Leaving you halfway through the installation of an STS turbocharger system on Project CT ("Bookin' by the Book, Part 5," Sept. '10) probably annoyed some of you. You were likely itching for the results and didn't want to wait another month to hear about them. I, Chris Werner, hereby personally express my deepest apologies for keeping you in limbo, as well as making you go back to skim through last issue's story. (As an expression of my gratitude for your patience, allow me to at least save you the time of looking at the table of contents: the story begins on page 58. If you can't find the previous issue, check the bathroom.)
Drafting multi-part story series also creates more work for an author because it necessitates writing a recap of past story segments; it's a bit of a mental chore to compose the same thing slightly differently each time. So here's the same recap from last month, with a subtle change or two that the detail-oriented reader might pick out. The May 2009 issue featured an introduction to the project along with a GM LS7 clutch and B&M shifter swap, and this was followed with CARB-legal K&N intake and Edelbrock exhaust upgrades (July 2009) purple monkey dishwasher. In last November's issue, a full corner-carving suspension treatment complete with Spohn hard parts, AFCO shocks, and aggressive Nitto rubber was had. Penultimately, the January 2010 issue showcased a totally awesome, badass AFR cylinder head/GM LS6 cam and intake manifold swap. This was, of course, followed by the first half of the turbo system install last issue, bringing us to the present day.
The installation of this kit represents the capstone for what has been a 50-state emissions-legal build in keeping with the strict emissions-related requirements of the California EPA's Air Resources Board. Today we answer the question of how much power can be had from an LS1 while staying within the bounds of the most comprehensive pollution-curbing regulations in the land, and since things would start to get dirty were we to try and feed our mill a heftier diet of unpressurized atmosphere (i.e., remain naturally aspirated), there is no arguing that forced induction must be involved in any such quest.
We mentioned last time that while the installation of an STS remote-mount turbocharger system is a straightforward affair, there are a lot of bits and pieces involved; it's just the nature of the beast. As you probably noticed, little modification is needed to the stock exhaust system. But the kit requires a good amount of intake pipe running from the turbo in the rear, to the intercooler up front, and finally to the engine. (Worried that that's a lot of tubing to pressurize? STS says its total volume is not that much different from conventional turbo setups, and that the company's systems compress the intake tubing in about 0.05 seconds!) Follow along as we install said piping and remark on some of the other features that set an STS remote-mount turbocharger kit apart. Check out the FAQ page on STS's website for a more comprehensive discussion than is possible here, explaining answers to questions spanning "If water hits the hot turbo, will it crack?" to "Doesn't heat create the velocity in the exhaust gasses to spool the turbo?," and everything in between.
Post-Installation Impressions First and most importantly, the power: it's impressive! Any time you add triple digits to your bottom line, it's sure to completely transform a car. And this is no exception. While CT is very docile to drive normally, getting into the throttle rewards the driver with a very progressive rush that really takes off over 4,000 rpm. As for "turbo lag?" Well, while it takes a few seconds for boost to build at low rpm in a high gear, in any other circumstance, fugeddaboutit! And then there's the sound: with nothing but an open pipe between the outlet of the turbine and the atmosphere, the driver is treated to the constant divinations of turbo spool, even at part throttle. While the rhythmic blowback through the air filter when letting off the gas is a little distracting (especially as it emanates from the rear of the vehicle), backing out of greater throttle positions causes the BOV to activate, creating a booming hiss that is pretty intoxicating.
The best news of all is this: should the desire arise for further power increases in the future, they're easily accessible. STS sells an Electronic Boost Controller for just $165 MSRP, which can yield adjustment up to 5 psi above wastegate boost pressure. Since our 67mm turbo is said to be efficient as high as 12 psi on our LS1, this would put us right in the range of max output with the system as it stands. Please note, however, that STS does not recommend running over 10 psi with a stock bottom end, and that an STS methanol injection is also recommended for these kinds of boost levels. (Plus, CARB certification is only good to 9 psi of boost, so anything beyond that would downgrade us to 49-state legal status.) Despite those caveats, it's clear that there's lots more room to grow, and quite easily indeed.
One downside we found is that while all components of the STS kit sit fairly well tucked-up underneath the car, the underside of Pipe 4 (the intake pipe that runs under the front subframe) occasionally kisses the asphalt. It's our view that this is less of an STS design issue and more due to CT's lowered front ride height, thanks to our AFCO shock/spring setup. (Our theory is bolstered by the fact that the rear of the car sits at stock height, and we have had no issues with anything back there scraping anything.) On a more minor note, we ended up having to cut and re-weld the section of pipe joining the BOV to Pipe IC1, as interference between it and our aftermarket anti-roll bar was rotating the forward-pointing section of that pipe downward. This caused the junction between Pipes IC1 and IC2 to hang too low. Here again, we chock this up to our use of aftermarket suspension components; as is always the case when fitting different types of aftermarket parts to the same vehicle, these kind of minor tweaks did not come as a surprise.
That about wraps things up! Further performance increases are not on our minds right now, because CT has more than enough power than is usable on the street. While I'm away completing my Masters in engineering, Pops will surely be having fun giving the car some exercise ... but considering that paramedics dragged him unconscious from the smoking wreck of our last turbocharged Camaro SS, I can only hope this one will still be around when I get back.