Semi-sequential Turbo Hack?

[rtune]

from

http://www.supraforums.com/forum/showthread.php?t=481292

is it technically possible to do what this guy did to his supra?

spool up the first turbo then open up the path to the second..

[R31Nismoid]

Of course its technically possible... he posted how it was done on the very first page.

To do it on a GTR (with twins), not possible.

[rtune]

Of course its technically possible... he posted how it was done on the very first page.

To do it on a GTR (with twins), not possible.

I realize he did it, they are selling the part on page 11..

why isn't it possible on the gtr tt? everything is possible ... no?

a custom exhaust manifold couldn't combine the exhaust to one then back to

split with a vacuum operated flap? sorry I must be missing something fundamental..

[paulr33]

go check out howstuff works and read some information on twin turbocharger applications (and singles for that matter)

then once you have exhausted all avenues and understand the inner-workings youll be able to answer your own application

if you cant be bothered (like most) then read on

nissan set up the GTR for optimal responce, power and balance being a std production car

they would have been able to get all of those from a good twin turbo setup

other cars experiement with Bi-turbo setups, that is, two turbochargers, of different sizes

common applications of this type are the subaru Libery B4

it has one small turbo and one large turbo, a wastegate control value / thingy opens and closes

directing exhaust gas between the turbochargers and so forth

the main problem is a big fat power and torque dip where the changeover point is

in most cases its unavoidable and you just have to deal with it (usually around 4k ish)

if you can avoid the big power dip from the turbocharger changeover then this is a good thing

so the idea of two turbochargers same size and split the engine is half is where the GTR setup comes from

why overcomplicate it and make a bi-turbo setup for no gain and a big dip in power / torque

now usually when you talk bi-turbo setups most guys pipe up and say

but the porsche 900 (or insert random model porsche) runs bi-turbos and it makes 2500BHP at 1500rpm

there is a big difference in engine, cost, research budget and target audience of porsche so dont bother comparing it

in summary

- it sucks

- overcomplicated

- costs

- big power dip during changeover

[govich]

In the linked thread they're talking about a single turbo with a twin-scroll turbine housing, not twin turbos.

http://i29.photobucket.com/albums/c266/tri...ivideValve1.jpg

Edited July 7, 2008 by govich

[R31Nismoid]

I realize he did it, they are selling the part on page 11..

why isn't it possible on the gtr tt? everything is possible ... no?

a custom exhaust manifold couldn't combine the exhaust to one then back to

split with a vacuum operated flap? sorry I must be missing something fundamental..

because its explained on the first page, as i said

single turbo, twin scroll... feeding from a manifold single port.

A GTR with twins wont have this. You'd need a HKS T04Z or similar with the split pulse rear (twin scroll) rear housing.

There is no twin scroll housing setup for small twins, mainly because there is no room among other things

[VB-]

you could turn the factory system into a twin sequential system but for all the effort and f*cking around, just add a supercharger in there. twin charging>sequential turbo

[urtwhistle]

if you wanted to run two turbo's of different sizes to get instant torque you could do what a diesal mechanic mate of mine did. he had a land cruiser turbo diesal and sourced a small turbo off a small truck. made up a log style exhaust manifold that both turbo's were bolted to. then instead of running 2 waste gates he then welded up part of the opening of the small turbo so that it could physicaly only have so much gas pass through it. and being a gas it takes the path of least resistance. so it would spool the small turbo up pretty much at idle but once the revs got up it would force the big turbo because it cant push enough through welded up housing. if it spooled to quick he just welded the little turbo a little more, if it spooled to late he took a die grinder to it and opened it a little.

this 4wd ended up being 1 of the most scary things i have ever been in. massive torque massive black smoke out the back with the most unreal turbo noise since the exhaust ended right under the drivers feet. I think this is how some truck's are setup. but then again there must be some reason why this is only done on trucks.

chris

[paulr33]

yeah sorry so its a twin scroll housing

well there are two ways to achieve a twin scroll turbocharger setup

1) use a suitable twin scroll housing

- evo lancer has them stock, some of the hi spec garrett units might have (t04z), some of the extreme HKS models might have them etc

