1fsttransam

Now this will not be an all out car. I am building this for my wife. I am looking to make 600hp at the top end and turn it down when she wants.

Car will rev to 6500 and will have a 3400 stall. So the question is

What A/r for 76mm and What wastegate if I want to lower to around 8psi?

Is a 38mm ok, or will I need to go with a 44mm for the lower boost?

ZL1Killa

iTrader: (17)

600hp can be accomplished with a 72mm and 38mm wastage, i have no problems with my setup and I have a 38mm wastegate making 650+

TC76 Ball bearing, .81A/R T4 housing 3" DP flange

I debated going with a .84 or .96 A/R

you could easily do a T72 or TC72 (only ~1.5" difference in housing size roughly) TC being smaller.

1fsttransam

I am not looking to push the turbo to its limits to get to my power goal... Where are you making max power at?

westtexasbuff

iTrader: (40)

.96 A/R and a 46mm Precision wastegate is what I would do. It's always good to go a little bigger with wastegates so you don't have to worry about boost creep.

frojoe

iTrader: (10)

Can this boost creep be controlled reasonably well with an electronic boost controller, or would that just be a bandaid fix, if creep does end up happening?

thanks!
Joe

1fsttransam

ok, so if I went with a .96 a/r over a .81a/r what would the difference in spool be... On a 346 is the 81 getting close to chocking the engine up. And what about a .68 (i think thats the other common ratio.)

If other info is required for some to help let me know I will try to get you what I am thinking.

Boo"SS"t

iTrader: (2)

IMHO, having an automatic wouldn't really matter much when it comes to spooling whether you go .96 or .81 a/r, and .68 would be too small for a single front mount regardless auto or m6, but I would go with .96 just incase she ever wants a little more in the future, keep in mind that boost is really addicting.

westtexasbuff

iTrader: (40)

If you're seeing boost creep, it's more than likely caused by too small of a wastegate or wastegates. What happens is that in high rpm’s, your engine is pushing out so much exhaust that even with the wastegate remaining open, it isn’t able to divert enough gas to keep the turbine from spinning faster, so your boost pressure continues to build until you let off the gas. It is a simple problem of the wastegate opening being insufficient to divert enough exhaust around the turbine. So yeah, I would look at a BC as more of a "bandaid" to the problem.

Either that, or the turbo(s) is/are too small for the motor.

You're going to spool faster with an .81 AR, but will choke off a lot sooner than a .96 AR.

1fsttransam

so it sounds like everyone would really do the .96 over anything else. and to go with a 44mm wastegate.

got-a-ls1

iTrader: (12)

if your going with a tc 76 yes go .96. The a/r matters with the size of your turbine.. i have a precision 76mm turbo and i have a .81 housing on my 5.3 liter and it spools very very fast. I havnt tried to boost lower but i have seen 10lbs of boost at 3200rpm at 50% throttle from 2600 rpm in 3rd gear... lol. hitting it from vacuum and using logs from hptuners, flooring it at 3100 rpm from 10% tps to WOT goes from vacuum to 172kpa (10psi) in 1.1 seconds and does so by 3800 rpm in 2nd gear.... 50-80mph takes 2.1 seconds in 2nd gear

the only thing i can say is dont fall into the trap of building for someting you will never need..

1fsttransam

thank you thank you thank you. That is very good information and I am glad that you were able to give some actual data.

got-a-ls1

iTrader: (12)

no problem man. btw i have a 46mm wastegate, forgot to add that

frojoe

iTrader: (10)

Thanks a lot... that was a perfect explanation!!

RealQuick

iTrader: (14)

.96 A/r and 50mm JGS gate [/thread]

Fbodyjunkie06

iTrader: (10)

44mm WG, 76gts, .96 a/r. With that tight(ish) 3400 stall, and a say 3.08-3.42 rear gear it should load the turbo up really quickly which in turn will make boost fast!

Tx91z28

this is exactly what i'm running, shooting for 650rwhp though a t56

TurboS10

iTrader: (12)

TC and GTS are different turbines. 68mm vs 75mm

.96 TC 76 will do what you want and will be easier to sell than a 72.


6500 and 3400 stall makes it seem like will want bigger.....more like a GTS or S475.