aliali

Anybody know the advantages of the single turbo & twin turbo ? an how much does it cost ? I have met my local mechanic here and say that you're getting more lag in single turbo (above 5K rpm) than twin turbo (above 3K rpm) ? But what's the consequences.. DO I need to chage the internal parts if I go for single turbo ? What's the necessary things to upgrade when going single turbo ? Please the expert advise. Any limitation for the automatic transmission.


Fyi, I have seen the options Jap. version magazine, most of the tuner goes for single turbo like HKS and Top secret.

Ben Davis

There is no garantee that twins will spool faster than a properly sized single turbo. As far as power as long as the PSI and CFM are equivalent then power production will be very close to eachother.

Things to get along with:

Fuel
Spark
IC
Plumbing
Guages

Ben

joeshow750

Which one, single or twin, will spool faster is dependant on the size of the turbo. Let's say you have a 20g, on a VQ35. Now let's say you have two 20g's on another VQ35. The single is going to spool faster than the twin in this case for obviouse reasons. Now let's say that you take out the two 20g's and replace them with 16g's, now the spool times will be closer...get it?
I would think a single 20g turbo would offer very good spool time and great power for the VQ35.
About what to upgrade for a single turbo setup...it doesn't matter if it's a single turbo or a twin turbo, what matters is how much hp you're making and can everything support that hp, ie. can my injectors squirt that much fuel, can my fuel pump pump that much fuel, etc. etc. etc. A single turbo setup doesn't automatically mean it makes more power.

Nismo240sx

I have heard that you can have a smaller turbo for fast spooling and a big turbo for more top end. Id say the single turbo would have the least lag opposed to twin turbo since its spinning just one turbine instead of two. But twin turbo can be much more powerful than a single turbo can in the long run. Also depends on what size turbo your talking about.

SleeperGT

Depends on what you plan to set up the car for: the 1320 or road racing/autocrossing?

Brandon@Forged

Typically on a V6 engine, twin turbo's are better, because on a V6 there is two exhaust manifolds with about the same amount of air coming out. These gases will spin these small TT's a lot faster than a single turbo. Not to mention, the Z doesn't have a lot of engine bay room, having to fabricate a dual exhaust manifold to single exhaust manifold, would be REALLY HARD, and there is no room for it anyway. A single or a TT will provide about the same hp on the Z. Now, if you take a I-6, the Supra one of the cheaper I-6's. With a Supra you have an I-6, so you have one header, so that's one exhaust manifold. If you have a T88 single turbo on a I-6 Supra, you will be pushing out major hp when you get it spooled. But if you get a HKS T51 single, it is smaller and it will spool faster than the T88; the Supra turbo comes stock with two turbo's, which to be specific, they are actually bi-turbo's (bi meaning two), the reason you wouldn't use twin turbo for the stock supra turbo is that twin turbo's are not sequential, the bi-turbo's are sequential on the supra. The reason for having sequential bi-turbo's is, let's say a rich doctor wanted a sports car but can't drive well. He goes to test drive a Supra, he's driving on the roads and kicking it, then he revs at a turn and kicks it, the sequential meaning they are on at different rpm's/speed. If the supra turbo didn't have sequential bi-turbo's, he would have spun out of control when he went around the corner. Getting back on the Z, man I got way off track. Go twin turbo, it would be better in the long run. The twin turbo will be smaller, spool faster, produce about the same hp as the single, and you won't have to make a dual to single exhaust manifold. I think any car would benefit with sequential turbo's, especially if you could control them. You could run both turbo's when you are racing, and turn one off when your just riding around town. The engine would definately last longer.

Ben Davis

Not if properly sized

But there is room for 2 snails instead of 1 and 2 sets of pipes to the IC?!?!?

WTF?!?!? Spin out?
Daily driveability that's it, after 4500 they are BOTH boosting the motor, one dosen't turn off after a while and both turbo's are identicle.

single dosent always spool slower
HP should be =
You will most likely be using custom manifolds anyways, on single turbos for the MX6 and For Probe many guys use stock headers, as is, unmodified.
Sequential is out of the question, sure a car could benifit but a 50 shot is much more logical.
You cannot "turn off" a turbo without an extreemly complex vacume/wastgate/exhaust manifold, you said plumbing a single turbo would be expensive think about the cost of sequential, mush less dyno time figuring out when to change them over.

Ben

Brandon@Forged

[QUOTE]Originally posted by Ben Davis
Not if properly sized

Quote:

[i]But there is room for 2 snails instead of 1 and 2 sets of pipes to the IC?!?!?

Obviously there is because Greddy, Top Secret, and HKS are using TT's.

I didn't know the rpm when they both come on. And I was passing this story on from Street Sport's.

You wouldn't be doing custom manifolds if you bought a kit as opposed to the single which you would have to fabricate.

Ben Davis

Just cause greddy does it one way don't make it the only way, they did it for marketing (ooooh 2 turbos are ebtter than 1) and because they had ot chose 1, they chose 2 smaller turbos to keep daily driveability, a PROPERLY SIZED singe can do the same.
T
he Buick grand national was a single turbo stock and can make in excess of 500 HP on the stock unit.

I guess cause greddy didn't do it than a SC is wrong too...

