AHC Sensor Lift + Override Switch Brainstorm (1 Viewer)

[LndXrsr]

Alright, thanks to @tzyz's homemade AHC override tutorial, I've been brainstorming a combo override switch plus a sensor lift. The plan would be to fine tune to a 1.75" sensor lift, or about the same as the increase in height between N and H from the factory. Then using the override, I could drive around in L, which would be about the same height as the factory N. I find factory L is essentially useless for anything other than unloading old people. Driving in L with a sensor lift would allow for a more factory ride, better handling, better fuel economy, and most importantly, no extra wear on the CVs during the majority of driving. I could then run in sensor-lifted N when off-road (equivalent to the factory H) and even go into H on command for an extra 2" if I need to crawl a tight section that requires better angles/clearance.

Essentially, the hope is to make:
Lifted L = Factory N
Lifted N = Factory H
Lifted H = 2" beyond old H (or the mythical factory "extra high" mode available on command)

Questions:
1) The shocks should have the range to do this given the existence of "extra high" mode, but can all 4 shocks go to that much extension at once? I assume so as long as I put enough AHC fluid in the reservoir. Basically would need the reservoir to be within the appropriate fill range when in L instead of N as would typically be done during a flush.

2) I think I'd shoot for AHC pressures to be on the low-end of spec when in L. That way ride should be close to factory in L and pressure would be acceptable to drive in the new N and H without overloading the system and reverting to L. Make sense? At worst if it went into safe mode and dropped to L, I'd just be back at factory height.

3) Still (embarrassingly) running the OEM ~31" tires. Planning to go to ~33s (285-75-16 or 295-75-16) when I wear them down a bit more. Despite adding lift, I can't go any larger since I'm not changing anything about the travel of the front suspension (control arms, bump stops, etc) and so anything larger would still rub when compressed, right?

4) Any other problems the AHC experts out there foresee?

 

[EastTN01LX470]

I just completed a mild sensor lift on my ride this month. I went for 21” hub to fender on the front. When I go into low i believe it’s still lower than the normal ride height. I’ll have to measure to be sure. So I’m thinking it would be too low still to ride around at higher speeds.

 

[LndXrsr]

The point would be to raise it with the sensors the same amount as lowering to L, about 1.75”. So it wouldn’t be too low in L but rather the equivalent of OEM N.

 

[Coin]

Doesn’t the suspension lower about 1” at highway sped under normal conditions anyway?

If so, what would be the problem if when using the override switch the “L” mode was slightly lower than the normal “N”?

Should still be within normal operating range, if < or = to 1”

 

[PADDO]

Guys, do you realize that when you interrupt the normal speed inputs to the AHC ECU via switching you’re also disabling the adaptive variable suspension? Ever noticed that when testing and tuning the system whilst in your garage that both step inputs (damping settings) are 8? Well they are 8s (midpoint of the variable damping range) because the vehicle isn’t moving. Interrupt the speed signal to stay in H or L whilst moving then you are going to be driving at step 8 non variable damping with no other speed sensitive variables either. It’s a simple system but you get unintended consequences when you fiddle with it.

 

[Coin]

Good to know!

 

[Coin]

Is there a way to interrupt the ECU signal to lower/raise the ahc before it gets to the pump/accumulator?

 

[jahawk]

I have about an inch sensor lift in front. Just enough to level the truck out. I also installed the Slee over ride and its more than just a toggle switch. I'm sure it addresses the concerns PADDO states. That being said I rarely use it. I'm running 275/50/18 and have no rubbing issues in normal height. Anytime I've ever needed high I was going under 20 anyway. The truck rides a lot rougher in high also.

Jim

 

[suprarx7nut]

Alright, thanks to @tzyz's homemade AHC override tutorial, I've been brainstorming a combo override switch plus a sensor lift. The plan would be to fine tune to a 1.75" sensor lift, or about the same as the increase in height between N and H from the factory. Then using the override, I could drive around in L, which would be about the same height as the factory N. I find factory L is essentially useless for anything other than unloading old people. Driving in L with a sensor lift would allow for a more factory ride, better handling, better fuel economy, and most importantly, no extra wear on the CVs during the majority of driving. I could then run in sensor-lifted N when off-road (equivalent to the factory H) and even go into H on command for an extra 2" if I need to crawl a tight section that requires better angles/clearance.

