Twins Vs Single turbo

[sart0ri]

Found some info on the web regarding the twins vs single turbo debate.

"Turbos respond better to pulsing exhaust flow. However, when many cylinders dump into a common manifold the individual exhaust pulses are smoothed out. When we run two turbos we effectively spread the pulses further apart & increase their amplitude. Therefore, when the turbo is spooling up to speed rather than receiving a constant push it will get a series of vigorous shoves that help it accelerate faster. It is for this reason that twin-turbos frequently manifest reduced lag than that they have smaller low-inertia turbine wheels. "
....
"In V-type & flat cylinder layouts it is easy to visualize how superior exhaust flow will be into twin turbos. However the same is equally true with straight-sixes. The other aspect, of course, is exhaust flow out of the turbine. Generally we will be hard pressed to find space down the side of the engine for anything larger than a 3" dump pipe. with two turbos, even small 2.5" dump pipes provide 37% more flow area to help turbulent turbine flows to more quickly settle, while 2.75" pipes provide 67% more area. "
....
"Also with exhaust flow divided, each turbo will run a touch cooler, which ultimately improves their service life."

(quotes taken from "Forced Induction Performance Tuning, pp 94-96)

 

[scientist]

Ok after reviewing things a bit more I realise my trend of thought was a bit misplaced with the twins vs single debate.

Turbo magazine compared a T78 vs twin HKS GT2835s, now the T78 is a laggy setup by all means, and these cars were tested @ 18psi
http://www.turbomagazine.com/tech/0103tur_single_vs_twin_turbo_supra/index.html

What was unexpected is they both hit 7psi boost @ the same RPMs

 

[Madhav]

Just to throw another spanner in the works, there is also the newest development of compound turbo kits.
http://www.supraforums.com/forum/showthread.php?t=527336

This new*revolutionary turbo kit will finally meet the goals of every turbocharger enthusiast. While compound turbocharging is usually used on diesel applications, we have devised a method for this kit to work on a gasoline powered engine. Unparalleled low and midrange torque coupled with high horsepower. There’s no need for nitrous as this kit spools up as if it’s always on nitrous. The compound turbocharger kit builds 20psi at 2800 rpms while flowing enough air to make 800+ RWHP!

A little over 300 ft/lb of torque at 3000 rpms and over 500 ft/lb by 4000 rpms. With more tuning and tweaking, I can see more power and torque in the low rpm range. We have just gotten the transition a little better so we will be working on getting the spool better even though it already has an insane spool.

 

[smohekey]

Need to be registered to view that..

 

[timmae2006]

i still think there will be a fair difference between spooling any turbo on a straight 6 as opposed to a v6 due to exhaust manifold lengths

 

[bradc]

Indeed, a single turbo on a V engine is kind of silly imho. On an inline 6 it isn't a bad idea, but then why do the factory Supra and GT-R's come with twin's? Surely the engineers did some testing on that one

 

[M0R81U5]

Is the 2JZ not sequential? That puts it in a different boat to the RB26....but I agree with your point nonetheless Brad

 

[sart0ri]

For me the question is exactly how much low/mid/top do you lose with a single ball bearing unit, eg GT3076R, compared with 2 x bush bearing TO4's from the WRX.

I understand that 1 per bank is ideal for a V engine, but if I am only losing 5-10% efficiency with long ugly pipe work and less than ideal gas flow then do it the easy way with the better turbo.

Unless someone way more technical than me does a group buy for some custom manifolds, twin turbos just looks too hard.

 

[-T8-]

Is the 2JZ not sequential? That puts it in a different boat to the RB26....but I agree with your point nonetheless Brad

2JZ is sequential

 

[Madhav]

Yeah the 2jzgte came out with a twin sequential system however single setups with smaller gt30-35 ballbearing turbos actually make better power at low rpm then the stock sequentials.

People have played around with hybrid setups, as in changing the cores and there is even a place over in the USA that is offering a bolt in kit that claims big horsepower, although Aussies that have done it report less power than claimed. See here

The 1jz which is a 2.5l on the newer chasers came out of the factory with a single turbo, toyota changed from twins to single and if you look at the result it made better power overall.,they frequently upgrade to the gt30r singles and make an easy 270kw atw with decent response also.

 

[Mortz]

If i was to upgrade Id go twins, despite the extra work, Why would you want to take away the responsiveness from factory? These cars are such a good all rounder it just seems pointless to go big single and lose that low/mid range grunt which make VR4's so great to drive.

 

[scientist]

The 3Si forums has quite a bit of information wrt twins vs singles, since their engines would be closer to what we experience than the I6 motors. The only problem is most of the single guys run GT40 and larger turbos when going single

 

[Guest]

There's a few single turbo V motors getting about.

The old VG30et out of the Z31 300ZX and the newer VQ30DET in the new Cima's and Stagea's. I still reckon it's a bit silly, but it works ok. Better off with a normal twin system on a V6 IMO. Sequential twins are really only any good on big V8's and straight 6's. Why mess with what Mitsu came up with, keep it twins.

But here's some eye candy for you guys

Nizpro's quad turbo VK56 based jet boat motor.

 

[Slinz]

Haha shiiiiat. Makes me wish boats were cool

 

[scientist]

Nice twin compound turbos

 

[Madhav]

Yeah 20psi by 2800rpm and 800whp is a pretty unbeatable and previously unheard-of combination. Most 800whp supras spool up by 4500rpm..

 

[scientist]

I will link a few 3Si threads on the twin turbo setups later.
But a few things that were summarized. All twins that made decent power similar to a GT30 or 35R spooled after 4000rpms on a stock block and head 6G72

 

[Madhav]

On the 2jzgte, the GT30R with a .62 hotside hits full boost at 3200rpm and makes 300kw atw, GT35R with .82 like mine makes min 350kw atw and hits full boost at 3500rpm. Not many people seem to go for twin setups... I would be very interested to see how the smaller GT30R would go on the 6A13.

We are spoilt with our small turbos on the VR4.

 

[bradc]

I just realised another reason why a single turbo is stupid, my number plate won't work any more

http://www.clubvr4.com/forum/uploaded/786/1250069802.jpg

http://www.clubvr4.com/forum/uploaded/786/1261041431.jpg

http://www.clubvr4.com/forum/uploaded/786/1204159657.jpg

 

[qball]

BWAHAHAAHAHAHAHAHAHAHAHAH