B4 may be known as a Spec-B

[Reddo!]

So fellars, I was going through some internet site and i came across where the GT B4 was also address as a Spec-B? Whats your thought about this??? Hollar back.

[b18b_turbo]

The GT B4 is the Twin Turbo version that was in production before 2005. It looked like this:



A model change was introduced in 2005 and called the GT Spec-B. It was no longer Twin Turbo but rather Twin Scroll Turbo. It is a single turbo with two scrolls. One spools for low rpm and both spool at high rpm. It is still essentially two stage trubocharging.

[Alpha_2nr]

One spools for low rpm and both spool at high rpm. It is still essentially two stage trubocharging.

I beg to differ.

All twin scroll turbos (in SUBARUS that is) improve spool by having the exhaust flow from each of the two "headers" (boxer engine right...so you have a "paired collector" on each end of the engine) separated to have less turbulence/interference as it heads up throught the uppipe to the turbine inlet.

Better spool lower down, and better overall characteristics. But there ain't anything "two stage" about it......no low or high rpm bizness.



The counter of this is the "single scroll" setup, which bunches all the flow into one pipe : not as good for flow....but the turbulence caused (along with the older unequal length headers found in the older Legacy's/WRX's/STi's gave the rumble we all love.

One spools for low rpm and both spool at high rpm

In fact, the TWIN TURBO Legacy had the "High and low" rpm thing you're talking about....as it used a twin turbo in SERIES setup, with a smaller one for boost at lower rpm, and a bigger one for higher ranges (and an ungainly lag in between both ranges )

The GT B4

The B4 denomination was limited to the older twin turbo cars, yes. But I have come across some >'05 GT's being listed as B4's on auction also.

Apparently, it involved "B4" side panelling and a few other things (which I'm not sure....I've seen some cars on acution listed as GT-B4's also...never seen them up close). Maybe it's an error on their part.

If this is true, the B4 trim was also available on some non-turbo cars, that came with sport seats and the door panel/ foot plate trim from the GT (I've seen only one of these down here).

[b18b_turbo]

One spools for low rpm and both spool at high rpm. It is still essentially two stage trubocharging.

I beg to differ.

All twin scroll turbos (in SUBARUS that is) improve spool by having the exhaust flow from each of the two "headers" (boxer engine right...so you have a "paired collector" on each end of the engine) separated to have less turbulence/interference as it heads up throught the uppipe to the turbine inlet.

Better spool lower down, and better overall characteristics. But there ain't anything "two stage" about it......no low or high rpm bizness.

Twin Scroll Turbocharger

"Two different-sized scrolls are generally used, a primary and a secondary. Typically, the primary is open for low-speed operation, and both for high-speed use. This creates the ability of the TST to be a small A/R housing at low speeds and a large A/R at higher speeds."

Courtesy: wiki.answers

In fact, the TWIN TURBO Legacy had the "High and low" rpm thing you're talking about....as it used a twin turbo in SERIES setup, with a smaller one for boost at lower rpm, and a bigger one for higher ranges (and an ungainly lag in between both ranges )

^^^
which is exactly what is meant by telling the man that it was Twin Turbo....


Plz confirm your information before you try to disprove somebody else's correct post, especially with the ":roll:" etc...

[Alpha_2nr]

Ah boy B18b-turbo.....before you go googling about, have you ever taken a look at one of these twin scroll turbos? Well...I don't have any pics, nor am I a crackshot mechanic, but let me see if I can dispel some of the "e-tuning" in your post.


PLEASE follow your own advise, and do PROPER research before coming on here and posting nonsense, and misleading those who don't know better.


Let's analyse:
YOU SAID:

It was no longer Twin Turbo but rather Twin Scroll Turbo. It is a single turbo with two scrolls. One spools for low rpm and both spool at high rpm. It is still essentially two stage trubocharging.

Basically...you're saying that the twin scroll turbo has "two scrolls" one for low rpm and BOTH for high rpm.

This is incorrect. That is not how twin scrolls/divided entry turbos work.



Here's an excerpt from "Street Turbocharging" by MArk Warner (a lovely book...try reading it sometime)....a good book for the fart can, vtec powered, e-racers and wanna be drag racers like myself.





Let me realllllllyyyyyyyyyy simplify for you:

A twin scroll turbo on the Legacy (VF37?) is classified as a divided entry turbo:

I quote:

"A typical didivded entry turbo uses two separate volutes, or spiral flow paths into the turbine housing " (as I said)

"Both these portions empty into THE SAME CENTRAL PORTION OF THE TURBINE HOUSING" (aka no high and low rpm/"stages" of the turbines as you've made it out to be...again as I said)

" The solution to the problem is, to keep the cylinder's exhaust stream separate from the others as long as possible.....To accomplish this, some turbine housings are constructed with twin inlets" - Again....AS I SAID....there are NOT "TWO SCROLLS" (WTF is that?), but ONE turbine with TWO INLETS which are ALWAYS open at ALL RPMS (in SUBARUS).

