Early celica IRS conversion

[timbosaurus]

Disclaimer

First things first. I haven't done this! I would like to, and one day I will! Hopefully the info here will give someone the incentive to try the conversion. (at least then i'll know if it's actually possible) Dont' blame me if you chop up ur baby and spend a trazillion dollars on the parts and it doesn't fit. Just let me know before I try it on mine

Details

The intention is to fit an entire IRS subframe from an s13 or s14 silvia/180sx into the rear of an early model live-axle celica. I'm targetting this at the RA23s and RA28s as they have the same rear suspension and floor pan as each other **EDIT: just remembered they don't... of course they don't!!! RA28's have fuel tank in the floor. Silly me!** TA22's are slightly different with respect to the diff/suspension used and also have a different floorpan and narrower track. Not to say it couldn't be done though. RA40's should also be possible, but I believe they have a wider track.

I know many threads in here have information about IRS into a 23/28, but buggered if I can find them! It doesn't help that you're not able to search 3-lettered-words like "s13" "s14" or "IRS", and no one seems to talk about it as "silvia" or "independant rear suspension"

So if someone can PM me any useful threads regarding IRS into early celicas, PM me and I'll edit them in here.

Useful related threads:

"3t-RA40's" IRS conversion

"sheepers'" R32 GTR conversion


Let's get started:

S13/S14 subframe




The subframe carries all of the rear mechanicals of the car. This includes the diff, the lower control arms, shocks, springs, driveshafts and CV's.



So by installing the complete subframe you benefit from having the later technology of all of the above in ur old celica. Some ppl may argue that the rear suspension in the s13/s14 still leaves a bit to be desired compared to more modern vehicles, but if it's done properly it will be a significant improvement over stock live axle. It wouldn't be as prominent in racing today if it was a real piece of shit.

Benifits:
- Strong R200 diff (or super strong if you go for the R230)
- Far less unsprung weight
- Relatively easy and well document 5-stud conversion
- Disc brakes with large upgrade potential
- Coilover rear shocks
- Huge aftermarket support in adjustable coilovers, brake packages and camber/castor/toe adjustment kits, driven by all the cashed up dorifto boys and girls.

Disadvantages:
- Fitting into the car will be a custom job. You'll want to be good with a welder an heavy metal tools
- Engineering will be required.
- Last, (but most importantly, IMHO) it is likely going to be an irreversable modification. I don't encourage you to do this with ur pristine original '28, so the mod is aimed more at those with a dedicated track car, or one that has already been beaten with the mod-stick and want's more

How the subframe is attached in a silvia/180:

As can be seen below, the subframe mounts to the chassis via 6 mounts. These have rubber bushes on them, but are often replaced by alloy blocks or "drift pineapples" by those drift kiddies we all know and love



next post coming soon... used up my maximum 10 images already :-(

[timbosaurus]

...continued from previous thread.

the original rear mounting locations of the subframe on the s13 body can be seen below



The chassis appears to have a crossmember running between the rear chassis rails where the subframe attaches. This crosses behind the rear torque box and in front of the spare tire well... but rearward of the diff.



The front mounts can't be seen clearly here, but actually attach to the chassis in a similar position to the lower trailing link mount on the celica.



I don't know the distance between the two rear mounts, or the two front mounts, or what distance is between the front and rear mount. Perhaps someone with access to a vehicle could measure the distances and PM me so i can include it. hint hint... IT would be great to be able to see what would actually have to be moved. Hopefully not the fuel tank.

The other dimension I would like to confim is the distance between the centres of the two strut tops and how high they sit above the centre of the hub (for lack of a better reference).

For those interested, the above pics can from a site where a guy was plonking a morris shell over a shortend 180sx. So crazy it's cool!

What's under a celica in these places:

The celica uses a four-link live rear axle which has pickup points for each of the links forward of the axle.



There are also outboards mounts for the springs which would have to be modified to fit the coilover shock. The shock mounts on the celica would no longer be required and neither would the panhard rod mounts.

[timbosaurus]

This is the post where I will collate information about different versions of nissan subframes/rear suspensions available.

I will try to stick with the RWD nissan varients, just for uniformality. The skyline and supra track is just too wide (although I'm sure sheepers will prove me wrong ), and I haven't thought of any other modern alternatives. Actually... I haven't thought much about this at all

I believe there are differences

Some information I have blatently copied from another forum to get by until I can find the info out for myself Hope plagerism is ok, as long as I do it obviously

FYI, Z32 is the early to late 90's 300ZX with the VG30 V6.

