All,
Just got my '04 Boxster S that's replacing my '86 944 Turbo. I'm moving the Recaro Pole Positions from the Turbo to the S, but my experience in upgrading the Turbo forces me to carefully think through all aspects of this upgrade (that is, with the Turbo one more than one occasion the upgrade went through 2 or 3 iterations until it was right).
I know there are other threads, but anyone who's done this conversion or is considering this, I'd appreciate your feedback.
Apologies for the length of this post. I could make my own website, but I figured this is a more direct way of sharing information.
1. Objective
Like the 944 Turbo, the Boxster’s “headroom” is limited – in fact, more so since this headroom is defined by the broomstick test for track use, and the Boxster’s roll hoops are far lower than the roofline of the convertible top. Even with the Brey Krause Roll Hoop Extension, which raises the height of the rear roll hoop by around 45 mm, an additional 30 mm is needed to clear the helmet (in my case).
My objectives for this project are thus to (i) minimize the seat height while ensuring it is positioned “correctly” fore and aft (ii) and has the “proper” rake (iii). Installed in the 944 Turbo, the Recaro Pole Positions were fixed to the floor and were a comfortable distance from the controls. Fore/aft adjustment was really not at all needed — in this respect, we got lucky with the 944, but there is no guarantee we’ll fare similarly with the Boxster. As reference, the seat was mounted so that the angle of the side mounting holes were pitched 6.6° down to the rear based on a level floor pan mount (the 944 was probably tilted with the rear lower than the front to some degree).
I’ve analyzed the mounting hardware with these objectives in mind and with the assumption that the Boxster floor pan is between 0° and 15° downwardly pitched.
In all cases below, “Boxster” means the Type 986 Boxster. While I cite potential vendors for the conversion parts, in no way is this meant as an endorsement of these firms. As I have not installed these seats yet in my vehicle, I cannot be held responsible for any omissions, etc. that cause you trouble if you follow my plan below.
2. Seat Components
The OEM hardware combines many of the functions of aftermarket hardware into two assemblies: the seat and the seat rails. Given that aftermarket equipment must be allowed to fit many vehicles, these components are separated into more basic, discrete units that are optimized for many installations:
2.1 Boxster Floor Pan Adapter
Several tuning companies have developed brackets that conform to the shape of the Boxster floor pan (specifically, the front mounting bolt is driven at a 45° angle to perpendicular towards the rear of the vehicle). Recaro’s Seat Track Adapter Kit (fvd.com, $119) and the Brey Krause R-9040 Seat Track Adapter Kit (ogracing.com, $119) allow the mounting of the Recaro 0.70.9NT seat sliders to the Boxster. These two items appear identical.
Brey Krause also offers the R-9044 Floor Mounting Solution with Integrated Sub-Bar which solidly mounts the R-9075/6 Brey Krause Recaro Pole Position Side Mount Brackets to the floor of the Boxster (ogracing.com, $206) and also provides a sub-belt mounting bar across the rails. It is not clear whether the seats can be mounted directly to the 9044 in such a way they are correctly located fore and aft.
2.2 Seat Rail Sliders
The existing Recaro Universal Side Mount Adapters have a forward mounting hole very near the front edge of the side mount adapter (this hole was drilled by me at the time of installation in the 944). On the 944 Turbo, a rear hole 300 mm back was also drilled by me. The standard holes were 40 mm behind the hole we drilled and 36 mm behind the rear hole (300 mm distance between centers; there was a second forward hole 64 mm behind the hole we drilled with 272 mm between centers to the rear hole).
The rear mounting point on the Boxster floor pan is around 150 mm forward of the firewall. The firewall is inclined so that at its top it is another 180 mm rear of the bottom of the firewall. Using the forward most mounting holes on the Recaro side mount adapter we believe will result in an 80 mm gap from the seatback to the firewall. This is increased by around 25 mm based on the fact that the floor adapter’s seat bracket mounting holes are 25 mm forward of the floor mounting holes. Thus, we believe the seat could theoretically be moved backwards by 100+ mm vs a direct-to-floor installation, if sliders were used.
Recaro offers the 0.70.9NT Seat Track Slider Kit which is the interface beween the Recaro side seat mount and the Recaro Seat Track Adapter Kit above (northstarmotorsports.com, $105).
The OEM seat track sliders can be used in conjunction with a special Brey Krause side mount (below).
The issues regarding these parts is twofold: First, they raise the height of the seat. It is estimated that the Recaro seat rails raise the seat by 20 mm and the factory rails raise the seat by 35 mm. It should be possible to recapture some of this loss provided that the space between the seat rails is empty, allowing the bottom of the seat to be mounted below the mounting surface of the side mount adapters. Second, there is the question of compatibilty, especially between the Brey Krause parts and the OEM seat rails.
The OEM sliders’ position release mechanism runs the entire length of the seat rails; we do not believe there is room under the seat to drop it further than the top surface of the seat rails. The Recaro seat rails have no mechanisms between the seat rails for all intents and purposes.
