IRS for Sigma GJ-GN

[Cottees]

I have been posting this in another thread, so I thought I'd post it in the right section. I am fairly certain that an IRS set up from a Starion, Galant Sigma or Eterna could fit into an Aus-Spec Sigma, without needing major modifications. Here is my research so far, just need to get others to either confirm part of it, or to try it out.

while researching for another thread (http://sigma-galant.com/viewtopic.php?f=24&t=1936), I came across a discovery:


See these 2 holes that appear to do nothing? I think they are just a left over from the IRS Sigma that wasn't changed from the Jap-Spec Sigma. You can't really see from this photo, but they seem to be in the same place and same angle as in this photo:

It is just in the Scorpion/Eterna, there is bolts there for the cross member. You can see on the other side of the Eterna photo that there is another bolt by itself further forward from the other 2 bolts. There is a hole in the chassis just like that too. I might have to try and get hold of an IRS set up to test out this theory, but the evidence points to it being a 'near' bolt in.

The distance between the 2 holes is ~105mm, and distance between the 2 rear most holes is ~760mm. Hopefully someone with IRS could kindly measure their cross member for us.



Here shows an image of a Starion's rear strut towers, and on the right hand side, you can see where the bolts go through the chassis to the cross member.

Instead of putting in a rear strut tower into the Sigma, which would require a bit of work, a coil over set like this would be good:

The top can mount to the mount that is already there the stock shocker, and a 2 bolt adapter could be made to mount to the Starion IRS.

Here is another example that might work :


When I say 'Sigma', I mean Sigma GJ-GN. The coil overs at standard height would need to be a little shorter than the stock shocks since the mount on the Starion axle is higher, and the adapter would make it a little higher again.

The Sigma GE-GN and the Scorpion all use a Monroe 15-0405+ rear shock absorber. Compressed length is 372mm (14.6") and non-Compressed is 607mm (23.9"). Bilstein have something that looks similar, but is a coil over. The model A411152530 and A411152510 have a compressed length of 280mm (11") and non-Compressed of 381mm (12.5"). With an adapter on them to mount it to the IRS, it would end up around 2" lower than it was before. The 2 Bilstein coil overs I have mentioned I don't think are adjustable, but if they were, they might be able to raise the car to stock height. Or, you could leave it lower. This one place that is selling them, which is where I got the measurement info from : http://www.heasmans.com.au/bilstein/product/index.html . They are "Hot Rod Shocks".

[Cottees]

Something dirtygalant pointed out was the front cross member on the IRS set up. There is a hole in the chassis at around the same position that would line up with that. I would have taken a photo, but my Sigma is in a 1 car garage at the moment, and the trolley jack was in the way.

[dirtygalant]

another thing is, you'ld have to totally change the bottom end of those coilovers so they support the hub - the IRS setup relies on the strut to as a major component of the suspension, it handles most of the load and controls the rate of camber etc - it's just like the macpherson strut at the front of the car!

just like a Starion the struts protrude about 60mm into a rather large clamp attached to the hub - the two bolt flange at the top is just to keep it staying put.

I had a live axle Sigma in my garage next to my Eterna and while I was under the car removing the diff from the Sigma I did not notice a great deal of similarities between the live axle and IRS models. I honestly think it's alot more difficult than you think, the IRS chassis is just that much different that they completely designated a whole different chassis number for them - A164A as opposed to A163A for the live axle models.

[Cottees]

Next time you are with your Eterna, could you take some pics of the top of the wheel well where the strut mounts, and a shot from inside the boot?

[dirtygalant]

from inside the boot it looks almost the same as inside of a Starion hatch, except notch-back body style instead of hatch of the Starion. In the meantime here's some semi-relevant pics I found on my photobucket:
























also, 10 points if you can name that green car in the background



Basically if you can find any pics of the wheel arches of a Starion, it'll be identical to the rear end of my Eterna. The Starion is based apon the chassis of my car and is 99% the same.

[Cottees]

From what I have seen and read, the Sigma and Starion have similar front struts (Starion have larger vented brakes), and have the same front engine cross member. Putting the IRS into the Sigma might not be the easiest, but it is worth checking out.

[dirtygalant]

Well yes the Sigma and Starion are going to be very similar mechanically, my Eterna is the two door coupe version of the four door 80-84 A16#A series Galant/Eterna-Sigma, and then the Starion was further developed from the two door Galant/Eterna-Lambda.