"Z32 and S13 rear parts are almost all the same... RUCA, toe link, traction rod are the same, not sure about RLCA. Upright is the same except for where the shock mounts to the upright (S13s can use Z32 shock, S14 can use R33 shock... or Z32 lower fork on a coilover), and the Z32 upright is aluminum versus the S13/S14 steel. The difference is the subframe itself, and the Z32 NA uses an R200 that will work in an S13/S14 subframe (need 5-bolt j30 axles though), vs the Z32TT R230. Don't know which of you guys have S13/S14, but if you do you probably know all this already, I'm just throwing it out there as specificly as I can type it at 2am for the benefit of all the other people reading "

"I know the S14 subframe is wider than the S13s by an inch or two (forget... it's been a while since I read that; some guy crammed an S15 subframe into his S13)."

"S14, however, all of the arms are swappable except the lower control arms. For example, if you wanted to run the aluminum hub housing from a 300ZX (Z32), you could, but you would also have to have the lower control arms from the Z because the ball joints on the LCA are different. Also, I believe the S13 hub assembly is different than the S14 so you would have to use S13 axles with the hubs (Smaller than Q45 and 300ZX). With the S14 there are four bolts holding the hub on and one giant nut holding the whole assembly together. Maybe when I get home I can post a pic of the hub assembly. I would go S14, just so you have more options later. S13 will work fine, but you will have to stick with S13 axles, even if you want to upgrade later unless of course you buy the S14 hub, housing and LCA."

"The problem that I see wuth useing the S14 is that it's 5" wider than the S30, and requires some big flares in the rear. The S13 is about 3" wider, so mild ZG flares will take care of that."

"There are lots of handling disadvantages to a live axle car in addition to what's already mentioned:

1. Anything that happens on one side has an affect on the other.
2. Wheel hop under braking.
3. Binding under compression.
4. Lateral location (panhard bar typically) is affected by sprung weight movement.
5. Wheelbase changes in roll.
6. Lack of compliance/suppleness due to unsprung wieght and the resulting shock valving needed to control that weight.
7. Asymentrical torque affects on the chassis under hard acceleration.
8. Engine torque loads affect suspension compliance.
9. Limited wheel travel due to the big punkin' banging on the floor of the car."


"Solid axle advantages:

1. Suspension designs allow more anti-squat = more traction out of a turn = can get on the gas more quickly. You can build some anti-squat with an IRS setup, but you will run into brake hop before you can get much.

2. More durable.

3. Less overall weight (due to extra frame bracing required for IRS).

Solid axle disadvantages:

1. More unsprung weight. - in a very light car, a higher proportion of total weight will be unsprung.

2. With a short wheelbase car like the Z, one needs to pay more attention to driveshaft angularity.

3. Not much (if any) camber - about 1* max. = less contact patch on uneven surfaces."

be back to add more soon!

Peace out,
Timbo

[timbosaurus]

More relevant pics... yet to find a home

[Turdinator]

<subscribed>

Interested to see how this goes. Not sure i'd do this with my road car but it would be very cool.

[timbosaurus]

If anyone's got any ideas of late model Toyota IRS of a similar nature (narrow track, LSD available, coilover shocks, plenty of secondhand discarded dorifto parts available cheap etc) I'd much prefer to stay in the family!

But I think this is asking too much

[tricky]

Timbo, I'm one of the crazies planning this conversion too. Early assessments lead me to beleive that not *too* much cutting of the celica will be required. My plan is to modify the subframe in favour of the chassis, although this poses problems of its own. One of the other hurdles (which probably won't turn out to be too bad) is the mounting of the strut tops.. Again, customness be required by the looks.

I've also been seriously considering checking out RX7, RS200 and GT4 subframes too. The FC RX7 design is quite nice, and space should be less of a constraint. The struts sit more vertically too IIRC. Although how relevant that is I dunno. As for altezzas and GT4's, I haven't checked anything out yet. These are harder to track down than S13 though, and the aftermarket crap available for S13 boggles the mind.

Next year I should be able to jump headfirst into this project with trepidation!

[WDE_BDY]

If anyone's got any ideas of late model Toyota IRS of a similar nature (narrow track, LSD available, coilover shocks, plenty of secondhand discarded dorifto parts available cheap etc) I'd much prefer to stay in the family!

But I think this is asking too much

Have you looked at the Altezza's? Not sure how easy they are to find in Oz but pretty plentiful in NZ.

Callum

[tricky]

The altezzas are on my to look at list too. The known problem with altezza IRS's is the camber control arm bracket flexing. Apparently every big power altezza has to replace the brackets with meatier ones.

