By Leo, Lead Tuner – EuroLab Ltd, Auckland
Let me be blunt. A massive chunk of the dyno numbers floating around the car scene – on Instagram, on forums, on the sheets tuners hand you – are inflated. Some are outright fake.
I’ve been tuning European cars in Auckland for years, and I can’t tell you how many times a customer has walked into EuroLab waving a dyno sheet from another shop claiming 500 horsepower, only for our Mainline ProHub to spit out 400. Not a “margin of error” difference. A hundred horsepower. That’s not a rounding issue. That’s someone lying to you.
So I’m going to break down exactly how it’s done, what to look for, and how to stop getting ripped off. I’m not here to be diplomatic about it. If you’re a shop doing this stuff, you already know who you are.
How They Inflate the Numbers
1. Dodgy Correction Factors
Every dyno applies a correction factor to adjust for weather conditions – temperature, humidity, altitude. The idea is that results are comparable no matter when or where you test. Fair enough.
The problem? There are multiple correction factor standards, and some are more “generous” than others. We use SAE J1349, the current accepted standard. Some shops are still running correction factors from the dark ages – or worse, they’ve cooked up their own proprietary correction that just happens to add a convenient few percent on top. Funny how that works.
2. Turning Off the Weather Station
The weather station plugged into the dyno records temp, humidity, and barometric pressure. That data feeds straight into the correction factor.
Some shops tamper with it. Some just switch it off entirely. No weather data = no corrections = numbers that look better than they should. In the right conditions, this alone can swing a result by 5–10%.
If your dyno sheet doesn’t show ambient conditions anywhere on it, you should be asking why.
3. Running AWD Cars in Two-Wheel Drive
This one is rampant, and it drives me nuts.
Your xDrive, quattro, or 4MATIC has a transfer case, a centre diff, extra axles – all of that creates drivetrain loss. That’s friction eating power between the engine and the wheels. It’s physics.
When a shop puts your AWD car on the dyno in 2WD mode, all of that loss disappears from the measurement. The number goes up, you feel good, and you never know the difference. But your car still has all that drivetrain when you’re actually driving it. The number was always a fantasy.
“If your car is AWD and the shop ran it in 2WD, the number is inflated. End of discussion.”
4. Chassis Dynos and the 500hp Problem
There are two types of dyno: a chassis dyno, which uses rollers, and a hub dyno, which bolts directly to your wheel hubs.
On a chassis dyno, your tyres sit on large steel rollers. Works fine for most cars. But once you’re pushing north of 500 horsepower to the wheels, the tyres start slipping on the rollers. The shop can strap the car down harder, but now they’re adding load to the vehicle, which reads less power.
So you either get tyre slip (garbage data) or over-strapping (suppressed readings). Pick your poison. Either way, above 500 wheel horsepower, a chassis dyno with rollers is not the tool for the job.
A hub dyno, like our Mainline ProHub, bolts directly to your wheel hubs. No tyres in the equation. No rollers. No slip. No strap pressure affecting the result. It’s why OEMs and professional race teams use hub dynos. Because they actually need the number to be right.
5. Straight-Up Math Channel Manipulation
I almost can’t believe I have to mention this, but it happens. Some dyno software lets operators create custom “math channels” – basically a formula applied to the raw data. A dodgy operator can take the real reading and multiply it by 1.2 or whatever number makes the customer happy.
Unless you know exactly what you’re looking at in the software, you’d never catch it. It’s brazen, but it works because most people trust the printout.
The 5,252 RPM Rule – Your Free Lie Detector
Here’s something most people in the car scene don’t know, and once I tell you, you’ll never look at a dyno sheet the same way again.
Horsepower and torque are related by a simple equation:
HP = (Torque × RPM) ÷ 5,252
That’s not a guideline. It’s maths. It’s non-negotiable.
What this means is that at exactly 5,252 RPM, horsepower and torque are always numerically equal. So on any dyno graph plotting HP and torque in ft-lbs, the two curves must cross at 5,252 RPM. Every single time. No exceptions.
