AHC, Bullbars and Rear bars

[dinibili]

I a recently purchased a new LC 100 TD with AHC (Sahara in Australia).(7500kms). I have added ARB Delux bar (74kg) 12000lb winch and synthetic rope (47kg) and ARB rear bar (80kg) and spare wheel carrier (25kg). Because of the AHC I am limited by the weight I can now carry as the vehicle will goes into Low mode if I put 4 to 5 passengers, 50kgs in the back and 100kgs of ball weight. What do I need to do to get some more carry weight without up setting the suspension. I have looked at previous threads which talked about what people were planning on doing. Has any body done anything and found that it was successful in terms of rear coils and/or heavier TB. I am not after more lift. ARB (Aust) are too scared to touch it for fear of upsetting the intelligence that would normally control the relationship between HT and Load.

 

[moooooooo]

Sounds like a nice LC! I too have the deluxe bar, but i have the Warne 9000lb winch with 30m of cable.

So the automatic height control kicks in and lowers the height when you have those extra passengers? Is there a manual override, or is automatic all there is?
cheers
peter

 

[hoser]

50kgs in the back and 100kgs of ball weight. What do I need to do to get some more carry weight without up setting the suspension. I have looked at previous threads which talked about what people were planning on doing. Has any body done anything and found that it was successful in terms of rear coils and/or heavier TB. I am not after more lift. ARB (Aust) are too scared to touch it for fear of upsetting the intelligence that would normally control the relationship between HT and Load.

Wow, Stud, 50kgs of ball weight? I guess it is true what they say about everything being bigger in Australia.

Both Christo and Siglo have carried heavy loads with their AHC cruiser. However, they also added lift. If you don't want lift, you might try custom made coils. They aren't that much more over here in the US. I would try using standard 80 series rear coils. If it creates too much lift, perhaps cut 1/2 a coil or so. But keep in mind cutting coils will also increase the spring rate.

 

[dinibili]

Yes I know. Thats why I have stooped shoulders!

 

[dinibili]

The AHC some how determines the pressure in the system (either by actual measurement or by the cruder break point) and presumably ceases to work and drops the vehicle onto the conventional suspension. From there it will not raise unless the vehicle is emptied and reset. If it is by a break point then I wonder if it is possible to replace the controller with one of a heavier setting. Currently there is no manual over ride. I am also assuming that because the front wish bone is supported by the shockers as well as the TB the likelihood of the "cracked IFS" is less, even if I do replace the TB with a slightly heavier version.

 

[moooooooo]

actually dinibili, when i got my deluxe bar put on at ARB HQ in Kilsyth (only 2 weeks ago), i asked about the extra weight and whether the suspension would need adjusting and he said yes and told me that they would adjust the suspension. I assume he was talking about the torsion bar.
My ride height is about the same as before i got the front bar, although my LC100 is the GLX and not the Sahara and also i dont have the ARB rear bar (yet) either.

I've also taken out the back seats so i only have the driver and front passenger seats in it.

i'm quite surprised how much room i have gained by doing this as i was travelling with the seats folded up previously. I already had taken the very back seats out.

I'm off for a week of offroading tomorrow morning (Sunday) and will see how it performs with stock suspension.

cheers
peter

 

[siglo]

My LC also has ARB's delux bull bar, warn 9.5xp winch and kaymar rear bumper with tire carrier.. I've recently lowered my LC back to almost its stock height.. I kept ARB's T-bar and replaced my OME863 coils with OME860 to lower it back to stock height.. The LC handles better now fully loaded with sub gas/water tank, full drawers, fridge, full cargo, misc light stuff on roof and 2 passengers (one of them is heavier than your ARB rear bar + tire carrier) .. If you plan on changing the springs and t-bars, and you probably should, make sure you read this post by uHu.. It will help you in maintaining stock pressure in your AHC system after adjusting the sensors..

ARB Australia was extremely clear in their communication to their dealer here that they do not endorse or support the use of their products on AHC equipped 100s.. I've personally ignored that and after a while of trial and error found out that for my need, their t-bars and OME860 were perfect for the job..

Adjusting the sensors of the AHC was my main problem.. I've learned that having a Toyota tester is very handy, so I made sure that all the adjustments I went through were done at Toyota's agent..

