Here in Geneva road tax is based on the power of the car (KW). If I remap my car or tune it in any way to increase the power output do I need to pay more tax each year, or is it just based on the manufacturer's original spec for that model?

Thanks!

Theoretically if you change the manufacturer's specification you must report the changes to the Canton car testing, department.
This can be very expensive, as they may insist on new testing of emissions, noise and hydro-carbons.

You must also inform your insurance company about the changes, and they will charge you more.

After everything, and all the risks, it's probably best to sell it and buy another more powerful car.

Hahaha tell them after a remap yeah right.. thats a nice dream land! A friend remapped his 330d from 231hp to 290hp with a 2
30% torque increase and improved mpg L/km. I am sure he went running to stva with details

Then the insurance would not pay out, and your friend might spend his life paying for his error. Is it really worth it?

Well yes. The insurance may not pay out if a) they notice the remapping and b) they can say that it was a cause of the accident.

Depending on the exact method used, it may be either difficult to detect or easy to remove. We have one that takes about 30 seconds to remove, leaving no trace, or just ten to blank off so you can say it was not in use, and only ever used for track purposes.

Lots of ifs buts qnd maybe involved there.

I would have thought if there are tuning companies doing the same remap 100s of times, and in some cases main dealers doing them, that they'd test it once and that would apply to all of their customers. For example to get through the MFK with non-standard wheels you need a certificate from the manufacturer of those wheels, but everyone with those wheels doesn't have to get them individually tested. It was more the impact on tax I was interested in, but I guess even if you play it safe and tell your insurance company you can probably get away with just not telling the car tax man.

This may be true with official manufacturer remappings, but third party ones are generally sold without any certification, or even a pretence of conformity to any national rules. Which is why some of them have the option of blanking off the new chip, enabling emissions and noise testing to be carried out without the ... err, no, sorry that's not right... enabling the user to fit the chip only for track use then remove it when using the vehicle on the road.

Yes, that's all we ever use ours for, honest hoccifer.

I did a Hirsch stage 1 on a Saab 900 turbo many years ago in Zurich. I told the insurance and they hammered me for the increase (12 francs per year).

I never did tell the STVA nor did the garage or insurance advise me to.

Zurich mind you charges on different criteria.

I'd bet if it's manufacturer-approved and dealer-installed that they don't care.

Most tuners in CH don't have homologated maps. Even those that do have them, have them only for some engines. It's simply too expensive for them to bother getting homologated, so they don't do it.

On the other hand, reputable tuners allow you to switch maps yourself (e.g. some device you insert into the diagnostics port or even from existing stalks). Not for STVA (though it comes in handy there as well), but maybe to have different settings for summer/winter, high/low altitude etc