To use this available space, the side mount adapters must allow the seat to be lowered as needed.
2.3 Seat Side Mount Adapters
We currently have installed the Recaro Universal Steel Adapter 820 745 0 side mounts that fit the 944 and the Boxster (fvd.com, $132). This will fit directly to the Recaro seat rail sliders above. The lowest mounting position places the bottom of the seat 3 mm below the mounting surface of the side mount adapters, with the mounting hole 102 mm above this plane. Due to the design of the Recaro side mount adapters, there is no provision to further lower the seat.
Brey Krause offer two side mount adapters for the Pole Position which fit our needs, based on whether we install the Recaro sliders or mount the seats directly to the floor:
The R-9062 for the most part serves the same purpose as the Recaro Universal Steel Adapter (ogracing.com, $99). However, it differs in that there are only three forward mounting holes and one rear mounting hole for the seat. In addition, the rear hole is around 115 mm above the mounting surface of the adapter vs 102 mm for the Recaro version. To its credit, it has ample space for additional holes to be drilled that would allow the seat to be custom mounted lower than what Brey Krause envisions, ensuring proper rake and maximum drop to the floor.
The R-9075 (left) and R-9076 (right) side mounting brackets (ogracing.com, $176 each) mount the Pole Position to the OEM seat rail sliders. These also have an integral tunnel-side seat belt receptacle mounting point which otherwise must be added separately (below).
2.4 Tunnel-side Seat Belt Receptacle Mounting Points
The OEM seats have a mounting point for the tunnel-side seat belt receptacles which these above solutions (other than the Brey Krause R-9075/6, which will not be considered based on our rejection of the OEM seat rail sliders). Our choices are:
Porsche 964.521.065.00 Seat Belt Receptacle Mount (northstarmotorsports.com, $60). This factory part mounts between the Boxster floor pan adapter and the seat rails. Additional shims appear to be available for a nominal charge.
Brey Krause R-9005 Tunnel Side Seat Belt Anchor (ogracing.com, $69) serves the same purpose and includes a shim for the outboard side.
2.5 Sub Belt Mount
Not included in the OEM seat system, the provision for a sub belt is provided by the angle iron solution used previously in the 944 Turbo. It adds around 3 mm to the seat height.
2.6 Seat Belt Receptacles
One poster on the internet lamented the difficulty of disassembling the wiring harness under the OEM seat, which includes a connector for the seat belt interlock system (which is part of the seat belt receptacle). Their recommendation was to purchase spare receptacles (ebay.com, $85 each), allowing the OEM seat to be removed after removing four bolts and disconnecting the harness.
3. Ideal Solution
It appears that the use of the Recaro sliders will provide the necessary space to drop the seat to negate the increase in seat mounting height, provided that the side mount adapters have the ability to accept this change. The Brey Krause units do.
Presuming the Porsche seat belt receptacle anchors come with a shim, these are preferred over the Brey Krause items in my mind.
Because we are using the Recaro sliders, the Recaro floor pan adapters should also be used. (One internet posting complained that the Recaro cap screws provided with the slider kit are too long to be used with the Brey Krause R-9040).
The drawback to all this is that we are combining adapters from two manufacturers at the seat/seat rail interface. The same internet posting above complained that the Brey Krause R-9062 allows the Recaro cap screws included with the slider kit are too long and interfere with the seat.
Thus, the Bill of Materials per side is:
Recaro Seat Track Adapter Kit $119
Recaro 0.70.9NT Seat Rail Slider 105
Brey Krause R-9062 99
Porsche 60
Sub Belt Mount n/c
Seat Belt Receptacle 85
Total $468
(I had a sub belt mount fabricated out of angle iron for the 944 installation. If you need your own, they are available from various vendors.)
4. Interim Solution
We already own the Recaro Universal Side Mount Adapter. For cost and aesthetic reasons, we should attempt to utilize this part prior to buying additional pieces. At a minimum, installing this part in the Boxster will give complete clarity as to how much lower the seat can be mounted as well as whether additional rearward placement can be accommodated. Afterwards, the Brey Krause side mount adapter can be purchased and modified to ensure the optimal installation.
In this manner, the above Bill of Materials is reduced to $369 per side, or $738 in total.
5. Expectations
We expect that the seat installation height will be 20 mm higher than optimal but that the seat can be positioned as far rearwards as allowed by the firewall and that the rake will be satisfactory.
If the Brey Krause R-9062 side mounts are needed, then unmodified they will have the effect of raising the seat an additional 12 mm. Thus, a custom rear hole will be drilled around 35..40 mm below the existing hole. This hole can also be moved rearward, allowing perhaps 10-20 mm of additional rearward positioning if necessary (not likely).
The Brey Krause R-9062 have only three forward mounting holes. Assuming the Boxster has a 10° downward slope to the floor pan, the front mounting hole will need to be 20 mm below the rear mounting hole. Likely, an additional front mounting hole will need to be drilled.
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Your comments are appreciated.
Mean Motor Scooter
Linear Mode
