turbo yes

[serialk11r]

Originally Posted by ryude

Roots is a pump, it draws the air through the inlet, the air heats up against the casing causing heat\turbulence. Cheap to build, easy to tune, and tends to be more efficient at lower boost levels.


Twin Screw is a compressor, it draws the air through the inlet and compresses the air within the screws. Less heat\turbulence, more expensive, better at higher boost levels.

Twin screw has less parasitic loss compared to a Roots, but you're talking 5-10 HP in our power range.

OEM's use roots style because they are reliable and cheap.

TS are used in lots of after market and racing applications.

Sorry man you're not exactly right, both are positive displacement pumps and operate on the same principles. Any difference would be attributed to mechanical friction, assuming good sealing.

[old greg]

Originally Posted by serialk11r

Sorry man you're not exactly right.

Right back at you.

They are both positive displacement, meaning they'll move a more or less fixed amount of air per revolution (volumetric efficiency not withstanding). But they don't work in exactly the same way. A roots blower simply moves air from from the top of the blower to the bottom, and once that air reaches the bottom the blower crams it in creating pressure.

A twin screw compressor moves air from the back to the front in an ever shrinking chamber. The air is compressed as it travels along the length of the supercharger, this is the 'internal pressure ratio' which is usually 1.4:1, though Kenne Bell makes some that will do 2:1. When the air is discharged into the intake plenum it is already compressed, and that was done in a more efficient manner than a roots blower is capable of (lower temps).

[serialk11r]

Alright my bad, but I fail to see how it is more intrinsically efficient at all...both adiabatically compress incoming air. If I'm wrong, could you point out what exactly is wrong with my thinking? In fact if twin screw has internal compression going on, then it would be less efficient if the boost pressure is lower than the pressure than the compressor produces, if I understand it correctly.

[nrclptcnsmniak]

too bad im more interested in the Subaru version than the Scion car. Lets see what subaru does. I just hope Subaru doesnt supercharge.

[carbonBLUE]

Originally Posted by youngxlos

Everyone always talks about turbo lag... from my experience there is barely any lag, and its only noticeable wen I'm in like 6 gear in the highway and i put my foot down, takes about 1 second to hit boost then the car is off.
So unless your using a massive GT35R you'll barely notice lag, I have a GT2860RS and when i put my foot down the car goes, there is no lag, and I'm using 9.0:1 CR

Supercharging to me is stupid, it takes power to make power, turbos dont.
we can sit here and argue about it all day, its all personal preference if they make a factory supercharged good for them, ill still rather turbo mine.

youngxlos!!! i was wondering when you were going to be on here from newcelica.org.... lol...

but if this car likes to cruise around in the high revs like the celica does, turbo lag shouldnt be a problem at all...

[Lucas]

Originally Posted by Jah1mon

I couldn't agree more. Elimnating lag, or making it less noticeable takes the right compression ratio and proper turbo sizing. Both of which Subaru can match. I do hope they go this route with a Sti model.

Compression ratio doesnt effect turbo response. Just sayin

[old greg]

Originally Posted by serialk11r

Alright my bad, but I fail to see how it is more intrinsically efficient at all...both adiabatically compress incoming air. If I'm wrong, could you point out what exactly is wrong with my thinking? In fact if twin screw has internal compression going on, then it would be less efficient if the boost pressure is lower than the pressure than the compressor produces, if I understand it correctly.

Adiabatic compression is an ideal, and so, does not exist in the real world. That's what the term 'adiabatic efficiency' is all about. It's how much work it should take to compress the air, divided by how much work it actually takes. The difference between those two numbers is all going into the air as heat. That's why people make such a big fuss over compressor maps. Roots, twin screw and centrifugal (and by extension turbos) superchargers all have different adiabatic efficiencies (between the types, and between different models). Even a single supercharger has varying efficiency throughout it's operating range. So you need to use a sc or tc that is efficient under the conditions you want it to operate under.

Anyway, twin screws generally have higher adiabatic efficiencies than roots blowers, especially at high boost levels. But you are absolutely right about that last part, though mostly it comes into play in part throttle situations. If there's vacuum behind the throttle plate the bypass valve opens. With a roots blower this is great because it totally unloads the SC and the parasitic losses drop to nearly nothing. With a twin screw, the already compressed air is simply allowed to re-expand uselessly and all the energy that went into compressing it is lost. So on a daily driven street car, a roots blower will give better fuel economy than a twin screw. But at full throttle, a twin screw will provide lower BSFC (and more power) since the higher efficiency means lower parasitic loss.

Originally Posted by Lucas

Compression ratio doesnt effect turbo response. Just sayin

You're wrong. Just sayin

[old greg]

Originally Posted by Driftster

The saddest part is..The pic you posted..
Actually shows the veins in a screw pattern....

Hey, Genius. You do realize I posted a picture of a twin screw supercharger, not a roots blower... Right?

If all the massive tech explanations that I've written up on this forum haven't convinced you that I generally know what I'm talking about, I'm not going to waste my time trying to convince you in this thread.

