Wanted to get feedback on running a twin set-up using T3 turbine housings with stage III wheels and .63 A/R.. Would this be a little too big to run on each bank??

 

I don't think so...SFR uses Stage III turbines on their twin 60-1 kit...

 

keep this in mind: What's the biggest turbo you'd run on a 1.75L motor with a 6500 redline and still have it streetable.

a t3/t4 can be used, but it'll be laggy. I suggested this elsewhere and I'll do it here, twin GT28RS turbos or twin GT2871Rs would be a better bet. Otherwise, you lose a lot of streetability.

 

chimmike your comparison doesnt work out quite IMHO correctly. driving characteristics would be nothing like a single 1.75L. We do not have 2 engines pushing 2 cars, we have one engine, a pair of 1.75L banks, working for the same goal of rotating the same crankshaft to push a single vehicle.

Lag is not as noticable in a car with more displacement as the car drives fine already. the low end torque of the 350z already dominates a 4 banger of 1.8L-ish of displacement... and once again we dont have 2 1.75Ls pushing 2 crankshafts, 2 transmissions, and 2 vehicles... its just a single 3200lb car.

You can get away with a larger turbo then you would think.

I will tell you this, our 350z with the twin greddy 18g's on it drives way WAY WAY better then a single 4g63 eclipse with a 18g on it.

 

well if you think about the twin setup, phunk, each individual turbo is driven by exactly 1.75L of displacement. Therefore, you're essentially driving each turbo with 1.75L as opposed to a total of 3.5L (driving the ST setups)

that amount of exhaust/thermal flow can only efficiently drive a certain size turbo before you use a turbo that isn't in its efficiency range or the compressor map is way out of whack, and then you have a laggy dyno queen,

 

i agree with you on how you are judging the ammount of exhaust energy given to each turbocharger... i am just saying that the larger turbos do not effect the way the car drives nearly as much

 

So you are saying, chimmike, to choose the best turbo for a twin setup, you calculate your airflow numbers based on half of the displacement of the motor?

Is this true?

It seems very logical, however, I've found other sources that say this is not the correct way, although unfortunately, no one has given me a definite answer on how to do it.

Anyone have any concrete info?

If this is the correct way, then yes, twin GT25 or GT28 would be the prime turbo.

In my opinion, lag is very over exaggerated. When you are racing (drag strip of course), as long as you don't fall out of boost when you shift, you'll never notice it.

I had a Precision SC61 (Stage V wheel, .63 / .83 AR) on a 2.0L Honda. Everyone said it was gonna be laggy. I made full boost (15psi) at 4800rpm with an 8200 rpm redline. It was scary fast. I completely annihilated/obliterated many modded Vipers, Porches, Corvettes, Mustangs, etc. Even 600cc and 750cc fuel injected bikes. I wasn't even in the max efficiency island of the map. Now this turbo is being used on 1.6L Hondas and making plenty of power. I'm actually considering using two on my G35.

Just my experience..

 

I'd personally think, for awesome power and great powerband, GT28RS, or GT2871R. Of course, as someone said in another thread, the 3071R is a 2871R with a t3 turbine housing, which means it'll flow better in the top end. the 3071R is good for something like 450whp if I'm not mistaken. That's a whole lotta powah!

twin SC61s would be way too massive imo

 

Or twin 60-1 Hi Fis like SFR... Each turbo can flow for over 470 HP and with a .63 A/R T3 on the turbine side the lag is not THAT bad. Again the displacment of the motor keeps off boost tq response pretty good. I think Tim spools up in the low 4s which isn't THAT much later then most other TT kits and his car is making 500 RWHP at 11.5 PSI on a bone stock motor...

 

Thats precisely why I'm seriously considering twin Precision SC61s. The SC61s are supposed to be significantly more efficient than the Turbonetics 60-1, flows more, and spools almost identically. I haven't performed any tests to confirm this so don't hold me accountable or taking it as bashing the 60-1.

Tim also has equal length manifolds rather than the usual log style so that definitely helps with spooling alot. Utilize the smallest version, SC6152E, coupled with Tim's manifolds and a true dual 3" exhausts and it should perform quite nicely.

Exactly what I plan to do.
I'm also gonna plumb in two electric cutouts so I'm pretty sure I can get it to spool at 4k when they are open.

Back to the main question at hand, the GT28s are a really good choice if you are that worried about lag, but no, I don't see those turbo's being laggy depending on the exhaust manifold you use to feed them. Manifold design and backpressure has the biggest determination on how it spools other than the simple size of the motor, imo.

 

I've heard both ways about the SC61 vs the 60-1...only way to find out for sure is to try one then switch to the other if you have the capital to do so..

 

you really should get the opinion of a professional shop on this. someone like jotech should have all of your answers.

keep in mind a few things
-lag
-power potential
-bb or not
-manifold
-will it fit?
-price
-curve?
-surging issues
-warranty on turboes