Transorbital
Not long ago I completed the “lobotomy” on my MR2. I removed around 15lb from under the dash, and another 35lb from the battery. There were many places where wires were either unused or excessively long. I also took that time to do some repairs or fix Toyota’s mistakes from when the car was originally made. In that process, I found many wires on the opposite side, in the body harness, that were also not connected to anything. It’s finally time for me to finish this project and go through the rest of the wiring.
I wanted to start with the body harness.
Several years ago, when I first 2GR swapped my car, I wiretucked the body harness and fusebox into the quarter well/trunk. This is really easy and only requires drilling one hole and extending a handful of wires. This is nothing new, and I won’t be covering details. One thing that always bothered me about this was how absolutely stiff the stock body harness is. It’s a bit of a pain to get through the quarter well above the fuel filler neck. Not impossible, just difficult. After removal, I got to work stripping it apart.
I had disconnected around 10-15 wires from the body harness connectors when I initially took my dash harness apart. Step one was to just tease those out of the harness. That alone wasn’t going to cut it. I decided to change some of the power distribution topology of this car. Typically, the alternator charge wire bolts into the fusebox, goes through the body harness all the way forward to the battery, then distributes from there, including a second wire that goes all the way back to the fusebox to power that system. That seems like a lot of unnecessary length, for weight and for voltage drop. I chose to correct this by bolting the alternator wire to the starter, and using the starter wire to charge the battery. I added a second wire to the same terminal, which routes back to the trunk to power the fusebox. Essentially, this added zero wire, and reduced around 20 feet of heavy gauge wire through the rest of the car. This also immensely slims down the harness.
Beyond reducing size and weight, I wanted to add some features. Primarily, I wanted to run CAN wires to the front of the car so I could put an OBD2 connector where the factory might have mounted it. Easy enough, CAN uses a twisted pair comm wire with flexible network topology. I don’t have a vise and bench handy, so I use a weight and jack handle to hold the wires while twisting them with a hand drill. Roughly the right length, I can cut it down more exactly later.
After getting the twist just right, I inserted them into the harness and started taping it up. Look how flexible that is, it’s so nice. I didn’t want to use the standard accordion type wire sheath that came with this, I found a split braided polyethelene loom on Amazon, it’s rated to 257F and melts at 446F, so it will be fine for this use. This type of sheath slides a lot easier, so it will be easier to install and remove the harness from the fender well in the future, if necessary. Body harness, done.
(Please ignore the red hose)
To compliment the modified body harness, I had to shorten the alternator charge wire, and bolt it to the starter, as previously discussed. I recently changed the starter out for a modern lighter weight model, and finally got around to changing the solenoid wire to match. I had this leftover from my original Sienna harness, which I removed when converting it to MR2 use. These things really go full circle. Anyway, tidied that up to match, and all is well. I just ran an additional wire from the alt wire terminal to the rear fusebox. Body and engine harness, done. What’d I actually save? a whole 3.62lb from the body harness!
After a couple more months, I finally got motivated to tidy up the frunk. I left that unfinished from my dash harness project. There were a few connectors left hanging out, taped up. This was the “taxicab leg” for those of you that read that post (see here for more details). Unfortunately, the frunk harness plugs in behind the dashboard, and it’s impossible to access that plug without removing the dash support bar. That means unless I wanted to remove the entire dash again, I need to work with the harness connected at the firewall. This was not difficult, but a bit tight.
This is a rinse and repeat of the last three segments, check what wires lead to nowhere, remove them, and remove the other end. There was only one really tricky part in removing this, and that’s the fact that the plastic shroud that holds the harness at the top of the frunk gets trapped by the clutch master cylinder. I was able to get it out without disconnecting the cylinder entirely, but I did unbolt it and move it away from the firewall. I was then able to sneak the harness out. In this area, there is a connector on the frunk harness plugged into a connector on the frunk harness. This is a bit silly, and probably a holdover for ABS vs. Non-ABS cars. My car does not have ABS, and I don’t intend to install one, at least not the factory SW20 ABS. So this one gets snipped.