- note these are SINGLE turbo setups with twin scroll housings on a single turbo manifold with collectors splitting between each of the 'scrolls' so cylinders 1,2,3 lets say goto scroll 1 and 4,5,6 goto scroll two

2) use a twin turbo setup

using a twin turbo setup is another way of achieve twin scroll setup, but with two turbochargers

two turbochargers std units, two manifolds, cylinders 1,2,3 goto turbo 1 and 4,5,6 goto turbo 2

[discopotato03]

In my narrow minded opinion sequential turbos are an overly complex (and expensive) way of getting the job done .

The big PITA is having valves open to allow exhaust gas to spin the secondary turbo up and others to not allow pressurised air to back flow through the secondary turbos comp housing till its up to speed .

Subaru tried it - B4 , Mazda series something RX7 , Toyota I think on some 2JZ ? turbo engines ?

I think it was a fad and marketing thing - hey everyone two turbos - twice the fun ....

Thing is a small primary turbo boosts at lowish revs and promises high turbine inlet pressure - at lowish revs .

IMO either a single twin scroll or parallel twins is a better sollution , far less complex and you gain from the pulse separation either way .

Subaru (some JDM STi/Legacy) Mazda (I think S4 RX7) and Mitsubishi (Evo 4-9 and possibly 10) Toyota (some GT4's) have used twin scroll singles with twin integral waste gate flat valves , simpler/cheaper more seamless .

For some strange reason their torque figures in ft/lbs are similar to their Hp numbers and they make a lot of torque in the low to mid range .....

Must be a fluke , A .

[Billet Ricky]

from

http://www.supraforums.com/forum/showthread.php?t=481292

is it technically possible to do what this guy did to his supra?

spool up the first turbo then open up the path to the second..

That’s the second thread on the Supra forums. There is another thread that has been kicking around with links to it from automotive forums all over the world for about a year now. In the other thread they claim to of invented this so called new technology. LOL.

The thing is it has been around for eons. Pretty common on heavy industry turbo’s. Nissan even had something similar on the early VG20’s.

What the guys on the USA Supra forums are doing is modified a twin scroll exhaust housing but it’s not being used in a split pulse application.

They are putting these turbos on open collector manifolds and simply shutting of half the scroll so all the exhaust gasses have to go through one side of the scroll. Effectively halving the A/R of the exhaust housing. Once the turbo is making adequate boost the second half opens and the turbo goes back to the whole A/R.

Example: With a 1.00 A/R Exh Hsg, At low rpm it is a .50 A/R Exh Hsg then once the set boost is reached the second half of the scroll is opened to be a 1.00 A/R Exh Hsg.

This system as been successfully being used in the heavy industry for years so as long as the parts can handle the exhaust temps of a petrol engine there is no reason it can’t work in high performance applications.

Regards,

Ricky.

[discopotato03]

Shoot me I'm guilty for not reading the links , if I've got this right you mean having a single outlet manifold and a twin entry turbine housing with a means of blocking off one half . Corky has a picture of something of that nature in maximum boost .

Personally I reckon once you have 3 litres to fight with there's no excuse for not making some serious grunt before a turbo starts to wind up . Don't forget a 2JZ is a dedicated 3L 24V DOHC 6 so I imagine to porting/valve area should be better suited to the capacity than say an RB25 or 26 head on an RB30 .

With the fuels and controls around today - plus good manifolds/cams/turbos you should be able to excite some pretty big turbos on that engine . Burning fuels with good anti detonation properties and running lots of advance everywhere should make a 3L 6 pull like a big block at not real big revs . Maybe burn E85 and mist it up with water methanol injection , 9.5 CR 30 lbs of boost and 30 degrees of timing .

Same old same old , contact Geoff Raicer at FullRace because he's developed systems for that car /engine . Not cheap but huge power rarely is .

Dunno what you do for traction in a 2WD Supra , cheers A .