I was wondering if someone could explain this to me.
What's the diff between a sequential and non-sequential turbo?
Also pros and cons.

And no, I'm not planning on putting one of these in my car. It's just something I want to learn more about.

Thanks.

 

Sorry man I really can't help here, I know the theory but I don't have any working experience with any Legacy RSK B4s yet...unless you have one for us to dissect and study

Red we need HEEEEEEEEEEEEEEEEEEEEEEEEEEEEEELP!!!!!

 

Yes?

 

From what I know sequential turbo works like this. At low RPMs first turbo operates. At some point, let's say 4000 RPM's, the second one starts to operate. I think this is done to reduce a turbo lag. I think Supra TT has this setup from factory.
Then some people modify it into non-sequential. They either put a single turbo or make those two turbos operate at all times.

 

Thanks, that's what I thought it was but wasn't sure. But why do ppl change to non-sequential? If it's for more boost, then instead of replacing both turbos, why not replace only the secondary turbo?

 

Ok,

This ones for me.
Both turbos are small in sequential mode. All the exhaust gases are used to spin the first turbo... so a quick spool up... minimal lag. Well the first turbo usually is too small to maintain the cfm necessary to carry boost into the upper rev range... There is a transition point where the second turbo comes on line.. sometimes a flattened area or even a dip in the torque curve. The second turbo then with the first turbo can flow enough cfm to carry boost and power in the the rest of the rev range.

In non sequential mode, both turbos are spun at the same time... so more lag but there is no transition point or power loss. Also, there is usually more overall power because the flapper and actuators for the transition mechanism are removed.. opening up the exhaust pathway. Also less failures of the complicated sequential mechanisms and the transition from single to twin turbos can be destabilizing especially on a road course.

Some people will change just the secondary turbo. But most people are either satisfied with the advantages of non sequential and spend very little extra money or they convert to two larger turbos or go with a Large single turbo. Changing just the secondary turbo makes the transition point of sequential turbo operation much more difficult... a bigger "hole" in the torque curve.

In my RX-7 I went from sequential to non sequential and then to Large single... all moves were definate power improvers.

 

Cheuk, is there anywhere on the web we can see this setup in DETAIL ...? Gotta know more about it just in case I have to fix the damn thing.

 

Thanks Cheuk. That cleared up most of it for me.

 

Glad to be of help.

Mechanix... You could search the web for RX-7 sites... there are several with the sequential system diagramed.

It is a severe headache. It took me forever to master all the solenoids, check valves, vacuum hose lines, pressure chambers, vacuum chambers and actuators. It got so frustrating having to wait a week for one stupid $5 part to arrive in the mail that I ripped out most of it for non sequential mode and then ripped the rest of it out for single turbo. There is a reason that RX-7 owners pay upto $400 to have all the vacuum lines glued / tie wraped.

 

Thanks man...!!! Say, uhh, I never had the chance to go into a sequential turbo'd engine bay before, is it scary in there? And is there anything I should know before I start the basic checklist?