What are five ways to reduce turbo lag?
There is no single solution to eliminating turbo lag, although there are many strategies that can help. Most importantly, though, is building a combo that includes converters, cams, compression ratios, displacement, gears, and even the right braking system for the turbo in use.
● Add nitrous oxide
If you're looking for a magic-like way to reduce turbo lag, look no further than nitrous oxide. Since a grain of nitrite can drive the cylinder pressure crazy, the same energy is then expelled from the exhaust, making the turbo boost almost quickly. We've seen a properly used nitrogen system reduce winding time by a factor of four, but be aware that if your air-fuel ratio is not corrected for the extra oxygen during winding, considerable backfire and engine can occur damage.
● Increase the compression ratio
In the 1980s, turbocharged engines typically used compression ratios in the 8:1 range to compensate for heat and pressure when boosting. But until the booster hits, you're basically driving a super-cam, low-compression engine with no power. With improvements in fuel and intercooling systems, turbo engines are now common in the 9:1 to 10:1 compression range, and those extra compression points really do wonders for turbos.
● Add a wastegate
The turbo can be tuned with a smaller exhaust cover to spin the turbo faster, and then an exhaust wastegate can be added to vent excess exhaust pressure at high engine revs. In most cases, a turbo frame has at least three or four different exhaust hoods available, so this type of change is relatively easy to make.
● Shrinking the powerband
Turbochargers are best for supplementing an engine that is in constant airflow, so having a narrower powerband helps reduce turbo lag. Both high-displacement engines (for a given power level) and multi-speed transmissions keep turbo lag to a minimum because the turbo is already operating close to its peak power production.
Sequential turbos work by pairing a small turbo for, say, 2,000 to 4,000 rpm for power, and a second turbo that takes over from 4,000 to 6,000 rpm, effectively creating a powerband with a huge working powerband engine. Unfortunately, these systems are complex and expensive, and are rarely used in gasoline—though they have been common in diesel performance for over 40 years.