What Is Turbo Lag? And How Do You Get Rid Of It?

Turbo lag is the time between mashing the throttle and feeling the torque rush from a turbocharged engine. The lag comes from the time it takes the engine to create enough exhaust pressure to spin the turbo and pump compressed air intake into the engine and is the longest when the engine is in a low-load, low-load cruising situation.

If you're wondering why someone does not make a turbo that makes full boost from idle to redline, there's a very simple answer for that: like all engine parts, a turbo needs to be matched to a specific rpm range to function correctly. A turbo that's small enough to make a significant amount of boost under low-rpm situations would be overspeed and possibly explode as soon as a full throttle was hit. The opposite is also true-a turbocharger that makes the most peak power will make virtually no boost until well into the engine's powerband. Most turbo setups are a compromise between these two scenarios.

Five Ways to Reduce Turbo Lag
There is no single solution to eliminate turbo lag, although there are many strategies that can help. Most importantly, however, it is building a combination that has the converter, cam, compression ratio, displacement, gearing, and even correct braking system for the turbo that is being used.

1: Add Nitrous Oxide
If you're looking for a way to reduce the turbo lag that's akin to magic, look no further than nitrous oxide. Since a shot of nitrous makes cylinder pressures go crazy, that same energy then gets directed out of the exhaust, spooling a turbo in almost no time. We've seen correctly used nitrous systems to cut spooling times by a factor of four, but be warned, if your air / fuel ratio is not corrected for extra oxygen during spooling, a pretty big backfire and engine damage can occur.

2: Increase Compression Ratio
In the 1980s, it was common to see turbocharged engines using compression ratios in the 8: 1 range to compensate for the heat and pressure as the boost came up. But until the boost hit, you were basically driving an over-cammed, low-compression engine that made no power. As fuel and intercooling improved, it's now common to see turbo engines in the 9: 1 to 10: 1 compression range, and those extra points of compression really do wonders for spooling turbos.

3: Add A Wastegate
A turbo can be tuned with a smaller exhaust housing that will spool the turbo faster, and an exhaust wastegate can then be added to bleed off excess exhaust pressure at high engine rpm. In most cases, at least three or four different exhaust housings are available for a single turbo frame, so this type of change is relatively easy to make.

4: Narrowing the Powerband
Turbochargers are best at complementing the engine that is at a constant airflow state, so having a narrow powerband is useful in reducing the turbo lag. Larger-displacement engines (for a given power level) and multi-speed transmissions both keep the turbo lag to a minimum, because the turbocharger will already operate close to its peak power-producing range.


5: Sequential Turbocharging
Sequential turbocharging works by pairing a small turbocharging power from, say, 2,000 to 4,000 rpm, and a second turbo that takes over 4,000 to 6,000 rpm, effectively making for a engine with a huge operating powerband. Unfortunately, these systems are complicated and expensive, and are rarely used in the gasoline world - although they have been common in diesel performance for more than 40 years.