If you need more specific info, let me know

 

[dinibili]

Thanks for that. A couple of questions. When you remove the plugs to fit the pressure gauge I assume that there is a significant pressure of fluid trying to escape. How do you deal with that? The LSPV is a brand of gauge or a particular type of gauge. If the pressure is not correct in the rear shockers how do you fix it in terms of the coils? Interestingly enough ARB (Kilsyth-Head Office) did not indicate to me that there was an issue with putting bars on the Sahara. I did question them about it. I am assuming, as the Sahara model (with AHC) had only been around for 3 months they were not aware of the potenial problems. They are now!!

 

[uHu]

See link above for updated info. (Edited old posting)
Will write more tomorrow here.
Good Night.

 

[siglo]

Interestingly enough ARB (Kilsyth-Head Office) did not indicate to me that there was an issue with putting bars on the Sahara. I did question them about it. I am assuming, as the Sahara model (with AHC) had only been around for 3 months they were not aware of the potenial problems. They are now!!

I've used the Toyota tester at the dealer so I wouldn't deal with an LSPV gauge.. I don't know which ARB office deals with international dealers inquiries, but IIRC, they did not endorse nor recommend installing any of their products on AHC LCs.. That was around May 2004 or so.. I remember reading their email at their dealer in Kuwait and they said something like these vechiles are not available in the Australian market, ARB did not perform any test etc, and therefore do no recommend installing any of their products on AHC LCs.. I would safely assume that some department at ARB (maybe not Kilsyth-Head Office) was aware of potential problems long before your case.. The easy way out for them is to say we do not recommend installing our products on AHC LCs.. I would image that since AHC is available now in Australia, that they would start supporting it sooner or later..

 

[dinibili]

See link above for updated info. (Edited old posting)
Will write more tomorrow here.
Good Night.

Thanks again for the update. I still not sure what is meant by LSPV. Also do you know what the thread size is for the bleeder plug. I do currently have 10-1000psi pressure gauges but will need to make up adapters.

Thanks again
Donald

 

[siglo]

You'll fine the details of the LSPV Gauge uHu mentioned in his post here.

 

[dinibili]

Thanks. LPSV is obviously a kit. Anybody out there know what the size of the bleed screw thread is. Once I get that, I will be able to sort my problems I hope. The information given here has been brilliant. Thanks again.
Donald

 

[uHu]

AHC suspension

The weight of the LC is distributed between steel springs and nitrogen "springs".
The load carried by the nitrogen spheres is transferred via the hydraulic oil (AHC fluid). Now, if the vehicle gets heavier than "normal", a greater proportion of the load has to be carried by the nitrogen spheres. This means that the pressure in the AHC fluid is increased, and that the nitrogen is compressed harder, resulting in harder springs. This is a similar effect to what happens when you put the suspension into the HI mode, with a harder and harser ride. If the gas pressure increases even more, there will in the end be no more travel available in the nitrogen spheres (like what happens when the nitrogen spheres are leaking/empty/finished, but that's another thread....)
So, there has to be a balance between the steel and the gas so that the gas springs get only the load they are designed for, also for optimal ride/comfort and handling. Remember that the shock-absorber function is in this system, so it better be in balance. (>> neutral pressure)

Not so difficult to balance it, just a lot of work finding the right springs (coils and torsion bars), and changing them.

Siglo:
Sounds like you found the balance with the springs you have fitted. Do you have specs for the springs u use?
How does it work without any passengers or other load/water or extra fuel?
Can you still get into LO?

BTW: updated the Neutral Pressure procedure again, more "Hints". https://forum.ih8mud.com/showpost.php?p=858169&postcount=11

 

[dinibili]

Where does the accumulator fit into all of this. Also I would assume it is easier to take the pressures at the sphere actuators in terms of access. Is there a down side to doing there. It would appear from the paper work that Toyota measured the pressures at the shock absorbers.
Stated
"Front shockers before adjustment 10MPA after 7.3MPA specs 6.9 +/- 0.5MPA. 8.5MPA at the rear".
I would have thought it easier to do it at the spheres.

Donald

 

[uHu]

As you can see in the link above (AHC Neutral Pressure procedure), the toyo' tester doesn't actually check the pressure at the shock. Just estimates the pressure from measuring the pump pressure. By measuring with a gauge at the actuator/sphere bleeder plug you do measure the actual shock pressure, so should be more acurate.

The accumulator just makes the small adjustments faster, by delivering oil/pressure faster than the pump, I think.

 

[siglo]

I don't have the specs for the springs but I would image you can get them from ARB.. I'm using OME860 rear coils.. These coils are the medium duty coils available for my LC model and are rated for 200KG of extra weight I believe.. When there is no water nor fuel in the sub tank, the AHC system doesn't perform as usual and the rear seems a bit bouncy.. I can still get into the low setting with the AHC but it is understandably different from how it behaved when stock.. When I lower the car now the rear just drops into the low position almost instantly.. In the low position the shocks are basically not functioning and the rear end gets extremely bouncy..

