Was the AU IRS a bad setup? - Page 2

HP Dude · 10-12-2005, 12:13 AM

FWIW, I'd say the AU, as a pure double wishbone set up, is technically a better design than the control blade IRS. But it was a little heavy. Control Blade is almost as good, and lighter, hence its adoption in the BA series.

Quote:

Originally Posted by Casper

ok, lets set the facts straight as far as LSD/IRS on the XR6's
There are 2 XR6s as we all know, the HP and the VCT. Both were avaliable from the very first AU (appox sept 98). In tha AU 1 BOTH came standard with LSD.. it was not an option. It was a standard feature..3.45 LSD. In addition the XR6 VCT (sedan) came STANDARD with IRS AND 3.45 LSD (mine has it and is a Nov 98 car that hade NO options fitted).
The XR6 VCT continued with IRS AND 3.45 LSD for the entire model life (AUI, II, III) whereas the XR6 HP lost the LSD as standard part way through the AUII model and it became an optional extra.

As for the IRS.. it is amazing to say the least. I would say its only shortfall over the BA IRS is weight (so yes, the BA IRS would be "better")... but given the "plumper" bodyweight of all the BA/BF's, any benifit it may have gained was lost by the weight of the car. Now an AU with the BA IRS... that would be DAMN impressive!

Thanks for setting the record straight.

Lukeyson · 10-12-2005, 12:34 AM

When BA 1st came out i remember reading a few articles saying the AU's IRS had better communication as to where its going

phillyc · 10-12-2005, 01:03 AM

Quote:

Originally Posted by Stampy

STD fitment on a AU I XR6 VCT is IRS and LSD 100% guaranteed ,I owned one for 2 years or more then got the XR8

Grip levels on the AU1 was fabulous compared to non IRS EF i had I use to hit a corner hard and wait for the slid , but it never moved .

LSD Had a dark red filler plug from memory
STD diff had black

Suspension/rear description Independent, double wishbone, lower transverse links, coil springs and anti-roll bar.

Yeah, my VCT has awesome rear grip. Love that and the communicative steering. Very enjoyable.

PS the weight difference between the live axle and the Double wishbone AU assemblies is 80kg. I dont know the difference between the live-axle in the BA/BF and the Control Blade. I too would guestimate about 50-60kgs. ie saving of 20-30kg between the two IRS setups.

10-12-2005, 01:46 AM

Quote:

Originally Posted by Casper

ok, lets set the facts straight as far as LSD/IRS on the XR6's
There are 2 XR6s as we all know, the HP and the VCT. Both were avaliable from the very first AU (appox sept 98). In tha AU 1 BOTH came standard with LSD.. it was not an option. It was a standard feature..3.45 LSD. In addition the XR6 VCT (sedan) came STANDARD with IRS AND 3.45 LSD (mine has it and is a Nov 98 car that hade NO options fitted).
The XR6 VCT continued with IRS AND 3.45 LSD for the entire model life (AUI, II, III) whereas the XR6 HP lost the LSD as standard part way through the AUII model and it became an optional extra.

As for the IRS.. it is amazing to say the least. I would say its only shortfall over the BA IRS is weight (so yes, the BA IRS would be "better")... but given the "plumper" bodyweight of all the BA/BF's, any benifit it may have gained was lost by the weight of the car. Now an AU with the BA IRS... that would be DAMN impressive!

Always new you would come up with all the facts.

LOL

Your an encyclopedia an AU's

Alan

**FTE217** · 10-12-2005, 02:44 AM

Quote:

Originally Posted by buickman

Third time? I've still the original mounts but have remove them once to check when I lowered the car. I would be ****ed to for the third time

Try Kelray on 1800 245 748 for tech support or kelray@kelray.com.au as they are the manufacturers of nolathane products which might have a product that would last longer in your car.

Me thinks being extra low and 19's don't help at all :dr_Evil:

BlueJ · 10-12-2005, 10:34 AM

I haven't driven an IRS-suspended AU, nor a BA, with a view to comparing their handing or grip thresholds...so my comments are based on what I have read.

The AU IRS setup is a classic double wishbone IRS. Design-wise there is absolutely nothing wrong with it at all. It has all the advantages and disadvantages of that design.

The double wishbone design has been around for 50+ years, and it gives excellent control over toe and camber as the suspension compresses due to bumps and body roll. This means that the tyre tread stays nearly parallel with the road surface as the suspension moves through its full range of travel. The tyre gives the most grip when its tread is parallel with the road surface. And of course the tyre wears evenly across the tread.

Hence the AU IRS was well known for giving excellent handling and excellent grip. It is a premium IRS.

Disadvantages? As some have mentioned it is heavier than the live axle, and chews out the upper mounts. Design-wise, with double wishbones there is the ride-handling compromise. The tight control over the suspension as it moves means that there is little 'give' in the suspension. Control results in good handling, 'give' results in a good ride. Few people on this forum would complain about good handling...

