I have a good friend over in Supra Land. He says the majority of Supra people take out their TT and replace them with one larger turbo. So I am just wondering why all the emphasis on our site seems to be with two smaller turbos vs. One larger turbo.

 

I think it depends on what you are looking to do.

One large turbo can give gobs of power, but will typically have significant lag as well. It is best for drag racing.

Two smaller turbos will usually spool faster and therefore have less lag, but will also cost more and be more complicated to install. Also, because they have a smaller capacity, they may end up with less overall power than a single large turbo. You might want two small ones for road course racing so the lag is less difficult to manage.


-D'oh!

 

I think it's easier to have a single turbo on a straight 6 versus a V-6. Consider the plumbing and the asymetrical result of using one turbo with the 350z. Not impossible, but probably difficult to design and tune.
--
Jeff

 

If I'm not mistaken, the Supra TT has a staged or serial twin design. Meaning there's a small turbo which spools fast in the lower rpms, and then in the higher rpms the larger one immediately downstream takes over to flow more boost. If I remember correctly the Supra has an inline not a V six.

This is different than the other sort of Twin design typical of V-6 engines. Here you have 2 equally sized turbos, one for each cylinder bank. An example of this is the Audi S4 2.7TT has this configuration.

 

Exactly. It takes some very crafty and extensive plumbing to make a single turbo setup on a V shaped engine, as opposed to an inline engine. Give me a twin turbo on a V engine any day. Makes more sense.

Personally, even on a Supra, I'd rather have two smaller turbos (in a sequential configuration like FRVRNGN mentioned above) than one large one. You might not get quite as much power with a dual setup, but you'll get less lag and things will be smoother and more manageable. (Assuming the kit is built right and you don't simply turn the boost **** all the way up!)

I'll always be willing to sacrifice a little top end power if it means I can get a more even and smooth distribution throughout the rpm range.

 

Not entirely true. Both turbos are the same size and the difference is how the compressor and exhaust wheels are configured. There are a few mkiv guys out there that's converted their sequential setup into a parallel setup.

I'll also add that the 300ZX Turbo (Z31) is single turbo.

It used to be that single turbos were laggy, but that is not the case anymore. A properly set-up single turbo can be better than a parallel twin turbo setup. For example, my friend's Andi's single turbo puts down 677rwhp/602rwtq and my 300ZX puts down 340rwhp/370rwtq. At around 4500rpms, we both put down around 300rwhp. Of course, he's also running waaay higher boost, but his turbo can flow that air w/o any problems. Mind you, my friend Andi is using this setup at HPDE's.

Michael.