Twin Turbo vs. Single Turbo V6: A Dissertation

b1adesofcha0s

Great write up Mike! I enjoyed Thermo I/II and Heat Transfer as well, just hated the exams. You can throw Fluid Dynamics in there as well

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Project: b1adeZmobile (2009 370Z) | Uprev Tune by AAM Competition | Berk Exhaust
Project: b1adeZmobile 2.0 (2014 C7 Z51) | Corsa Xtreme Exhaust

Mike@GTM

Thanks for the compliments everyone! I tried to keep this as fact based as possible. One thing I did forget to mention is that this dissertation was mainly related to performance and engineering.

I must concede that cost was not as much a part of the discussion as it could have been. A single turbo system does have that one, distinct advantage. Despite the lower cost, however, a single turbo is not half as much money as a twin turbo system. As such, a person must still factor in the cost/benefit ratio between a single turbo system and a twin turbo system. In some cases, the cost is the deciding factor, and performance is secondary. For other cases, the performance benefits are worth the incremental investment.


I'm pretty sure that my original post gave all the technical details that would ultimately establish my stance on any single turbo kit. You may want to consider re-reading it?

Turbochargers are designed specifically to operate in high temperature environments. If you look at any factory turbocharged car, the turbos are always mounted as close to the engine as possible. No OEM has ever mounted a turbocharger more than 5ft away from the engine (I think Subaru has the record on the turbo mounted farthest away...and the lack of performance shows).

There are places you want heat, and places you don't want heat. I'll go into more detail in another post.

The advantages of a single turbo were mentioned in my original post. However, the advantages are significantly outweighed by the disadvantages (as described in my orignal post).

The single biggest advantage of a single turbo is cost...not performance.

Again, this is only related to V6 engines. If we were talking inline motors, we would be having a different discussion.

True, and definitely something to watch out for with single turbo designs as not all of them are designed that way.

I'm not aware of any.

So far, I have not seen anything to the contrary. Again, as the single turbo's only competitive edge is cost, anything other than the reuse of the stock exhaust manifold would work against that advantage.

Until I am proved wrong, I'll stand by it. But unless someone can invent a reverse entropy device and defy the laws of physics, I'll be standing for a long time yet.

On a V6? It would require a substantial amount of number crunching to find that crossover, but from some of the numbers that I have looked at, I suspect my original estimate of 1300+ may actually be conservative.

You know, just for giggles, I shot an e-mail to a contact I have at Garrett just to see if we can get the actual MOI numbers. In his estimation, a pair of GT2860RS turbos will have a very close total MOI when compared to a comparably sized single turbo (GT4094R). Remember that MOI is based on the square of the radius.

Furthermore, due to the loss of enthalpy from a longer exhaust pipe routing (required for a single turbo setup on a V6), the twins will be receiving more total enthalpy than the single and since their MOI's are so close already, the Twins will respond faster.


That's a good question. It's been awhile since I looked at it. Keep in mind that the stock exhaust manifold has two ply heat shields as well. I'll see if I can dig up those calcs at home.

I'm back at work now.

You know, I saw that dyno graph. No boost graph, no AFR. The thing that makes me wonder, is when Tower only made 438 at 8psi before he installed water/meth injection. Something just isn't adding up. The lack of information and dyno graphs is not helping your case.

Whether you are running a single turbo, twin turbo, or a supercharger, the 370Z needs additional cooling. Period.

If we, as human beings, were unable to control heat, you'd be riding a donkey, my friend...not a 330hp sports car.

I'll be making a more detailed post about heat, shortly.

Kingbaby

So twin turbos are always better? Is that what your ultimately saying?

Thank you for the information, and sorry if my question makes you pass judgment on another companies product.

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Mike@GTM

I am saying that twin turbos have excellent response thanks to their proximity to the enthalpy source.

I'm sorry if you are looking for something that isn't there.

blackonorange

The reason tower made less I would assume is the auto tranny , chinook I think made 470 on 7 psi as well correct me if I'm wrong , another factor is tower left his stock cats in

blackonorange

Sorry chinook made 452 on 7psi

Kingbaby

Your mistaken, I'll rephrase. Simply asking what you thought of their setup. If stressing the "IF" you did a single setup yourself on the HR/VHR how would you go about it. You can pm seeing this may be off topic.

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07 Silver Alloy Nissan 350Z Nismo #0191 "Lin'da"
2amR--------------------> VQ I.N.C. - Like us!

blackonorange

Tower the cost in a Tt setup is on the install time as well

Mike@GTM

To be honest with you, I would do something similar to what JTran Studios did. Maybe a different turbo choice and intake piping, but overall, very similar. The schedule 10 piping on the exhaust piping was a good call on their part...that and the fact that the piping is equal length so that the turbo receives evenly spaced pulses. The car clearly makes good power. It's just a little late spooling for my personal taste...but that's part of the trade off.

Because I like quick response though, I'd do twins all day, every day. I'm a bit impatient when it comes to getting that kick in the pants feeling from a turbo...I want it right now and for it to pull for days...from 3k to redline. Hell, I don't let my Subie drop below 3k rpms unless I'm stopped at a light.

Kingbaby

Thankyou Mike!

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07 Silver Alloy Nissan 350Z Nismo #0191 "Lin'da"
2amR--------------------> VQ I.N.C. - Like us!

Cell

I believe the first 370z to get an STS kit also had long tube headers. I mentioned about this a while back in the STS post. I guess it was ignored.

So most of the guys that are making more power with the sts kit are running HFC/test pipes and LTH.

tower74

Good to know...

O&G

Mike is correct, the twin set-up on our platform is superior for boost response, getting to peak boost faster and hopefully staying there throughout the rev range. Heat is essential for getting proper spool @ the turbo which is another win for a twin system, the turbos are right there. On my build we chose to use wrap and good piping to keep the heat temps up as much as possible in and around the turbo. I've learned a lot about both systems on the VQ platform over the years, for example if we would have run two smaller diameter pipes into a divided T-Flange @ the turbo we would have increased spool up time significantly and the next kit we design will incorporate that change. We also designed the system to be as A-semetrical as possible, keep everything even. Bottom line is price is the biggest attraction the single system has over the twin, I'm not going to sit here and say the single is better, even if I have one. I've had both and I loved them both equally. Like I've said numerous times GTM makes a quality part and you can't go wrong doing business w/ them. I just love turbos.... 2, 1 doesn't matter as long as it isn't a supercharger

I plan on donking Ron's TT Nismo stg II after he's done w/ the install!

Keep up w/ all the great info, I <3 LuRNenG!

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Ron

Yes I mentioned that too and got ignored, he had some other stuff too. STS is just not worth it to me. Jtran's single is far superior IMO

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blackonorange

I know I noticed that as well, they make quite a difference and that would solve the cat breaking apart "issue" as well ......