Part Two: Dyno Tuning
Rather than drop the small-block into our project truck and attempt to tune it by reading the spark plugs, we opted to transport the LS2 to Westech Performance Group in Mira Loma, California, for a dyno-tuning session. One of the many benefits of doing so is that Westech stocks a full array of BG carburetors, and our testing revealed that our initial pick of a 650-cfm Road Demon carb was a bit undersized. Westech had a 750-cfm Race Demon carb in stock, and we swapped it onto the motor to straighten out the fuel curve and improve power output across the board.
1. Here's the key to firing the coil-on-plug ignition system of the LS2. At the time of our test, the only company that offered an ignition system for the LS2 was UMI Racing. This is because unlike earlier LS-series engines that featured a 24-tooth reluctor wheel on the crankshaft, our '06 model-year LS had a 58-tooth reluctor wheel. UMI had a computer in stock that is easily tailored to work with either carbureted or fuel-injected late-model LS engines and the new 58-tooth wheel. | 
2. UMI's computer does more than just tell the ignition coils to fire the spark plugs in a timely manner. This computer offers real-time analysis of the engine's ignition timing, which can be viewed via a laptop when connected to the computer. The benefit here is the option of tuning the ignition timing across the entire rpm band in 50-rpm increments. During our dyno-testing, we were able to discover our engine liked more timing in certain rpm ranges and less in others. We were literally able to gain 20 hp over stock, just by playing with the ignition timing. Additionally, UMI's computer includes relays to trigger the electric fuel pump, as well as to turn on and off the electric cooling fans at specific engine operating temperatures. The computer mounts to the rear of the intake manifold in the same area the distributor would go on a traditional small-block Chevy. | 
3. Installing the UMI part is a plug-and-play affair. The first step involves plugging the computer harness into each bank of coils on the valve covers. |
4. On the passenger side of the engine block, just above the starter, is the connector for the reluctor wheel on the crankshaft. The reluctor wheel tells the computer what position the crankshaft is at, so that the computer can fire the ignition system at the proper time. The gray connector on our block indicates that we have a 58-tooth wheel. If the connector was black, that would indicate a 24-tooth wheel was inside and that we had an older LS engine. | 
5. At the front of the block, just below the water pump, lies the plug for the camshaft position sensor. The UMI computer hooks into that plug, as well. | 
6. The engine coolant sensor is also used by the computer for two reasons. The first is to monitor the engine temperature and adjust the ignition timing to avoid detonation. The second reason is that the computer will cycle the electric fans at the radiator on and off, depending on the temperature of the engine after you program in a specific operating temperature range. We set our fans to turn on at 180 degrees F and to turn off once the coolant was at 160 degrees F. |