AHC Specs?: Petrol and Diesel (1 Viewer)

[ikellymo]

Does anyone have a good number for the AHC suspension cylinder bore diameter for the UZJ100 with AHC models, and for bonus points, the HDJ100 (diesel) models with AHC? Anyone know if the diesel AHC system is the same or different? As in, are the target pressures any different than the petrol version?

The bore diameter + pressure will yield the force on all the AHC points.

I'm looking at the HDJ100 for insight on how to tune the suspension for a loaded LX470 AHC.

Thanks in advance!

 

[nukegoat]

Guessing they're the same but the supplemental springs are different.

 

[Moridinbg]

@nukegoat is right. UZJ and HDJ are spec'd with different rear springs and torsion bars.
As long as the pressure is in spec, the AHC doesn't care. Now how do you bring it to spec is a different question.

This thread suggests that non-AHC torsion bars + King springs work pretty well for a loaded AHC vehicle.

 

[ikellymo]

Thanks guys, I found the part numbers of the different springs, listed here (I'm also looking for spring rate numbers). Since the AHC is designed to be an active damping system that carries part of the vehicle weight, I'm wondering if Toyota designed it to also support more weight in the diesel version, or if they just put the additional weight on the springs, as both of you suggest. There seems to be some debate in the forums of how much weight the AHC system can handle, so I thought this might offer some insight into what Toyota thinks.

For example, if the AHC is designed to take 20% of the weight, then it will be much less effective if the vehicle is loaded up, the suspension tuned to regain target pressures, and now the ACH only holds 5% of the target weight. Of course I'm just making up these numbers, which is why I'd still love to know the actual bore diameters, or if Toyota has higher target pressures in the diesel version. Anyone have a HDJ FSM?

 

[Moridinbg]

This is the global FSM - https://lc100e.github.io/manual/
It won't tell you those differences. But if you dig deep enough in the part numbers here - Toyota parts catalog - you will see that the AHC system is exactly the same between HDJ & UZJ, only the spring and torsion bars are different.
The factory carrying capacity of the AHC, when within the correct neutral pressure is about 550kg (~1200lb). You can find the exact number somewhere in the first link.

I too have wondered if two cars with the same neutral pressures due to springs, but one is say 500kg heavier than the other, will behave noticeably different. My theory is no.

 

[ikellymo]

@Moridinbg Awesome, thanks! I'll have to see if I can find the carrying capacity of the AHC in the manual. It might be quite a search! But can def start with 550kgs.

 

[IndroCruise]

@Moridinbg Awesome, thanks! I'll have to see if I can find the carrying capacity of the AHC in the manual. It might be quite a search! But can def start with 550kgs.

Hi @ikellymo -- I may be misunderstanding your purpose.

Before getting to that, my understanding is that the AHC/TEMS system – meaning the whole bunch of AHC/TEMS components end-to-end from front bumper to rear bumper – is common across all LC100 models (whether fitted, with either 2UZ-FE gasoline engine or 1HD-FTE turbodiesel engine) and also is common with LX470 models (2UZ-FE gasoline engine only) as well.

It is the same system, same design, same components across all of these models where AHC/TEMS is fitted, with only a few minor differences regarding detailing of some brackets, switches, relay positions, AHC pump position, some pipe and harness routes and various fittings such as DLC3 location, height control and damper switches on central console etc, to accommodate the differences between right hand drive and left hand drive. Nothing in the FSM at https://lc100e.github.io/manual/ reveals any different versions of the stock AHC/TEMS system for different engine versions nor has any significant difference been found on any IH8MUD post – unless any other IH8MUD Member can point to it?

As @Moridinbg already notes, there are some differences in rear coil springs between right hand drive and left hand drive vehicles related to driver position and fuel tank position and whether the additional fuel subtank is fitted or not.

For vehicles fitted with AHC/TEMS, there are differences in torsion bars and torsion bar Part Numbers for LC100 fitted with the 2UZ-FE gasoline engine versus LC100 fitted with 1HD-FTE turbodiesel. Heavier duty front torsion bars have been used by Toyota to compensate for the heavier turbodiesel engine in LC100 with AHC/TEMS.

The Height Control Accumulator is Part No. 49130-60010. It is the same across all models.

I have just purchased a new Height Control Accumulator for my 2006 LC100 with 1HD-FTE turbodiesel and AHC/TEMS and so I had good reason to double-check all these details.

One way to check the details is simply to go and ask a Dealer's Parts Department to look up the Part Numbers. A 'sanity check' can be done on-line by entering the Part Number on the Megazip website (a reliable wholesaler of Toyota/Lexus OEM Parts in Singapore with a good on-line catalogue) and then scroll down to the the list of model types, click on these one by one and match the actual Landcruiser models to which the part applies. For example, go to:

49130-60010 - Accumulator Assy, Suspension Control Pump, Toyota OEM | Megazip.net

In my own case, at this link I go to LANDCRUISER then click on HDJ100 then scan the list looking for my model which is HDJ100R-GNAEZQ as plated on my vehicle – and sure enough this Model appears in this list to which Part No. 49130-60010 applies.