With double wishbone IRS, the engineers can choose the spring rates and bush compliance to give fantastic handling, or a superb ride - but not both at the same time. Of course the engineers can choose to mix reasonable handling with a reasonable ride. I remember most reviews of the AU Fairlane praising the handling, and a few reviews complaining about a jiggly ride. So we could conclude that the good handling of the AU IRS cars came at the expense of ride quality.

The 'control blade' IRS design used in the BA and Territory is a new design originally developed by Ford engineers in Europe (I think). It was first used on the Focus Mk1, and is suitable for small FWD cars as well as large RWD and AWD cars.

Control blade IRS is a step forward from double wishbone IRS because it allows for an excellent ride while giving excellent handling. So the engineers are less constrained by the ride-handling compromise. Control blade IRS achieves a better ride while giving the same good handling as a double wishbone IRS.

Technically speaking, control blade de-couples the vertical and lateral forces on the rear suspension. The design allows for compliance when the wheel moves vertically - this means that the ride is good. However - and this is the key point - the compliance in the vertical motion doesn't result in loss of control over toe and camber.

In other words, the tyre tread stays parallel with the road surface as the suspension compresses, giving good handing as with double wishbones, but there is also vertical compliance so the bumps are better absorbed, so the ride is better too.

With double wishbones, tight control over toe and camber comes at the cost of compliance with vertical movement. I think this is the main difference between these two IRS systems.

All BA reviews that I have read praise the fantastic ride, even in the sport models. And BAs are universally praised for their excellent handling and rear-end grip. So it looks like the Ford Oz engineers made the most of the potential that control blade offers.

outback_ute · 10-12-2005, 12:15 PM

Sorry for the slightly off-topic question (now that the original has been answered) but earlier it was mentioned that you could stick AU irs in an XE-EL - has anyone actually seen this done?

LUXO_8 · 10-12-2005, 12:21 PM

i havent, but i have gone over the whole rear of both cars with a measureing tape, as well as checking out the cut-away setup they have at the ford discovery center...

the setup has its own "cradle", which mounts to the chassis.

the front mounts attach to the factory front lower arm mounts, and for the rear you have to remove the brackets off the chassis and weld them into the earlier "rails".
the shocks mount in the same shocker mounting position i believe

the only thing keeping me from doing it is
a) you'd just about have to get an engineers certificate, and
B) i simply cant afford to at the moment...

but it would definatley be something i'd love to do in the future....

BlueJ · 10-12-2005, 03:58 PM

I'd like to know if an AU IRS can be retrofitted to any of the leaf spring models, and what would be involved?

LUXO_8 · 10-12-2005, 06:08 PM

would be a LOT more involved as you need the existing lower arm mounts as in the XE-EL

it'd just about require a half floor graft or something like that.......a lot of work id guess

**FTE217** · 10-12-2005, 06:23 PM

Quote:

Originally Posted by BlueJ

I'd like to know if an AU IRS can be retrofitted to any of the leaf spring models, and what would be involved?

Why bother :hihi: for the grief and trouble just buy a nice AURX8 or T3 :hihi:

10-12-2005, 10:30 PM

I have raced both AU & BA with IRS at the drags & on track days & theres not much in it. The AU is a wisker better, it hooks up better at the drags, & also gives better drive on the track. I think the BA is a tad more heavy from what I can remember..

HP Dude · 10-12-2005, 11:49 PM

Quote:

Originally Posted by ELMER FUDD

I have raced both AU & BA with IRS at the drags & on track days & theres not much in it. The AU is a wisker better, it hooks up better at the drags, & also gives better drive on the track.

Yeah, this makes sense to me. I still think the double wishbone is a 'purer' design.

BlueJ · 11-12-2005, 10:50 AM

Quote:

Originally Posted by MADNC_8

would be a LOT more involved as you need the existing lower arm mounts as in the XE-EL

it'd just about require a half floor graft or something like that.......a lot of work id guess

I was wondering if there was room under the rear floor of the leaf spring cars to fit a 'cradle' that would provide the mounting points for the IRS?

MADNC_8: I don't suppose you have measured up any of the leaf spring cars? What do you think?

It would be a lot easier and cheaper to fabricate and fit a cradle than it would be to cut and replace the rear floor, wouldn't it? If there was room for the cradle, that is.

Ford used this 'cradle' idea to allow the IRS to be fitted to the body of the Watts link cars, without requiring body modifications. So the cradle concept provides enough strength and durability if done properly.

outback_ute · 11-12-2005, 08:00 PM

Cradle aka subframe, the Jag irs uses the same idea, has gone into heaps of hot rods. Modding the subframe is a good idea, as you already have 4 mounting points from the leaf springs, they are just in a different location from the Watts linkage mounts.

