Just what the title says...


What is the difference in a Turbine A/R .83 and A/R .63?

I am "guessing" that the .83 allows more exhaust to flow intn the turbine housing, thus spinning the compressor faster causing more lag, BUT more higher rpm power.

Please help. The Turbine section of the turbo is the only part I can't seem to understand.

Thanks

 

With a .83 housing you have more space between the housing and the turbine blades. it will spool slower because more gas can flow past the blades with out being forced to spin the blades, but as you incease power it prevents choking the exhaust.

A .63 has less space between the housing and blades. This allows less gas to pass the impellars with out spining them, so at lower exhaust flow you get more pressure against the blades and quicker spool up. But you could choke the exhaust flow up top.

As I see it for, .8x is too big for street with a 3.0L
.6x is the best choice for street/strip. .5x is best for street, you will have very quick spool up but will choke up at higher HP levels. If you want to see 500whp+ .8x, 300-500whp .6x, 200-300whp .5x. This is a very general thing though, their are so many variables. This is why well engineered turbo kits cost so much, it takes pleanty of dyno time to figure the turbo specs out.

I have a T4/60-1 (trim unknown! O or P) with a .81 on my stock 3.0L, I think spool up time is WAY TOO SLOW! I am considering a .6x housing, but since I am doing the 3.5L build up soon and have a 7200rpm limit I am torn... I will wait and see if a housing change is needed until I get the 3.5L done and some dyno time on it. Its got power, it just dosent jump like a SC when you initially mash the gas

 

at what rpm do you get full boost wiht the .8x housing and at what rpm do you think it would spool with a .6x

 

Well, full boost is a relative term. 1spi@2600, 5psi@3500, 11psi@4500. With the .6x perhaps 1psi@2200, 5psi@3100, 11psi@4k. Eventually I want to run 14-17psi, what ever the injectors will support. I dont think I would see 14psi unti 5000 with the .81. But what I really miss is the instant throtle response of the SC.

 

Thanks matt for explaining it to me.

 

If those are your ONLY two choices, then I'd go:

1)T4 turbine
---0.63 for quicker spool-up
---0.83 for higher top end
or

2).83 for a T3 turbine

If you're still shooting for 400+whp, I think you're limited to the T4 for sure, however how far over that you want to push should decide 0.6 vs 0.8 A/R.

 

Since we are on this subject.. What are your opinions on this setup

GARRETT T3/60-1

COMPRESSOR SPECS:
T04S housing
flow: 61 lbs/min 781cfm
.70 A/R housing
60 TRIM wheel

TURBINE SPECS:
T3 housing
.82 A/R housing
HIGH FLOW 76 TRIM stg3 wheel

Will this give you a balance on low end acceleration and high end power???

 

Bad combo IMO, since the T3 is too small for that large of a compressor.

If you can find BOTH wheel diameters, the compressor-to-turbine ratio should be within 15% or the slip losses will negate the T3s low inertia.

Could be mistaken though.

 

Understood... I thought by having a larger AR, say .63 or .82, on the T3 turbine will allow the exhaust to spool the 60-1 compressor effortless and efficently... Are there any Flow-charts with this setup...

You know, it would be nice if someone with lots of money did R&D on VQ30DE maximas, with turbos ranging from small to large and provided performance specs for each setup... Well just a dream...

 

Morfeus,
Those are the specs on Shadow's turbo. It spools reasonably quickly but he's got an auto so you can't really see it on the dyno graph. He's planning to run it at 12-14 psi eventually and it should be well sized for that application.

IceY2K1,
Do you look at it from the perspective of the compressor wheel or the turbine wheel? B/c the compressor is 17% larger than the turbine or the turbine is 14% smaller than the compressor.

 

Compressor to turbine. 17% vs. 15% isn't a big deal. It's when you start getting into 20+% that you have problems, like the GT25/40 hybrids different companies offer.

I'm not sure what wheel size for the 60-1, but I thought it was rather huge compared to the punny T3s. The 15% is just a general tradeoff NOT exact.

I still think anything bigger then a T04E and maybe even a T04S, should be mated with the T4 for our cars.

Then again, I'm not up-to-date on T-series specs/performance.