And my freinds T88 firebird is wrong as well

It is kinda like people who say you cannot boost an 11:1 motor, it is just plain stupid. I get annoyed when people act like CR, single, twin, sequential, are all cut and dry. Look at what you want response wise, get some flow charts for some different singe and dual set ups, look at cost, look at the current chericteristics of the motor, then decide what you wanna do.

Just top end power? get yourself a nice single turbo.....

Wanna keep the currect power delivery? Maybe twin smaller turbos would suite you better

Mid to top end, 2 meduim or one larger might suite you well

How much boost? How much lag? what size IC? how much $$$ for instal?

Ben

Brandon@Forged

Quote me where I said you can't boost an 10.3:1 motor. To boost one, would be pretty stupid unless you run safe psi or get internals. I agree on look at dyno's etc. But we don't have the option of a single turbo or any turbo for that matter. You sound like your getting pissed because people that don't know about turbo's start asking people who do and when people who do can't answer their ?'s or are getting annoyed blow them off leaving them clueless and down the drain 8grand for a custom single turbo setup that they thought would benifit then leading them to blowing their engine.

Brandon@Forged

Greddy is wasting their money then, because it costs more to produce two of the same turbo's, 2BOV's, etc. than a single, with 1bov, etc. Why did Greddy,HKS, and Top Secret (those are the only brands we know of) go with TT setups, they aren't cheaper to mass produce. There has to be a reason for them, like like MORE HP.

aliali

Thanks guys for the hints and tips.

Maybe I'll go for HKS single turbo which they say increase to 326ps with the internal stock.

Cheers

TJZ

No, they should make the same hp w/ the same boost. The most likely reason, IMO, is that they couldnt or didnt want to fit the piping for the exhaust manifold (ie no room in the engine bay).

Ben Davis

Agreed....

as beofre stated, 2 turbos does not = more HP

If CFM and PSI are eqivalent and the IC pressure drop is kept = than in most cases a properly sized single can = twins. End of story.
Why 2 BOV's.... you still only have 1 TB.....?!?!?!

you mean 2 wastegates, not BOV's

No they aren't wasting their money.... never said they were, they are prolly doing the smart thing IMO cause guys like you assume that more = better

I am NOT AGAINST a TT setup, simply saying that the are not arbitrarily better.

Ben

Brandon@Forged

I was in a rush, i meant two wastegates. I don't think more = better, if more means more hp, then I am for more, but if less means more HP, i am there too. I never said they were better, I like the T51 single on the Supra, but I wouldn't care about lag either, b/c it would be making a lot of HP.

And TJZ: I stated that there is not a lot of room in the engine bay earlier, open your eyes

TJZ

I know you did . I was just saying that's most likely the reason (as opposed to more HP, which is false).

Ben Davis: Your, "You need to think before you speak," comment was really not needed. He made a mistake. Give him a break. BTW, I agree with you 100% regarding how a properly selected single turbo can be just as good as a twin setup.

Ben Davis

Edited and noted, just a reminder that the little things make a huge impact in how one is perceived online when voice and face to face interaction is not present.

Ben

EDIT: tried to edit it but this forum (unlike any others i have ever been on) only lets you edit within 90 minutes, sorry bro nothing personal.

TJZ

Nismo240sx

Ive seen the top secret 350z in the modified magazine which had a twin turbo setup running 484 rwhp at 18 psi with stock internals. Pretty amazing for a stock motor to withstand that much power.

demon

iTrader: (2)

Just had to respond here because this is some of the most misinformed discussion on turbos I have ever heard.

Firstly, there is no reason two smaller turbos that make the same power as one single could spool faster. If you have 2 banks of 3 cylinders putting out X amount of exhaust gas, when you channel them into one turbo (assuming there is no restriction in the piping) you will end up with 2X gas. So, if the single turbo was double the size of the twins, the turbo would spool in exactly the same way (this is assuming alot of other factors are consistent, such as exhaust housing size, etc). There is no great benefit to having two turbos unless you are looking for monstrous power which one giant turbo cannot provide. These are extreme cases however, and judging by the general userbase here won't apply to anyone here.

The Supra sequential system uses 2 identically sized turbos - the first one is operational to about 3300rpm when the second turbo comes online - at that point they are BOTH spinning which is why it feels as if the second turbo is so much bigger. It is NOT POSSIBLE to have two differently sized turbos on any system as you would end up with a total mismatch in flow to each bank of the engine. In a sequential system you would end up with compressor surge due to the size mismatch. The advantage of a sequential system is obviously that you can run two small turbos and have one working at low rpm, and both at higher which gives you a very useable powerband with minimal lag. The way this works is that while Turbo #1 is spinning a very small amount of pressure is being leaked into Turbo #2 to "pre-spool" it so that when it comes online it a) doesn't get such a hard shock and result in twisting of the shaft, and b) the coming online of Turbo #2 is much smoother as it is already spinning at a low speed anyway. There is no way of simply "turning off" turbos - the only way would be to drive with less throttle or to stay out of certain rpm's at full throttle. Unfortunately the complexity of creating a sequential system is immense and you are unlikely to see any aftermarket option.

Having had experience with turbo cars for the greater part of a decade, I would lean towards the single turbo route if it were an option. Two of everything simply creates two sets of checklists when troubleshooting is required (and it WILL be required at some point). However unless anyone decides to go a custom route, your choice will be dictated by your options.

My $0.02

--
94 Supra
95 RX7
02 Mustang Turbo