If you look at a dyno sheet and those lines don’t cross at 5,252, the numbers have been manipulated. Done. No argument. It’s mathematically impossible for them not to cross there on an honest graph.
Next time someone shoves a dyno sheet in your face, check where the lines cross. Takes two seconds.
(This applies when both values are in imperial – HP and ft-lbs. Different units, different crossover point. But in NZ and the US, most dyno sheets use imperial.)
What I’ve Seen Walk Into My Workshop
I’m not naming names. But these are real.
“I’m on a custom tune, bro”
BMW owner comes in, tells me he’s running a custom tune making 500 horsepower. We plug in our diagnostic tools. It’s a stock MHD Stage 2 map. Off-the-shelf. Nothing custom about it whatsoever. Someone downloaded a map anyone can buy, flashed it onto his car, called it “custom,” and charged him accordingly. That’s not tuning. That’s a con.
The M5 With the Missing Hundred
An M5 owner rocks up claiming 650 horsepower. “Custom tune,” naturally. We strap it to the Mainline. It barely cracks 550.
Was his car faster than stock? Absolutely. But he paid for 650 and got 550. That’s a hundred horsepower he was told he had that never existed. He’d been driving around telling everyone he makes 650, posting it online, genuinely believing it. Because why would your tuner lie to you?
Nobody Measures the Baseline. That’s the Real Problem.
“A dyno is a tool to measure improvement. Not a horsepower bragging contest.”
This is what gets me more than anything else.
A proper tune starts with a baseline pull. You put the car on the dyno before anything is changed. You record exactly what it makes in stock form. Then you tune it, run it again under the same conditions, and measure the difference.
That’s the entire point of a dyno. It’s a measuring tool. You’re measuring improvement. How much did I gain?
But most shops don’t bother with a baseline. They tune the car, run it once, hand you a sheet with a big number, and send you on your way. You’ve got no reference point. They could tell you the car gained 200 horsepower, and you’d have no way to prove otherwise. Your car feels faster, so you believe it.
Here’s the reality: you were told you gained 150hp. You probably gained 60. Your car is faster, but you were charged for and told a story that doesn’t match the data. Because there is no data. Nobody measured the starting point.
What to Ask Before You Hand Over Your Money
Before you book a dyno session or a tune, arm yourself with these six questions. They’ll separate the honest shops from the ones making it up as they go:
1. “What correction factor standard do you use?”
SAE J1349 is the current benchmark. If they can’t answer or give you something vague, walk.
2. “Are you running my AWD car in AWD?”
If they want to run your quattro in 2WD, your numbers are going to be fiction.
3. “Show me the weather station data on the printout.”
If it’s not there, the corrections are either wrong or missing entirely.
4. “Are you doing a baseline run before tuning?”
If no, they can claim any improvement they want and you can’t verify a thing.
5. “Hub dyno or chassis dyno?”
Both have their place, but above 500 wheel horsepower, you need a hub dyno. Full stop.
6. Check the 5,252 RPM crossover yourself.
Look at the graph. Do the HP and torque lines cross at 5,252? If they don’t, the sheet is manipulated. It’s that simple.
Why We Don’t Play These Games
At EuroLab we run a Mainline ProHub AWD CCS 3600. A hub-coupled dynamometer rated to 3,600 horsepower and roughly 5,000 Nm of torque. We’re not running out of room to test anything you bring through the door.
It’s calibrated by Mainline. We use SAE J1349. The weather station runs on every single pull. AWD cars get run in AWD. We do a baseline before every tune. And we’ll walk you through exactly how the system works. Nothing hidden, nothing tweaked.
“I can take a car that makes 300 horsepower, show you the honest number, and then, without opening the bonnet, without touching the ECU, without changing a single line of the tune, make the dyno read 500 horsepower. Same car, same engine, same tune. Just manipulation tricks. That’s how easy it is to fake, and that’s exactly why we don’t do it.”
A dyno number only means something if it’s real. We make sure ours are.
EuroLab Ltd – 27a Neilpark Drive, East Tamaki, Auckland
Book a dyno session or tuning consultation at eurolab.co.nz or call 0800 276 968
