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Discussion Starter #1
Why don't more companies use a biturbo to combat turbo lag (a la the Audi S4)? Is lag just not a big concern or is some sort of cost/reliability issue?

-Matt
 

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I don't believe the bi-turbo takes out turbo lag. The S4, a sweet car, has a turbo for each cylinder bank. I first thought it was a fancy name for a twin turbo. By my understanding the twin turbo has a small and big turbo to combat lag. But anyway the S4 is a 2.7L V-6 with two turbos. I would think since it is a V-6 it has some torque.
 

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There is a sequential twin turbo setup, like on my Supra, where one turbo kicks in first, then the second one kicks in, both turbos on my Supra are the same size though. Then there is a true twin setup like on a 911 turbo or the old 300Z where both turbos kick in at the same time.
 

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I think the sequential turbo acts like a turbo-lag deterrent....one spools up quicker than the other and then the larger one takes over. Of course, I thought the S4 is a "true bi-turbo" design where they are both the same size turbos that kick in at the same time.
 

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ok, so sequential means just one after another based on setup...right?

so, a "true bi-turbo design" would be one where two turbos are in boost at the same time? obviously smaller turbos i would imagine just based off hoe much boost one large turbo can make.
 

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Re: Homologation

Correct.

The bigger the turbo the more boost it can produce but the longer it takes to get going(more turbo lag). The smaller the turbo the quicker it can spool up but the less boost it can produce. I think most companies use twin turbos so they spool up quicker but can also produce a decent amount of boost compared to a larger single turbo. I always wished I could get bigger turbos for my Supra but keep them sequential, but no one makes a setup like that. HKS has a twin turbo setup, but it's a true twin setup where both turbos spool at the same time. A Supra I was in that had the HKS twin turbos had real bad turbo lag which suprised me but it looked nice. Once those turbos spooled up though, hold on. Most people I know go with one big turbo in place of the smaller sequential turbos the Supra comes with stock. I questioned it and was given good reasons why to go with one big turbo but I don't remember all the reasons, other than a big turbo can produce more boost than a smaller one. I think it's easier to overcome turbo lag in a modified car than it is to produce more boost when you reach the limit of a small turbo.
 

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Cool, explanation, but I think that explanation for the Liberty is actually a sequential turbo.

MKIVSupra, how do you like the supra? I really like them a lot. any major problems with the car? I guess I like the idea of a mega-fast sedan over a coupe.
 

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91TB78, I love the Supra. I am actually on my second one. My first one was a daily driver that I put almost 100k miles on. I don't want to say I beat on it, but I put it through it's paces on a daily basis and never had a single problem with it. There were not even any recalls on it. After I bought my 98 Legacy GT, I found a Supra exactly like mine but a 6spd and only 4,500 miles on it. So for a few $k difference I sold the one I had and got that one. Right now for the money there is not really any other sports car I would rather have. You can't beat being able to get 50hp for free, or 150 reliable hp for under $1k. Also the Supra engine is known to be able to handle up to 600hp with stock internals and fuel system. It just sux not being able to drive it everyday all year around. That is why I want an STi so bad.
 

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It seems there is no convention for naming twin or bi turbos.

Just to say that 'twin turbo' is most commonly a turbo for each bank of cylinders. Bi-turbo is no doubt a gimmicky phrase. Similar to 4wd vs. Awd.

Sequential twin turbos are usually called just that, sequential, to differentiate them from the more common twin turbos.

In the case of the Liberty B4, the sequential is employed, but there is apparently a noticeable 'gap' in power, at the peak of the smaller turbo before the larger kicks in.

Properly tuned, a sequential turbo can greatly *reduce* lag, but turbo lag is caused by having a turbo. Period.
 

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MKIVSupra,
YEah, I love the car! Its so bulletproof and a proven sports car, but I know what you mean about all-year driving. I have always loved the Type-R, but as a main car for my wife and I it's a little impractical being a two-door sports hatch. Not too mention I am 6'4" 235..so I like my room. I think the Supra tt would be quite nice..however it is getting to the point where good, non-beaten, Supra tt's are hard to find. Do you have any pictures? I would love to check it out. How much hp do you estimate you are running at the crank/wheels?
 

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You can click on the "WWW" button below my posts and check out my little website for some pics. They are old though. I went to a dyno after installing all my mods and only put 385 to the wheels. I am pretty sure my cam gears are set wrong and my plugs are gapped wrong. I might even need new plugs. I am gonna take care of all this when I go in for some new brakes once I make up my mind on what rotors I want to go with. A friend of mine with the same mods as me put 416 to the wheels. When we were stock I put 305 to the wheels and he put 301, so I am thinking with my mods I should be around 416rwhp myself. Yup it's hard to find a nice non-beat Supra for a reasonable amount of money. Some prices I see Supras going for is crazy. Not that I am really complaining cause I could probably sell mine and make money off it, even with what I have into mods. As a daily driver the Supra has decent room in it for the driver :) but once I switched out the suspension it's almost unbearable for daily driving, especailly on Chicago streets. Did I mention how bad I want an STi?
 

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MKIVSupra,
Man, I love the ride. how many mile do you have on it now? Do you still have the stock wheels on or did you get something else?

Yeah, I love the STi b/c it is such an awesome and versatile daily driver, speed demon, track monster, all-weather car!!!! :D

Are you planning on selling the Legacy or Supra when you get the STi? I would look at getting a used Supra or the Type-R, but the wife wants a 4-door, and personally I love a supercar sedan...very fast, but a total sleeper if you keep the external mods down. Your car looks like a sleeper with no external mods on it (albeit not a total sleeper b/c of its wing and the fact that its a Supra). When I get the STi, I am going to have it debadged and get it in black. I am also going to change the wheels out and either keep them or sell them to buy me some Prodive P7s or P1s in anthracite!!
Like your car though..
 

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Discussion Starter #20
Is the STi really a good daily driver? All the reviews I've read of the WRX say that it's rather stiff for driving around town. I can only assume that the STi's suspension is stiffer (re: rougher) and would make it even less suited to be a daily driver. However, having never driven either I can only speculate based on reviews that I've read.
 
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