what is pretentioner seat belts ? how they do work ? retro fit is possible

I have seen only top model e.g. i10 , ritz having seat belt pretentioner .

1. what is this system ?

2. is this difference than ordinary seat belts ?

3. can it be fitted/replaced with ordinary seat belts in mid level model which does not have airbags and ABS.

4. does it have any connection with air bag system ?

In effect seat belt pretensioners will 'hold' the passenger in the seat in the event of an accident. The technology has been around on high-end cars for more than two decades. This will achieve:

- The passengers (and driver) will not be violently pushed forward in case of a crash. Travellers won't get thrown forward fast, which can be life-threatening or injuring even with  airbags

- This is an enhancement to ordinary seat belts where the seat-belts will be automatically tightened to a snug fit within microseconds (or less) of an accident. You can't 'see' this feature and you hope you never have to experience it ;)

- This is practically not possible

The possibility cannot be ruled out. As you can image, both these technologies work to protect passengers in case of a possibly fatal crash. The pretensioner -> airbag-out sequence is definitely defined beforehand.

For very detailed information (in order), read the links below. Most US cars do have mechanical ones - and in last few years, electrical ones have also started being standard in mid-level cars (again US). I do think it is possible to change to mechanical version in Indian cars too - these are slightly bigger and you run the belt (inside) into the frame with unit close to the bottom (close to the rear end of the seat assembly - near the pillar). However, you will need someone familiar with these to make such modification so that the belts do what they are intended for when you need them most.

http://auto.howstuffworks.com/seatbelt4.htm

http://www.tierone.com/seatbeltpretexcerpt.html

http://en.wikipedia.org/wiki/Seat_belt

Its not same as the ordinary seat belts.

In simple terms Seat belt pretensioners have a connection with the car's electronics system, and with the help of sensors it detects the accident impact and triggers the pretensioner, which pulls the seat belt tighter and activates the airbag. All these trigerring will happen in milliseconds. (This is the mechanism in top end Ritz and i guess the same in all the new cars). It's mentioned in the handbook that some smoke and spark can come from the pretensioner in case of accident/activation, which is a common phenomenon.

Since its connected with the car's electronics system, this cannot be fitted seperately. A complete airbag/pretensioners system fitting for cars may be possible in the near future.

Hey i didnot know that Bjis

Nice info

I have seen only top model e.g. i10 , ritz having seat belt pretentioner .

1. what is this system ? - This system, tightens the seat belt, so that the driver/passenger is pulled into the seat in the event of a crash.

2. is this difference than ordinary seat belts ? Ordinary seat belts prevent the occupant from moving forward. While a pre-tensioner seat belt, pulls the occupant behind,, and into the seat.

3. can it be fitted/replaced with ordinary seat belts in mid level model which does not have airbags and ABS.----> This has no lnkage to the ABS. However in cars which have air-bag and the pre-tensioners... impacts upto a certain level do not tirgger the AIR BAGs, and the occupants are protected by the pre-tensioners only. Usually you cannot retrofit this as this would require programming the belt with the impact sensor and the engine ECM (Computer).

4. does it have any connection with air bag system ? Yes. See answer #3.

Seat belt is known as primary restraint system(in term of sccident).

Airbag are known as secondary restraint system(SRS also).

Airbag & Pretensioner seat belts are connected electronically. Inside pretensioner there is mechanisam that pulls back the passenger/driver to the seat. at the same time airbag also opens to give cusioning effect.

SRS stands for Supplemental Restraint System and not 'secondary'.

The idea is that actual full safety provided by the air bag is only possible if the person is belted up in the first place.