I bought my 2010 Accord LX with manual transmission in 2013 over ebay (sight unseen) with 40,000 miles. I loved the handling and shifting quality, but the seats did not agree with me. The top edge of the seatback pushed against my upper back, and the headrest made my head tilt forward unnaturally. I like to sit up straight, not reclining back, and the seat just did not work for me. I showed up at work at least 4 times with a crick in the neck for several days because of the seat. I removed the headrest, and made a custom contoured seatback cushion to "correct" the "wrong" seatback profile, and it helped somewhat, but I could never get the seat to be comfortable for me.
Something had to be done. I decided to put a 1987 Mercedes 300E seats in my Accord. This has been a 3-year project that I just completed.
Mechanically getting the seats to fit was one thing, involving Sparco seat bases, custom-made steel brackets that were welded together, and a lot of fussing to get everything to fit and for the seat belts and buckles to be attached appropriately.
The hard part was the electronics. Each seat was connected to the car via 3 harnesses.
The driver's seat had buckle sensor, seat position sensor (to sense if the driver was very close to the steering wheel), and of course the side airbag connection.
The passenger's seat also had 3 connections: buckle sensor, side airbag, and the infernal ODS (Occupant Detection System). I reverse-engineered as much of it as I could to "fool" the car to think that all the proper sensors were connected and that the front airbag would work.
First, the driver's side:
A 2 Ohm resistor connected to the side airbag harness "fooled" the car to think it was still connected to the side airbag. Easy.
The position sensor was so that it could detect the nearest one inch of the track travel, so that the airbag would fire with less force if the driver was very close to the steering wheel. What a joke, it has only two states, "near" which means the first ONE INCH of the track travel, and "not near" which is the rest of the travel. Obviously a hare-brained scheme to satisfy the regulators while having absolutely no bearing to 95%+ of drivers! It was a hall effect sensor, but curiously, Honda managed to have only 2 wires, not 3 wires. I measured the voltage and current and "guessed" that a resistor in the range of 800 Ohm or less would work. I used a 470 Ohm resistor, and voila! The car thinks the sensor is working fine and the position is "not near," which is what I want.
Finally, I bypassed the seatbelt sensor on both sides. My wife does not always put the seat belt on right away, and the chime was annoying. Again, a hall effect sensor. Again, only 2 wires, not 3. I measured the volt and current and guessed that a 1000 Ohm resistor will work. And it did.
So that is what it took to bypass the electronics on the driver's side.
Now, onto the passenger's side, where the fun really begins.
Airbag: 2 Ohm resistor to bypass, easy.
Seatbelt: 1000 Ohm resistor to bypass, again, no problem.
Finally, the ODS. Ah, yes, the ODS, which includes the OPDS (the sensors in the seat back that detects the sitting height of the occupant). You can't just plug a resistor and call it a day. The ODS unit in the side of the seat back is a little computer in itself, and it communicates with the car via 4-wire harness. What those signals say, who knows?
But the ODS is connected to the seat in 2 ways.
First, there are 4 weight sensors at the base of the seat. I "guessed" that these are hall effect sensors. There are 3 wires to each sensor. Input is a constant 5 volts (NOT 12 volts, I found out the hard way after hearing a "pop" and burning out the sensor while testing it, result being that I had to purchase a whole new seat off ebay!). Second wire is ground. Third wire is output, and it measures like 1.5V to 3.5V or so, depending on the weight. Heavier the weight, lower the voltage! Normally the sensor puts out about 2.5V. I figured I could "fool" the ODS into thinking that it was connected to the weight sensors by hooking up some hall effect sensors that put out 2.5V when there is no magnet next to it.
Finally, the piece de resistance. The OPDS! These are the sensors in the seat back, which are thin flexible membranes. There are 7 sensors total, 6 on the back for the "height" and 1 on the side to make sure a child was not leaning into the path of the side airbag. They seem to be capacitive sensors. The resistance is 0, so they are not resistors. I bought a capacitance meter. The "height" sensors registered about 45 pF with no load, and 55 pF with load. The difference was truly tiny, measured in picofarads. The side sensor was even more finicky, measuring 158 pF with no load, and 161 pF with load. Holy cow, how sensitive does the measuring electronics have to be?
So I connected variable capacitors to the ODS, and "tuned" them to put out approximately the "right" values. I am tuning everything so that the airbag would fire as if there was an adult in the passenger seat, since only my wife (or another adult) would be riding in that seat.
All this took dozens, if not hundreds of hours of reverse-engineering, on a scale which truly boggles the mind. I mean, the complexity of these delicate picofarad-range sensors in a rough environment like a car! All this so the airbag is "smart" enough not to fire if there is a child or a child seat in the front seat. Rube Goldberg had nothing on these guys who designed it.
I hook everything up, and... the dreaded "airbag" light comes on.
I actually even bought a Honda HDS diagnostic system, the real deal with a Panasonic toughbook and the legit OBD-2 to USB connector, all costing more than a couple of thousand dollars used. I got the HDS to "see" what the car is "seeing" so I could reverse engineer the front seat electronics.
