Twin Scroll Vs Single

[Lithium]

Interesting, what a pain in the ass - regarding the "S_PS" thing. Its still respectable, probably better than a typical GT3582R plot but still.

[SimonR32]

Interesting, what a pain in the ass - regarding the "S_PS" thing. Its still respectable, probably better than a typical GT3582R plot but still.

We did it with my GTR, graph saying 680hp looks cool and scares the shit out of people when you mms it to them during tuning haha

[simpletool]

I'm just putting out a guess.I just think that with twin turbo the exhaust housing is unsplit and maintains an optimum flow path through the turbine. wheras twin scroll just has a divider over the one turbine (divider leaves a compromised flow path) which can't be as efficient as having two seperate optimum flow paths over the turbine?twin scroll would certanly work better than one large path but not sure it would work better than two smaller seperate pathsnot sure if i'm making much sense:i think the next thing that is to be adopted is them size varying turbines (dont know what they are called?) from diesel truck world. as the turbine speed increases the turbine opens up creating a bigger turbine so you get response and top end! seen them but only on trucks so far

Twin turbos as probably not more efficient. The surface area to volume of twin turbos is higher. Greater surface area means greater heat loss plus the issue of friction and boundary layer effects (plus double the bearings)

[discopotato03]

Always the but , you could argue the surface area difference with one split pulse manifold vs two compact short ones as well .

A .

[PSI Parts]

I might buy into the whole RB25 with a 1.06 A/R debate, as we have just finished building our project car.

Its got the Full Race TS Manifold, Twin 38mm MVS Tial Wastegates, ATP TS GT3582R T4 Flange, the engine has just been fully rebuilt and is running a CR of 9:1.

The plan is to keep the car on 98 for the street and then run it on E85 for the track and eventually run it on E85 when this comes more available at the pump, after all I drive it every day to work

As far as traction goes, it can get a bit tail happy but that probably has more to do with the way I plant my foot instead of easing the power on a little more gently.

Graphs are on 13psi for 98, and will be turned up to 23 PSI to match the 1.6Bar springs that are currently in the wastegates.

It hasn't seen the track yet, as I'm currently overseas and we had some dramas with the RacePak electronic dash, but as soon as I'm back I will get it on to the track and see how it goes.

[Lithium]

Will be interesting to see how it goes... No rpm on the plots, where do you get full boost and how does out drive?

[Beer Baron]

270kw seems a bit low to be honest? but I guess it's only on 13psi? why not 20psi for the 98 tune? that would wake it up a fair bit.

[Lithium]

How on earth do you run 13psi on 1.6bar springs? Good power for that boost though really.

[juggernaut1]

As is typical with twin scroll - power curve looks reasonably progressive.

[simpletool]

I'm guessing 200kph = 7500rpm so it looks to be 4500rpm for full boost currently.

Can't wait to see the results fully tuned.

[Lithium]

Hmm 13psi by those rpm isn't especially impressive tbh, but the torque curve will be the real teller.

[Rolls]

a RB25 with a 1.06 A/R would be yuck unless you wanted a drag car

[discopotato03]

The trouble is that GT3582Rs are a factory bastard as sold mainly because they don't have the right housings for their wheels . The only "real" GT35 BB turbo is the OE large frame one Garrett did for Hino and Isuzu and they appear to use twin inlet T4 International flanged GT40 turbine housings .

Anyway I agree that a GT35 turbo regardless is getting a little big for an RB25 , airflow wise from their comp maps they are supposed to be good for 600+ Hp so for a 25 to use it properly thats 240 hp/litre .

The thing to realise is that twin scrolled systems were designed to allow engines to make more torque at low revs . I'd lose the idea that twin scrolling allows you to use much larger turbochargers than standard and not introduce any more "turbine lag" .

If you look to the few manufacturers that used twin scroll systems on OE performance petrol engines ie Mazda Mitsubishi/Subaru/Toyota note they didn't fit huge turbos or turbine housings .

Virtually all of these big twin scroll turbine housings are intended for BIG slow revving diesel engines and the reason for their size is the huge capacity of these detonating mountains of torque .

