. If not, I require further enlightenment.

[Prok0]

Usually in alot of the factory passenger car applications is actually 2 turbos of the same size, and its just one spools first and then the secondary turbo comes online...

and yea, usually the exhaust manifolds are connected...Check out stock supra TT setups and you can see how the stock exhuast mani's are routed together

[idreamidrive]

the way i understood squential turbo charging is this...

you have one smaller turbo and one larger one. its easier to spool up a smaller turbo so that it gets spooled up first and works in the lower rpm. the larger turbo is spooling up to but not as fast as the smaller one. so at this point you have one spooling up quickly and the other one lagging behind. you cant feel this "lag" because the small turbo is working. the smaller turbo will hit a maximine velocity at which it can spin/work. This is the point at which this turbo will not produce anymore power. At this point the larger turbo is needed and should already be spooled up to take over on the job.

just think of it this way... most manufactored cars with turbos on them have a small turbo to give you that feeling when you mash on the gas at a low rpm that you will take off quickly, this is true up until a point. subarus are notorious for this stock. they have no top end power. but if you put a bigger turbo on it, you will have no low end power and a shit load of top end. you can also see this in supras. a stock supra takes off pretty well. but one that is modified to be a single turbo is slower than shit until it hits the power range, where you pretty much have to shift once you get there. stock supra = mash gas peddle, a little bit of "lag" then accleration. single turbo supra = mash gas peddle, wait, wait, wait wait, OMG POWE-shift.

hopefully i helpped you out, if not point out what you still don't understand, and ill try to get some better info

[Sean @ NDF]

you pretty much just explained turbo lag, and what sequential turbo charging does to prevent it.

Koto - are you wondering about the crossover? It has to be electronic or something. EIther when the car hits a certain hp, or perhaps even rpm in first.

[idreamidrive]

you pretty much just explained turbo lag, and what sequential turbo charging does to prevent it.

Koto - are you wondering about the crossover? It has to be electronic or something. EIther when the car hits a certain hp, or perhaps even rpm in first.

there is no cross over... both are going at the same time.... one just isn't effective when the other one is

[Sean @ NDF]

There IS a cross over, I guess you could say there is a crossover for all turbocharged vehicles. On sequential its not to say the smaller turbine stops spinning, but the point when the boost pressure in the manifold is the same as the smaller turbine inlet pressure. Right?

[idreamidrive]

There IS a cross over, I guess you could say there is a crossover for all turbocharged vehicles. On sequential its not to say the smaller turbine stops spinning, but the point when the boost pressure in the manifold is the same as the smaller turbine inlet pressure. Right?

i guess so... but i never said that the smaller turbo stopped spinning. it just reaches a critical velocity where it can't spin any faster

[Sean @ NDF]

right - like mine does everytime I hit 8k and start losing power

[kotomile]

Thanks for the explanations, Proko pretty much answered it.