So it was disheartening to have the "airbag" light come on. I connect the HDS, and it gives me some error with ODS, also an error with OPDS, and something about the sensors not being right. Can't remember the exact wording on the screen. Basically, the car was not fooled by the fake sensors (hall effect sensors, capacitors).
Fortunately, the front airbag was "enabled," meaning it would fire in case of a crash. So at least it would work properly with an adult passenger. It will also fire with no passenger (no big deal for me) and it would also fire with a child or a child seat (gotta make sure nobody does this with my car, and if I ever sell it, I will put the OEM seats back in, calibrate it again, and return it to the factory state).
So now I know that my efforts to fool the car was not successful, but that the front airbag would still work. The "airbag" light on the dashboard did bother me. It is just a whole lot easier not having to explain it to the passenger ("Uh, that light? Don't worry about it. The airbag will deploy just fine." Passenger looks at me like I was out of my mind.)
I decided to put a black tape on it. I actually took the instrument apart as much as I could, and put a black tape on the BACKSIDE, so that from the front, it looks completely legitimate, can't tell at all. The only way to tell is that the airbag light does not come on during ignition, but that is a minor quibble, really.
After all is said and done, how does the W124 seat feel? Heavenly. It fits me like the designers knew my body exactly. It holds me on each side of the torso just right, so during turns and corners, I am not working to keep upright, the seat is doing that for me. For all intents, it feels like a giant baseball glove cradling me just right.
The W124 seats have some drawbacks. The front of the seat bottom cushion is too springy, and sags when weight is put on it. That makes it uncomfortable, as you are forever fighting the sense that your body is sliding forward. So I put some very nice custom hard padding pieces cut just right and stacked, inside the seats, IN ADDITION to the rubber/foam inserts that came with the seat (inadequate in themselves). The seat feels great.
Now, sometimes, the seat feels perfect. Other times, I could use a bit of lumbar support. So after all this Herculean effort, it's not always "perfect." But it is such a dramatic improvement over the torture chamber that came with the car. The tan leather also complements the charcoal interior very nicely.
Finally, I wanted leather steering wheel and leather shifter knob cover. I bought a used steering wheel with factory leather off ebay, so that part was easy.
The leather shift knob is my own handiwork, with automotive leather cut into precise pieces, and stitched together by hand. It is perfect. I would honestly say there is nobody in the world who could do such a nice job with leather.
People have asked me why I didn't just get a Mercedes, instead of going through all the trouble modifying a Honda. It's hard to explain, but it comes down to the philosophy of Honda, the mindset of the people at Honda who brought it into existence. The combination of reliability, handling, precision and ease of shifting, styling, everything makes the 8th generation Accord a pinnacle, in many ways, of what Honda could do. It just could have used some seats from a Mercedes or a Lexus.
Something had to be done. I decided to put a 1987 Mercedes 300E seats in my Accord. This has been a 3-year project that I just completed.
Mechanically getting the seats to fit was one thing, involving Sparco seat bases, custom-made steel brackets that were welded together, and a lot of fussing to get everything to fit and for the seat belts and buckles to be attached appropriately.
The hard part was the electronics. Each seat was connected to the car via 3 harnesses.
The driver's seat had buckle sensor, seat position sensor (to sense if the driver was very close to the steering wheel), and of course the side airbag connection.
The passenger's seat also had 3 connections: buckle sensor, side airbag, and the infernal ODS (Occupant Detection System). I reverse-engineered as much of it as I could to "fool" the car to think that all the proper sensors were connected and that the front airbag would work.
First, the driver's side:
A 2 Ohm resistor connected to the side airbag harness "fooled" the car to think it was still connected to the side airbag. Easy.
The position sensor was so that it could detect the nearest one inch of the track travel, so that the airbag would fire with less force if the driver was very close to the steering wheel. What a joke, it has only two states, "near" which means the first ONE INCH of the track travel, and "not near" which is the rest of the travel. Obviously a hare-brained scheme to satisfy the regulators while having absolutely no bearing to 95%+ of drivers! It was a hall effect sensor, but curiously, Honda managed to have only 2 wires, not 3 wires. I measured the voltage and current and "guessed" that a resistor in the range of 800 Ohm or less would work. I used a 470 Ohm resistor, and voila! The car thinks the sensor is working fine and the position is "not near," which is what I want.
Finally, I bypassed the seatbelt sensor on both sides. My wife does not always put the seat belt on right away, and the chime was annoying. Again, a hall effect sensor. Again, only 2 wires, not 3. I measured the volt and current and guessed that a 1000 Ohm resistor will work. And it did.
So that is what it took to bypass the electronics on the driver's side.
Now, onto the passenger's side, where the fun really begins.
Airbag: 2 Ohm resistor to bypass, easy.
Seatbelt: 1000 Ohm resistor to bypass, again, no problem.
Finally, the ODS. Ah, yes, the ODS, which includes the OPDS (the sensors in the seat back that detects the sitting height of the occupant). You can't just plug a resistor and call it a day. The ODS unit in the side of the seat back is a little computer in itself, and it communicates with the car via 4-wire harness. What those signals say, who knows?