Looking under my actual vehicle I also can see Height Control Accumulator Part No. 49130-60010 showing clearly on the original Height Control Accumulator fitted to the vehicle at the factory in Japan in 2006.

For comparison, a search for suspension details for a US-marketed LX470 such as Model UZJ100L-GNAGKA arrives eventually at the same Height Control Accumulator Part No. 49130-60010. See Height Control (Auto-Leveler) for 2002 - 2007 Toyota LEXUS LX UZJ100 | U.S.A. sales region, , 17824902-917385

I usually cross-check with Partsouq (a reliable wholesaler of Toyota/Lexus OEM Parts in Dubai, also with a good on-line catalogue) to be sure about Part Numbers and also to check prices. Working through PartSouq Auto Parts Around the World using Model Types leads to the same Height Control Accumulator Part Number 49130-60010 for LC100 and LX470 vehicles with 2UZ-FE the gasoline engine and also for the LC100 with the 1HD-FTE turbodiesel engine.

The link https://lc100e.github.io/manual/ is an excellent FSM source but the the specific internal dimensional details you seek for the Height Control Accumulator are not shown anywhere in this Manual.

However, there are some drawings without dimensions although some volumes are shown. At the FSM link, suggest from the top tab through New Car Features > CHASSIS > Suspension > Active Height Control and Skyhook TEMS.

This path leads to an illustrated summary of the AHC/TEMS system including a cross-section of the Height Control Accumulator. Dimensions are not shown but perhaps by taking external measurements of an actual accumulator it may be possible scale the approximate internal dimensions from the drawing. By the way, this summary also includes at the bottom of the second page the limiting weight conditions for a stock vehicle fitted with AHC/TEMS.

The usual and quite effective strategy for heavier loads on LC100 and LX470 is to recognise that the aim is to keep the front and rear AHC/TEMS pressures within their FSM-specified ranges (actually towards the lower end of the range) for best damping performance (and to avoid compromising the hydraulic system and seals with over-pressure) -- and then modify the mechanical suspension components -- specifically: adjust, re-index or replace front torsion bars, and, make a choice at the rear between airbags fitted within the coil plus new OEM springs possibly with spacers, or, stronger springs (KING KTRS-79 is a common choice). In my own case, tightening torsion bar adjusters at the front and replacement of rear springs with KING KTRS-79 was sufficient. I already had some airbags so they went in as well -- but it remains to be seen whether they are a necessary addition.

In summary, different Height Control Accumulators are not available (and if they were then different mapping of the AHC/TEMS ECU would be involved) and so it is suggested that the well-tested strategies for increased load be considered, as discussed in many IH8MUD threads. Naturally, GVWR remains a consideration.

 

[ikellymo]

@IndroCruise Thanks for the detailed response, that's great and good to hear from someone with a turbodiesel. I still need to put some time in reading through your links.

Would you mind posting a measurement of your torsion bar diameter/circumference? I think you have P/N 48161(/2)-60020 on the HDJ, whereas I have 48161(/2)-60040 on the UZJ. I've dug up references to most all the available tb diameters, but the list is lacking the OEM diesel versions. I explain my thoughts more in this post. It would help to estimate what torsion bar options would be optimal for a loaded AHC.

 

[IndroCruise]

@IndroCruise Thanks for the detailed response, that's great and good to hear from someone with a turbodiesel. I still need to put some time in reading through your links.

Would you mind posting a measurement of your torsion bar diameter/circumference? I think you have P/N 48161(/2)-60020 on the HDJ, whereas I have 48161(/2)-60040 on the UZJ. I've dug up references to most all the available tb diameters, but the list is lacking the OEM diesel versions. I explain my thoughts more in this post. It would help to estimate what torsion bar options would be optimal for a loaded AHC.

Thanks @ikellymo -- I can now see where you are going. In reply, I am travelling without access to a vernier or micrometer at the moment. I used a paper tape to measure the circumference of the original front torsion bars which are still in place on my vehicle and came up with circumference = 82 millimetres, then divided by 3.142 (pi) which gives a diameter of 26.1 millimetres. My understanding is that the Part Numbers for my torsion bars are 48161-60020 (R) and 48161-60020 (L) as you also suggest. I don’t have any knowledge of the design issues such as particular steel material nor material properties such as shear modulus and how much that might change with number of cycles, age, etc. I did see some hearsay that some torsion bars were longer than others but I have not been able to run that to ground.

