Lexus IS Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
19,476 Posts
Discussion Starter #1
When you look at cars like the 3000GT VR-4, 300ZX turbo, Mazda RX7 turbo, and Toyota Supra turbo (all since extinct by the way) they all have dual turbos. In the 3000GT and 300ZX you get the boost of both turbos at the same time. However, the RX7 and Supra have a sequential turbo system in which you get the first turbo intially and the second one further up the RPM range.... Which is better...?? I have driven the Toyota Supra turbo and have noticed that second surge around 4000 RPM's or so. I'm not sure about the S4, but when my friend drives his I don't notice that the individual turbos are activated sequentially (due to the linear power deliver...... Just a thought for you guys to ponder. Personally I liked the turbo system of the 300ZX more than I did the Supra (with the boom.. BOOM)..
Eric....
 

·
Registered
Joined
·
4,250 Posts
it depends on the size of the turbos and stuff like that. most people actually prefer a single big turbo(supra owners) but the twin system works alright either way, although i'd rather have two of the same sized turbos coming on at the same time
 

·
Registered
Joined
·
666 Posts
I thought some of the reasons for the twin turbo set up was because a single big turbo would take a little longer to spool up some boost. So the thought was to start off with a smaller turbo which spools really quickly. Then the bigger turbo would kick in the later rpms.
 

·
Registered
Joined
·
666 Posts
I'm no expert in this...
but I think that the drag racing track preference has always been one big turbo....launching at some mad RPM to build the boost.

but for normal smooth easy everyday driving without that turbo lag, that's why the twin turbo's existed. The smaller turbo would spool up quickly.

I dunno...I could be wrong.

[This message has been edited by wazzup (edited November 13, 2000).]
 

·
Registered
Joined
·
58 Posts
I thought the sequential turbos were for I6 engines and the other kind was for V6 which my their nature requires 2 turbos?

Rick
 

·
Registered
Joined
·
19,476 Posts
Discussion Starter #6
Well I remember back in 1988 reading a Car & Driver magazine road testing a Ferrari F40 (twin turbocharged V8) & Porsche 959 (twin turbocharged Flat 6) in Europe... They said that there was a 4000 RPM wakeup call in both cars at which point the engines accelerated like crazy to the redline (7750 RPM = redline for the F40).... So I'm assuming both of those engines had sequential turbo systems as well...
Eric....

side note (although F40 was released in Europe in 1987, it didn't hit our shores till 1990).....




[This message has been edited by EricK (edited November 13, 2000).]
 

·
Registered
Joined
·
178 Posts
i think the S4 is a bi turbo which means that each turbo is rigged to only apply boost to one bank of cylinders (3) which is why the boost is seamless and available at low rpms... can anyone confirm this???
 

·
Registered
Joined
·
19,476 Posts
Discussion Starter #8
Originally posted by fishtail:
i think the S4 is a bi turbo which means that each turbo is rigged to only apply boost to one bank of cylinders (3) which is why the boost is seamless and available at low rpms... can anyone confirm this???

Yes, I can confirm that... you're right... http://www.chip-tuning.com/usa/fzg/ukaudis4.html
Eric...


[This message has been edited by EricK (edited November 13, 2000).]
 

·
Registered
Joined
·
1,991 Posts
Sequential turbo is good for daily driving because you can almost eliminate the feeling of turbo lag, but still have lots of power at high rpm. The problem with sequential setup is its complexity compared to the normal twin turbo setup. I have heard many of the RX-7 owners had problems regarding the vacuum line that activate the second turbo in the sequential setup, so this could be one of the reasons why not everyone is going with the setup yet.
 

·
Registered
Joined
·
6,168 Posts
The idea behind the sequential turbo system is to eliminate as much lag as possible on the low rpms and still have punch at the big rpms. The sequential turbo setup is complicated and none of the aftermarket turbo upgrades are sequential. They are all parallel. If you don't like the feeling of sequential turbos the Supra can be converted to parallel twin mode (true twin) pretty easily. As far as twin or single turbo upgrades...in general, the single turbo spools faster simply because the exhaust gasses from all six cylinders are used to spool one turbo instead of two. If you can keep your rpms high (read: racing situation) then a huge turbo will offer the most power. But for street driving the amount of lag could make things pretty unpleasant. Although Clint says (don't get mad at me if I said this wrong please) "lag is highly overrated." He has a big twin turbo setup if I'm not mistaken. A big twin setup should theoretically be able to hit higher power numbers than a single because of the amount of air flow they can provide.

------------------
By making this post I am not claiming to be an expert of any sort on the topic and should not be taken as such. It's just my opinion and worth what you paid for it.
 

·
Registered
Joined
·
3,221 Posts
The sequential arrangement is a brilliant idea, and (in theory) should provide some benefits ... But so many other factors (engine design, turbo design, etc) that you can't really say that a sequential turbo'ed car is automatically going to be better than one that isn't.

And yes, the sequential design is easier to implement on a car with both turbos next to each other (like the Supra Inline 6 or the Mazda Rx7 rotary). It is a bit more "messy" to plumb on a "V" engine.
 

·
Registered
Joined
·
6,168 Posts
Originally posted by EricK:
Thanks for that description Scott...

Eric...
No prob, just make sure to take note of my sig.

Person A:"Are you an auto expert?"
Me:"No, but I did stay at a Holiday Inn Hotel last night."
Like anyone is gonna get what the hell I'm talking about right there...oh wells.


[This message has been edited by HIBBoyScott (edited November 14, 2000).]
 

·
Registered
Joined
·
12,157 Posts
Originally posted by HIBBoyScott:
The idea behind the sequential turbo system is to eliminate as much lag as possible on the low rpms and still have punch at the big rpms. The sequential turbo setup is complicated and none of the aftermarket turbo upgrades are sequential. They are all parallel. If you don't like the feeling of sequential turbos the Supra can be converted to parallel twin mode (true twin) pretty easily. As far as twin or single turbo upgrades...in general, the single turbo spools faster simply because the exhaust gasses from all six cylinders are used to spool one turbo instead of two. If you can keep your rpms high (read: racing situation) then a huge turbo will offer the most power. But for street driving the amount of lag could make things pretty unpleasant. Although Clint says (don't get mad at me if I said this wrong please) "lag is highly overrated." He has a big twin turbo setup if I'm not mistaken. A big twin setup should theoretically be able to hit higher power numbers than a single because of the amount of air flow they can provide.

you are right about the supra being converted easier. it has also been proven that the supra stock turbos, will make more hp on the dyno in parallel mode, but most people don't like it and convert back, because of the extra lag time.

as far as singles spooling faster, it depends on the amount of rotating weight and a host of other things, to determine whether a big single will spool faster than 2 smallers, being a given that they are rated for flowing the same amount of cfm's.
 

·
Registered
Joined
·
6,168 Posts
Originally posted by IS300GTE:

you are right about the supra being converted easier. it has also been proven that the supra stock turbos, will make more hp on the dyno in parallel mode, but most people don't like it and convert back, because of the extra lag time.

as far as singles spooling faster, it depends on the amount of rotating weight and a host of other things, to determine whether a big single will spool faster than 2 smallers, being a given that they are rated for flowing the same amount of cfm's.
I was talking about big twins, not small. The key phrase being "in general."
 
1 - 15 of 15 Posts
Top