Top 10 Tuner Secrets to Free Horsepower cont'd
4. Remove Nonessential Belts
Cost:
$0.00
Average Horsepower Improvement:
0 to 10 horsepower
Our SR20DET Results (@ peak):
+ 1.7 horsepower / + 0 lb-ft torque
Besides producing horsepower at the flywheel, the engine also uses up some energy to spin A / C compressors, power-steering pumps and (on some applications) even smog-pumps.
No-Cost Solution
Due to the arrangement of belts on the SR20DET, we were able to remove both a power steering and an air conditioning compressor belt. You need to leave the belt(s) that spin the water pump and alternator. On the SR20DET, a single belt takes care of both.
Our Dyno Experience
A little bit. We picked up almost two horsepower near the top end of the powerband.
For a Fistful of Dollars
On some applications, manufacturers offer underdrive pulley systems that feature lightweight pulleys with modified diameters to spin accessories at lower speeds. These sets generally start at around $120.
5. Remove Exhaust System
Cost: $0.00
Average Horsepower Improvement:
5 to 40 horsepower
Our SR20DET Results (@ peak):
+ 25.1 horsepower / + 20 lb-ft of torque
Engines waste horsepower pumping exhaust out of the cylinders. A restrictive exhaust system limits the amount of fresh air and fuel that fills the cylinder on the next revolution. Making the exhaust system as free-flowing as possible frees up a nice amount of power. On naturally-aspirated engines, the gains are usually on the order of 5 to 10 horsepower. On turbocharged applications, the boost pressure also experiences a slight increase and power increases can be from 15 to 40 horsepower on most applications.
No-Cost Solution
We unbolted the exhaust system right before the catalytic converter. Since this 240 still had the original "choke" exhaust system used on the factory KA24E (KA=Kan't Accelerate), it's no wonder we saw a big increase in power.
Our Dyno Experience
Step off. Twenty-five horsepower and twenty pound-feet of torque is no joke.
For a Fistful of Dollars
An aftermarket exhaust system is a must, especially on turbocharged vehicles. For 240 / SR20DET conversions some Japanese manufacturers offer turbo-spec exhaust systems. These systems offer the large-diameter tubing optimized for the SR20DET. Cost for most systems start around $400.
6. Shim Wastegate
Cost:
$0.00 to $0.40
Average Horsepower Improvement:
0 to 15 horsepower
Our SR20DET Results (@ peak):
+ 1.5 horsepower / + 7.9 lb-ft of torque
More boost, more power. Small increases in boost pressure will generally allow more power to be produced. On actuator-type wastegate turbo systems, increasing the tension on the wastegate actuator rod can increase low-rpm boost pressure by delaying the opening of the wastegate.
No-Cost Solution
Six washers that we found in our scrap box were bolted between the actuator and the mounting pad.
Our Dyno Experience
Below 400 rpm, this mod picked up five to eight horsepower. At peak power the mod was only worth an additional 1.5 horsepower.
For a Fistful of Dollars
An aftermarket boost controller can make sure you get all you can out of your turbocharged vehicle.
