Sequential Turbochargers

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Where are they placed? are they besides each other? where else would they be placed??

posted by  BuggatiV

Diesel or petrol?

posted by  Wally

I know but I dont have time to tell you. Sorry.

posted by  CarEXPERT

basically ones bigger, ones smaller, the small one spools up, and then the bigger one spools up a little later in the rpms... my friends supra is sequential... the small one spools up at about 2000, and then at aabout 300-3500 the 2nd one spools up gives it a lot more power

posted by  mazda6man

THanks for your help.

posted by  BuggatiV

what confuses me about sequential turbos is that if only one works at one time, then what happens to the exhaust gases when it switch.

In an I6 only 3 header ports are connected to one turbo right? then the turbo wont be getting engough gasses to spool it up.

posted by  CarEXPERT

do a search on these forums, we had a topic about it a while ago and it was pretty informative.

posted by  Inygknok

didnt know you could have diesel turbochargers..

posted by  BuggatiV

[QUOTE=CarEXPERT]what confuses me about sequential turbos is that if only one works at one time, then what happens to the exhaust gases when it switch.

When it starts off, the smaller turbo would kick in and then when at higher rpm, the bigger one starts working as well, so both are in use. I think the exhaust from the smaller would go through the bigger one but there wouldnt really work until there is more exhaust.

posted by  BuggatiV

well, thanks so much for your input.

Theoretically, can you take something like a supra TT and get same size turbos? You'll have insane turbo lag, but the high end RPMs would make up for it. Thoughts?

posted by  Godlaus

most modern diesels have turbos,

Not to be a post whore:

The idea behind is that you dont het so much turbo lag, becuase your entire driveable engine range is covered by a turbo, so the power is more evenly delivered, the disadvantages, more things to go wrong, uses more fuel, more expensive to implement, complicated to service. Good for some aplications especially with restrictive class rules or emisions regulations where turbos can be made cleaner than super chargers.

posted by  cinqyg

hmm, but why would you want so much lag? unless your only racing and not street driving, and even then theres so many other options to get the same power and less lag.

posted by  BuggatiV

Yes they are fairly common, if not in the US then elsewhere (I understand US diesel does not have all the desirable properties found in other countries).

cinqyg, a turbo charged engine has a more consistent MEP because of lowered expansion ratios, thus a smoother power stroke.

Godlaus, twin turbo doesn't mean you will have more lag than a single setup. There are lots of combos that will give adequate response. If you look at a SAAB you may see a turbo being powered by half it's cylinders for instance. On the flip side, guys here convert the twin turbo soarer V8 to a single unit for better performance.

BuggatiV you are right. A hybrid designed for the application could well see good spooling throughout the range.

posted by  Wally

just if you had something like an s2000 (not positive on the TT setup on that engine), and it's already powerful as a NA motor, and the lag won't really slow it down in the low RPMs, and having same size turbos would be kinda cool to brag about, and it would be awesome to have that major pull at the top end.

Wait, same power less lag? You just talking about a powerful supercharger? or basic NA tune up parts?

posted by  Godlaus

I think same sized twin turbos spool up hella slow because only half of the exhaust gases is going into the first one and the other half go into the second. An S2000 is I4 so would a twin turbo work? only 4 exaust ports so only 2 ports control one turbo. Are there any I4 with twin turbos?

posted by  CarEXPERT

Yes, I stated that the spool lag would be immense, but the top end would pull amazingly, which would be cool, because you have a race car with stock low RPM power. I'm not sure if you can get a TT setup in an s2000, but it was my only example, because it's the only fast NA I4 that I know of. Well, there's the SRT-4 also.

Dunno about the TT I-4 though.

posted by  Godlaus

What the hell? I don't think I've ever seen a big rig without a turbocharger. You can clearly hear the blow off when they shift on the highways..


Turbo lag is something you don't want. Thats why the Bugatti Veyron has a sequential turbo set up. One turbo connected to 4 headers on each side.(I beleive the Buggati V is a V16.)

Oh and CarEXPERT, Exhaust from four cylinders is more than enough to power a turbo. Even a very large one.



