Relatively Simple/Less Expensive Modifications:
* Cold Air Intake (CAI): A CAI replaces the restrictive factory air intake system with one that draws cooler, denser air into the engine. This can yield a small horsepower increase and improve throttle response. However, ensure it's properly tuned and legal in your area.
* Exhaust System Upgrade: Replacing the restrictive factory exhaust system with a performance exhaust (headers, high-flow catalytic converter, and free-flowing muffler) can improve exhaust flow and slightly increase horsepower. Note that this might increase noise significantly. Check local regulations regarding noise levels.
* Performance Tuning (Chip Tuning/ECU Flash): This involves reprogramming the engine's computer (ECU) to adjust fuel delivery and ignition timing for improved performance. A reputable tuner can optimize the parameters for your specific modifications (if any). This can yield noticeable gains but requires caution; a poorly done tune can damage your engine.
* Improved Spark Plugs and Wires: High-performance spark plugs and wires can ensure a more efficient and consistent spark, leading to a minor horsepower boost and smoother running.
More Involved/Expensive Modifications:
* Engine Modifications (Internal): This involves more significant changes like:
* Port and Polish: Smoothing and reshaping the intake and exhaust ports of the cylinder head to improve airflow. This requires professional machine work.
* Camshaft Upgrade: Performance camshafts can alter valve timing for better power and torque at specific RPM ranges. This usually requires other complementary modifications.
* High-Flow Cylinder Heads: Replacing the stock cylinder heads with aftermarket ones designed for better airflow. This is a significant undertaking.
* Forced Induction (Turbocharger or Supercharger): This is the most substantial and expensive modification. It involves adding a turbocharger or supercharger to force more air into the engine, significantly increasing horsepower. This requires extensive modifications and is generally not recommended for a DIY project. It also significantly changes the engine's stress levels and requires careful tuning and reinforcement.
Important Considerations:
* Reliability: More aggressive modifications always carry a risk of reduced engine reliability. A well-maintained engine is crucial before undertaking any performance enhancements.
* Cost: The cost can escalate rapidly, especially with more significant modifications. Carefully budget your project.
* Professional Installation: Unless you have significant mechanical expertise, it's best to have professional mechanics perform the more complex modifications.
* Tuning: Proper tuning is crucial, especially with any significant modifications, to prevent engine damage.
Realistic Expectations:
With relatively simple modifications like a CAI and exhaust system, you might see a modest increase of 10-20 horsepower. More significant modifications could yield larger gains, but the cost and complexity increase proportionally. Expect to spend several thousand dollars to achieve substantial horsepower gains.
Before starting any modifications, thoroughly research the specific components compatible with your 1996 740iL's M60 engine. Consult online forums and communities dedicated to BMWs, particularly those focusing on the E38 chassis (7-series). They are a valuable resource for information and advice.
