Ive looked all around the forum cant find the specs on the stock SS t/c turbo. If anyone knows tell everything you know or a link about the brand, mm, any spec that you know. I've been talking to a lot of ricers and all they care about is the turbo and i don't know what to tell them just that it but it puts out around 15lbs

 

Its a borg warner k04 turbo, its good for around 290-300whp.

 

I know it's a twin scroll design. Instead of just being fed (on the exhaust side) by two cylinders there's one shaft leading to two and another to the other two for quicker spool up.

For all I know that may be typical and just how the K04 is designed. But even after looking up the K04 I didn't know that. I found it on some design features article or something specific for the SS/TC

 

I want some of what he's smokin!!!

Theres only 1 shaft bro. The scroll (housing)that feeds the turbine wheels is split so it increases the velocity at lower speeds.

 

Maybe I was thinking wrong or worded it wrong...

The 2.0L Turbo’s turbocharger applies a unique, twin-scroll design. Each of two scrolls on the turbine is fed by a separate exhaust passage—one from cylinders one and four, the other from cylinders two and three. The twin-scroll design virtually eliminates turbo lag at low engine speed—the time it takes for the impeller to spool up and generate boost pressure—and delivers the throttle response of a high-performance naturally aspirated engine

https://www.cobaltss.net/forums/2-0l-lnf-performance-tech-153/gm-powertrain-website-posts-lnf-info-85804/ Found under "Engine Information"

PS - I don't smoke..... ANYTHING!

 

Cept for the pole... hahaha! just playin'~

Are you plannin' on getting one or did u just get one?

 

I got an Ultra Silver with Sunroof, LSD, and high rise not quite a month ago. Already did a drop in K&N and Hahns BSR PPC Tune.

 

More than you ever wanted to know (I posted this in another thread):




Using (P1 + P2) / P2 = Pressure Ratio
P1 = Desired boost pressure in psi
P2 = ambient atmospheric pressure (14.7psi)

Our engines are almost 122 CID, so at 100% VE our engines should flow close to 220 CFM. Assuming 80% VE this means approx 176 CFM at 6,250 RPM, which is approx 12 lbs/min at that rpm

Quick calculations (it takes several calculations to calculate a single data point on that map) show our 260hp to be at about the 0.12 mark on the X axis. I believe the X axis is Kg/s, so you can convert to lb/min if you want to by multiplying the numbers by 7. (7 is not the exact number to convert, but it will get you very very close and is easy to remember)

This also assumes many variables that are not listed here such as air temperature, altitude (assuming 14.7 psia for sea level), etc. The chart shows the calculation used to achieve nredV using 183.5, which means they are using 83.5% VE for their calculations.

Using assumed variables, and assuming that this chart is the correct one (lots of assumption there), that would seem to indicate that at the very outside edge of the efficiency island is around 22 psig before the compressor will surge - this lines up with both the overboost protection in the computer and what some tuners have run into already. 21 is about the max safe boost level on the stock K04 (which is what Hahn's tuner sets the boost to, so this lines up as well).

 

Just asking for curiosity, not contradiction... cause I think you might be able to answer.

I have the Hahns tune. When the tune was first applied, it would surge to 25 and then fall back to 21-22ish. After a few runs it settles. But even after that it will surge to maybe 23 or so and fall back. (So still surging and falling back but less extreme now)

So my question is in your opinion do you think the tune is set for higher boost or these surges are because the turbo is so near it's max?

 

Well the BSR/Hahn tune is still within the safe window. As long as it doesn't stay at 23 or 25 psi for long term there should be no problem. That almost sounds like it is "learning" your specific car, shooting for the target 21psi.