numb1300z

ummm. Anytime twin turbos are used one smaller turbo is used 4 bottom end because the smaller the turbo the quicker it spolls. And the second will be the larger turbo for the top end.

But by all means correct me if im wrong.

jfairladyz

Not all setups use a small and a large turbo though. The Supra and Skyline both use two small turbo's of the same size. The RX7 (FD) however used a small and large turbo. But the reasons for using two different sized turbos have been taken cared of, same for twin turbos. Turbos are now very efficient, especially the ball bearing types. Turbine and compressor wheels have advanced phenomonally as have housing design. Ah hell, everything about modern day turbochargers has improved upon older designs. So you can get the quick spool up and still have the top end all from one turbo. Twin turbo's on an inline motor just no longer make sense. But in the case of a V layout twins makes more sense since you cant place the turbo optimally near all the exhaust ports. So you can put one on each side, like the Z32TT. Which by the way uses two same sized turbos.

In the case of sequintial turbocharging (one small, one large), YES, it is designed for what you described. But with todays turbos there's just no need to go with twins unless you have a V layout, and even then it's not all that neccessary. There are kits being manufactured for cars that places the turbo all the way back by the muffler And they supposedly still have minimal lag and excellent top end.

craZed

^ Well put. But,you are mistaken, the supra uses a sequential set up.

Now lets try to get back to the main focus of this thread.

AZ-ZBum

Was the word "FOR" really that difficult to spell out?

And yes. You are wrong. Most dual turbo setups were same sized turbos. Supra, Z32, Skyline, Porsche 911, etc. I can only think of the RX7s were different sized turbos were used. I know there must be others, but that's the only one I can think of right now.
No it doesn't. They use two same sized turbos as well. Each turbo is fed by 3 cylinders.

numb1300z

You might be right AZBum but isnt the basic idea to have two turbos for reduced spool times because two smaller turbos can spool faster than one large one.

jfairladyz

But what you have to remember when using two smaller turbos is that it is proportional. See instead of having 6 cylinders spooling one small/medium size turbo you now only have 3 each spooling a slightly smaller turbo. I'd say twins are actually more beneficial for the top end then they are for the bottom end of the power band. Think about it, if you have one small/medium sized turbo you're still going to get excellent spool up cause you've got 6 cylinders spooling it. But that turbo can still only push out so much air in the end. Now take two smaller turbos. With only 3 cylinders spooling them they're not going to spool up super quick. It's going to be about the same if not unnoticeably worse then the slightly larger turbo. But now you get to combine the air flow outputs of those two small turbos. Now if you add those two airflow totals up you end up with a couple of small turbos pushing more air at the top end then that single turbo and you still get to MAINTAIN the lower end response. So you see, twin turbos isn't about better bottom end response. It's about maintaining that response while allowing for a slight increase in the top end. But this whole set up is VERY limited which is why you traditionally see it tossed in favor of a single turbo in high horsepower applications. Think about it, if you slapped two large turbos on an engine then you'd never be able to spool them.

Twins make sense for OEM's looking for a slight boost in power without hurting driveability. 2 small turbos will NOT spool faster than a properly sized single turbo. PERIOD. Of course now adays you can slap to small turbos on a V layout and still hit upwards of 500HP while still mainaining the bottom end. Of course, you can do the same with a single turbo on an inline motor. Then you gotta factor in the extra weight of twins. Not that huge of a deal, but if you could get the job done just as well with a single turbo wouldn't you take the weight savings? Not to mention the savings in cost?

And to justify all of this it does tie into helping you decide what to do with your car Crazed

AZ-ZBum

Holy CRAP! It's as if you didn't read anything posted above. Let me copy it for you (as well as you should read jfairladyz's detailed responce).

numb1300z

Yes I understood what he said But I didnt belive spool times were based on amount of cilinders as much as the size of the spinning thing inside the turbo. Bigger turbo=slower spooling. Smaller turbo=quicker spools.

jfairladyz

But what spins that ? Exhaust Gas. The more air fuel you burn the more exhaust you'll have. Now as AZ-ZBum said, when you split the turbos so they are fed by 3 cylinders each you now only have 1.5 litters feeding each turbo as opposed to 3.0 liters feeding one. The 3.0 liter is burning twice as much air/fuel and pushing twice as much exhaust through that one turbo then the 1.5 liters to each smaller turbo. Exhaust is the ONLY thing that spins those turbine wheels. Without it the turbine doesn't spin. So it would make sense that unless those two small turbos are each LESS than half the size of the one turbo then they are NOT going to spool faster. Now a T3 turbo can flow quite a bit of air and a T3/T4 hybrid can flow enough for any street vehicle. You'll be hard pressed to find a turbo half the size of those let alone even smaller than half the size. Of course this is not exact and there are variables but thats the gist of it. But if they are only half the size of the bigger turbo then they're not only going to only spool as fast as the one turbo but they also will only be able to flow the same amount of air on the top end as well. So two SLIGHTLY smaller turbos will put out more air at the top end and will most likely spool just slightly slower than a slightly larger single turbo.