[ryude]

Unless you're somehow storing all of this boost pressure somewhere, you have to build boost each time you press the gas pedal. This is called Boost Threshold, or turbo lag. Modern technology has done wonders to minimize this, but it is still there. And yes, I've owned many turbocharged cars in my life so I know how great they are. I'm not going to say they have no disadvantages though, because they do.

[Giccin]

Originally Posted by old greg

Hey, Genius. You do realize I posted a picture of a twin screw supercharger, not a roots blower... Right?

If all the massive tech explanations that I've written up on this forum haven't convinced you that I generally know what I'm talking about, I'm not going to waste my time trying to convince you in this thread.

Just report him for trolling. That's all he's been doing when hes on this forum. Lol

[Ryephile]

Originally Posted by subaruslow

This is ridiculous, you are clearly a reader not a driver. You are generalizing beyond idiocy.

This is why;

-Australian v8 supercars are turbo'ed
-Some lmp1 american leman cars
-FERRARIS BEST and many other f1 cars until 1989 when turbos were banned. Ferraris 1980's turbo f1 car was a dominator

You don't even understand the argument you are making. There is some validity to joe schmoe saying his z06 or whatever it may be has good low end and response compared to a car with a turbo (generally against a stock car). However a similarly displaced car with a turbo charged, or a correctly matched turbo/engine setup can easily dominate an n/a car and give far better response. N/A cars like m3 have zero torque and crap low end, so low end could easily be matched by a turbo'ed car.try driving one.

Saying they detract from emotional response is utter horseshit. The rush oh a high horsepower turbo car is hard to beat, and if fast with a robust powerband theres nothing better.

If ferrari had a turbo you'd crap yourself in the drivers seat. Ferrari knows only a certain amm of power combine with handling is needed and at a certain point more power is too much, and thats true of any chasis/drivetrain.

Also trashing mclaren is idiotic and makes you look foolish.

I've been called many things, but called foolish and having my driving competency questioned are not among that resume'. It's obvious you're trying to elicit an emotional response from me, however such immaturity never positively contributes to a discussion. Since you have very few posts, I went a read your previous posts to get an idea who you are. You appear to be an angry individual with a narrow perspective and little tolerance for others with perspective wider or centered differently from yours. Your modded STI is the center of your universe and anyone claiming otherwise elicits a deep-seeded emotional reaction. This makes your presence on this forum rather ironic, as the BRZ's context is one of passion, not lap times.

Regarding your response to my comment, you are very distinctly confusing competition with enjoyment, fun from entertainment, and demographic consistency with negativity.

Boost threshold does not equal boost lag. Boost lag is what turns an engine from the fun connection of an n/a or supercharged engine to an entertaining show of latent power. They both have satisfaction, but for different reasons.

Your constant reference to competition is endearing, but those looking for individual fun make drag races and lap times irrelevant.

McLaren cars have always focused on being a clinical tool for the job; they do not emphasize emotional connection with their cars. This has been consistent since Ron Dennis has come on board. I have exceptional respect for him and his organization. At no time did I "trash" them, only point out their forte and focus and how that differs from the FT-86 and Ferrari road cars in general.

[tranzformer]

Originally Posted by Snoopyalien24

??

That kit was never released from what I know. It was show at SEMA on the Forester Prototype with the rear flatbed ala Baja.

I don't know anything else besides that. Any one know anything about output of that SPT kit?

[madfast]

Originally Posted by Driftster

They're the same thing..

it's just a pos displacement force induction that works off of interlacing lobes dude..

Wrong! You fail supercharging school.

roots blower = no internal compression
twin screw = internal compression

eaton TVS = a roots blower with 4 lobes and 160 degree twist that has 70+% adiabatic efficiency, just about matching the twin screw chargers.

[Matador]

Originally Posted by Ryephile

I've been called many things, but called foolish and having my driving competency questioned are not among that resume'. It's obvious you're trying to elicit an emotional response from me, however such immaturity never positively contributes to a discussion. Since you have very few posts, I went a read your previous posts to get an idea who you are. You appear to be an angry individual with a narrow perspective and little tolerance for others with perspective wider or centered differently from yours. Your modded STI is the center of your universe and anyone claiming otherwise elicits a deep-seeded emotional reaction. This makes your presence on this forum rather ironic, as the BRZ's context is one of passion, not lap times.

Regarding your response to my comment, you are very distinctly confusing competition with enjoyment, fun from entertainment, and demographic consistency with negativity.

Boost threshold does not equal boost lag. Boost lag is what turns an engine from the fun connection of an n/a or supercharged engine to an entertaining show of latent power. They both have satisfaction, but for different reasons.

Your constant reference to competition is endearing, but those looking for individual fun make drag races and lap times irrelevant.

McLaren cars have always focused on being a clinical tool for the job; they do not emphasize emotional connection with their cars. This has been consistent since Ron Dennis has come on board. I have exceptional respect for him and his organization. At no time did I "trash" them, only point out their forte and focus and how that differs from the FT-86 and Ferrari road cars in general.

He's been too busy reporting me for calling him a r****d and trying to get me perma-banned, to learn that competition cars focus on being fast, not fun.