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Dyno

Car culture term

Dyno
Photo: Marek Ślusarczyk (Tupungato) / Wikimedia Commons · CC BY 3.0

What is Dyno?

A device that measures engine power output (horsepower and torque) by applying load to the wheels or crankshaft.

Dyno (dynamometer) is a device that measures engine power output by applying mechanical or electrical load to the engine while measuring resistance. Two main types are used. Chassis dyno (also called rolling road) measures power at the wheels by spinning the drive wheels on rollers connected to a load device. Engine dyno measures power at the flywheel by connecting the engine directly to a load device.

Chassis dyno results are typically lower than engine dyno results due to drivetrain losses. A typical drivetrain loss is 15-20% for FWD/RWD cars and 20-25% for AWD cars. So a car producing 400 horsepower at the flywheel might dyno at 320-340 horsepower at the wheels (FWD/RWD) or 300-320 (AWD). The differential is consistent enough to estimate flywheel power from wheel dyno readings, though direct comparison between dynos requires care.

Major dyno manufacturers include Dynojet (US, the most common in North America), Mustang Dyno (US), MAHA (Germany), and Dynapack (New Zealand). Different dynos can produce different numerical results on the same car due to calibration differences. The Dynojet 248 (the standard model) is the most common reference point in tuner culture; "248-corrected" numbers are referenced for consistency.

Related terms

ECU tuneTurboRedline

Frequently asked questions

Why does my car dyno less than the factory rating?
Drivetrain losses (typically 15-25% from flywheel to wheels). The factory rating is at the flywheel; chassis dyno measures at the wheels. So a 400 horsepower factory rating might dyno at 320-340 wheel horsepower in normal conditions. Different dyno calibrations and atmospheric conditions also affect readings.
How accurate are dyno readings?
Within ~5% of true power for properly calibrated dynos in good condition. Dyno-to-dyno comparison can vary 5-10% even for identical cars. Atmospheric conditions (temperature, humidity, barometric pressure) affect readings. Multiple runs on the same dyno on the same day are highly repeatable; runs on different days or different dynos require correction factors.
How much does a dyno session cost?
Diagnostic dyno (a few runs to check power): $100-$200. Tuning session (multiple runs with adjustments): $400-$1,500 depending on tune complexity and shop rates. Many shops include a dyno session in tune package pricing. Self-tuning rentals (renting dyno time for personal tuning) typically cost $100-$200 per hour.
What is the difference between Dynojet and Mustang Dyno?
Dynojet and Mustang use different load mechanisms and slightly different correction factors. Dynojet readings are typically slightly higher than Mustang readings on the same car. Both are common in North America; specific shop choice depends on availability and personal preference.
Can I dyno a stock car?
Yes. Many shops offer dyno sessions for stock cars to baseline power before modifications, verify factory ratings, or troubleshoot issues. Stock cars typically dyno close to manufacturer claims (within 5-10%). The session also helps identify any factory power deficiencies (worn parts, marginal tune from factory).
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