Rear Turbos... I know, but it was coming anyway :)

**pajeff02** · 05-12-2011, 03:35 AM

GMHTP featured the STS system install on an F-body in a couple of articles. Here are the links:

STS Install - Part 1

STS Install - Part 2

(Note: In the articles, these are labeled Parts 5 and 6, but there was a lot more done to the car than just the STS system)

**35th-ANV-SS** · 05-12-2011, 05:45 AM

There are wastegate size calculators online.

You do not want to get one too small. If your exhaust gases (your "waste") can't escape fast enough, your turbo will continue to spin fast, creating even more boost. This isn't a good thing. You can create more boost than your max.

The purpose of the wastegate is to regulate your maximum boost pressure.

I believe TiAL has this information on their website. In general, most wastegates have a corresponding HP rating with them I believe.

**joejenkinsglass** · 05-12-2011, 01:01 PM

A turbo system is all about efficiency, with mismatched parts it will not perform as well as it could. I Dont think a larger than needed wastegate will "hurt" but may not perform as well with it. If it didn't matter every turbo system would have the same wastegate.

**JoshuaGrooms83** · 05-13-2011, 12:26 PM

Alright so form what i understand

Low boost - mid to large wastegate 44-50mmish
High boost - small to mid wastegate 38-40mmish

?? kinda ??

For my setup with of 5-8 Psi max, A 50mm wastegate should be just fine with controlling boost right?
I now am looking into a spool valve as well since i learned about it on Zombies thread about it.. AND since i do have a twin scoll coming

that my .84 would do well with it. Im trying to find where i can locate one though.

**joejenkinsglass** · 05-13-2011, 12:35 PM

I have never heard of a spool valve.

**JoshuaGrooms83** · 05-13-2011, 12:50 PM

From what i understand from Zombies thread and other searches,
It is used to help spool large turbos faster.
On twin scroll turbos, a plate with a valve is placed in between the turbo and exhaust inlet pipe.
On 0-low boost settings the valve stays closed on one of the openings going into the turbine chamber.
As max/desired boost is reached, the valve is opened and flows as normal.
THe end result is reaching full boost faster in larger turbos. In short terms, it halfs the turbines AR in half, forcing all the exhaust into one side of the turbo creating more pressure to spool faster initialy.

SO if you are runing somthing that has like a 1.0 AR, initially in theory it can spool like a .50 and get your boost up faster. In rear turbo set ups, this is a god send since we are at a disadvantage on effeciency anyway.
My dream setup would be an oil-less twin scroll turbo with a spool valve

**JoshuaGrooms83** · 05-17-2011, 08:23 AM

And its here!! my first turbo

Its a cheapy but it seems alright. I played with the shaft and it didnt move anywhere other then spinning.
Its a T70 with a .84 AR. I believe its a T4 with a 4" compressor inlet with a 2.5" outlet and a 3" Vband turbine outlet. Seems like a good start.

**JoshuaGrooms83** · 05-17-2011, 09:59 AM

Ok so im looking into wastegates and i found one thats 44mm with adjustable 4-7psi with vbands and a 38 to 44 adaptor.

ALso im trying to find a turbine inlet flange but im having a hard time trying to differentiat between T3 and T4 turbos. From the pics above, i do have a T4 right? (theoreticly lol) Are they the same bolt pattern?

**JoshuaGrooms83** · 05-22-2011, 10:09 AM

Appartently ive mixed up T3/T4 thing a bit a guy that looked at it with me said its a t3 connection. my bab. Still learning turbo stuff so i may mess up a few things every now and then lol ITs still a T70 but i think its on the small side. I may go T72 or even T76 form what i can tell. If this T70 seems small, the T60 that went with the STS system must have been TINY lol

**joejenkinsglass** · 05-22-2011, 01:09 PM

Probably gonna be a good street turbo.

**JoshuaGrooms83** · 05-22-2011, 01:29 PM

Thats mostly what its gonna be

i dont plan on being a all out drag car. or RR car.

**JoshuaGrooms83** · 05-30-2011, 08:32 AM

So a t3 will do for now right? it should spool rather quickly, the on ly thing im worried about is back pressure. I think ice i wil be dealing with higher speed driving, i might go with a T76 later with a T4 inlet. gives me room to grow as well. I start with this one first

**joejenkinsglass** · 06-01-2011, 06:54 PM

yes it will work, as you said probably a little small. Would probably be well suited for a 3.8 f-body. either way it gets you started.

**JoshuaGrooms83** · 06-02-2011, 01:15 AM

yeah, i misunder stood the T3/T4 thing when i bought it. Oh well, still can get a T4 turbo for cheap too.

**parnelligq** · 06-02-2011, 07:53 PM

I here that a larger waste gate prevents "boost creep". So I guess it would be better insurance against over boosting and as you add more boost, the larger waste gate would handle controlling boost better. I would go with as large as I could afford.

**JoshuaGrooms83** · 06-03-2011, 04:22 AM

Im not installing an STS, im fabricating my own rear setup. Im gonna go with a 44mm. Im using a twin scroll not a twin turbo set up.
Im keeping boost to a moderate 8psi. not sure how bad boost creep can get on this. i figure with a decent sized wastgate with a 8lbs spring shouold keep boost creep and spike down. with a rear turbo, long tubing, a decent intercooler, and normal pressure drop I should get about 6psi with maybe a creep up to 8 after getting into higher RPM. we will see.

**35th-ANV-SS** · 06-03-2011, 06:46 AM

Sounds like you're making some good progress and have all your ducks in a row now.

**JoshuaGrooms83** · 06-03-2011, 02:06 PM

lol slowly working on it. trying to get the hardware together first.

**JoshuaGrooms83** · 06-14-2011, 07:49 AM

heres some intercoolers that i found laying around
from left to right to bottom
Skyline, dont know, Saab, and BMW

Im kinda thinking the BMW one (long one) is the best bet for now. Would fit pretty much anywhere. The one that i dont know looks like it would fit laying like the procharger intercoolers do.

Got my turbo inlet flange today. Its comfimed. Its a T3 turbo inlet. oh well, ill upgrade later to a T4 later. This ones jsut to get me started.

**Smittro** · 06-14-2011, 07:33 PM

Originally Posted by JoshuaGrooms83

heres some intercoolers that i found laying around
from left to right to bottom
Skyline, dont know, Saab, and BMW

Im kinda thinking the BMW one (long one) is the best bet for now. Would fit pretty much anywhere. The one that i dont know looks like it would fit laying like the procharger intercoolers do.

Got my turbo inlet flange today. Its comfimed. Its a T3 turbo inlet. oh well, ill upgrade later to a T4 later. This ones jsut to get me started.

Yeah I was gonna say I have the T3/T4 in twins (can't remember the AR @ moment) and they look different from that snail flange, I don't have the seperation in the flanges. Also, that turbine outlet looks very small..imho