Essentially, the hope is to make:
Lifted L = Factory N
Lifted N = Factory H
Lifted H = 2" beyond old H (or the mythical factory "extra high" mode available on command)

Questions:
1) The shocks should have the range to do this given the existence of "extra high" mode, but can all 4 shocks go to that much extension at once? I assume so as long as I put enough AHC fluid in the reservoir. Basically would need the reservoir to be within the appropriate fill range when in L instead of N as would typically be done during a flush.

2) I think I'd shoot for AHC pressures to be on the low-end of spec when in L. That way ride should be close to factory in L and pressure would be acceptable to drive in the new N and H without overloading the system and reverting to L. Make sense? At worst if it went into safe mode and dropped to L, I'd just be back at factory height.

3) Still (embarrassingly) running the OEM ~31" tires. Planning to go to ~33s (285-75-16 or 295-75-16) when I wear them down a bit more. Despite adding lift, I can't go any larger since I'm not changing anything about the travel of the front suspension (control arms, bump stops, etc) and so anything larger would still rub when compressed, right?

4) Any other problems the AHC experts out there foresee?

What does a mild sensor lift not do that this might solve?

A few quick thoughts, with the intention of being helpful and not lecturing too much:

1. "Flex" is what matters in most off road situations - not lift height. You will not be changing flex at all. If anything, you'd make it worse by limiting droop.
2. Notice how there are a TON of 1-2.5" lifts and almost no lifts for 4" on the 100? There's a good reason. Beyond an inch or two you really start to stress the hell out of the CVs and you reduce droop to very little. That's not a good thing for performance, nor durability.
3. You'll need to somehow de-couple the rest of AHC's function and it's height. Factory L rides like crap and I don't think that's strictly due to the height. The suspension portion of the system isn't meant to "drive" in L. Apparently, as PADDO says, there are steering functions to consider as well.
4. Tires matter. Lift doesn't (much). You can fit 34" tires with some simple hammering and a heat gun or 33" tires with no mods at all. That'll get you more performance at stock N height than 31's in ultra-high mode.
5. If you lift for normal driving in what was high mode, you now need to buy a diff drop, or you're going to ruin $400 CVs at a fast pace.
6. In your point number 3 you mention you're not doing anything to suspension travel. If you raise each height setting you will be messing with travel - you'll be reducing it.
7. Why does anyone care how tall their car "looks" when driving. You can't tell. Is anyone outside your car going to even notice? I don't think so. If the appearance matters, pop it into H when you're in a parking lot. Problem solved.

Most importantly: Go drive the car and find your limits. I've driven every Colorado trail I've wanted to in my stock height 99 LC (no AHC).

If you want to lift it to look cool, it might be a cheaper proposition to buy an old Toyota Pickup or 4Runner or Jeep on craiglist and drive that around while you keep the LX stashed away at home. It's stupidly expensive to try to cheaply lift a 100 series.

 

[Coin]

The PO's initial thought was to be able to drive in High over 20mph, and then some other stuff. I drive through some tall grass and shrubs occasionally and would like to stay in high over 20mph, but if it's bad for the car then it's no biggie, just an interesting brainstorm.

 

[LndXrsr]

Points well taken from everyone, but I think I'm maybe not being clear enough. The overall goal of this is not an "uber-lift" or to ride around at some extra height and put more strain on the system. My real thought was to eliminate the relatively useless L setting and ultimately have the "extra-high" mode available on demand for some rare situations.

@PADDO, your point is the most interesting so far. Did not realize that an override would mess up the TEMS. Have to think about that a bit. At least it doesn't default to 1 or 16 and could probably handle a static 8 setting. I assume the the side-to-side valves for leveling when corning would also not close as usual? This is probably enough to make me not move forward with this theoretical lift plan if true.

