Twin Scroll Turbine Housings For Gt30 Based Turbos .

[discopotato03]

Hi all , hearing good things about the T3 flanged split pulsed turbine housing ATP sells as an option for GT3071R turbos . In the US some work is being done on larger A/R versions of this housing that should better suit the GT3076R type turbos . The aim is to have better response with less exhaust restriction so should have more torque at lower revs and boost pressure . The down side is that it means external wastegates with two being better than one .

I'm trying to find out more about the larger ratio housings which sound like .82 and 1.06 , ATP's is .78 so not really enough for a GT3076R to pulse properly and not choke up . Also will look around to see who has the most compact external wastegates .

Cheers A .

[BHDave]

do you have a link where anyone has done a direct comparison with say a .63 vs the .78 twin scroll?

I've looked at it a few times and wondered how it would perform on my hks manifold with a 56 trim 3071

[discopotato03]

No and those looking at this stuff are in the US and working with SR20DET's and KA24DE+T's . Not the same as an RB six but I like to look at things from an individual cylinder capacity point of view .

Jeff Raicer who posts here occasionally has put a lot of effort into micky mouse split pulse exhaust manifolds and twin scroll turbos and says he can get big turbos to spool more like smaller ones do with single entry turbine housings . I'd say it has a lot to do with getting the most advantage from the exhaust gas energy innitially ie when the valves first crack open into an area of low restriction and reasonably low pressure . So hopefully low restriction and best energy gain by the turbine so least pumping losses/reversion and more ignition timing to make the most efficient use of the charge air and fuel .

You can find him at FullRace.com and there is a forum there .

Cheers A .

Edited February 23, 2007 by discopotato03

[extreme turbo manifolds]

you can run a single gate on twin scroll turbines as i have done here.

[discopotato03]

There are some good reads on the net about this stuff . Search PDX Tuning Results with GT32 Turbokit and APS twin scroll rotated mount turbo system model designation TSR 70 . There's a lot of wading through the dross on this 2nd one , APS has made a split pulsed manifold kit and sells a GT3582R (with fancy drilled port shrouded comp housing like the TO4Z at ATP's site) with a petrol material spec (read high temp capable) twin entry .82 A/R T3 flanged Garrett turbine housing and 3.5" V band outlet) as part of the kit . It uses a single TiAL external gate fed by twin pipes sort of like the pic in the last post . If you don't have half an hour to read through it they're hinting that it spools up ~ 400 odd rpm sooner than a normal GT35 .82 turbine housing - on an EJ25 anyway .

More later cheers A .

Edited February 24, 2007 by discopotato03

[carl h]

i too would be keen to know what kind of gains can be had converting to the twin entry turbine housing.

after all a gt30r on a rb20 isnt exactly the fastest spooling thing in the world and the hks cast manifold is already setup for twin entry...

[discopotato03]

Hi Carl , there is not as much out there in the way of T3 flanged twin entry housings for GT30BB turbos as I had hoped .

A couple of interesting things though . First Garrett have had for ages a series of GT bush bearing turbos called GT32 ie GT3267 and GT3271 . They use either a .69 or a .78 A/R turbine housing with 70 or 73 trim turbines . They are reasonably cheap and not a bad thing for approx 350+ wheel Hp .

Secondly ATP in the States appears to be machining these housings to fit the real GT3071R turbo in .78 A/R . You really need a larger A/R version of this housing for a GT3076R and while there's a few different types out there I dont have their details . I've been looking into TA/TB34 housings but nothing screaming eureka yet .

With your RB20 I don't know where to go with a GT3076R , they are not easy to excite with an RB25 and single entry housings (not without small turbine housings anyway) . The smallest propper housing I know of for that turbo is the HKS .61 A/R and it is non gated and T28 flange . You could try ATPs divided housings but its a lot of stuffing around plus an external gate and still may not get you what you want . Selling the GT30 and buying a GT28 based turbo like a 2530 may be a better solution .

Your call .

[paulr33]

wouldnt you need a suitable split pulse manifold to actually benefit from the twin scroll design? or there is some gains to be had from just twin scroll and if you can run split pulse (sr20) then its even better?

[discopotato03]

To get any benefit from a divided housing yes the manifold has to be split pulsed .

Not sure what you mean by the SR20 bit .

Cheers A .

[StockyMcStock]

split pulse manifold and split pulse housing (all else being equal) is always better than open collector and open housing. less turbulence at the gas merge, less chance of a cylinder's exhaust valve being caught open when another one is pulsing as well (so less pressure spike variations across all cylinder's exhaust runners = lower average backpressure when the valve is open).

i would only go an open collector if it was significantly cheaper, or there was no other choice. manifold must be split pulse as well though.

[carl h]

well ive already got the gt3076r mounted onto a hks cast manifold with an external gate...so that really isnt a problem.

im currently running the .63 ar 't' 2.5" outlet and it comes on full song round 4.1k give or take.

would the divided entry help in spool time some, i dont want to plunk down the coin only to have a slower spooling turbo.

[StockyMcStock]

it will not make a noticeable difference at all. but if you were starting from scratch, i'd advise to go to split pulse manifold, split pulse housing.