The main difference in the front end between two door and four door is the way the front sway bar mounts, in my Eterna the Starion the sway bar has seperate mounts to the chassis rails, while in the four door Sigma sedans and wagons the sway bar mounts to the strut bar chassis mount. The main difference between my Eterna and the Starion front end is the angle of the struts, and mine uses four bolt strut tops like the Sigma sedan and wagon, while Starion uses three bolt strut tops. Crossmembers, struts (by themselves, not including brakes), suspension arms, strut bars, bushings etc are the same between my coupe, Sigma sedan/wagon and Starion. Another difference is in the steering rod - the Starion has balljoints as part of the main drag link rod, while on mine and the Sigma sedan/wagon the inner rod ends and the idler/pitman arms have the balljoints and the drag link just has holes.

Mine also has the same vented front and rear discs as the Starion, along with the 4G63 ECI-Turbo and KM132 box - the A164A platform was the first to showcase this in 1980, before the Starion came along in 1982.

[Cottees]

I just roughly measured the mounting on a full Starion rear end i picked up on eBay a while back. I had the same kinda idea a while back but never even bothered looking properly for anything like that as i have a wagon which is based on the gh design so unlikely to be that similar. At the very least i figured it might come in use as parts to build a decent diff if i needed too or test out swapping diff centres with the many diffs i have here.

If you were looking at doing this to gain independent rear suspension then it may be worth it but if you want an lsd to go with it i would be looking at a 180sx rear instead. It may require a little more modification to fit but the lsd would be more readily available. For a Starion lsd setup you are looking at over a grand typically.

It may be possible though to combine the two and use the rear diff cradle from the Starion and combine that with a suitable different model independent rear setup with some playing about and brackets.

The distance between the holes centre to centre is about 100mm, the distance at the rear mounting holes is 760mm and the front mounting holes is about 710mm.

From the measurements I have taken, that looks to line up to holes already in the chassis. I would like to stick with Mitsi parts if possible, but might look at other options too. At the moment this is all 'what if' till I can get my hands on a cheap set up, or someone else tries it. It is times like this that I kick my self for not picking up the front and rear suspension from a Starion I found at U-Pull-it. it was there, had cash for it, but I thought I better not. Idiot! Later I might try and get just the sub frame, as in everything minus the diff centre and drive shaft, and do some experimenting.

[panda]

From what I have seen and read, the Sigma and Starion have similar front struts (Starion have larger vented brakes), and have the same front engine cross member.

Yes, they are similar, but but identical. The Starion struts are about 8mm shorter than the GJ strut, & the camber angle (angle between strut & stub axle) is slightly different as well.
However, the Starion strut will bolt straight in to a GJ Sigma without any issues.
panda.

[Cottees]

I did some educating my self about MacPherson suspension systems. Some of the ideas I had about getting the IRS bolted into the non-IRS Sigma look to be wrong. I do still think it is possible to do. I probably wont know for sure till I try it, so I might try and get my hands on an iRS setup to try it out.

[lpgalant]

good old leyland marina, lol, ps why r u doin this conversion, or thinking about, is it just for a lsd, or trackion..................

[Cottees]

I am thinking about doing it cause it is different, and no one else (that I have seen) has attempted to do it on an Aus-Spec Sigma. Sorta like my unconventional intake mod.

[woops]

The biggest problem i can see you having is sorting out the strut towers as you would have to get them pretty close to perfect as compared to the starions. Any change in angle when compared to the starion setup would result in undesirable camber and caster problems. Also you would have to get them welded to a acceptable standard to pass engineer certificate. Although I do remember seeing a seeing an LA lancer which had modded a 180sx suspension into it on the site previously.

You could probably get that starion from the wreckers and get a rear cut from it to be able to measure up all the mounting points and have a comparison to what you have.

[mbrallying]

Maybe weld in a big section of the starion floor with the towers and crossmember mounts and everything.

Big job but do-able, and all will line up.

Cool idea but mate, always like seeing stuff thats different.

Mark..

[Cottees]

That would be a pretty good idea. If I got the rear cut, cut the towers + wheel wells out of the Starion, and place them over the existing wheel wells, cut out part of the Sigma wheel well to allow the strut to pass, then weld the Starion wheel well to the Sigma wheel well. it'll make it a little heavier, but it would be very strong. Because I am in a place with room for 1 car, and I have 2 cars at the moment, I wouldn't have room for another half a car. Might be easier for me to just get it cut at the wrecker. That is something to try in the future when I have a little more money. Currently I have access to an angle grinder and MIG welder, but it might be an idea if I do some MIG welding first before attempting something like this.