I wanted to make this really worth my time, so I found as many places to save weight and size as I could. First and foremost, I could remove the frunk section of the original alternator charge wire. Due to the previous changes, that wire was just sitting in the driver footwell doing nothing. Beyond that, there were a lot of wires that were unneccessarily long. The wires would run to one side of the frunk to a crimp, then all the way back to the other side. After some consideration, I believe these were some kind of RHD holdover, where they placed crimps in specific spots, which ended up adding a lot of length in the LHD models. I noticed some similar examples in the dash harness. The biggest example of this I found was the headlight control ECU. This typically sits on the left side of the frunk, right in front of the steering shaft area. The entire frunk harness enters through the right side of the firewall. There are about 16 wires that actually run to that module, so the way I’m seeing it, all of those wires are about 4 feet too long. I can shorten every wire there, mount it on the opposite side of the frunk, and lose zero functions.
Past that, the next place I saw excessive wiring was the fan power. Specifically, the left side. The power wire runs from the front fusebox, up and around the entire frunk, then forward and towards the center. I realized a much shorter path would be to go from the fusebox straight forward, then run across right above the radiator area to the other fan. This entire length can be removed. Note that these holes are not required, I just drilled them for ease of access and some slight mass reduction. There were a handful of other places I found excess wire. None as noteworthy as the above two examples.
Past this, it was just a matter of tidying up the harness one last time. I used more of that braided loom, for consistency. I also removed the plastic bit that got in the way of the master cylinder, in case I have to remove this harness again in the future. One less thing to worry about.
There was one additional project I wanted to finish with this swap, and the software was finally ready. Marc at Frankenstein Motorworks has been working on a huge QOL software update for 2GR Sienna ECUs, including AC idle-up, cruise control, a higher idle, and some tune improvements. I’ve had the AC idle-up in my car all summer, and it’s been nice. He finally got the cruise control update ready for a user acceptance test, and I was first on the list. I added the necessary wires, including the stalk, brake input, and clutch input. Speed is obviously required but I already had that connected so I didn’t have to do more work there.
In total, my frunk modifications saved me 6.4 pounds. I was not happy with that number so I had to find something to round it off to an even 6.5. I don’t see myself going back to a large battery, since I’ve been happy with my tiny lithium, I don’t see a reason to keep this piece. Away it goes! That rounds me off to a nice 6.52 pounds, so I’m happy claiming “over 6.5 pounds” saved from the frunk alone!
With the wiring wrapped up, I have a few other parts laying around to install. A few months ago I randomly opened Facebook and saw that David Faircloth had listed used Wilhelm aluminum knuckles mere minutes prior. I jumped on them before anyone else could. Luckily these are the version with separate bolt on steering arm. They’re much stronger, provide a little extra bump steer adjustment, and saves ~5 more pounds, which is great for the narrative.
At this point the only adjustment I’m missing is caster.
Unfortunately in one small oversight on my part (or maybe David’s, I dunno) was that David had installed extended studs in these hubs which were not fully threaded. That is normally okay, but the bolt-on wheel spacers I have are not thick enough, and I can’t tighten my lug nuts down completely. Unfortunatley, that meant I had to go back to double-stacking spacers. Not the end of the world, but now I have a 10mm and 25mm spacer instead of just a 25mm. I did try a 30mm spacer I have around and it was also not thick enough. Back to the old days now. My previous knuckles were drilled out for 5/8” bolts thanks to T3 parts, and I believed this to be a source of a knocking/clicking noise I occasionally get when turning. I was hopeful these knuckles would solve that issue; unfortunately; they did not. Something else to investigate.
With this car slowly losing weight, I’ll have to get it back on scales at some point. Last time I did so it was sitting at approximately 2650lb with a half tank of gas. I’ve done a fair bit since then, and I’m not slowing down.
Simplify and add lightness.
