YACT: Which type of twin turbo is better?

[Fenixgoon]

this just popped into my head.. which is better when having two turbos in a car:

two equal sized turbos

or

sequential turbos (1 small for low rpms and gears, 1 big for higher)

i have no idea, so i though i'd post.

 

[deadlyapp]

well, sequential would allow for faster acceleration, but you hit a higher top speed quicker, depending of course on the sizes of the turbos. And the configuration would be a nightmare.

I have identicals on my stealth, and its very nice. They kick in around 2k rpm with stock dp and everything. If I upgraded the DP and exhaust I would probably have much faster spool time.

Edit: personally I think a single large turbo is better in most cases when modifying from an NA car, but if you come stock with twin turbos, then it makes sense to switch it around.

 

[Safeway]

The former. Two equally sized.

 

[Pacfanweb]

Depends on what you're trying to accomplish. Very smooth driveability, or max HP.

 

[NutBucket]

Sequential turbos are usually for smaller engines (say 2L). Larger engines are usually afforded identical turbos since each bank can easily move enough air to for a single turbo.

 

[PowerMac4Ever]

Most, if not all, sequential turbo systems use equal size turbos. Basically one turbo spools before the other, so there's a more linear powerband.

 

[QuitBanningMe]

One turbo and a built engine.

Then turbo lag isn't much of an issue.
My experience....my car....YMMV

 

[deadlyapp]

How does that work powermac, so one starts spooling at 2k or so, then the other one starts spooling at 4 when the first one hits its limit? Kind of wierd... but makes some sense.

Most cars wouldnt come stock with different sized ones for sequential system, but its been thought about and makes perfect sense.

The small one spools much faster, but hits it's max flow early on. Say it starts spooling around 1000 rpm, is limited to 5 psi or so @ 2500 rpm, the wastegate diverts the air to the next turbo, which is very large in size and takes much longer to spool, but kicks in around 2500 rpm, and carries the car the rest of the way

 

[Fenixgoon]

Originally posted by: PowerMac4Ever
Most, if not all, sequential turbo systems use equal size turbos. Basically one turbo spools before the other, so there's a more linear powerband.

wouldn't that be counterproductive to a sequential turbo system, though? the whole point (i thought) was to have a smaller turbo that provides low, but quick boost in the low end while heavier one begins to spin up, that way turbo lag is reduced.

 

[Apex]

Originally posted by: Fenixgoon

Originally posted by: PowerMac4Ever
Most, if not all, sequential turbo systems use equal size turbos. Basically one turbo spools before the other, so there's a more linear powerband.

wouldn't that be counterproductive to a sequential turbo system, though? the whole point (i thought) was to have a smaller turbo that provides low, but quick boost in the low end while heavier one begins to spin up, that way turbo lag is reduced.

No, PM4E is correct. Take for instance the last RX7. It used twin T25 sized turbos. Only one runs at lower RPM's, then it switches over to both.

My preference is for twin parallel turbos. A well designed parallel setup tends to be more efficient, and you only have one lump in the powerband instead of two.

Lots of people convert from sequential to parallel on the RX7.

 

[SilentZero]

Inspired thoughts of the RB26DETT *Drools*

 

[TomKazansky]

it all depends on the engine. Although most prefer linear (equal size turbo) but one spins at a much lower rpm compare to the 2nd one (you can adjust their boost differently)