@suprarx7nut, thanks for the extensive feedback. I've read through a lot of your recent build thread and you do great work. Your website has helped me figure out sizing plans for my next set of tires when the time comes. Thank you. I've off-roaded everything from Wranglers to modified golf-carts and am not looking for some cheap lift mod for cosmetic reasons. I have driven the LX out on trails, including 4,000 miles to CO and back last week with some San Juan wheeling and other off-roading involved. Nothing crazy, and I was limited by my tires more than anything as you mention. But I like to think outside the box, love the AHC system and its uniqueness, and this was something the popped in my head during many long, boring miles in TX and OK on the way home. My detailed responses to your detailed comments, collated into a couple major points:

1) I totally agree with your points about tires matter more, articulation/flex not changing, etc. I know my proposed plan changes none of that, and I know that a regular non-AHC lift doesn't either. You are simply moving the default or static point in the articulation arc. It doesn't reduce travel as you mention though, one just has more compression travel at the expense of droop travel, not that that's necessarily helpful. I plan to put some 33s on when the current tires wear out, but I'm not going to ditch perfectly good tires and rush the process. I can wait. This is a long-term adventure vehicle for my family.

2) However, regarding your comments about how a car "looks" while driving, and putting extra wear on the CVs, I think you are missing what I'm getting at. I want quite the opposite of a goofy lifted rig to drive loudly through my paved neighborhood and look cool, and definitely don't want to rip down the highway lifted higher than stock and in doing so rip up my CVs. Instead, I want to drive at the height of and ride with the damping of the OEM N to not put extra strain on any of the suspension/CVs, especially for long road trips. What's weird/unique/stupid/brilliant about my proposal is that I want that height to be labelled as L instead of N by using a sensor lift and AHC override switch. You are right the car rides like crap at the OEM L height, but it's less the height and more the lack of pressure in the AHC pistons (shocks) resulting in underdamping and too much weight on the non-AHC metal springy bits (TBs and coils). The height of the truck is a result of the pressure in the system which is why it also generally rides crappy at OEM H (too much pressure, very stiff). But I want the both the height and pressures in my lifted L setting to be equivalent to the OEM N setting and raise up form there as needed using the AHC height selector switch. My new lifted N would have the same height and pressures as OEM H, and my lifted H would be the equivalent of of OEM extra-high, which is usually in accessible manually. These two higher levels would be used at <20mph and crawl speeds, respectively.

Again, to @Coin's most recent post, I don't want to drive in a lifted mode above 20mph. I really just want more control over extra lift in the rare situation I need better approach/departure/breakover angles at crawl speeds, acknowledging that will be rare but still at least more useful than the OEM L setting is now.

 

[ramangain]

Sounds to me like a better solution is firmware/software in the AHC ECU to just remove the ride height vs. speed defaults, correct? Is there an (unknown) parameter which Techstream can modify to accomplish this goal, perhaps? Maybe some ECU junkies would take up the challenge.

 

[suprarx7nut]

Points well taken from everyone, but I think I'm maybe not being clear enough. The overall goal of this is not an "uber-lift" or to ride around at some extra height and put more strain on the system. My real thought was to eliminate the relatively useless L setting and ultimately have the "extra-high" mode available on demand for some rare situations.

@PADDO, your point is the most interesting so far. Did not realize that an override would mess up the TEMS. Have to think about that a bit. At least it doesn't default to 1 or 16 and could probably handle a static 8 setting. I assume the the side-to-side valves for leveling when corning would also not close as usual? This is probably enough to make me not move forward with this theoretical lift plan if true.

@suprarx7nut, thanks for the extensive feedback. I've read through a lot of your recent build thread and you do great work. Your website has helped me figure out sizing plans for my next set of tires when the time comes. Thank you. I've off-roaded everything from Wranglers to modified golf-carts and am not looking for some cheap lift mod for cosmetic reasons. I have driven the LX out on trails, including 4,000 miles to CO and back last week with some San Juan wheeling and other off-roading involved. Nothing crazy, and I was limited by my tires more than anything as you mention. But I like to think outside the box, love the AHC system and its uniqueness, and this was something the popped in my head during many long, boring miles in TX and OK on the way home. My detailed responses to your detailed comments, collated into a couple major points:

1) I totally agree with your points about tires matter more, articulation/flex not changing, etc. I know my proposed plan changes none of that, and I know that a regular non-AHC lift doesn't either. You are simply moving the default or static point in the articulation arc. It doesn't reduce travel as you mention though, one just has more compression travel at the expense of droop travel, not that that's necessarily helpful. I plan to put some 33s on when the current tires wear out, but I'm not going to ditch perfectly good tires and rush the process. I can wait. This is a long-term adventure vehicle for my family.