[timbosaurus]

In the grand scheme of things.. I guess an aftermarket CCA is not that much of a deal.

'scuse my ignorance of all things not Celica... but how common are the Altezzas? I don't even know what they look like

[oldcorollas]

lexus IS200

[timbosaurus]

hmmm.. I will have to look at that.

The guys at work have all good things to say about a certain lexus IRS. They even admit it is a better design than the one they've just released! I've no idea which model lexus they mean though :s

Now to find out how much they are worth

and the track?

[twentyEight]

I saw this yesterday, but I wanted to make sure you had enough posts reserved before I commented!

Great tech article Timbo... I shall be keeping a close eye on this to see how it ends up!

With regards to other models, don't some of the RA65s have IRS? Would they be suitable?

Also, here is a link from "sheepers" thread that you may enjoy - Link to TA22 w/ GTR IRS

[timbosaurus]

Thanks 28. I know it will be a while before I can start the conversion. I just hope I can keep interest in the thread until then. Maybe someone will take the bait and start chopping theirs before I get a chance to. If they do... they better post pics!

This's probably not a true tech article until I get a chance to add some practical input either

Oh... that link to Jamie's 22 is great! I should've added that, but that car is just... well... undescribable! Don't want ppl thinking converting a 28 to IRS is in the same league as fitting an AWD twin turbo 4V driveline into a 22

WRT the RA65, I will look into that. At this stage i'm thinking it might be a little old in the tooth, and not have use the recent multi-link, adjustable designs. Also, I'm not sure of the track, I think the 65's still had drums, and it wont have the same aftermarket support of the s13. Having said that... you would think you'd be able to pick one up cheaply

Cheers for the input

[twentyEight]

WRT the RA65, I will look into that. At this stage i'm thinking it might be a little old in the tooth, and not have use the recent multi-link, adjustable designs. Also, I'm not sure of the track, I think the 65's still had drums, and it wont have the same aftermarket support of the s13. Having said that... you would think you'd be able to pick one up cheaply

Cheers for the input

Also, the other variants similar to the RA65... eg. Celica XX...

[tricky]

With regards to other models, don't some of the RA65s have IRS? Would they be suitable?[/URL]

Yes, it's been done by a dude with a 3TGTE RA40... Well he used a corona/cressida mix of parts, but the basic design is the same... Fab wise, this is the easiest option, but compared to more modern designs, the 1980's toyota gear is arse. *A70 and JZA80 supra stuff is seriously heavy, and the track is significantly wider, so for most this wouldn't be an option. I'd love to have a look at IS200 gear, because they handle so well from the factory. The CCA mount flex is an easy fix- Just remake the mount with thicker steel.

The more I look at FC stuff, the better it looks too! I haven't checked parts availability though. Other options involve going nuts with the grinder and swapping floor pans with the donor vehicle... Of course, this is the point of no return!!

[ViPeR_NiPPleX]

RA65/MA61/MX73/MZ10/etc has semi-trailing arms. Simple stuff really, just not great for adjustability.

For the ultimate IRS setup, you could contruct a custom cradle with rose joints and run double wishbone. Probably not practical or cost effective in a 70's celica however.

[TurboRA28]

The track width seems one of the biggest problems..

I've helped a mate with an IRS conversion into a live axle car. Lots of work but the results are awesome. We used a Nissan 280zx setup as width wise it was the narrowest one we could find. But its semi trailing arm.. Nicer to have a double wishbone style.

[timbosaurus]

The track width seems one of the biggest problems..

I've helped a mate with an IRS conversion into a live axle car. Lots of work but the results are awesome. We used a Nissan 280zx setup as width wise it was the narrowest one we could find. But its semi trailing arm.. Nicer to have a double wishbone style.

The track of the silvia is quoted as 1360mm on the rear - this the same as the RA28. What I don't know, though, is what constitutes "track" in each of these figures. I'm pretty sure it would be hub-face to hub-face in both situations.... but I would want to confirm this.

Joel, you posted a reply in the old forums saying you saw a '28 with s13 diff and disc brakes.

http://forums.toymods.org.au/index.p...eaffcb541f13f4

Do you remember whether this was the whole cradle? Any idea who's car that was now that ur older and wiser?

[Turdinator]

The track of the silvia is quoted as 1360mm on the rear - this the same as the RA28. What I don't know, though, is what constitutes "track" in each of these figures. I'm pretty sure it would be hub-face to hub-face in both situations.... but I would want to confirm this.

I believe track is measured from center of tyre to center of tyre