Geoff Raicer (Full Race Geoff) used to say that the twin scroll GT32 T3 flanged (Euro T4 flanged actually) turbine housing worked reasonably well up to nearly 500 Hp and some Stateside found their way onto GT3071R and GT3076R turbos with a little machine work . At least the Americans try , at times , to emphasise torque and they realise its a factor of better engine scavanging thats making it not just the turbo trying to wake up to a degree a little earlier .

I know you Nissan people don't really like to hear me speak of Evo stuff but its hard to argue that they didn't make fairly impressive torque from a production two litre four cylinder . They never used anything larger than a TD05H turbine and a 10.5cm turbine housing in std form on the 4G engine anyway . In fact the first twin scroll one (E4) used a 9cm housing and the cooking model 7 and 8 had 9.8cm turbine housings std .

Anyway on with the debate .

A .

[PSI Parts]

Will be interesting to see how it goes... No rpm on the plots, where do you get full boost and how does out drive?

Full boost is around 3800rpm, I'll be getting a graph displaying RPM soon.

270kw seems a bit low to be honest? but I guess it's only on 13psi? why not 20psi for the 98 tune? that would wake it up a fair bit.

Just wanted to keep it safe for the time being on 98 as I get used to the car, and with the slightly higher CR it's ideally been set-up for a higher octane fuel.

How on earth do you run 13psi on 1.6bar springs? Good power for that boost though really.

That was actually a typo. The Wastegate came with 1.6Bar springs and I replaced them for the run in tune and initial settings.

Tial use in an inner and outer spring that combine to make the desired boost pressure.

We have currently have in the car: Copper (Outer) + Brown (Inner) = 0.8 Bar (11.60psi)

and will run this combo on E85: Copper (Outer) + Maroon(Middle) + Beige (Inner) = 1.6 Bar (23.20)

[FJdat]

found this article and thought it may be useful for this thread

http://www.epi-eng.com/piston_engine_technology/exhaust_system_technology.htm

"According to the turbocharger engineers, the most important aspect of designing a good header system for a turbocharged application is to maximize the recovery of exhaust pulse energy. This energy recovery has at least two components.

The first is to provide evenly-spaced exhaust pulses to the turbine. To accomplish that, it is helpful first to be working with an engine (or bank of an engine) which has evenly-spaced firing intervals. In an application in which the cylinders feeding a given turbine or turbine section have even spacing, the lengths of the primary tubes should be as close to equal length as possible.

The second component is to maximize the recovery of pulse velocity energy. For that purpose, turbine housings are available in split housing, or "twin-scroll", configurations, in which there is a divider wall in the center of the turbine nozzle housing to separate the incoming flow into two separate streams. That allows the nearly ideal pulse separation of 240 crankshaft degrees to be achieved on an inline-6 engine by grouping the front 3 cylinders into one side of the housing and the rear three cylinders into the other side. The same effect can be achieved on a V6 engine by grouping each bank separately.

Although the split housing arrangement adds wetted area (hence boundary layer drag) to the gas flow, the advantages more than offset that drag increase. In instances where pulse energy recovery has been optimized, it is often possible, based on calculations using pressure and temperature losses across the turbine, to observe very high turbine efficiencies, which some experts say are in excess of 100%.

Pulses which are evenly-spaced but too close together will reduce the effectiveness of this pulse energy recovery. Apparently, that phenomenon is seen on even-fire inline 4-cylinder engines as well as on individual banks of flat-crank V8 engines, where the pulse separation is 180°. I was told that the ideal pulse separation was in the neighborhood of 240 crankshaft degrees, and that, on an even-fire (single-plane crankshaft) inline-4 (as opposed to the two-plane crankshafts used in some Moto-GP motorcycle engines) it is better to separate the end cylinders into one side and the center two into the other side of the turbine than to run all four together into an undivided scroll housing. The same reasoning applies to each bank of a V8 with a single-plane crankshaft.