2) However, regarding your comments about how a car "looks" while driving, and putting extra wear on the CVs, I think you are missing what I'm getting at. I want quite the opposite of a goofy lifted rig to drive loudly through my paved neighborhood and look cool, and definitely don't want to rip down the highway lifted higher than stock and in doing so rip up my CVs. Instead, I want to drive at the height of and ride with the damping of the OEM N to not put extra strain on any of the suspension/CVs, especially for long road trips. What's weird/unique/stupid/brilliant about my proposal is that I want that height to be labelled as L instead of N by using a sensor lift and AHC override switch. You are right the car rides like crap at the OEM L height, but it's less the height and more the lack of pressure in the AHC pistons (shocks) resulting in underdamping and too much weight on the non-AHC metal springy bits (TBs and coils). The height of the truck is a result of the pressure in the system which is why it also generally rides crappy at OEM H (too much pressure, very stiff). But I want the both the height and pressures in my lifted L setting to be equivalent to the OEM N setting and raise up form there as needed using the AHC height selector switch. My new lifted N would have the same height and pressures as OEM H, and my lifted H would be the equivalent of of OEM extra-high, which is usually in accessible manually. These two higher levels would be used at <20mph and crawl speeds, respectively.

Again, to @Coin's most recent post, I don't want to drive in a lifted mode above 20mph. I really just want more control over extra lift in the rare situation I need better approach/departure/breakover angles at crawl speeds, acknowledging that will be rare but still at least more useful than the OEM L setting is now.

Good clarification, thanks! Thanks for following the build. I'm anxious to get moving on it again. Glass shop has had it for a while.

Do I understand correct that the intent is to use the system as designed from Toyota with the exception of using extra-high on demand (in your case acting as H) while off-road?

If that's the idea, I think a far easier approach would be to simulate the extra-high triggers (I think just wheel speed variance while in Low and in high). That could be a simple frequency generator on the input line from one speed sensor to the AHC ECU. Of course, you'd want to make sure that doesn't also disable other functions.

Would that be an alternative approach?

*Edit, also follow up: In your trail driving as is, did you often bash undercarriage/sliders/skids plates?

 

[LndXrsr]

Sounds to me like a better solution is firmware/software in the AHC ECU to just remove the ride height vs. speed defaults, correct? Is there an (unknown) parameter which Techstream can modify to accomplish this goal, perhaps? Maybe some ECU junkies would take up the challenge.

If that's the idea, I think a far easier approach would be to simulate the extra-high triggers (I think just wheel speed variance while in Low and in high). That could be a simple frequency generator on the input line from one speed sensor to the AHC ECU. Of course, you'd want to make sure that doesn't also disable other functions.

*Edit, also follow up: In your trail driving as is, did you often bash undercarriage/sliders/skids plates?

It does seem that an electrical rather than mechanical override would be ideal here. Too bad my comfort zone is far more in the realm of turning wrenches than redoing 12V electrical. If anyone more electrically savvy finds this proposal interesting, let's dig a bit deeper together.

I did have some rear departure angle issues and one or two belly scrapes while out in CO. Granted I'm still in a basically bone-stock 100 with OEM tires and the rear hitch. Probably keeping the hitch for now, but need to upgrade the tires when the time comes and get back out that way to try again! HIHXI, here I come!

 

[white_lx]

Simplest solution would be to fool the AHC controller by running the 3 sensor outputs through a circuit with a variable offset. That way you can select any height as your N setting and the L and H settings would still be available as well with the same offset.