I can only have 5 people in my LC since I removed the third row seat.. Last time I've had more than one passenger with me was a couple of months ago and I didn't feel a difference in handling.. I don't even remember how it handled when stock with full passengers to even compare.. My second row seats are rarely used that I'm actually thinking of removing them..

Siglo:
Sounds like you found the balance with the springs you have fitted. Do you have specs for the springs u use?
How does it work without any passengers or other load/water or extra fuel?
Can you still get into LO?[/COLOR]

 

[Jim_Chow]

According to the 03 LX FSM, there are two ways you can measure the pressure in the AHC system. One is with the Lexus hand tester. You plug it into an plug under the DS dash, choose the appropriate function, and it reads some kind of pressure sensor for the system at each wheels (works similarly for the brakes). The other way is with the LSPV SST. You have to bleed the valve (i.e, like if you're bleeding the AHC), remove the bleeder plug and install the LSPV in its place, then turn the ignition "on" so the AHC levels the vehicle. The pressures for each method differ, as the Lexus meter reads a sensor that has some offset or something. Anyways, there's a spec for each method. The FSM says to adjust the t-bars until the front AHC units read a pressure in spec., and that 1 turn of the t-bar amounts to about 28 psi of pressure in the front AHC. I don't recall the FSM saying anything about adjusting the rear, so I'm guessing you'd have to have a supply of different coils and just try them out, as spacers won't reduce the pressure on the AHC at all. In all cases, the AHC should be in "N" mode and fueled up w/ no passengers/gear inside.

So it sounds like there's an AHC pressure sensor (the thing the Lexus hand tester reads) that reads the pressure, then supplies that to the AHC ECU which then shuts the AHC off if the vehicle is overloaded. At least that's my guess.

 

[dinibili]

For the rear would you adjust the setting on the Ht sensor? I presume any changes here would result in an increase or decrease in the shock springing pressure as it attempts to lift or lower the suspension?

Donald

 

[Jim_Chow]

For the rear would you adjust the setting on the Ht sensor? I presume any changes here would result in an increase or decrease in the shock springing pressure as it attempts to lift or lower the suspension?

Donald

There are really two types of adjustments to make w/ the AHC. First is to get the balance between the springs/t-bars and AHC correct. The FSM says to do all the checks w/ the vehicle empty by fueled up. If using the LSPV, you connect it to either of the front dumping force control actuators (the bleeder that's part of the assembly w/ the globe). (turn engine on, set AHC to "L", turn engine off, discharge fluid from the bleeder, remove bleeder, install LSPV SST, start engine, put AHC in "N", then adjust AHC to "L", then back to "N", stop engine. The gauge should read 825+/-43psi. Now adjust the t-bars so you get a pressure reading in this range. One full turn of BOTH the left and right t-bars changes pressure by about 28psi (pressure increases if bolts are loosened). Once you get it right, remove the LSPV by starting the engine, put AHC in "L", stop engine, bleed LSPV bleeder, reinstall bleeder plug, bleed air. FSM says to bleed the bleeder plug w/ LSPV SST installed only once. For the rear, you do the same except connect the LSPV to either of the rear dumping force actuators. The pressure should be 640-697 psi. The FSM just says if the pressure isn't correct, a load may have been added/removed from the vehicle to cause it. Yeah, your ARB rear bar! You'd have to fit stiffer springs in to get the correct rear pressure. The FSM assumes the vehicle has no mods, obviously.

Once you have the pressure correct, you check the sensor heights. There's a detailed way to measure voltages between pins to determine the neutral position. To inspect the height, start engine, put AHC to "L", then to "N". Now for the front, measure the difference between the distance between the center of the front spindle and ground and the center of the bolt on the front lower suspension arm to the ground. It should be 82.7mm. For the rear, the difference between the distance from the center of the rear axle shaft and ground and the center of the front bolt of the lower control arm and the ground should be 71.2mm. You then adjust the sensors to you get these values. Make sure to locktite the turnbuckle bolts if you adjust those.

So the height adjustment via the sensors and spring tension are two separate adjustments one needs to make for the AHC to operate correctly. If you have the Toyota/Lexus hand meter, you don't need to bleed anything. It measures the pressure of each shock absorber via the output pressure of the AHC pump. I'm sure this is what the dealer would do if you took it there.