single Vs. twin turbo

[dfedzina]

In a recent thread, a member had responded saying that a single turbo would be just as fast and possibly more efficient than a twin turbo. I admit to knowing nothing about turbos or how they work, so I was wondering if this statement was try and why.

[Mikael]

That really is a minimum of concern. Getting it to fit is the bigger concern for a late model street car. And as was already said, the spooling characteristics are dictated by the size of the turbo/turbos, not how many you have.

[dfedzina]

I really was trying to ask about turbos in general and not just on an f-body. And to be more specific, using a single (for example) T3 turbo Vs. a twin T3 turbo setup. If i'm not makin sense to the turbo world though i'll just shut up. lol

[slacker69]

Well the point of having a single is so that it can be bigger. Like a t4oe at least and upto a t72. The efficancy is alot higher and so you can run more boost whice means more hp. Most of the 1000 hp plus cars run 1 large turbo. Like a PT90 or a PT120. Most supras that had twin turbos and they want more hp they go to 1 large single.

[dfedzina]

thanx slacker, that's what i was tryin to get at

[Dominic]

The major thing with twin turbo is what kind of twin we're talking about.

Parallel systems work like single systems but utilize two tiny compressors to get the same amount of boost. Using twin tinies they tend to spool slightly faster and they allow the header design to be more free flowing, you can run true dual if needed for example, and you can keep the turbos in the engine bay close to the exhaust ports (if the engine bay is large enough). Generall this setup is not done aftermarket, since its difficult to place in the already crowded engine bay.

Sequntial twin turbo is another interesting deal where one large turbo and one small turbo trade-off boost at a certain RPM. The small turbo is there for low-end boost, the large turbo is fed by the small one and kicks in at a higher RPM and load. Using this setup allows you to run a larger turbo for the final rpm range...

Single turbochargers are fine until you get into boost limitations and CFM flow capability limitations. Twin turbos are often hard to tune and by having two turbos you are risking more moving parts to reliability factors. The more moving parts, the more that can break, so the reliability plummets.

[Darknight]

There is a property of fluid dynamics that says that a fluid (gas or liquid) flows better in one large body than in several smaller ones, thanks in part to less friction against the area of the containing shape. (This partly explains why rivers flow faster than smaller streams, though the streams appear to flow faster.)

This is also partly due to inertia. Given that you have a mass flowing through a determined channel, the mass will better conserve its inertia if held in one form. Consider this...one 10 ton rock will roll farther than two 5 ton rocks, when first accelerated to the same speed.

That said, the larger body of mass would be harder to initially accelerate, but would exert the maximum peak force, which would result in higher overall boost pressures, and from there, more horsepower.

DK

Upon further thought, the additional rotating mass of two turbos, as well as the added bearing friction, could actually prove to slow down the spool up time, thus making it inferior both in spool up time and peak boost. It all depends on the size of the turbos, and the size of the exhaust, the engine displacement, etc...

[ July 20, 2003: Message edited by: Darknight ]</p>

[dfedzina]

So, to Dominic and Darknight, who seem to have a good understanding of this...just out of curiousity(b/c i don't have the money now), which do you think, if working perfectly, would work better on our v6's - the big single turbo, or the sequential twin turbo with one little turbo and a second larger turbo? Again, it's just speculation so you don't have to elaborate.

[ChronoGN]

Twin Turbo = Less Turbo Lag = Good for Auto x and road racing.
Thats all I know.

[Darknight]

I say a single large turbo. I also say, since turbos create so much backpressure, that you could use as large of an exhaust as you want, after the turbo. After all, the less the pressure on the other side of the turbo, the faster it will spool up.

That said, I say to use a 5" single exhaust after the turbo. Yep, you heard right, I say.

DK

[ July 21, 2003: Message edited by: Darknight ]</p>

[Mikael]

<blockquote>quote:</font><hr>Originally posted by dfedzina:
So, to Dominic and Darknight, who seem to have a good understanding of this...just out of curiousity(b/c i don't have the money now), which do you think, if working perfectly, would work better on our v6's - the big single turbo, or the sequential twin turbo with one little turbo and a second larger turbo? Again, it's just speculation so you don't have to elaborate.<hr></blockquote>


A. AFAIK there is no sequential setup in existance that uses two different sized turbos. The 4th gen supra uses a sequential setup, but both are the same turbo (#2 has a slightly larger exhaust housing). It is a good system, but few people stick with it, since there is a large hole in their power curve when trying to bring #2 online. Spool can be overcome by other means (nitrous, reving higher, higher stall, studder box, etc)

B. Look into how complicated this system is. There is no aftermarket sequential setup out there- way too much to do.

C. I sometimes don't know why i try here, there are so many morons. TWINS WILL NOT SPOOL FASTER THAN A SINGLE TURBO. HOW MANY TURBOS YOU HAVE DOESN'T HAVE A MEASUREABLE EFFECT ON THE SPOOL OF TURBOS. THE SIZE OF THE TURBO IS WHAT MAKES THE DIFFERENCE. (this isn't at you dfed, i just quoted your question for sequential/single debate)

D. Again, i would try and find the setup that will be easiest to work for your car. Maybe you can find a way to fit a pair of twins right off your manifold, maybe having 1 air filter and 1 intake pipe would be eaiser. Each car is different.

[ July 22, 2003: Message edited by: Mikael ]</p>

[slomaro]

an import mag did a review on this they messured the spool up tim of a single turbo to a twin turbo car the mods were i think all the same the color of the car was even the same

the graph showed they spooled together at the same time, barly did the twin spool up first just barly maybe 100 rpms thats it and thats on a low compression motor pushing alot of boost


now from car to car is diffrent
tiagos car i dont think see's boost till atleast 3k rpms
have a friend with a 2002 porsch 911 twin turbo and he sees boost at 2k or soo and full by no more then 2500 but remeber this is a 120K car it has some niiice turbos and the car was built to perform like that from the factory

[Josh R.]

Didn't we talk about this not too long ago :D


http://www.camarov6.com/cgi-bin/ulti...c&f=4&t=000934

[Arctc Wolf]

the closer the turbo is to the heads, the quicker it'll spool up. if u have to put 1 large turbo far away, then maybe a pair of smaller ones, 1 off of each exhaust manifold, would spool better. yes, the whole twice as much 2 go wrong theory and twice as much inertia make sense, but the bigger turbo has a bigger wheel, meaning more weight as well, and rotational weight get heavier as they spin. u can spin faster if u keep ur arms around ur body than u can spinning w/ ur arms out. same principal applies to wheel weight. we can make up for this weight tho by using lighter materials such as ceramic for wheels, but these materials tend to break at higher boost pressures, ceramic tends to break at 17 psi. this is known because the Nissan Skyline uses twin ceramic turbo's and ppl who want to max out their boost stay at 16-16.5 psi because the ceramic turbo's have a history of breaking after 17 psi. ball bearings also help spool up.

in our instance, a twin setup might be as good or better than a single, but requires a lot of work with clearancing in the engine bay, whereas the single is easier to place and route piping.

[qksl2]

How fast a turbo spools is not directly related to its distance from the head.

I also don't see how anyone here can say whether one turbo spools faster than two... too many ambiguities!

The idea is that you can spin two smaller wheels up with the less energy than you can one larger wheel, because weight that is farther away from the axis upon which it spins requires exponentially more energy... due to centrifugal weight, the farther out it gets.

It's why a 15" wheel weighing 10lbs is better than a 17" wheel weighing the same.

Ian