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RPD_FKTARD
06-27-2007, 01:18 PM
came across this while browsing
original post: http://www.s2ki.com/forums/index.php?showtopic=143847

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I'd like to start an informative thread on race harness installation in the S2000. I've done a lot of reading on the subject and think our community would benefit from these reports followed by critiques, corrections and support for these concepts.

**Disclaimer - I am not a safety engineer, just an S2000 enthusiast that has read a lot of literature from harness manufacturers and posts on racing web boards. The following information is summarized from sources cited at the end of the post.**

Overview:
The restraint systems in the S2000 is very effective at reducing the likelihood of injury or death in the event of an accident. However, even the most sophisticated restraint system in the world cannot protect against all foreseeable impacts. If you choose to use aftermarket restraint systems, it is very important to recognize the disadvantages as well as the benefits as compared to the stock system.

During a crash, the main goal of your restraint system is to spread deceleration forces over as wide an area as possible, to prevent you from being ejected from the vehicle, and keep you from moving around in the cabin. The factory restraint system achieves these goals very well, with its main drawback of not holding the body in position when driving hard. A properly installed aftermarket harness system achieves this latter goal, and should achieve the former ones, but is difficult to install and wear properly.

Harnesses:
There are 2 types of harnesses in the market. Harnesses designed for use in racecars that meet the standards of various race organizations (e.g. FIA, SCCA), and those that are designed for "street use". In my opinion, even if the belt is designed for use in street cars, they can be lethal if installed improperly and/or without rollover clearance.

Installation:
The correct installation of an aftermarket harness system requires sufficient rollover protection. Since the 3-point factory seatbelts allow the occupant to move to the side in the event of a rollover it is possible for an occupant to avoid head injury with relatively little clearance. However, when a 4, 5 or 6 point aftermarket system is installed properly, this is no longer possible and thus requires a roll structure high enough to allow clearance above your head (or helmet) while sitting upright. For example, the SCCA requires 2" of space between your head (or helmet) and the imaginary line drawn from the top of the windshield header and the top of the roll structure. Some people with short torsos may be able to fit these guidelines with stock roll hoops, but for most of us the only way to achieve this is by adding a higher aftermarket rollbar and/or lowering the seat.

Another important consideration is the secure mounting of the harness. The mounting points are subjected to extreme loads during an accident and must not fail. The only way I know of to correctly mount shoulder straps in the S2000 is with an aftermarket rollbar that allows the attachment of the shoulder strap mounts high enough. Since we sit relatively upright in our car, it is important for the shoulder straps to extend rearward at no more than a 15 degree downward angle from the horizontal. If the shoulder straps are mounted improperly (e.g. looping the strap over the shoulder and down to a floor mount) you greatly increase the risk of severe injury from spinal compression. Submarining is also a concern with a 4-point harness system for 2 reasons. 1) Since the shoulder straps pull up on the lapbelt, it is possible to raise the lap belt above the pelvic crest bones and onto the abdomen. If the lap belt is too high, serious injury can occur to internal organs. That's why 5 and 6-point systems are used in racecar restraint systems. However, it is not possible to use these anti-submarine straps without the installation of an aftermarket seat that allows the straps to pass directly down to the floor. It is not safe to loop the anti-submarine belt over the front of the seatbecause it does not provide the correct downward force and still allows submarining. 2) A 3-point system allows some chest rotation. The right side of the chest moves forward in an accident, decreasing the tendency to slide under the lapbelt. In all but one 4-point systems, this rotation in prevented increasing submarining risk. Schroth makes a 4-point harness with an anti-submarine feature that does allow some chest rotation and decreases submarine risk.

Here are 2 scenarios to consider before slapping on those cool 4 point belts:
Rollover
In a rollover, the A-pillar and roll hoops are designed to leave some room between the passenger compartment and the ground. However, ever notice how low the stock roll hoops are? Obviously, if your body stays in driving position it is possible that your head will hit the ground. However, the stock 3-point system allows lateral movement that has been reported to prevent head injury in these types of accidents. If you were wearing a 4-point harness, lateral movement would be limited, increasing risk of severe injury to the head and neck in a rollover accident. That is why 4-, 5-, and 6-point harnesses should only be mounted in cars that have a roll structure that extends above the head (or helmet).

Frontal Impact
In this scenario, the primary OEM restraint is the 3-point seatbelt. It, combined with the airbag, is designed to distribute the energy of the impact to the strongest parts of your body and over a wide area. Our 3-point belt also has belt pre-tensioners that reduce forward movement. A properly installed 4-point harness will distribute crash forces over a larger surface area of the body, but you lose the pre-tensioning benefit. There is also the increased risk of submarining as compared to the stock seatbelt system (see above). Using a 5 or 6-point harness that has the anti-submarine straps routed downward through the seat to secure mounting points on the floor can greatly reduce submarine risk.

Resources:

http://www.corner-carvers.com/wiki/index.php?Notes%20on%20Race%20Car%20Harnesses

http://www.schroth.com/english/container_english.htm

http://www.scca.org/

RPD_FKTARD
06-27-2007, 01:31 PM
for installations on schroth Rallye 4 harness on evo here's a great link:

http://www.evolvedperformance.com/Installs/675B9F59-809F-4778-83C8-FD30BEF75046.html

you can get them at roadrace:
http://www.roadraceengineering.com/eclsafety.htm

best of all... it's DOT approved and legal for street use O0

Jdm9
06-27-2007, 08:50 PM
wow thats very informative. seems like you did your research. props

RPD_FKTARD
07-10-2007, 05:27 PM
legal docs in case cops don't believe you
http://www.hmsmotorsport.com/docs/FMVSS_209_Specification.pdf

http://www.hmsmotorsport.com/docs/NHTSA_Letter_of_Approval.pdf