"Four cylinder engines employ a a divided-entry turbine that is usually plumbed to combine 1 and 4 cylinders together. These two cylinders feed one of the turbine volutes. Cylinders 2 and 3 are then combined to feed the other volute". - again....as I stated above...the paired collectors from EACH end of the boxer engine run along separate paths to the the SAME turbine, to reduce turbulence and increase spool...as stated by me here:

I beg to differ.

All twin scroll turbos (in SUBARUS that is) improve spool by having the exhaust flow from each of the two "headers" (boxer engine right...so you have a "paired collector" on each end of the engine) separated to have less turbulence/interference as it heads up throught the uppipe to the turbine inlet.
Better spool lower down, and better overall characteristics. But there ain't anything "two stage" about it......no low or high rpm bizness.

So even the blind could see, that what I was saying, is correct.

In a nutshell, as has been bolstered by my reference, all a twin scroll turbo does is have a "smoothed" exhaust flow to the turbine inlet by SEPARATING the pairs of cylinder exhaust streams (in the case of the boxer 4 cyl) into two separate streams, thereby redcing turbulence, and increasing "spool" characteristics of the turbo There is NOTHING in a divided entry turbo (as used in the SUBARU SPECIFICALLY) that has a LOW RPM AND A HIGH RPM "turbine". That's just nonsense..



So we've proved that notion that you have...or HAD...about twin scroll turbos having "two scrolls" (whatever the heck that's supposed to mean) is incorrect, as the twin scroll has nothing to do with one turbine spinning for low, and another for high....there is ONLY ONE TURBINE...with two INLETS!!!!!


My 2c....please try to learn when unsure...and PLEASE double check and re-read your research before posting misinformation, you'll only get flamed.


And please don't resort to wikipedia for technical advice.

[Alpha_2nr]

Oh an I'm not finished yet./ Read this:

http://www.boricua-racing.com/forum/sho ... .php?t=692

What is a twin-scroll turbo? Generally speaking, it is a turbo with a divided turbo inlet to isolate the pulses coming from each exhaust port to maintain more of the pulse energy from each cylinder all the way down to the turbine wheel. A twin scroll setup will respond faster and produce boost quicker than a equally CFM sized regular turbo. Twin scroll setups are generally costlier and require more components than the average turbo ugrade to work efficiently though due to their requiring a true twin scroll header to operate correctly. Fitting a regular header to a twin scroll turbo basically negates the pros of this type of turbo.

Which is THE SAME THING I said. There is no "high and low" rpm "two-scroll" part to the turbo. All it has, is that the pulses from each end of the boxer engine are separated/isolated (as was correctly said above) all the way through the uppipe to the turbine.

What you're saying about a twin scroll turbo having "two scrolls", one for low rpm, and both for high rpm (unless both myself and that site I posted are wrong)....is utter nonsense. Thwe twin scroll turbo's characteristic feature comes from divided/isolated exhaust pulses......NOT from having a hig and low rpm "staged" setup.

[15devils]

VF38 in the 03 and up lgts.....nice info knight1

[Alpha_2nr]

^^Yeah sorry my bad. VF38. VF37 on the STi's ent? I always get my numbers cris-crossed with those IHI turbos

Glad at least someone appreciates the useful info I've put out 15devils. Hope the info helps the otherwise mis-informed about what twin scrolls really are all about.....

.....they are NOT a single turbo with "two scrolls", but rather a SINGLE turbo with a SINGLE turbine element, with dual entry ports for more efficient flow and spool. That's all there is to it.

It's really amazing how such a simple development can make the world of difference in spool and power.

[Reddo!]

yeah guys...I just wanted to know if the GT-B4 is also known as a Spec-B? Other than that...I like the info put out there by Knight1. However the car that I'll be getting is a 2004 and it is said to be a (GT B4). Not the older model as posted there...but, the one that I have as my pic.[/img]

[b18b_turbo]

[Reddo!]

lol. No scene breaddo!

[Ragnarok]

yeah guys...I just wanted to know if the GT-B4 is also known as a Spec-B? Other than that...I like the info put out there by Knight1. However the car that I'll be getting is a 2004 and it is said to be a (GT B4). Not the older model as posted there...but, the one that I have as my pic.[/img]

The car in your avatar is not a spec-b...sorry

[Reddo!]

no scene bubby...cool Ragnarok