"What do you mean the turbo is in the back?" This was a question posed by a hot rodder while hanging in the Fuddruckers parking lot. When we popped the hood and nothing but an STS Turbo decal and a cold-air intake tube were visible, we saw a very perplexed face. "Look under the back of the car," we said. As each skeptical enthusiast looked under the back of our '02 SS Camaro and scanned to the void where they expected to see a muffler, they were stunned by a cool turbo system hanging in place of the muffler! "Does it work?" we heard next. "Why? Do you want to race?" we said with a grin.
It was as if we had brought the first small-block Chevy off the line to a Friday night cruise. Yes, people had seen turbo systems before, but never at the back of the car. It's understandable that your average car guy is skeptical. After all, the hot rodding world is filled with false claims and snake oil, but we told all who peered into the engine bay: the Dyno never lies.
STS Turbo Systems has been around for a couple of years, but until recently we had only heard of them as some company in Utah mounting turbos at the back of cars and trucks. It wasn't until we saw a live installation that we understood how cool the concept of remote mounting a turbo really is. We were under the impression that a turbo system needed a great deal of heat to function, which as we found out was not entirely true. While heat does play a factor in turbo function, it's not the most crucial dynamic. The cone effect, whereby velocity increases inside the turbo housing, is much more vital than the slight heat loss caused by moving the turbo system to the rear of the vehicle.
The engineering behind STS's remote turbo mounting is actually quite simple. By moving the turbo to the back of the vehicle, the need for heat shielding in the engine bay no longer exists. The exhaust gases flow through the manifolds, past the catalytic converter, through the exhaust and into the Garret turbo. The exhaust gas velocity increases about 4,000 percent inside the turbo housing causing the turbine to spin at over 100,000 rpm. The compressed fresh air is pressurized through HPC-coated intake tubes running the length of the chassis, back into the engine bay, directly into the throttle body. While the intake charge must travel the length of the vehicle to reach the motor it is simultaneously being cooled by the ambient air surrounding it, and as a result an intercooler is not required. The patented rear-mount turbo/wastegate assembly is designed to hang from the OE exhaust hangers and move with the rest of the exhaust system.
Oiling for the turbo is probably the most beautiful part of the system. The engine's pressurized oil is routed from the oil filter mount through a braided stainless line back to the turbo. The return is pumped back to the engine and is dumped right through the valve cover oil cap. A 12-volt oil pump is installed in-line on the oil return to keep the line scavenging whenever the engine is running. Should any problem occur with the oiling system, an audible alert will sound and the engine can be shut off before any damage occurs to the turbo. Unlike many other forced induction systems, no drilling of the oil pan is necessary for plumbing. While many traditional systems require a turbo timer after running the motor, STS's patented oiling system has much lower oil temperatures making carbonizing of the turbo bearings almost impossible.
On six-speed applications like the install on our '02 SS, a blow-off valve is installed up front just below the MAF sensor. Between gears, the boost is dumped when the throttle blades shut, keeping the turbo spooled up. On an automatic transmission installation, a blow-off valve is not necessary because 'lifting' of the throttle never takes place during a power run.
The STS LS1 system functions at a base level of five pounds of boost, but can be run at seven or eight pounds of boost provided that you purchase the optional methanol injection system. While many of you are familiar with injecting methanol into the intake path you may not be aware of its function. The slight amount of methanol serves two main purposes. First and foremost it supplements the OE fuel system, making the stock injectors satisfactory for an increase in horsepower. Secondly, the methanol cools the intake charge helping to nullify detonation. For most applications the windshield washer fluid reservoir is converted to a methanol tank, but if the installer is inclined to do so, an additional tank can be installed elsewhere in the rear of the vehicle.
At this point you probably have more questions than answers, as did we when we first learned of remote-mount turbocharging. The biggest question on our mind was turbo lag. How is turbo lag avoided with the turbo so far back? According to STS, their systems are designed specially for remote mounting. They use custom sized housings that function awesome in back, but if mounted in the traditional location up front would perform less efficiently. On the flip side, if a traditional front-mounted turbo was moved to the rear, lag would become a major issue.
We also wondered, doesn't it take a while to pressurize the intake tube with so many feet of intake tubing? To our surprise, a molecule of air can travel from the turbo to the intake inlet in .05 seconds, which provides boost almost instantaneously. "All the intake tubing adds up to less than half a cubic foot of space," says Rick Squires, owner of STS Turbo Systems.
When we asked Squires about the difference between turbocharging and supercharging he said, "A centrifugal supercharger impeller works much the same way as a turbocharger. It spins at a high rpm to compress air into the engine. The biggest difference is that while a supercharger is driven directly from the motor, a turbocharger is driven only from exhaust. Due to the correlation between crank rpm and impeller speed, a centrifugal blower only makes big boost at high rpm. Conversely, once a turbo starts producing boost, it pulls straight to redline. The higher the rpm, the greater the increase in efficency. So, if you desire gobs of torque throughout your useable powerband, go with a turbo."
When we began our fact-finding project we decided that the best way to determine the true bolt-on nature of the STS System was to find a bone-stock LS1 F-body. A much more difficult task than we originally figured, many of the LS1 yielding F-body owners modified their machines the day they rolled off the showroom floor. Lucky for us, Dave Stoker, advertising salesman for our sister publication Custom Rodder, had just the machine we were looking for, an '02 Sunset Orange, box-stock, six-speed F-body. With the exception of a K&N filter and SLP factory three-inch exhaust, Dave's machine was as virgin as they come.
After receiving the kit from STS we opened the box like a couple of kids on Christmas and went through the parts list to be sure everything was accounted for. We pulled Dave's '02 onto a lift purely to make the photography easier. Starting on the install just after 1:00 pm, we had the system installed minus the methanol by 5:00pm. Over the next couple of hours we installed the methanol system, removed the factory ECU and replaced it with the re-flashed turbo-ready ECU from STS.
We rolled up the garage door and fired our turbo wielding F-body for the first time. Keeping in mind that the STS system replaced the factory muffler, we were expecting loud obnoxious exhaust notes. To our surprise, the '02 actually idled quieter than stock. As we pulled out into the street with our variable boost controller set to five psi, we slowly depressed the go pedal and instantly heard the spooling turbo noise we had been yearning for since the day we ordered our system. By the time 3,000 rpm was on the tach we were pinned into the seat with only the thought of a night in jail in the back of our minds.
After a few minutes behind the wheel, we flipped the "oh boy" switch to seven psi, and with the assistance of a little methanol we were incinerating the tires in every gear. It became plainly obvious that a set of drag radials and a long stretch of road were in serious order.
What do we think? We think it's time to check out the dyno numbers. We baselined the stock '02 at L.A. Performance Division for a grand total of 313 rear-wheel horsepower. After installing the system and going back onto the same dyno, we produced 463 horsepower and 511 pound feet of torque the very next day. What does this mean to you readers? Lots of big, smoky burnouts for about $4,000!