If @Moridinbg is still working under his vehicle on his mega-project, he may be able to offer better measurements?

Hope all goes well with your plans. (By the way, if not already considered, suggest including reinforcing brackets where the torsion bars join the Lower Control Arm – popular in this part of the world to alleviate cracking at LCA under hard use with heavy loads).

 

[ikellymo]

Thanks! Thats that's great info. @Moridinbg I checked out your build thread, looks pretty awesome.

Here's the table I'm putting together, just to give an idea.

Variant	PN Variant	Link	Diameter (mm)	Diameter Reference	Calculated Spring Rate	Price	Vehicle	AHC	Vehicle Curb Weight	AHC Corrected Weight (VCW-1200lbs)
Toyota OEM - 48161-60040	48162-60040	FRONT SPRING & SHOCK ABSORBER	25.5			$680.08	UZJ100 AHC	Yes	5004	3804
Toyota OEM - 48161-60020	48162-60020	Front spring & shock absorber for Toyota Land Cruiser HDJ100R - Auto parts	26.1	AHC Specs?: Petrol and Diesel			HDJ100 AHC (diesel)	Yes	5666	4466
Toyota OEM - 48161-60030	48162-60030	FRONT SPRING & SHOCK ABSORBER	28.87			$822.00	UZJ100	No	5004	5004
Toyota OEM - 48161-60010	48162-60010	Front spring & shock absorber for Toyota Land Cruiser HDJ100R - Auto parts					HDJ100 (diesel)	No	5666	5666
OME			30.5
Sway Away - 1661		Torsion Bar Set - Toyota F100, Land Cruiser (Late Model) & LX470 Gas - Sway-A-Way | Racing Technology	31			$213.00
TJM			32
Ironman			32

Perhaps the data could be plotted like this to be helpful for selecting new torsion bars, but I hoped that these points would fall on a line so that we could extrapolate. The AHC corrected weight is just the curb weight - 1200lbs.

Its a work in progress and definitely some gaps that need to be filled in. Some preliminary research is telling me that metallurgy doesn't actually change the spring rate much, only perhaps reliability, strength and yield points (transition from elastic to plastic deformation). I'll try to post some more info on this too.

 

[IndroCruise]

Thanks! Thats that's great info. @Moridinbg I checked out your build thread, looks pretty awesome.

Here's the table I'm putting together, just to give an idea.

Variant	PN Variant	Link	Diameter (mm)	Diameter Reference	Calculated Spring Rate	Price	Vehicle	AHC	Vehicle Curb Weight	AHC Corrected Weight (VCW-1200lbs)
Toyota OEM - 48161-60040	48162-60040	FRONT SPRING & SHOCK ABSORBER	25.5			$680.08	UZJ100 AHC	Yes	5004	3804
Toyota OEM - 48161-60020	48162-60020	Front spring & shock absorber for Toyota Land Cruiser HDJ100R - Auto parts	26.1	AHC Specs?: Petrol and Diesel			HDJ100 AHC (diesel)	Yes	5666	4466
Toyota OEM - 48161-60030	48162-60030	FRONT SPRING & SHOCK ABSORBER	28.87			$822.00	UZJ100	No	5004	5004
Toyota OEM - 48161-60010	48162-60010	Front spring & shock absorber for Toyota Land Cruiser HDJ100R - Auto parts					HDJ100 (diesel)	No	5666	5666
OME			30.5
Sway Away - 1661		Torsion Bar Set - Toyota F100, Land Cruiser (Late Model) & LX470 Gas - Sway-A-Way | Racing Technology	31			$213.00
TJM			32
Ironman			32

Perhaps the data could be plotted like this to be helpful for selecting new torsion bars, but I hoped that these points would fall on a line so that we could extrapolate. The AHC corrected weight is just the curb weight - 1200lbs.

View attachment 2402936

Its a work in progress and definitely some gaps that need to be filled in. Some preliminary research is telling me that metallurgy doesn't actually change the spring rate much, only perhaps reliability, strength and yield points (transition from elastic to plastic deformation). I'll try to post some more info on this too.

Hi @ikellymo -- just checking in concerning torsion bar details as fitted to my 2006 LC with AHC and 1HD-FTE turbodiesel. I asked my Independent guy to provide actual measurements. The torsion bars are still the original factory-fitted versions. He measured them while the vehicle was on the hoist and advised as follows:

Diameter: 25.7 millimetres (measured by vernier)
Length: 1,250 millimetres (measured in situ by tape between splines)
Markings: "60020 L" and "60020 R" are still visible.

Our revised understanding is that the Part Numbers for my OEM torsion bars are 48161-60020 (R) and 48162-60020 (L).

I am unable to confirm for sure whether the torsion bars on similar vehicles fitted with AHC and 2UZ-FE gasoline engine are of different diameters and lengths.