I've never seen an S2000 with a twin turbo setup. But the car setup is quite rare for this case. The S2000 actually gets higher power in the lower RPM's with a turbocharger and gets good response after 5K with the Comptech and Vortech cetrifugals. Two turbochargers would probably hurt this engine more than it would help it. Maybe when the S2000 becomes a V6, but until then no TT setups on 4Cylinder engines.

posted by  DSMer

Im not too familiar with diesel, just kno the basics, ppl usually dont get into diesel engines and modifications. seems very interesting tho




interestingly enough, its actually a W16 (combining V8 + V8 = W16)

posted by  BuggatiV

incorrect, its combining 2 VR8's. no VR8 engine has ever been officially produced for commerce to this day, but rumor has it that they might come out soon. u can look this info up anywhere.


anyhow, next up, the 300zx has a twin turbo set up with both turbos spooling up at the same time and they are both working full time. since the turbos are quite small, there isnt really that much lag. bigger engines dont have too many problems spooling up more than one turbo at the same time.


third, the SRT-4 is turbocharged, not NA.

u can twin turbocharge any engine, its just a matter of costs and tuneability.


cars with 2 full-time turbos of big sizes do have problems in the lower rpms, obviously, but they are usually used for special purposes in which they dont even bother going down into the lower rpms (JGTC, maybe some rare drift cars, etc.).

posted by  Inygknok

The question I was asking, was as to whether or not it was practical on a car like an s2000. if you had 20 grand laying around, would you do it?

posted by  Godlaus

no i wouldnt, and i dont find it practical. single turbo set ups are much more efficient in MANY more ways. i wouldnt twin turbo my own car, and my g/f is planning on buying a supra TT (newer model) for one of her bdays or christmas, and i would still turn it back to a single turbo set up.

posted by  Inygknok

Thats a very blanket statement. There are many cars that perform a hell of alot better under twin turbo setups than they probably would with a single. So long as the twin turbo setup is very well though out and tuned properly, it "should" be more productive than a single turbo setup covering both good power in low and higher RPM range.

While you may feel that single turbos work better, lots of automakers and engineers care to disagree with you.

I highly doubt this rest solely on personal preference, but more on the engine characteristics as well.

posted by  DSMer

i guess the whole part of "efficient in many more ways" just passed right by u. i never stated in which ways they are more efficient since i was expecting everyone to be smart enough to figure out in which areas they are more efficient.


first off, pushing one turbo is much easier than pushing 2, therefore we find more efficiency.

another thing u might learn if u ever bother learning engineering.
lower costs = higher efficiency
less energy spent = higher efficiency
less weight = higher efficiency
easier/cheaper maintainance = higher efficiency
less heat = higher efficiency

so on so on. in terms of power, duhh. 2 turbos can produce more power, BUT ONLY if, and IF, they are larger than the single turbo in terms of combined size, and IF PROPERLY tuned correctly. in order to be more "efficient", car makers would have to insert smart pills into people who would buy their cars so they can be able to achieve this, or just simply afford maintainance, buying the vehicle, etc etc.

if u SERIOUSLY pay any attention to drag racing, circuit racing, drifting, etc, u will notice that the higher percentage of vehicles use single turbo set ups for all of these reasons, thats if they dont go with supercharges or stick to NA set ups, or nitrous for drag races. rally events stick to misfiring systems mostly, but that heats up the system quite largely and wears out the turbo faster than normal, but atleast it gets rid of the lag (and its a very expensive system).

posted by  Inygknok

what is a MISFIRING system? do you mean nitrous or what do you mean

posted by  CarEXPERT

There's lots of factors to consider e.g. more pumping losses with two instead of one, losses as two fluid streams collide regardless if they interlace. Skin and fitting losses on the pipes are also exagerated. etc

posted by  Wally

how do you turn up the boost for your single turbos. Im not sure but there is a manual and electronic boost controller. I know what a manual does but what about the electronic one. do they do the same thing but how diffrently?

posted by  CarEXPERT

The way to maximise boost on a turbo (without modifying it) is to increase the wastegate setpoint. You can do this by controlled bleeding of the actuator line or if the gate starts lifting off, increasing the spring tension of the actuator. Obviously the turbo has a maximum head it can act against before it chokes.

posted by  Wally

You need a boost controller to do that. The manual boost controller makes the wastegate think that there is less pressure than there really is. this is done by twisting the top of the controller. how does electronic ones work????

posted by  CarEXPERT

You don't need a boost controller to raise the setpoint:- there are other much cheaper ways.

Electric ones can hold off opening of the wastegate for faster spool, effectively changing the operating range of the actuator, and as well it can adjust the setpoint. The signal pressure to the actuator is manipulated by the use of a solenoid(s) ultimately reacting to boost pressure.

posted by  Wally

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