Twin Turbo vs. Single Turbo V6: A Dissertation

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.

Red__Zed

it is not terribly difficult to construct one though.

you are neglecting the efficiency opportunities afforded by a larger turbo.



I always laugh when people make statements like:

and back them up with this:
rather than numbers. I understand you are running business, but isn't it good enough to just point at that there is nothing on the market that offers similar performance in a single, rather than broad, sweeping statements that cannot possibly be supported?

Can you share the numbers you've looked at? I would love to see them.



I understand that, but you don't necessarily increase the MOI a lot to bump up flow. You wind up coming VERY close in terms of total MOI, and the efficiency of a single turbo can get things very interesting. Turbine clearance needs alone create a huge opportunity for gains in efficiency, not to mention the pulse density.





At some point this becomes trivial relative to other gains (pulse efficiency, etc). Obviously systems like the STS don't effectively leverage it.




I'd love to see them. I imagine the wrapped SS will be much better than you expect.