Nick-Crispy

I am building a 96 s-10 i finally got the ls1\t56 combo in and i want to do twin turbos but i dont know what to get. Right now the motor is stock from a 98 camaro but i want to but turbos once and next year i will build a motor and i want to make 700 wheel what turbos woud be enough. also can i get internally gated turbos or will that caus boost creap. one person sugested presicion turbos for the best bang for the buck. any help would be greaT

prostock_bigblock

iTrader: (11)

twin 61s would be nice.

Nick-Crispy

ok 2 61 whats would be best

Chewy72SS

Twin 61's or GT35R's would work very well with a stock cube (346ci) LS1. If you plan to build a stroker or change the engine size, you will need bigger turbos to get enough air into the engine.

Turbonetics and Garrett turbos are probly the best. Although, I wouldn't consider them for the best "bang for the buck".

As for integrated wastegates...
Most of the larger, "non-production" turbos do not have wastegates on them.

_Baca

CALL911

iTrader: (17)

If you are dead set on having a Turbo car, my only reccomendation would be to stay away from the STS setups.

If you just want to attain 700 HP, then the cheeper route would be to go with a supercharged application. Either way, plan on spending some serious $.

DrTurbo

iTrader: (3)

The best advice is talk to someone who know about turbos. Let them explain all of the units to you and the differences and what you are purchasing for the extra money.

Nick-Crispy

ok great the gt35r is great but for all day every day that wont work. my buddie has one in his tallon and is is cool but he is on his third set ov barrings i was kind of thinking a non ball berring wiuld be better. i am building the whole truck and plus i had a vortech kit in my other toy and whell i hated it . whell mabie i should more precice with what i am asking i have two tile 44 and two tile bov and i realize that i need two like 60 trim but i was thinking that some could suggest a part number and where to get it so i can resurch it i looked at the flow charts from the fac on the forum but i cant find what i need to figuar it for twins.

Nick-Crispy

almost forgot i see that you are using twin t70 on a 408 how did you figuar that .......
thanks again for the help

Chewy72SS

OK. For any turbo application, turbo selection is a very important part of the build. After you find out how much airflow (lb/min) is required for your particular engine (cid), you need to start sifting through all of the turbo compressor maps out there.

Here is the formula I use:

Cfm=
C.I.D. x .5(RPM) x V.E
1,728

VE is at least 100% for a turbocharged engine so use 1.0 for VE.

Take that number, and multiply it by your Pressure Ratio (PR).
PR=
14.7 + boost psi
14.7

10psi = 1.68PR
15psi = 2.02PR

The result is the required cfm for your boosted engine. You now must convert that number to lb/min. To do this, multiply the required Cfm by 0.07.

This final number is the required lb/min of airflow required on your boosted engine, for a single turbo. (Divide that number by two for twins.)

Looking at turbo maps, use the lb/min (bottom of graph) and your PR (left side), you want them to intersect somewhere in the middle efficiency island (preferably to the right of said island). I usually do this with two PRs that I plan to run (i.e. Street psi and Track psi).

Follow this post loosely, because I am no expert. Although, this has worked for me several times in the past.

Nick-Crispy

ok im stumped mabie you could show me how that works i will have a 408 i will rev to 6800 rpm and i want 700 at the wheels so how do i know how much boost i will need ? soo confused. thanks again for being pacient

Chewy72SS

...Lets go through the equation.

408 x .5(6800) x V.E.
1,728

0.2361 x 3400 x 1.0

Cfm (Naturally aspirated) = 802.778

Boosted:
802.778 x 1.68PR (10psi) or 2.02 (15psi)
Cfm (boosted_10psi) = 1348.667/1621.612

1348.667/1621.612 x 0.07
Corrected airflow = 94.407lb/min (10psi)/113.513lb/min (15psi)

Go through the formula once with 10psi (red), and then another for 15psi(gray). The corrected airflow should be divided by 2 for a twin setup.
So,
10psi (1.68PR) = 94.407/2
10psi ~ 47lb/min

15psi (2.02PR) = 113.513/2
15psi ~ 57lb/min

Now...lets look at the T70 compressor map.
T70 Compressor Map
Notice how the Corrected airflow(lb/min) and the PR intersect near the center efficiency island. Although this example is a bit conservative, you want to keep the lines from intersecting near the Surge Limit.

Hope this helped. If you have any questions, PM me.