Street Legal HP

Can someone PLEASE explain to me if horsepower has anything to do with being street legal? And if yes how much is it ad how do they find out?

No, hp has nothing to do with being street legal.

choosing the amount of hp a car company ultimately ends up with is based on many factors. Its mostly internal at the company, but its a dance around projected insurance costs (higher hp cars cost more to insure and it affects sales), reliability of the engine at certain horsepower levels, target customer, etc.

but some things you do to increase power might not be exactly legal... but its only illegal if you get caught ;)

Thanks for clearing that up. Someone keeps telling me that 500 and under is street legal but that would be rediculous since the Murcielago, Enzo, CCR, etc make over that amount officially, from the factory.

(higher hp cars cost more to insure)

How do insurance companies know what hp your car has? Most blown civics make 2 or 3 times their orginal hp.

but some things you do to increase power might not be exactly legal... but its only illegal if you get caught ;)

I've heard that before but when I ask them to be specific or name a certain part they can't...can you give me an example?

if you remove any of your emission control systems or alter them in any way it is illegal. nitrous is also illegal. running leaded race fuel on the highway is illegal. and if you live in Cali im sure there are bunches of other stuff i dont know about

Nitrous is still legal in CA on pre-emission vehicles.

Pimp, I thought you were talking about stock vehicles. The insurance company knows their HP since its published. Aftermarket modifications don't necessarily raise insurance since they don't typically need to be claimed unless you want them to be covered under the policy.

Many aftermarket performance parts are not legal for use on the street. If you have a vehicle that is no longer tested by smog (for instance in CA any 1976 or earlier car or any diesel vehicle) you can do those illegal things since there is no one looking over your shoulder. You can also do these on newer cars in areas that don't test for smog, but be warned that even rural areas are starting smog programs and you may need to undo what you've done.

Cars that still fall under smog jurisdiction can still have aftermarket parts installed as long as they have the proper certification. In CA that means it must be considered either a stock replacement or a performance part which has been proven to not increase emissions. Such parts carry an Executive Order number, often abbreviated as EO. These are certification numbers that are given by CARB (california air resources board)

So a car could be legal regardless of how much hp it has?

Pimp, I thought you were talking about stock vehicles. The insurance company knows their HP since its published.

Actually I'm talking about both. For example, if you swap in bigger turbos on a 911, and substantially increase hp, does that make it illegal automatically?.

Aftermarket modifications don't necessarily raise insurance since they don't typically need to be claimed unless you want them to be covered under the policy.

But how can you have something covered (or even report it openly) if its illegal? Are there specific performance parts that are illegal? For example a rollbar? Seatbelts?

if you remove any of your emission control systems or alter them in any way it is illegal. nitrous is also illegal. running leaded race fuel on the highway is illegal. and if you live in Cali im sure there are bunches of other stuff i dont know about

Yes, I've heard that before about emissions...is there anything else though?

Thanks for everyone's response, I really appreciate you taking your time for this.

there's nothing inherent to horsepower that makes something illegal.

There are lots of Legal Hot Rods out there. As long as you comply with the state emission and safety laws you are O.K.
You caninstall a roll bar, no problem. You can shorten your rear end and run wide tires, as long as they have sufficient tread, and don't stick out from the fenders. You can have a low restriction exhaust as long as it is not too loud. You can increase the output of your engine, as long as it passes emmisions and you don't remove any of the factory installed emmision components. Have fun, and buy an exhaust gas analyzer.

There are lots of Legal Hot Rods out there. As long as you comply with the state emission and safety laws you are O.K.
You caninstall a roll bar, no problem. You can shorten your rear end and run wide tires, as long as they have sufficient tread, and don't stick out from the fenders.



Note that this only applies to the US.

Here in NZ for example a roll cage or bar requires certification, as does modification to things like axles or some changes to the vechiles body work.