Engine Bay Organization 2011/01/01Posted by Michael in my IS300.
Fitting a supercharger into the IS300 engine required a little more work and effort that I originally bargained for. The stock location for the ABS block is right in the path of where the compressor stage should sit, so it needs to move. And unfortunately the most convenient alternate location for the ABS block is where the battery sits. So, I set about moving the battery to the trunk.
It seems as though some Engineers at Toyota at one time thought the battery was going to be in the trunk from the factory; in the right side of the trunk there are two threaded studs welded into the body sheet metal, a tab with a thru-hole suitable for a grounding strap, and a drain hole with rubber plug ideal for a battery vent. I purchased an MT-47 from Interstate Batteries; a liquid lead-acid battery with a sealed top and vent tube. Note that vent tubes are a *must* for trunk-mount batteries to prevent explosive gases from collecting in the enclosed space. The MT-47 fits nicely into the recessed well in the right of the trunk. I fabricated a mounting plate out of aluminum bar stock that attaches to the existing threaded studs and mounts two eye-bolts so that the battery can be secured with a Nylon strap. The battery vent runs down and out through the drain hole (lined with a rubber grommet) in the bottom of the trunk.
For the wiring, I ran #2 AWG from the battery to the engine bay (running it beneath the rear seat, along the passenger-side door sills, and then through an existing rubber grommet in the firewall, about 15′ is needed). A 175 AMP slow-blow fuse is connected within 12″ of the battery +ive terminal. A #4 AWG connects the battery -ive to the sheet metal tab in the trunk (cleaned with a wire brush to ensure good electrical contact), and a second #4 AWG runs up to the stock battery -ive connection point in the engine bay (following the same bath as the #2 wire). Note that the stock starter is a 1400W motor (117A @ 12VDC). I originally had run a #4 AWG for the battery +ive from the trunk but the voltage drop was too significant and resulted in what sounded like a dying battery every time I started the car. (Refer to for further information on current ratings for conductors and a voltage drop calculator).
Next I set about relocating the ABS block. This turned out to be easier than expected as each of the brake lines leading to the ABS block only needed to be bent to the new location (they didn’t need to be shortened and re-flared). Care was taken to ensure that new bends in the brake line were in the virgin material to avoid fatigue cracks. All bends were made with the smallest brake-line bending tool I could find ($10 at Princess Auto). I also took the opportunity to flush the brake fluid, install braided SS brake lines, and refill with ATE Dot4.