BlueJ · 11-12-2005, 08:14 PM

Quote:

Originally Posted by outback_ute

Cradle aka subframe, the Jag irs uses the same idea, has gone into heaps of hot rods.

That's what I thought may be the case. Any problems with the subframe moving relative to the body?

outback_ute · 12-12-2005, 12:33 AM

It is mounted via rubber bushes, it is designed to have a bit of compliance for nvh reasons, very similar to engine mounts really

jspec_sti · 12-12-2005, 10:55 AM

Thanks for the info guys. Great stuff. Went for a run yesterday with a mate who owns an AUIII XR6 VCT (very nice machine) out to Blackwood then through Trentham and Woodend. Nice roads to test out the IRS, especially the run up the hill from Greendale to Blackwood.

I travelled behind the XR6 because (a) it's damn quick around the bends and the V8 really needs to wind up before it can catch it, and (b) I wanted to get a good look at the IRS in action.

I must say I was more than impressed with seeing the IRS in action. My mate hardly used his brakes at all, and seeing the suspension grip and pull the car through corners was quite amazing - the back wheels just seemed to grab the road, the back end "lowered" itself a bit and off it went powering out through the corners.

Well done Tickford.

outback_ute · 12-12-2005, 12:52 PM

Here is a pic of the AU IRS from the Discovery Centre yesterday

BlueJ · 12-12-2005, 01:22 PM

Sorry to keep this thread off the original topic, which was how well the AU IRS works.

Great photo, outback_ute. Thanks, it shows the configuration very clearly.

No wonder it's heavy! Those wishbones look like they could take a lot of abuse. Cast iron was used for cost control reasons, apparently.

Looks like there are only four mounting points - the two at the front, which mate to the existing lower control arm mounts in Watts link cars, and the two top mounts.

Re: subframe movement. The bushes between the subframe and the body would have to be pretty strong to control fore-aft and lateral forces. I wonder just how much compliance there is?

Does anyone make polyurethane bushes for the IRS subframe? There would probably be a lot more NVH with harder bushes though.

LUXO_8 · 12-12-2005, 06:03 PM

Quote:

Originally Posted by outback_ute

Here is a pic of the AU IRS from the Discovery Centre yesterday

there is also an operational display upstairs that shows how it mounts to the chassis....

Van D · 13-12-2005, 03:02 PM

Quote:

Originally Posted by MADNC_8

the AU setup is great. its also able to be retrofitted into XE-EL as well...which would make a great conversion...

Is that so?

Good news for me. I'm planning on finding a written off AU XR6 or similar and get the engine/gearbox out of it.
If that's the case, I might just get the whole rear setup as well if it's undamaged and it could be worked in there, anyone know if that would be possible?Also, how much that would roughly cost (XR6 engine, gearbox, IRS setups, diff etc)?

Mark351 · 13-12-2005, 03:10 PM

Quote:

Originally Posted by HP Dude

Incorrect. AU1 XR6HPs came with LSD standard. Series 2 and 3 did not; it was an option.

Incorrect. AU1 XR6HPs and early AUII's came with LSD standard. Late Series 2 and 3 did not, it was an option.

_2:

HP Dude · 13-12-2005, 03:24 PM

Yes, well, ok!

blackers10 · 14-12-2005, 04:08 AM

my AU1 Fairlane ghia 6 cyl with VCT has traction control and IRS but no LSD sadly!!
would love to get 1 fitted tho and if it would screw with my traction control..

geckoGT · 14-12-2005, 04:11 AM

Quote:

Originally Posted by blackers10

my AU1 Fairlane ghia 6 cyl with VCT has traction control and IRS but no LSD sadly!!
would love to get 1 fitted tho and if it would screw with my traction control..

The only way it will mess with your traction control is you will spend less time on it. All BA Xr's (sedans) have traction control and LSD

blackers10 · 14-12-2005, 04:19 AM

cheers gecko

any idea how much an LSD conversion will cost me? im guessin in the 600-800 mark?

geckoGT · 14-12-2005, 09:46 AM

Not really sure, I would thik that would be pretty close to the money. Time to give your favourite diff specialist a call. Certainly a worthwhile mod.

Paxton · 14-12-2005, 10:17 AM

Quote:

Originally Posted by geckoxr8

The only way it will mess with your traction control is you will spend less time on it. All BA Xr's (sedans) have traction control and LSD

Even the manuals?

I remember looking at a BAII XR6 in Manual, and I was told that to get traction control I had to get an Automatic.

Gambit · 14-12-2005, 02:47 PM

Quote:

Originally Posted by paxtonandrew

Even the manuals?

I remember looking at a BAII XR6 in Manual, and I was told that to get traction control I had to get an Automatic.

All the manual xr's (not including xr6 & the utes) & fpv's I have been in have traction control.