Ali2GS300

I did a single turbo aristo swap a few months ago
BW 60mm single scroll turbo 177280 ( the turbo manifold is actually twin scroll BTW)

• Compressor Wheel OD: 3.29 in.
• Compressor Wheel Inducer Diameter: 2.36 in. / 60 mm
• Turbine Wheel OD: 3.00 in. / 76 mm
• Turbine Wheel Exducer: 2.66 in. / 68 mm
• Turbine A/R: .88

Turbo spooling is too slow. almost 3800RPM
i want to go lower A/R but i heard that i might end up with turbo surge ?
what would be the best for my goal (whatever hp a stock ecu will make with 14-16 psi) with less lag

So i found this turbine housings and i'm thinking about upgrading to the .68 A/R.
but then i found the twin scroll .88A/R
so what should i go with ?

upgrades:
1 Walbro 255
2 Gates timing belt
3 Front mount intercooler
4 dual 3" straight pipes exhaust
5 B&M 70268 Automatic Transmission Cooler ( on stock A340E )
6 HKS wastgate (12PSI spring with boost controller)
7 Greddy boost cut controller ( to boost more on stock ecu )

lsflame

My question for you, what type of bearing is in your turbo charger? Also consider gettign a quick spool valve.

JeffTsai

iTrader: (1)

Your turbo should spool relatively quick because it's on the smaller side of things when it comes to 2JZ. Realistically, a 3800rpm spool isn't really too bad. Of course it won't spool as fast as the stock twins because those things have compressor wheels the size of a golf ball lol.

Going to a smaller AR on the turbo has its advantages and disadvantages. You will spool faster, but lose top end power if you plan on boosting higher. If you are running low boost, then there will not be a huge difference in power loss close to redline. Going to a divided .88 will not gain much spool advantage over an open .88 housing unless you have a race style fully divided turbo manifold with twin wastegates. The true twin scroll manifolds with 2 WG can separate the exhaust pulses on the opposite banks and gain a spool advantage with using a divided housing. If you have the normal ebay style manifold that has the WG going to both banks of the engine, then you will not gain much spool by going divided housing. If you are just planning to stay 14-16psi then you can run the .68 housing and gain spool advantage without losing too much top end. However, if you plan on running 25psi range then you will lose significant power at redline on that .68.

This is the same reason why factory turbo cars have a really small AR exhaust housing to spool fast. For example, look at the BMW 335i. It spools super quick and gets off the line fast, but the power falls off very significantly after 80-90mph. They have small AR and made the assumption that most drivers will want faster responding low end power for the tradeoff in top end.