How does a remap work? Is it harmful for a car?

Question

I was having a look at some remaps for a few cars, and for some cars like the new F-Pace, you can get an extra 60hp, which is just under 20% more horsepower just by getting a remap. How on earth do they do this? Surely they have to replace like half the engine, like you see at car shows and stuff..

Another example is the Vauxhall/Opel Zafira 1.9 CDTI, the 150BHP version can be remapped to get an extra 40HP, which is like 25% more power.

What general changes do they make to do this? Surely it's harmful for the engine to make this much power...

Answer 1

The manufacturers place very conservative tunes on the vehicles from the factory. They do this for two reasons. First of all for longevity. By placing the conservative tune on there, the engine will last longer. Secondly, they do it to ensure they meet things like mileage and emissions goals.

It's very easy for engines with turbo chargers on them to create more horsepower. All you have to do is to allow the turbo to build more boost and add more fuel to cover the increased volumetric efficiency.

It's also easy to have more horsepower in diesel engines, just by allowing them to spin higher (increase the redline on the engine).

However you do it, the remap is pretty simple, but should really be done by someone who knows what they are doing. It's just a file which gets put into the engine control unit (ECU) usually via the data link connector (DLC). It takes special software, which is has specific protocols for specific vehicles.

Does it hurt the engine? Only if you abuse it. If you never use the increased power, it really doesn't matter. Is that realistic? Not at all. The reason you put it on there is to get more out of the engine. Most engines can handle the relatively small boost in horsepower, as can the powertrain. When you have to change out parts to get things to make the power you are looking for (such as larger injectors to flow the needed fuel, or a larger turbo to produce enough boost), then you need to start worrying about the longevity of the engine and drivetrain. We were discussing this on chat earlier. The basic consensus is, the candle which is burnt at both ends burns twice as bright, burns only half as long. What this means is, the harder you push the engine, the faster you can expect it to deteriorate. There is no magic formula for this, but it is true nonetheless.

Answer 2

Hitting the two basic points first:

1. How does a remap work? On a modern car, nearly everything is under control of the engine computer. This includes everything from fuel:air ratios to throttle and steering response (in fly-by-wire cars). A "remap" is a replacement program for that computer.

2. Can it hurt the vehicle? Oh yes, absolutely. A poorly programmed ECU can easily destroy your engine. For example, a reflash for my car could hold the wastegate closed, allowing the turbo to spin up to a dramatic overboost and, eventually, cause the engine to detonate bits of itself all over the road.

... which is just under 20% more horsepower just by getting a remap. How on earth do they do this?

There are some easy ways to get "more horsepower":

1. A remap that removes flexibility can sometimes allow the car to push the envelope a bit. For example, I ran a map on my car that required 93 octane fuel. That allowed the car to use more boost and aggressive ignition timings and generate more usable power. The default configuration allowed the car to use 89 octane in a pinch but was more conservative in other settings.

2. It's also useful to lie. Some marketing numbers are only achievable in a climate controlled environment where the car is being fed refrigerated air. In real life, you might see some improvement but will likely never match the marketing claims.

Surely they have to replace like half the engine, like you see at car shows and stuff..

If you are willing to replace major components, tuning flexibility increases quite a bit. For example, if you free up the air intake path and add higher volume fuel injectors, a retune can make use of both for dramatically higher power. Of course, you've left the stock car far behind at that point.

Surely it's harmful for the engine to make this much power...

As always, it depends. If you're making a race engine that will be rebuilt regularly, your tolerance for reliability is different from me driving to work every day.

Answer 3

I agree with Paulster2, engine damage is primarily a result of abuse. Keep the lubricants fresh and have serviced by a qualified technician. Don't abuse the car, enjoy it. I have performance mods on a xfr, however I can feel and enjoy the increase in power without running to 6500 RPM's at every traffic light.