DjohnsonFTW

Hey guys! I'm throwing together a junkyard build that I was trying to also build for the future. heres my current setup:

4.8L
Holley 96 pound injectors
Stealth fuel pump (rated for 750 HP forced induction)
3'' header collectors with t4 flange
3.5'' exhaust turbo back
(2) 50mm wastegates
Turbo: S300SX3 Turbocharger
66mm / 2.60'' Compressor Inducer Dia.
3.60'' Compressor Wheel O.D.
73mm / 2.89'' Turbine Exducer Dia.
80mm / 3.14'' Turbine Wheel O.D.
0.91 Turbine A/R
T4 Twin Flow Turbine Inlet
Straight Compressor Outlet


Heres my question!!

I'm learning about turbos so id like to describe to you my build to replace my 4.8 and if the turbo will support my next build.

6.0 forged rods and pistons destroked with 4.8 crank
LSA heads
LS9 Cam
Max RPM 6500
700HP goal
(not looking for a debate on why to destroke or not, although if it makes the thread more popular... have at it )


Will that turbo be too small?

Any thoughts on how this turbo will behave on a stock 4.8?

im pretty close to completion at which point i plan to start building the block while i drive the S*** out of that 4.8 this summer. This is all sitting in an 86 el camino with a T56 and 3.55 rear gears


Thanks in advance
-Dane

SikkyMFG

I would recommend going with something in the S400 series that's T4.

That turbo will likely run out of steam before you power goal. If it does make the power goal it's going to be falling off hard on the top end.

JoeNova

Turbo is way too small for a 6.0.
3" header collectors are way overkill. You're only hurting spool and gaining nothing in return.

DjohnsonFTW

I figured thatd be the response. not what i wanted to hear haha but i appreciate the info. Down the road I move to the larger displacement and an 400 series turbo- my 3.5'' exhaust would no longer be sufficient i assume?

DjohnsonFTW

can you explain? sorry i guess when i built this i figured the turbo would apply the necessary back-pressure so collector size would only be limiting not over done?


Also to clarify it would be end being a 5.3L with a 4'' bore(4.8 stroke)

SikkyMFG

It's about velocity, the more volume in the piping the more exhaust it takes to pressurize it. With a small motor such as yours you don't need a ton of volume in the pipe.

My 5.4L engine has 2.5" collectors and 2.5" piping up to the T6 turbo.

JoeNova

I run a 2.25" crossover pipe to the turbo at 800+ HP. There are guys using 2" piping and running 8s @ 160 mph.

Turbos act different than N/A.

2 50mm gates is probably a bad idea as well, unless you plan on running a good boost controller. Otherwise, the gates would barely have to crack open to vent enough exhaust to keep you from building boost. You can could a 12 PSI wastegate spring and have no idea why it won't build over 7-8 PSI.

Your current 4.8 would hit 700 HP with the right turbo.

DjohnsonFTW

man.. haha what a wealth of knowledge all leading to the things if dont wrong :p

Joe or Sikky. How burnt am i goign to be with having that 3'' pipe for 550-600 crank hp? i can re do it if its going to make a world of difference but i was hoping if the loss is minimal i can make new pipes on the next build.

-Dane

JoeNova

You would notice pretty significant difference between 2" and 3".

DjohnsonFTW

2'' just confuses the hell out of me haha. i believe you i just cant comprehend why my exit is supposed to be 3.5 but hte feed can be 2''. backpressure to the turbine but no backpressure after?

Alright so- do i have to do the whole pipe? or can i just cut the end off. put a 3'' to 2'' reducer and 2'' to t4 adapter? not trying to be cheap but that 3'' stainless wasnt cheap haha

JoeNova

Run it. See how it behaves.

You didn't say whether your goals are crank or wheel HP numbers either. A stealth 340 will not make 700whp.

Get a bigger pump. Get the 83mm turbine T4 version of the S475.
That same turbo has made ~800whp on a stock cam 4.8.