Twin Scroll Vs Single

[discopotato03]

I hope they did these in the high temp material . Do they mention what ARs and for what turbines the "T3" flanged ones are intended ?

A .

[Lithium]

.61, .83 and 1.01

[AngryRB]

Considering the increased scavenging effects and efficiency of a TS system, there would be less back pressure in the manifold?, so If using a TS system, would the use of poncams and playing with exhaust cam timing be of more benefit for a 300kw setup

or is it no different to the single scroll senario?

Edited April 24, 2013 by AngryRBGTX

[bradsm87]

I would say you can definitely tweak the ex cam timing. I think back pressure at the exhaust ports would definitely be lower with an equivalent sized twin scroll.

[discopotato03]

Generally you go a bit larger with a twin scroll turbine housing , the reason being that because the pressure within them is lower you need a reasonable sized passage to flow the gasses . Also you want the cylinder to blow down as quickly as possible so that it can be scavanged by clean air .

The thing to realise is that a 300+ Kw turbo on a 2-2.5L engine doesn't suddenly come on boost at 2000 revs just because of a change to a twin scroll housing . We are accustomed to production cars doing something from around 22-2500 revs and up usually with responsive and slightly restrictive turbos . They are designed to make boost at lowish revs and on load at cruising speeds . Its probably a lot to expect a GT3076R with a 0.82 AR TS housing on typical RB25 to be doing much at 80-100 in 5th . The engine itself should work a bit better because its exhaust tract sees less restriction and acts as a slightly better piston pump because of it .

A .

[Lithium]

Really? Define "much"? I used to only down shift at 90-100kph with mine if I really wanted to get the hell out of dodge with an open .82 GT3076R, and it would be sufficient acceleration to be done for "excessive". Hell, from 100kph in 5th it was more than enough for most situations.

Fwiw I used to start making boost from 2000rpm with little effort, even if far from "full" boost. 3-4psi at 2500rpm was typical.

Imagine something like a 1.01 TS VBand housing on a GT3076R HTA on a built RB? 1.4bar near 3500rpm? I want one, immediately.

[AngryRB]

Generally you go a bit larger with a twin scroll turbine housing , the reason being that because the pressure within them is lower you need a reasonable sized passage to flow the gasses . Also you want the cylinder to blow down as quickly as possible so that it can be scavanged by clean air .

The thing to realise is that a 300+ Kw turbo on a 2-2.5L engine doesn't suddenly come on boost at 2000 revs just because of a change to a twin scroll housing . We are accustomed to production cars doing something from around 22-2500 revs and up usually with responsive and slightly restrictive turbos . They are designed to make boost at lowish revs and on load at cruising speeds . Its probably a lot to expect a GT3076R with a 0.82 AR TS housing on typical RB25 to be doing much at 80-100 in 5th . The engine itself should work a bit better because its exhaust tract sees less restriction and acts as a slightly better piston pump because of it .

A .

Would it not make sense that the 0.82 is actually 0.82 and that the Garrett engineers have accounted for the divider being there, On the evo forums there are some making over 450hp so im wondering if the internal size could be the same.

Im interested to see how quick the gt3076 can be on full boost with all that can be done, eg E85, 6boost, cams etc

[Lithium]

Spool should be only part of the improvement

[bigmikespec]

Would it not make sense that the 0.82 is actually 0.82 and that the Garrett engineers have accounted for the divider being there, On the evo forums there are some making over 450hp so im wondering if the internal size could be the same.

Im interested to see how quick the gt3076 can be on full boost with all that can be done, eg E85, 6boost, cams etc

More internal surface area inside the housing with a twin scroll will also mean losses not directly related to the A/R.

[wolverine]

More internal surface area inside the housing with a twin scroll will also mean losses not directly related to the A/R.

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The son of rajab giveth and the son of rajab taketh away.

[discopotato03]

I look at it like this . In the distant past OE exhaust manifolds were crude cast lumps and for your typical Olden Falcon Valiant had six holes on one side of the lump and one on the other for the tubular engine pipe . Nice not and crude rude and inefficient yes . Call it 6 into 1 .

Then when the manufacturers wanted better effencies from their engines the manifold had two outlets and they sometimes made some attempt to group the cylinders together to take advantage of the exhaust pulse timing . These have two engine pipes merging into one at an optimised distance . Call this 6 into 2 into 1 .

In the bad old days cast turbo exhaust manifolds had a hole for each pot and one for the turbo where in more modern times they sometimes make an attemp to split the manifold and have two outlets into the single scroll turbine housing . Going all the way means having a twin scroll turbine housing and separate waste gate paths . This is effectively the same 6 into 2 into 1 but this time theres a turbine at the 2 into 1 junction .

You can see the obvious parallels and its easy to see how the basic piston pump (engine) prefers a 6-2-1 system to a 6-1 system .

