So I got around to adjusting my AHC neutral pressures today as I finally have everything I needed to do this.
I have an '06 LX470 with 72k miles.
Using a Mini VCI cable with Techstream software (purchased here - http://www.uobd2.com/wholesale/mini-vci-for-toyota-tis-techstream-v500028-single-cable-2442.html) I was able to read my current neutral pressures from the AHC ECU:
Before Pressure - 7.5 MPa Front / 6.8 MPa Rear
Spec calls for 6.9+/-0.5 MPa front and 5.6-6.7 MPa rear. You can see after 6 years, the pressures are just out of spec. This means that the AHC system is shouldering more load than optimal. It also is reducing the load carrying capacity and ability to go into high clearance mode when loaded. That's why it's so important to have the pressures in spec to both preserve the AHC system and ensure that the vehicle can perform when loaded.
So now is where my take is a bit different. Instead of replacing the rear springs, I opted to get a set of trim packers for the rear springs to basically, pre-load them to account for the settling. The spacers are to springs what cranking is to torsion bars.
Trim packers specific to the hundy aren't readily available. I figured since 80 series springs can drop in, their trim packers can be used as well which was the case. Without an existing knowledge base on this, I bought 5mm trim packers (http://man-a-fre.com/parts_accessories/Trim Packers.htm). Go for 10mm trim packers for anyone else doing this from the same link.
You'll also need spring compressors to install. I used these - http://www.harborfreight.com/macpherson-strut-spring-compressor-set-3980.html
With AHC set to high, I lifted one rear corner of the vehicle with a hydraulic floor jack on the frame and set a jack stand. The idea is to get as much pre-load off the spring. Then working one corner at a time, compress the spring on car with the spring compressor. Slip in the trim packer when there's enough space.
Before Pressure - 7.5 MPa Front / 6.8 MPa Rear
With only rear trim packers - 7.3 MPa Front / 6.7 MPa Rear
A good change, but should have went with the 10mm packers! The AHC rear spring are quite tender as you can see in the pic. Hopefully by adjusting the fronts, I'll see a positive change the rear too.
After cranking the front torsions 3 full turns driver side, and 2.75 turns right (left height sensor showed incrementally more sagging:
Before Pressure - 7.5 MPa Front / 6.8 MPa Rear
With only rear trim packers - 7.3 MPa Front / 6.7 MPa Rear
Cranked and trim packers - 6.7 MPa Front / 6.6 MPa Rear
Spec - 6.9+/-0.5 MPa Front / 5.6-6.7 MPa Rear
Really wish I got the 10mm trim packers but I'm in good shape for now. Project costed me all of around $70.
I have an '06 LX470 with 72k miles.
Using a Mini VCI cable with Techstream software (purchased here - http://www.uobd2.com/wholesale/mini-vci-for-toyota-tis-techstream-v500028-single-cable-2442.html) I was able to read my current neutral pressures from the AHC ECU:
Before Pressure - 7.5 MPa Front / 6.8 MPa Rear
Spec calls for 6.9+/-0.5 MPa front and 5.6-6.7 MPa rear. You can see after 6 years, the pressures are just out of spec. This means that the AHC system is shouldering more load than optimal. It also is reducing the load carrying capacity and ability to go into high clearance mode when loaded. That's why it's so important to have the pressures in spec to both preserve the AHC system and ensure that the vehicle can perform when loaded.
So now is where my take is a bit different. Instead of replacing the rear springs, I opted to get a set of trim packers for the rear springs to basically, pre-load them to account for the settling. The spacers are to springs what cranking is to torsion bars.
Trim packers specific to the hundy aren't readily available. I figured since 80 series springs can drop in, their trim packers can be used as well which was the case. Without an existing knowledge base on this, I bought 5mm trim packers (http://man-a-fre.com/parts_accessories/Trim Packers.htm). Go for 10mm trim packers for anyone else doing this from the same link.
You'll also need spring compressors to install. I used these - http://www.harborfreight.com/macpherson-strut-spring-compressor-set-3980.html
With AHC set to high, I lifted one rear corner of the vehicle with a hydraulic floor jack on the frame and set a jack stand. The idea is to get as much pre-load off the spring. Then working one corner at a time, compress the spring on car with the spring compressor. Slip in the trim packer when there's enough space.
Before Pressure - 7.5 MPa Front / 6.8 MPa Rear
With only rear trim packers - 7.3 MPa Front / 6.7 MPa Rear
A good change, but should have went with the 10mm packers! The AHC rear spring are quite tender as you can see in the pic. Hopefully by adjusting the fronts, I'll see a positive change the rear too.
After cranking the front torsions 3 full turns driver side, and 2.75 turns right (left height sensor showed incrementally more sagging:
Before Pressure - 7.5 MPa Front / 6.8 MPa Rear
With only rear trim packers - 7.3 MPa Front / 6.7 MPa Rear
Cranked and trim packers - 6.7 MPa Front / 6.6 MPa Rear
Spec - 6.9+/-0.5 MPa Front / 5.6-6.7 MPa Rear
Really wish I got the 10mm trim packers but I'm in good shape for now. Project costed me all of around $70.