With regard to the uneven pulse spacing of each bank of a two-plane crank V8, there is agreement that it is very difficult to organize the pulse spacing in a useful way. It has been demonstrated that where a small turbo is used on each bank, the use of a short-tube 4 into 2 system (same idea as the 4-2-1 discussed above) feeding a twin-scroll turbine could take some advantage of the resulting 450 - 270 separation in terms of pulse energy recovery. If a single, large turbo can be located in such a way that the tubing lengths from each bank can be fairly equal, then splitting the primaries to achieve 180° separation would be an advantage.

Whenever practical, reducing the heat (energy) losses before the exhaust gasses reach the turbine allows the turbine to be more effective. This has been done with double wall tubing, reflective coatings, and wraps. However, insulating the pipes to reduce heat loss will, of course, raise the operating temperature of the pipes themselves, which can require extreme-duty materials where more affordable materials would suffice in the un-insulated form.

Another important exhaust system consideration, in order to provide the most effective operation of the wastegate in controlling boost, is to position the wastegate inlet port so that it is subject to exhaust stream total pressure, rather than off to the side where it sees only static pressure."

[discopotato03]

Read this again and I still think the affordable reality for most punters is some form of twin scroll twin integral wastegate turbine housing . In the real world most people are not going down the road of twin external gates and or fabricated exhaust manifolds , some may but most won't .

I'd like to see Garrett alter the Evo 10 TS twin gate GT30 turbine housing so that it uses the Euro T4 (T3 twin) inlet mounting flange . Big power engines can work better with the larger T4 International sized mounting flange but would they sell in acceptable volumes ?

Very early in this thread there was mention of a 300Z with a single twin scroll T04Z on it . I think I'd be going with two turbos purely because of packaging reasons with V bank engines , inline ones are easier for obvious reasons .

The debate will go forever with GTRs and TS singles vs twins . My reality is that RB26s are designed to rev and will never be something that makes good low to mid range torque - not without a 30 under them anyway .

A .

[fomby639]

been saving for a regular gt35r for a while but after going through this thread im sold on twin scroll. bit unsure on which brand of turbo to go tho, BorgWarner S300SX 8375 91 A/R Twinscroll T4, Precision Turbo PT6262 T4 Divided .84 A/R with 3 5/8" V-Band discharge or the Garrett GT3582R with the ATP 1.06a/r T4 twin scroll rear housing are the one's im interested in. going onto a stock 26 that will be rebuilt to 2.8 with 9:1 compression in the near future. my power goal in 500/550whp, not sure if 550 will be achievable with the turbo's im chasing but definitely want to crack the 500whp mark. any other suggestions would be great

[GTR_JOEY]

After talking to Geoff at fullrace he recommended a 83/75 with 91. to make my goal of 400rwkw, approx 535rwhp from memory... Also using a twinscroll

I'm running a 2.6 on stock compression so I don't see why u wouldn't make that power with a higher compression 2.8L.

As for the gt35r Ive read of 350rwkw+ on 2.6l so I imagine u would get ur 500 there as well

Remember the Borg Warner is a plain bearing so may be a touch laggier but will come on harder and b more Fun to drive

I also got my 83/75 with v band for around the $900 mark where the Garret is more expensive I imagine.

Hope that helps

[fomby639]

cheers joe but i think im gona go the gt3582r twin scroll from fullrace, good price at $1395, guess it will prob cost a fair bit more by the time it gets here from the states. does anyone know if there is a Aus distributor for the 35r TS or is the custom ATP rear the only one?

[GTR_JOEY]

Maybe talk to gcg,

Remember mate, on top of the twin scroll ull need to buy two waste gates, I got 2

Tial ones from full race for 500..

And setting the plumbing up on a twin scroll is goin to be pricey as well...

Other things to note with the twin scroll from full race is that ur

power steering reservoir will need locating

I personally had to chop a bit of reinforcement out of my bonnet cause the turbo sat high (not sure if that's due to the turbo or manifold, or both)

My a/c compressor no longer fits as it fouls on the manifold

And if u plan on running twin afm with a greddy "Y" pipe u will probably have to remove ur window washer bottles to fit ur intake