Twins isn't about the spool up, it's about the top end. They are, for the last time, only meant to PRESERVE spool up.

numb1300z

No. Not what powers the turbo but the screw inside. I thought spool times were based on the effincey and size of the screw inside.

And the term screw comes from superchargers, I dont know what it is called on a turbo.

NismoPick

There are several things that affect the turbo performance.... You should read the book "MAXIMUM BOOST" by Corky Bell.

Turbine... compressor... fan... wheel.... it has lots o names.

jfairladyz

Turbine wheel would be the most common term. But yeah the size of the wheel and housing does make the difference. But that's what I've been trying to explain with the size of the turbo. When I said size, those were the things I was referencing.

AZ-ZBum

On the same size engine, absolutely. On different sized engines, not even close.

i.e. a 1.0L engine will not spool a T25 as fast as a 3.0L engine will spool a T3.

A turbo is fed by exhaust gases. The amount of gas exiting the engine is what feeds the turbo. A 1.5L motor has half the available air to feed the turbo than a 3.0L motor.

The biggest factors in the spool time of the turbo is the size of the turbo and the size of the engine feeding it.

When you run twin turbos, you are essentially halving the amount of air available to spin each turbo.

The size of the engine is essential to the spooling of a turbo.

i.e. You would NEVER put a T25 or even a single T3 on a 5.7L V8. It would kill the turbo in no time.

Likewise, you'd NEVER want to put a T78 on a 1.5L Geo. You'd never spool up.

jfairladyz

It's all yours. I give up

Didn't somebody need help spending $20k?

DriftekZ31

First thing first this guy deserves the
of the year award....


Sometimes? He's a complete dick with internet hostility and ***** envy issues....
I have not seen one post from this guy that was anything than to try to one-up someone else or to degrade something someone else said....

You can be a walking dictionary of Z information and have Z factory service manuals memorized and whatever else you guys think he's a god of Z's for, but its useless when your trying to find a decent source of information.....Answer a question and dont emply that your the smartest guy ever and then someone will respect you....

No-one likes a know it all, especially a smart ***, one-up, know it all....

Dont mind him man hes just revered as a god by all the others that are too afraid to tell him hes a *****.....

That is all.......

entropy31

oh, we remind him on a regular basis that he is a *****, and he is fully comfortable with that fact. he does bring up good points quite a bit. he is;nt afraid to tell someone when they are acting like an idiot. i'm glad we have zbum around here.

DriftekZ31

Cronnies.....

jfairladyz

Hey thats not a bad idea. The first ever ZDriver awards. In addition to the catergory mentioned above we could have catergories like: Most helpful, Least Helpful, Post *****, Friendliest Member, Strangest Member, Most Obsesive Member. I mean the list goes on. Alright I'm going to stop jacking this thread now. I swear

AZ-ZBum

Why thank you very much! I will always cherish this award.

Are you still pissed off that you can't advertize your shop in your signature on 300zxclub? Or is it that I pointed out you didn't read the rules about it? Or the fact that I responded to your responce about the "warm welcome"? Hell dude, I was even nice about telling you that you weren't allowed to do that.

BTW: As soon as they fix the avatar selection thing, this is going to be my new avatar:

Thanks!

DriftekZ31

Nah im just enjoying calling you a *****...... I kinda relate with you, i think its a conflict of personality (The same) We'd prolly be great friends in the real world....

The shop doesnt need advertisement i just put it in all my sigs.... Just kind of found it rediculous i specialize in S chassis cars and you thought it was a conflict of interest, but none the less i agree with your point of view, if everyone else has to pay or whatever why should you bend the rules for me.... Bad mood had me going that day........

But: the entire post was about all I read that you post being a complete *** to everyone you come across....

Who cares its the NET and it gives me something to do....We can be like the redskins, cowboys rivalry if you want, might spice up the forum.....

AZ-ZBum

Actually, AMZPerformance is also an S chassis shop.

I'm not a complete *** to everyone. Just the lazy people. Which the NET seems to attract in vast numbers.

DriftekZ31

I must be lazy...... Fair trade, i'll be lazy you be the asshat....

Wanna make me a lazy hat picture?

That was a joke, im trying to get along with you here!

entropy31

ok. all done. no more of this. CLOSED.