CoralDoc

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:

Notes on Racecar Harness Design and Installation

Schroth USA Website

SCCA

CoralDoc

Here is a pictorial post on the installation of my Schroth 4-point ASM system in my car. I use this configuration in Solo II autocrossing. An anti-submarine 5th point will be used when my Sparco seat is installed for Driver's Education days on the track.

The first priority was to increase roll bar height and lower my seating position. That was achieved with the Bitterman rollbar and Sparco Roadstrer seat mounted on modified Taitec rails. Here is the completed harness installation with the Sparco seat in place.
HM 4-point setup.jpg
Note that the shoulder straps do not pass through the seat. This is because my torso is so long that my shoulders are several inches above the holes. I will be using a sternum strap to prevent the chest straps from sliding off the sides of my shoulder.

The left shoulder strap is simply looped around one of the legs on the rollbar:
HM Left Shoulder Strap.jpg

And the right shoulder strap is mounted to special hardware allowing a very secure mount to the cabin rear cross-member. Normally you do not want to have the force perpendicular to the sheet metal, but you should notice a very beefy backing plate behind the sheet metal that bolts to two other locations below the seatbelt retracter mount.
HM Right Shoulder.jpg
HM Shoulder Mounts.jpg
HM Right Shoulder Clip.jpg

The lap belt mounts to the stock mounting point on the left and to this bolt installed in a reinforced area of the transmission tunnel on the right.
HM Lap Belt Bolt.jpg

The lap belt is not mounted as vertical as I would have liked, but I'm counting on Schroth's anti-submarine system and the crotch strap to prevent submarining.

rlaifatt

I notice that you run the lap belts over the side-rails of the seat. If you run them through the side-openings that are usually provided for the lap belt, then the lap belt would be more vertical over the pelvis even though the anchor points are a bit rearward.
As long as you cah fit into the seat the lap belt (being so flat) should be able to go through the openings unless the adjuster buckle gets in the way.

CoralDoc

Good eyes, the seat belt straps are routed over the sides of the seat. You are correct that the correct way to route lap belts with race seats is through the holes on the sides. However, the Sparco Roadster is relatively low profile and does not have these holes. I am investigating a taller more race-oriented seats that will put the shoulder strap holes in the correct position behind my shoulders and with the lap belt routing holes.

cbender

Great thread! Thanks for sharing this with the rest of the community.

CB

s2000turbo

Who makes the roll bar that you have? how much $$$ you pay?

CoralDoc

Contact Aaron Bitterman of Speedventures fame, his screen name is desert tortoise. The bar cost me about $650, but that was a year ago.

Here's a link to a very informative thread about the bar, including contact information for Aaron. He's a great guy to deal with, and also provided the shoulder strap mounting hardware.

NammyBoy

I tried out different race buckets this past weekend and I found that the Sparco Corsa seat is very tall and was the only seat that had the shoulder strap holes in the right place.

I sat in the following seats: Recaro SPG, Bride Zeta III, Sparco EVO 1-3, Sparco Rev, different Momo seats, Sparco Roadster, Pro 2000, Ultra, etc. They were all too short for my shoulders.

I'd give the Sparco Corsa a try. I am 6'0 and 165 pounds, with most of my height in my torso, and they are a perfect fit and has very good lower back support.

Also, I was told that the Sparco Corsa is the tallest Sparco seat. Recaro also makes a tall seat, but that one has helmet supports (i.e. those huge antlers that pro racers use). Bride also makes a tall seat called the Zeta II Type-L, but I haven't sat in that one.

~Nam

Nobody

Good post CoralDoc. We're running very similar setups. The right harness attachment still concerns me--the sheetmetal will fold like a piece of salami in a high speed accident--even with bolt-on reinforcement. I'm going to run the excess length back and wrap it around the rear stabilizer which should work until I have a horizontal bar welded to the Bitterbar. Also, I wrapped the left harness around the smallest (diagonal) member of the rollbar....would you forsee any issues with this?

I also see you've put all the stock plastic back in--I admire the work you've done there. My interior is still naked unfortunately most likely always will be!

One question--where did you get the C-clamp? I've got a couple of clamps, but the threads weren't the same as the stock seatbelt anchor....

Nobody

Oh yeah--and how have you mounted the 5th/6th anchor point? I noticed that fuel lines run directly under the center of the driver's seat.