# Understanding Turbo Lag
> What is turbo lag, and how does it affect your car's performance? Learn the difference between turbo lag and boost threshold, and why you shouldn't worry.
Source: https://help.flyinmiata.com/en_us/understanding-turbo-lag-S16wXxQ3lg
Last updated: 2026-05-06T21:32:14.204Z
Even if you’re new to turbocharged engines, you’ve probably heard of “turbo lag.” It’s often described as an annoying delay after pressing the gas pedal, before feeling the extra power from the turbocharger. But is it really something to worry about?
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## What Is Turbo Lag?
A turbocharger runs on exhaust gases. At low RPMs, exhaust flow is low, so the turbo spins slowly and produces little (if any) boost. As engine speed rises and exhaust flow increases, the turbo “spools up” and delivers extra power by cramming even more air into the engine.
The short delay between asking for acceleration and the turbo producing boost is what we call turbo lag. Several factors influence how noticeable lag is:
* Turbo size - Bigger turbos can make more power, but usually take longer to spool up.
* Exhaust design - Long or restrictive piping slows down exhaust flow; short, efficient routing improves response.
* Turbine & compressor weight - Heavier wheels take more energy to spin.
* Wastegate control - Too little actuator preload or sourcing the boost reference before restrictions/pressure changes (such as an intercooler) can delay spool-up time.
* Tuning - Fueling and ignition settings impact how quickly boost arrives.
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## **Turbo Lag vs. Boost Threshold**
A lot of people use the terms "turbo lag" and "boost threshold" interchangeably, but they actually describe two different things.
Boost threshold is the engine RPM at which the turbo begins to produce useful boost pressure. Below this point, there simply isn’t enough exhaust energy to spin the turbo fast enough to create meaningful boost. This is mostly determined by turbo size and engine characteristics. Larger turbos typically have a higher boost threshold, which means you need to rev the engine higher before they start adding significant power.
A simple way to think about it:
* Boost threshold: When the turbo starts to work and compresses air.
* Turbo lag: How long it takes to respond once you ask for power.
For example, if you’re cruising at low RPM and suddenly floor the throttle, most of the delay you feel comes from being below the boost threshold, not from lag. The engine first has to build enough exhaust flow before the turbo can do its job. But if you’re already in the powerband and quickly get back on the throttle after shifting, the short pause before boost returns is true turbo lag.
In real-world driving, this means a car that feels slow at low RPM doesn’t necessarily have “bad lag” - it may simply have a higher boost threshold because it’s designed to make more power at higher RPM.
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## Should You Be Concerned?
A common misconception is that a turbocharged car feels slower than a naturally aspirated car before the turbo spools up. In reality, that’s not true - below the boost threshold, the engine is still performing like a normal naturally aspirated motor, and in many cases, it’s actually making a bit more torque thanks to the improved airflow design of a turbo setup. In everyday driving, most drivers naturally stay near the engine’s boost threshold by shifting at normal RPMs, which is why turbo lag often feels much less noticeable than people expect.
The difference is simply that once the turbo builds pressure, power climbs much faster:
In daily driving, this means:
* Off-boost response is still perfectly usable and not “dead.”
* Lag is really just the wait for extra power, not lost power.
You’ll mostly notice lag only if you stab the throttle suddenly at low RPM. With normal driving or proper gear selection, it’s barely noticeable.
Rather than thinking of lag as a handicap, it’s better to see it as a transition point - the car goes from being a solid naturally aspirated performer to something with an added kick once the turbo lights up.
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## Mechanical Factors that Influence Spool Time
The goal isn’t to completely eliminate lag (that’s nearly impossible) but to make it so short that you barely notice it. If you’re building or modifying a turbo setup, here are some common strategies:
**Turbo Size and Design:** Smaller turbos spool up faster because their rotating parts are lighter and need less exhaust energy to get moving. Modern turbo tech (like twin-scroll or ball bearing turbos) helps balance quick response with higher top-end power.
**Exhaust Setup:** Shorter, smoother exhaust piping keeps exhaust gases moving quickly into the turbine. Reducing restrictions and preventing turbulence (sharp bends, oversized pipes, poor transitions, etc.) lets the turbo react faster.
**Lighter Moving Parts:** Turbine and compressor wheels made from lightweight materials (such as titanium-aluminum alloys) reduce inertia, allowing them to spin up more quickly.
**Engine Tuning:** A skilled ECU calibrator or tuner can adjust ignition timing, fuel delivery, and boost control to make the turbo respond sooner. This makes a huge difference in everyday drivability - sometimes more than hardware changes. In racing, advanced systems like anti-lag may be used (not practical for street cars).
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All of these considerations have already been addressed if you have a [Flyin' Miata turbo system](https://flyinmiata.com/search?q=Flyin%2527+Miata+stage+1+turbo+system&options%255Bprefix%255D=last)! Our in-house engineering team has decades of experience designing and testing Miata turbo kits from the ground up, so you don't have to worry about getting it wrong with a DIY setup.
Need a visual aid from our resident Axl Rose of horsepower? We covered this same topic in a YouTube video: [Should you Fear TURBO LAG?! - Tech Talk with Jeremy Ferber](https://www.youtube.com/watch?v=oPzpMZSwmXU)