But the ODS is connected to the seat in 2 ways.
First, there are 4 weight sensors at the base of the seat. I "guessed" that these are hall effect sensors. There are 3 wires to each sensor. Input is a constant 5 volts (NOT 12 volts, I found out the hard way after hearing a "pop" and burning out the sensor while testing it, result being that I had to purchase a whole new seat off ebay!). Second wire is ground. Third wire is output, and it measures like 1.5V to 3.5V or so, depending on the weight. Heavier the weight, lower the voltage! Normally the sensor puts out about 2.5V. I figured I could "fool" the ODS into thinking that it was connected to the weight sensors by hooking up some hall effect sensors that put out 2.5V when there is no magnet next to it.
Finally, the piece de resistance. The OPDS! These are the sensors in the seat back, which are thin flexible membranes. There are 7 sensors total, 6 on the back for the "height" and 1 on the side to make sure a child was not leaning into the path of the side airbag. They seem to be capacitive sensors. The resistance is 0, so they are not resistors. I bought a capacitance meter. The "height" sensors registered about 45 pF with no load, and 55 pF with load. The difference was truly tiny, measured in picofarads. The side sensor was even more finicky, measuring 158 pF with no load, and 161 pF with load. Holy cow, how sensitive does the measuring electronics have to be?
So I connected variable capacitors to the ODS, and "tuned" them to put out approximately the "right" values. I am tuning everything so that the airbag would fire as if there was an adult in the passenger seat, since only my wife (or another adult) would be riding in that seat.
All this took dozens, if not hundreds of hours of reverse-engineering, on a scale which truly boggles the mind. I mean, the complexity of these delicate picofarad-range sensors in a rough environment like a car! All this so the airbag is "smart" enough not to fire if there is a child or a child seat in the front seat. Rube Goldberg had nothing on these guys who designed it.
I hook everything up, and... the dreaded "airbag" light comes on.
I actually even bought a Honda HDS diagnostic system, the real deal with a Panasonic toughbook and the legit OBD-2 to USB connector, all costing more than a couple of thousand dollars used. I got the HDS to "see" what the car is "seeing" so I could reverse engineer the front seat electronics.
So it was disheartening to have the "airbag" light come on. I connect the HDS, and it gives me some error with ODS, also an error with OPDS, and something about the sensors not being right. Can't remember the exact wording on the screen. Basically, the car was not fooled by the fake sensors (hall effect sensors, capacitors).
Fortunately, the front airbag was "enabled," meaning it would fire in case of a crash. So at least it would work properly with an adult passenger. It will also fire with no passenger (no big deal for me) and it would also fire with a child or a child seat (gotta make sure nobody does this with my car, and if I ever sell it, I will put the OEM seats back in, calibrate it again, and return it to the factory state).
So now I know that my efforts to fool the car was not successful, but that the front airbag would still work. The "airbag" light on the dashboard did bother me. It is just a whole lot easier not having to explain it to the passenger ("Uh, that light? Don't worry about it. The airbag will deploy just fine." Passenger looks at me like I was out of my mind.)
I decided to put a black tape on it. I actually took the instrument apart as much as I could, and put a black tape on the BACKSIDE, so that from the front, it looks completely legitimate, can't tell at all. The only way to tell is that the airbag light does not come on during ignition, but that is a minor quibble, really.
After all is said and done, how does the W124 seat feel? Heavenly. It fits me like the designers knew my body exactly. It holds me on each side of the torso just right, so during turns and corners, I am not working to keep upright, the seat is doing that for me. For all intents, it feels like a giant baseball glove cradling me just right.
The W124 seats have some drawbacks. The front of the seat bottom cushion is too springy, and sags when weight is put on it. That makes it uncomfortable, as you are forever fighting the sense that your body is sliding forward. So I put some very nice custom hard padding pieces cut just right and stacked, inside the seats, IN ADDITION to the rubber/foam inserts that came with the seat (inadequate in themselves). The seat feels great.
Now, sometimes, the seat feels perfect. Other times, I could use a bit of lumbar support. So after all this Herculean effort, it's not always "perfect." But it is such a dramatic improvement over the torture chamber that came with the car. The tan leather also complements the charcoal interior very nicely.
Finally, I wanted leather steering wheel and leather shifter knob cover. I bought a used steering wheel with factory leather off ebay, so that part was easy.
The leather shift knob is my own handiwork, with automotive leather cut into precise pieces, and stitched together by hand. It is perfect. I would honestly say there is nobody in the world who could do such a nice job with leather.
People have asked me why I didn't just get a Mercedes, instead of going through all the trouble modifying a Honda. It's hard to explain, but it comes down to the philosophy of Honda, the mindset of the people at Honda who brought it into existence. The combination of reliability, handling, precision and ease of shifting, styling, everything makes the 8th generation Accord a pinnacle, in many ways, of what Honda could do. It just could have used some seats from a Mercedes or a Lexus.
