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Comment by Melatonic | Hacker News Reader

What cars is this true for and does it include all insurances ?

It's true of all 'sub-models' of a given make and model.

Consider the BMW G20 3-series petrol cars. Essentially all trims except the M340i have twin-turbo 2-litre inline-4 B48 engines. The engine output is tuned by the engine control unit (ECU, which is a bit of software running on an embedded computer) depending on the trim: 318i gets 115 kW, 320i is 125 kW, 330i is 190 kW. There are occasional hardware differences—typically the intake manifolds, radiators, and maybe belts, but the engine block is exactly the same across these trims—they're all B48. This is public knowledge; there is a detailed table on Wikipedia[1].

Engine 'tuning' is exactly tweaking numbers in the ECU. A stage 1 tune could involve mapping a 318i to a 320i or better without even popping the bonnet; just a laptop plugged into the OBD2 port above the driver's foot rest.

Naturally, as mentioned by others, some of these tunes are less than legal, because the price, road tax, and other legalese surrounding motor vehicles are determined by the performance and fuel economy of the vehicle from the factory. A car is so computerised that nowadays there are plug-in 'chip tuners' that remap the ECU signals on-the-fly and just-in-time, and can be removed before inspections. It's not dissimilar to overclocking computer chips.

This applies across all car makes, not just BMW and not even just European ones.

[1]: https://en.wikipedia.org/wiki/BMW_3_Series_(G20)#Petrol_engi...

Intake and exhaust manifold shapes affect the power and torque characteristics of the engine. Also, these are not cheap parts. Also a quick glance at the parts catalogue suggests that the example engine, BMW B48, has different pistons and connecting rods for different tune levels, suggesting that the cast engine block is one of the few components which are actually interchangeable between the versions. Didn't check, but I'd guess the turbocharger compressor and turbine wheels might be different, too.

THIS.

The idea that those engines don't differ is an urban myth that exists at least since the mid 1990s and the first TDIs.

Of course they differ in more than one way and using the higher configuration can easily destroy them.

Different variants of B48 have different turbos and injectors (and the HPFP until the year 2020)

Manufacturers have been shipping cars with detuned engines forever, and tuners have been tweaking them to unlock the hidden power for just as long. Back in the beginning of the century I owned a 2000 Audi S4 twin-turbo. The torque curve on it looked like a perfect plateau between 2,500 and 5,300 rpm. I replaced the entire ECU with a chipped duplicate (a five minute swap) and instantly gained 50 horsepower. Of course, Audi limited the torque for a variety of reasons, including reliability and the fact that otherwise the car would have encroached on their higher-end RS4 line.

Similarly, the car I have as a track toy, a 1986 Porsche 944 Turbo, was famously limited by Porsche to avoid competing with their flagship 911 Turbo. Tuners figured this out and came up with all sorts of modifications, from mild to wild, to extract more performance.

Back in the 2000s I didn't have a problem with insurance. Probably not the same today.

I hesitate to call turbo cars detuned just because you can turn up the boost or add timing. A lot of the "hidden power" in turbo cars is for emissions and reliability. Just because you can run 30psi doesn't mean the car is gonna last 200k miles like that.

This is an honest question, because I have no knowledge about cars at all. Could the "detuning" rather be interpreted as akin to the "binning" that CPU manufacturers do? So, if you buy a higher model car, you get qualified and tested parts for that performance rating. And if you buy a lower model, and "overclock" it, you're on your own?

I don't know if I exactly follow the analogy, but engines are not binned like CPU's. If you have questions about if you're "on your own" with mods, check with whoever has your warranty and insurance. It might be different car to car or even state to state. Likely, you can get some work done at a dealership that won't void your warranty and tune to a level that doesn't affect your insurance.

The short answer is no. OEMs don't really do quality control tiers. They'll do new vs service tolerances and that's about it.

> Could the "detuning" rather be interpreted as akin to the "binning" that CPU manufacturers do?

No, it is typically for emissions and fuel economy purposes. Engines are pretty consistent in specs when they come off the line.

I don't think the analogy works because you're not getting different hardware, just different mixtures of fuel/air/timing that trade reliability and mpg for more performance.

I was into sports cars more in the 90s, so my knowledge of this stuff today isn't great, but I mean it was at least true of most sports cars. Most famously the Nissan Skyline R34. The RB26DETT engine is known to have been under-tuned from the factory. You can get so much more horsepower out of it.

That's different. Look up the gentleman's agreement for why, but every Japanese car from that era had 276hp on paper. The supra had close to 320 as sold. The skyline had a marked boost controller hose that you could remove part of and turn up boost for more power. None of this was to sell a higher power variant using the same parts but software locked. It was all to secretly continue the horsepower war while publicly sticking to the agreed limits.

This was the whole point of the grease monkey scene starting back in the 50s. You take the car from the dealer, and then start adding, tweaking to get every last bit of power from it. Take a set of twin single barrel carbs off to be replaced with a single four barrel. Add a better set of manifolds. Add better __________. Once computers were introduced for air/fuel mixing, fuel injection, and any of the other things it can do, there have been shops that specialize in tuning them to max out performance. Just watch any show on your favorite streaming platform about building/enhancing cars.

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