LX470 AHC question.......help!!!!! (1 Viewer)

[HDJ100L]

Folks! I recently aquired a Lexus lx470 but would like to install an ARB front and rear bumper. since adding weight to the vehicle will cause the AHC to pump hard to raise it. is there any technique to do it? how to adjust torsion bar or spacer for the rear coils? any help you be appreciated.

 

[LX470Pilot]

This is a question that haunts me everytime I take a longing look at my off-road wishlist.

Unfortunately, I don't have an answer for you, but I'll be following along to see if anyone does.

Here're a couple other questions that directly relate:

What is the limiting factor for weight on the AHC? is it the pump itself, the hoses?

Would it be possible to change these out, kinda like upgrading brake calipers and stainless steel brake lines?

And here's a word problem for all those who miss highschool math:

Useful Load Limit
Definition: Max weight a vehicle can carry, after Driver is accounted for. Useful Load Limit includes passengers and any cargo inside/outside the vehicle.

The stock '00 LX Max. Load Limit
in the Normal mode of 1261lbs. minus Driver weight
in the High mode of 975lbs. minus Driver weight

If the Driver weighed 200lbs, the Useful Load Limit in Normal mode would be 1061lbs.

You add ARB bumpers Fr & Rr, which lowers your useful load limit by X lbs.

You then add an OME or other(?) shocks/springs/struts - by themselves, they Increase your useful load limit by X lbs.

Would these two technologies cancel each other out to a degree, leaving you with Original, slightly Higher, or slightly Lower Useful Load Limit?

 

[LX470Pilot]

This is also an issue to pay attention to when considering an Auxilliary Fuel tank.

Gasoline weighs approximately 6lbs/gallon.

Stock tank of 24.5gal = 147lbs of fuel

Running the Stock tank at Full is a given in the numbers I listed above - called a vehicle's 'wet weight' - meaning the vehicle has full Fuel, all types of Oil, washer fluid, proper tire pressure, etc. before the Driver weight is added.

Whenever you add an Aux fuel tank, the weight of the tank, and of the fuel in it, eats into your Useful Load Limit.

90liter Aux tank = 22.5gal = 135lbs fuel
160liter Aux tank = 40gal = 240lbs of fuel

Technically speaking, you could trade weight between cargo and fuel. For instance, running half a stock tank would give you 73.5lbs more Useful Load Limit, but that's a bit more active math than most of us wish to deal with, and starting a trail with half a tank wouldn't be helpful anyway.

 

[Jim_Chow]

Your payload capacity is about 650 lbs for all passengers + gear. If you strip out the 3rd row seats like most of us, you'll save 80-100 lbs in the rear. The AHC is designed to handle this much load, so whether you put an aux fuel tank where the spare was or whatever, you are just losing cargo/passenger carrying capacity. If your passengers weigh less, you can carry yet more weight. The front of my LX dropped maybe 1/2" with engine off and AHC in low. Otherwise, it appears to be at the same height. Rear is the same. I pulled out the 3rd row, so the weight gain from the Kaymar bar is probably a wash.

For the front, the FSM says you are supposed to adjust the t-bars if you put more than 20 lbs up front so the AHC pressures on each front shock are in the spec range (IIRC, it's like 28psi for each half turn of the t-bar). If they are in range after adding the sahara bar, no worries. I think you leave the sensors up front the same regardless. If you put a winch up front, you will definitely need to do something w/ the t-bars. Without a winch, we know the LX will hold a ARB bullbar, as Val678 had one installed. The sahara bar is lighter, so it shouldn't stress out the AHC. I don't think it's any worse than a heavy driver and front passenger.

 

[LX470Pilot]

Without a winch, we know the LX will hold a ARB bullbar, as Val678 had one installed. The sahara bar is lighter, so it shouldn't stress out the AHC.

Val678's is a '99 - no AHC.

 

[hoser]

LX470Pilot, you are thinking of VSC and ATRAC. All US market LX470's have AHC.

 

[LX470Pilot]

I stand corrected - thanx hoser.

Good point about the 3rd seats too, Jim, I almost never use them, so I didn't even think about them here.

 

[Zimm]

ok. so how do you decide how much to turn the bars?

 

[Val678]

Val678's is a '99 - no AHC.

I have AHC, lol

 

[Jim_Chow]

ok. so how do you decide how much to turn the bars?

You either need the LSPV or lexus hand tool to measure the AHC pressure. Once you know the pressure, you know how many turns to take up on the t-bars to get it into spec since the FSM tells you that.

 

[hoser]

ok. so how do you decide how much to turn the bars?

The non-scientific way people have used to adjust the front is to set the AHC on low and measure the height. Then add all the weight (bumper, battery, etc) and adjust the T-bars to the same height. In the rear, you could use trim packers. But the FSM method Jim stated is probably preferable.

 

[Texasoil]

AHC and weight added accessories

The AHC system has pressure relief valves integrated into the system. When the rated Gross vehicle weight (GVW) is reached, the AHC system simply shuts down and the vehicle drops down. (actually the AHC works on 'sprung weight,which does not include wheels,tires, and the suspension& driveline parts not supported by the suspension springs.

The way to 'fool' the system is to tighten up the front torsion bars and add spacers to the rear spring seats.

The goal is to get the hydraulic pressure back to 'in spec' at the 'N' position with the added accessories.

Please note, modifying your vehicle- adding weight to the front or rear ends, and deliberately exceeding the GVW by altering settings-- MAY cause your insurance Co to deny a claim if you have a loss of control or wheel/tire failure accident.