[edit] Even easier: you can add a fixed resistor in series with the supply voltage of the height sensors. That will offset the sensor output down. It will affect the L and H settings slightly. Start with 1/4 or 1/3 of the total sensor resistance. (This is assuming the output will be lower for a lower height. It it is the other way around the resistor needs to be added tot the ground leg of the circuit.)

 

[white_lx]

Turns out there is an off-the shelve solution that does exactly this: Data System Air SUS Active Suspension Control Kit - ASC680 - RHDJapan

Mostly used by the by air ride Celsior/LS folks, but it can also be used for the AHC system as per list of compatible vehicles. Havn't looked into it in too much detail, but I assume it is just a sensor override.

 

[Travis Bickle]

You guys should learn to wheel your trucks first.

I've got stock size tires and don't have much of a problem doing most moderate trails here in Colorado.

I had 285's on my 2000 LC and hated the drop in mileage and power. On my LX I kept the stock size tires and haven't regretted it, still able to do all the trails I did with the LC. But I guess it looks cooler... and that's what counts.

 

[LndXrsr]

It's not about cool or looks. Just interested in learning more about AHC, experimenting with it, having more manual control if desired.

 

[GTV]

@LndXrsr what direction did you end up going?

I’ve recently come to a similar conclusion, that the factory L setting is uselessly low. I previously camped in L height but recently switched to H and my back has been thanking me.

I’ve also been in a couple situations in the last few months that would have been really nice to have the additional height at speeds higher than 30kph.

To me the H setting seems to come with another compromise and that is suspension compliance. H feels much stiffer and less flexy than N and I assume that is because the pressures go up to achieve lift. Lifting gets the alignment out of whack as well (which I feel would be hard to solve if you’re driving around in L at correct alignment then things are going to be way off in H).

My current idea is to use the Japan 4x4 shock extenders (I believe they are 40mm taller?), extended sway bar end links and a diff drop to make the suspension geometry and CV angles as close to factory as possible. I’ll only do a modest 40mm (1.6”) sensor lift which is what the difference is from N to H. L will then be roughly at the standard N height which still makes for easy ingress and egress, it would make L a lot more useful than it is now. 34” tires for another 1.5” of lift would get the floor up 3” total in N height with everything functioning as the factory intended.

 

[LndXrsr]

@LndXrsr what direction did you end up going?

I’ve recently come to a similar conclusion, that the factory L setting is uselessly low. I previously camped in L height but recently switched to H and my back has been thanking me.

I’ve also been in a couple situations in the last few months that would have been really nice to have the additional height at speeds higher than 30kph.

To me the H setting seems to come with another compromise and that is suspension compliance. H feels much stiffer and less flexy than N and I assume that is because the pressures go up to achieve lift. Lifting gets the alignment out of whack as well (which I feel would be hard to solve if you’re driving around in L at correct alignment then things are going to be way off in H).

My current idea is to use the Japan 4x4 shock extenders (I believe they are 40mm taller?), extended sway bar end links and a diff drop to make the suspension geometry and CV angles as close to factory as possible. I’ll only do a modest 40mm (1.6”) sensor lift which is what the difference is from N to H. L will then be roughly at the standard N height which still makes for easy ingress and egress, it would make L a lot more useful than it is now. 34” tires for another 1.5” of lift would get the floor up 3” total in N height with everything functioning as the factory intended.

I think all that makes a lot of sense. I thought about the Japan 4x4 spacers as well, but ended up keeping things fully stock from an AHC standpoint (minus King Springs, I guess that’s not stock).

Primary reason being that using an override switch to keep the truck in “low” at driving speeds, whatever height that may actually be, is accomplished by disconnecting wheel speed sensors. That deactivates the TEMS portion of the hydraulics (variable stiffness, comfort/sport). Also, from what I’ve read, it’s unclear if any unwanted effects on things like ABS or ATRAC would happen as well.

I think it may still be worth exploring, but I’m personally quite happy on 33s with no lift at the moment, great ride, and knowing that things aren’t under much extra strain down there. Japan 4x4 spacers leads to making a switch, getting a diff drop, closely watching CVs, new alignments, maybe new upper control arms, etc. I’m not at the point where I need that for my adventures nor does my wallet need it.