Turbo engines , petrol car ones , don't always run on boost and the better the exhaust tract works the better the engine performs even at part throttle low revs and with no positive inlet manifold pressure .

Mr Lith again I'm not biting but I will say that an optimised TS system based around a GT3076R and an RB25 should have better low speed part throttle torque than a single scroll one . Wheather the effort and cost justifies the result is up to the individual and what their goals are ie doing that or a questionably legal engine numbers wise RB30 .

Because I happen to be looking closer at automotive diesel turbochargers these days its evident that VNT is an effective method of pulling the bottom end boost and torque levels up and if they ever get them working for petrol engines its going to be simpler in some ways than twin scrolling and twin gates .

For me the $64 question is how do VNT turbos go with cooler cleaner burning E70 + fuelled engines .

A .

[AngryRB]

thanks for the history lesson, my up coming setup will hopefully be a ball tearing response monster with all the add on's and smash out well over 300kw's

Even before with a single scroll GTX3076 there was a solid 10psi at 3000rpm so with a twin scroll hopefully ill see a solid 1 bar and the rear tyres fighting traction and some f#$k yeah action from 3000ish onward lol

Edited April 27, 2013 by AngryRBGTX

[scotty nm35]

For me the $64 question is how do VNT turbos go with cooler cleaner burning E70 + fuelled engines .

When you push any setup you will have high exhaust temps, no matter the fuel. I have seen well over 900 degrees C in my manifold. I doubt any VNT will take that for long, other than some brittle ceramic ti composites perhaps.

[Lithium]

Mr Lith again I'm not biting but I will say that an optimised TS system based around a GT3076R and an RB25 should have better low speed part throttle torque than a single scroll one . Wheather the effort and cost justifies the result is up to the individual and what their goals are ie doing that or a questionably legal engine numbers wise RB30 .

Because I happen to be looking closer at automotive diesel turbochargers these days its evident that VNT is an effective method of pulling the bottom end boost and torque levels up and if they ever get them working for petrol engines its going to be simpler in some ways than twin scrolling and twin gates .

For me the $64 question is how do VNT turbos go with cooler cleaner burning E70 + fuelled engines .

L

I think you misinterpreted what I was saying, I am totally pro twinscroll and have had some decent sized rants on here about it... I guess I shouldn't be shocked that you would assume otherwise. What I wad saying is my average single scroll setup performed at least as well as you were saying a good twin scroll setup would, which meant I figure your expectations are quite conservative.

I am totally unconvinced on VGT on spark ignition cars at the moment. Was just chatting about this with a mate who works with Euro cats, even the new Porsche GT2s which 'have it sorted' are already coming in with busted turbos.

[bigmikespec]

I am totally unconvinced on VGT on spark ignition cars at the moment. Was just chatting about this with a mate who works with Euro cats, even the new Porsche GT2s which 'have it sorted' are already coming in with busted turbos.

Even major OEM diesel guys are having major problems. VNT mechanisms don't like carbon build up!

[GTScotT]

I've got a couple of VNT turbos at home which have shit their control boxes. The control box mounts directly to the exhaust housing, so I don't know how it could have failed

the part number is GT3063KLV but they are more so 28 sized on the turbine side and only 48 trim on the comp. Has a .78 VNT rear though, which I think could be useful in an aftermarket application, high flowed to a GT30 size core and using a boost driven actuator to open the VNT once a certain boost pressure is reached.

its got a round entry also so I could probably make an adapter for my tial flanged manifold

[Lithium]

Moar good genuine Garrett stuff.... yay

http://atpturbo.com/mm5/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-HSG-210&Category_Code=GTH

[hypergear]

Been working into split plus and VNT turbine housings, split pulse housing if engineered correctly working with the right turbine wheel it can have a significant affect in the turbocharger's response regardless wither a split pulse manifold or gate is used.

It comes to how far and how thick the pulse is as well as the height of the inducer of the turbine wheel. If the divider has been machined matching same profile as the turbine wheel, then obviously it will create the fastest discharging velocity to the wheel. However in upper revs it might not be efficient enough to discharge all the exhaust gases coming from the engine quick enough creating a restriction. Which appears to be the reason that most of the divider has been shifted back couple of mms to compensate. Once again it comes back to power response trading.

The only none power response trading option for very effective out comes would be some thing that can alter its A/R size referring to boost and rpm level. That is the VNT setups.

[34GeeTeeTee]

Moar good genuine Garrett stuff.... yay

http://atpturbo.com/mm5/merchant.mvc?Screen=PROD&Store_Code=tp&Product_Code=ATP-HSG-210&Category_Code=GTH

Haha you are always on the ball man

[AngryRB]

was looking at the supra site and found this, is this pretty much the same as Hypergears VNT?

http://www.supraforums.com/forum/showthread.php?530737-Turbo-matching-for-the-road-course...plotting-success/page5

Edited July 27, 2013 by AngryRB