Carlson used SCT Live Wire to log and manipulate the ECU tune, which he had modified when the shop added a Steeda cold-air kit to our test subject. He said this about the tune on the nitrous, "the jets supplied by Nitrous Pro Flow were well matched. The low and mid-range rpm was a little lean and the top-end was a little rich. It would be fine as is, but I am picky so I changed the base fuel table in the tune. I richened the low-end and mid-range and got the air/fuel ratio to run consistently in the 11.5:1 to 11:1 range." The car was tuned for premium fuel, in addition to the Steeda cold-air kit, so Carlson removed a few degrees of timing to keep it safe.
On the 100-shot, three more degrees of timing were removed for a conservative overall timing package, due to the stock spark plugs. Carlson did inform us he modified the top-end timing table due to the nitrous flow. "When the system was activated, it was displacing some of the fresh incoming air through the MAF with force fed nitrous. The MAF counts (mass airflow meter voltage) actually dropped a little with the nitrous on. This caused the engine load, which is calculated by the ECU, to be reduced. The engine load calculation was reduced to the point where it dropped down to the next row on the spark table. At that lower engine load, the computer tune calls for several more degrees of spark advance," he states. Carlson used SCT Live Wire to data-log the runs, identify this problem, and solve it.
In just one day, the '08 was more than capable of going deep into the 12s and take on the latest street machines like the Challenger and forthcoming '10 Camaro--due out by the time you read this issue.
The jets, or pills as some...
The jets, or pills as some people call them, regulate the nitrous and fuel being sprayed into the engine. Different jet sizes are used to determine the horsepower settings. Based on the nitrous jet size, a properly sized fuel jet is used for the correct nitrous/fuel mixture. Nitrous Pro Flow provides a chart to properly size the nitrous and fuel jets.
Nitrous carries more oxygen...
Nitrous carries more oxygen into the engine, which then requires more fuel to help burn it in the combustion process.
Additional fuel is added and...
Additional fuel is added and this block is mounted on the end of the fuel rail to siphon off the fuel not used by the injectors. The fuel solenoid then sends the fuel to the nozzle via a -4 line.
Carlson and Mulholland cautioned...
Carlson and Mulholland cautioned that the nozzle's spray pattern in aftermarket cold air kits should be checked. The S197 cars use a twin-bore throttle body. If the nozzle is located improperly, then distribution will be messed up. They chose to move the nozzle further away from the throttle body in order for the fuel and nitrous to mix properly and not shoot past the front two runners in the intake manifold.
Speed of Sound made this gauge...
Speed of Sound made this gauge pod for the cup holder in our '08 test car. It features a single hole for a 21/16-inch gauge and three switches. We have the switches controlling the bottle heater, nitrous arming, and purge. Speed of Sound labeled each switch.
This is the electronic box...
This is the electronic box that reads the TPS sensor for WOT. Once it reads 100 percent throttle at 3,000 rpm or more, it opens the solenoids, which then shoot nitrous and fuel into the engine.
Rob demartinis handled the...
Rob demartinis handled the dreaded wiring for the nitrous system, bottle heater, purge solenoid, and gauge. Here are the wires for the TPS and solenoids.
The bottle heater had to have...
The bottle heater had to have wires soldered into place and then run up the switch in the cup holder.
A sensor is tapped at the...
A sensor is tapped at the bottle-end of the main nitrous feed line. The sensor sends a signal to the Cobalt gauge to show the pressure inside the bottle. Auto Meter provides a six-foot long harness to run from the sensor to the gauge. Mulholland ran the harness under the carpet and center console.
The Speed of Sound gauge pod...
The Speed of Sound gauge pod fit flawlessly. We had to just use a light scuff pad on the body of the gauge in order for it to slide in easily.
Demartinis wired in the Cobalt...
Demartinis wired in the Cobalt gauge to the dimmer switch, so it goes on when the headlights are activated.
The gauge light will dim when...
The gauge light will dim when the driver dims the dashboard as well.
We dig the look of the Cobalt...
We dig the look of the Cobalt gauge. It glows nicely at night and even matches the blue in the My Color dash.
The finished gauge setup is...
The finished gauge setup is clean and factory-appearing.
The 75 hp hit was worth a...
The 75 hp hit was worth a gain of 69 RWHP and 131 RWHP.
The low rear gear proved to...
The low rear gear proved to be a problem on the dyno with the 100hp hit of nitrous. Running the car in Fourth gear put too big of a load on the clutch and it slipped. Carlson ran the 100hp test in Third gear, where the clutch held perfectly fine. He says the car had larger rear gears it wouldn't have been a problem on the dyno. Despite the Third gear results, the 100hp jets provided 90-rwhp and 157-rwtq gains.
One of the biggest differences...
One of the biggest differences between the '05-'07 models and the '08-'09 ones are the spark plugs. On the right, the '08 plug has a more traditional plug strap--making it easier for aftermarket companies to reproduce plugs. The plug on the left is the goofy '05-'07 plugs that have an obscure end that has to be crushed in order to re-gap the plug. Only two companies make aftermarket plugs with colder heat ranges for power-adder combos. The end isn't the only difference; the body of it is funky too. We stuck with the stock '08 plugs, which are fine for up to 100 hp worth of nitrous. Anymore than that, Carlson suggests getting one heat range colder than stock. The aftermarket is said to be working on colder plugs, due out by the time you read this issue.