Another idea I had was to use the strut from a Starion, and shorten it. Then make a bracket so the top of the strut can mount onto the existing place the shock absorber mounts to. That would involve cutting the bottom strut sleeve and putting in a shorter shock absorber and spring. at the top of the strut, I could make an adapter that would fit into the existing mount, and the strut top can bolt to that. Just would need some bushes like that which is used between the front control arm and the sway bar. A plate would be welded to the bottom of the adapter so the spring could rest against that. My previous idea of putting in a stock style shock absorber with coil over was a bad idea. The bottom of the strut has to be fixed and non-tilting to the control arm. I think the strut would be at the correct angle, and with a bit of re-enforcement, it should be strong enough. That would be an option to prevent any cutting of the car, but would probably would need a little welding still.

With the mounting of the rear cross member in both cases should only require a bit of drilling. there is already 2 holes each side at the bottom of the chassis. It would just require drilling through to the top part of the chassis. It would require drilling very straight, something I am not the best at. The drill would come up through the floor of the boot next to the wheel wells. Would just need to put through the mounting bracket, and bolting the cross member to that. For the second cross member for the IRS, there looks to be a hole at the bottom of the chassis already like the rear holes, but I havn't checked it out properly yet since there is a car jack in the way at the moment. That would all be the 'easy part'. It is just a matter of sorting out the struts.

There is definitely pros and cons for and against both ideas. Cut and weld idea would use stock parts, but would need to mod the body. The shorten and adapter idea would not require cutting the body, but would require a custom strut to be built from scratch or from a stock strut.

Cool idea but mate, always like seeing stuff thats different.

Yeah. I like seeing things a little different. I could just do what everyone else has done, or I could try something new. If it doesn't work, then it has been tried and tested. If it works, then it gives others ideas on what they could do too.

[panda]

Cottees, I have a complete spare Starion rolling shell with the IRS still intact. If you want to borrow the car any time to make measurements & comparisons, you are welcome. (No its NOT for Sale.) But I realise you are short of space ATM

[Cottees]

Thanks for the offer. I might take it up when I get my Sigma running, and can take it for a nice drive to check it out. At the moment I live in a unit that has space for a car in the carport, car outside the carport, and another in front of the outside car if I get really close. I have had my Sigma in the carport, Commodore just outside, and a Holden Nova in front of that, and it only just fit. When I crashed my first Sigma, I had it sitting on tyres for a while. One of my neighbours got real shitty about it. If I could find a shell, or intact rear half, I might have a couple people that could store it for me. If I did get at least the rear half of a Starion, Sigma or Scorpion, and I end up not being able to use it, I shouldn't have too much trouble selling off at least the IRS stuff.

[panda]

If you find a place one day to store it, I'll bring it to Adelaide for you. I go there every 6-8 weeks for work, so no big issue for me.
panda

[Cottees]

That would be great. I may be moving soon, so hopefully it is to somewhere that has more room.

[FUGITIVES]

What about an skyline R33 Suspension, anyone tried this?

[Cottees]

I am not sure, but I think the IRS from an R33 would be too wide for the Sigma. I have checked out the width of the EVO IV IRS, and that would just fit under the Sigma with stock wheels with around 3mm either side. Both of them could fit if you can modify the diff to be shorter, or make the Sigma wheel arches wider.

[FUGITIVES]

well we are planning to try one on mines and we do have to shorten it by about 4 inches, its about 60'' from end to end , i think if we can make it 56'' itll work, also the measurements are very close to the scorpions irs posted here, ll pst the r33's specs soon

[turbosigma]

Don't know about the r33/r32 but the s14 cradle will go in - see djgyro car on cardomain http://www.cardomain.com/ride/410085

s13 fits too http://walkercorp.ath.cx/brakes/Picture%20006s.JPG - stock sigma rim 15mm to the guards give or take - keep in mind that you should then be using the same offset wheels that the cradle comes from.

so all though it maybe wider, the wheel offset may bring it in.

and if the s13 fits - the GTR cradle will too.

[FUGITIVES]

thanks for the info, The S14 diff is the same as the r33 i have from those pics, but what i might do is use a cifero Frame which might make it shorter from rotor to rotor, I will also have to make some strut towers , heres the slight differences i worked up, the top is the IRS from the post and the other is the R33

[A112H]

[Rallyant]

Good find, would be interesting to see how easy one could go in.

If interested i may be persuaded to part with my starion rear end. i wrecked a starion a while back and i kept the IRS and i also cut out the rear end and kep that, I had ideas about IRS in my galant.
I sold the struts form it tho,. and there was no diff in it, i also stole the brakes off it

[A112H]

Can I throw a spanner in the works here guys
I would love to convert the coupe to IRS. Has anyone thought about GTiR Pulsar rear ends??? I would think they would be about the perfect width