yeah I hear what your saying. I'm hoping with extra preload (not over the top amount) it might grip up better on corner exit but still give some slip in the corner.

Kaaz will be in as soon as I can get my hands on one (Pending the results of this of course).

All finished today.
ended up putting 2x0.7mm shims in which increased the final breakaway torque to 95ft-lbs.
Rest of the diff went back together nicely. Contact pattern shows a little towards the toe but acceptable.

happy to have it all back together.

A couple of photo's below:

Clutches looked clean



New double spring installed ready for shims



Thicker double springs added a heap more preload on the clutches



Home made bearing cap adjuster, checking backlash with dial gauge :)



Set bearing preload



Check ring gear run out



Final test install, home made break-a-way check (welded wheel nut onto a metal plate which is connected to two wheel studs)

not such a great day.
Rebuild the diff to spec again (With the shims installed) and installed it all only to find out the breakaway torque was now well over 150ft-lbs, WTF. Anyway, when I took it out to see why, I when I first tested it I did not torque the LSD centre, so when it was torqued properly it added extra load to the spring. But it got worse, I realised I had shim'd it to the point where the spring was bound solid, not only that but when I removed the spring it was deformed, in stead of being 27mm free length, it was now 24mm and no good.

Anyway I stipped down the 4.3 LSD I had and found the spring and spider gear setup on that one different. Firstly this spring was 7.5mm thick and had a second spring inside(old spring was 6mm, this makes it nearly twice as stiff). The free length was 31mm, so it wouldn't fit into the spider gear housing :( The two housings are slightly different, overall height is the same but the end caps are different thickness to accommodate the difference in spring free length. I think Toyota softened the spring in new model LSDs and reduced clutch preload (Toyota needs to learn to make a decent LSD).

Anyway I swapped the spider gear housing and reinstalled in the 3.5 LSD centre. Late tonight I tested the breakaway torque with 1x0.7mm shim and it was 85ft-lbs, which is in the ball park. So tomorrow I'll hopefully finish this bloody thing off properly.

On a side note I found a problem with my rear brakes. The piston has a notch in them that locates with the pad. I however got race pads and the stud in the pad is slightly larger and doesn't locate with the piston correctly, ergo, I have been pushing the pad with less then 5mm stud on the piston, in lieu of the 30mm + piston, will be interesting to see how much that makes a difference now it's fixed (probably had no really effective rear brakes with it the way it is).

More to follow tomorrow, hopefully good news.

Quick update.
Spool option fell through. I bought one but had reservations from the time I got it, was able to return for a refund. Looked for a Kaaz or Cusco but non in stock till April....
Decided to have a close look at the LSD that is in there, no wonder it is single pegging, breakaway torque was around 35-40 Ft-lbs.
Stripped the LSD down and shimmed up the clutch plates to return backlash into spec and found a few shim washers to add extra pre-load on the spring. Anyway made a rookie error and checked breakaway on the bench with the centre in a vice and used one axle, measure it at 100ft-lbs. Thought all was good and re-installed into carrier and back into the car. As a last check before dropping off jacks I check the breakaway torque with one wheel locked (out of gear) and got 50 ft-lbs breakaway (slap forehead).
Scratched my head for a bit and realised in the vice it was required to breakaway both sets of clutch packs hence the double reading. In the car it only needs to break one set of clutches to open peg.

Well centre back out, stripped down and re-shim, wasn't sure how much to add, after a couple of tests (done by dummying up in carrier, reinstall into car). Now managed to get break away up to 85ft-lbs, this required 6mm of shim on the spring, about as much as I'm willing to add. This is still over double what I had to start with so will see how that holds.

Tomorrow I'll finish the job and get ready for a test run in early March.

Andrew,
How do you find the Caltrac on the circuit? in comparison to your old coupe do you think they are a worthwhile upgrade or do they bind under curtain conditions on the track?

Bryan

Well Christmas break is over and car is now prepped for the 2015 race session.
Will have the old girl at Big Rock Toyota (Balcatta) this Wed @ 5pm for pre-session audit if anyone wants to come and have a look.

Was having trouble selecting 4th gear on some corners so dropped the oil and found a heap of metal in that.
Decided to drop the gearbox (No easy task) and replaced it with one I know to be good.
Whilst gearbox was out, removed the engine and cleaned up a few small leaks I had from the sump (very minor but annoying).
At the same time I installed an oil accumulator to assist with high g corners and to pre-lube the engine.
Also installed an airbox to ensure the filter is only getting clean air.

No diff upgrade yet, will probably just install a spool to start the season and see how that goes. Left money in the bank too long and my wife decieded we need to go on a holiday so no KAAZ LSD. leason learnt, spend it first.

Looking forward to getting the old girl back on the track.

Haven't made a nationals yet, unfortunately 2015 won't be any different. Would like to go but too far from the West Coast, would cost me a small fortune in transport.

yeah but Stoichiometric ratio is only one element to fuel economy.
Smart ECU will lean the engine out during cruise, which will increase fuel economy. What this does is increase the engine running temperature, which in turn promotes knock.
So theoretically a higher Octane fuel with has a lower Stoichiometric ratio (and coincidently lower relative energy output such as ethanol compared to petrol) can produce better economy figures because the engine can run leaner and hotter without pre-ignition.

Not saying that is a given, just it is possible given the right circumstances and equipment.

For racing situations only.
There are a number of equations involved in working it all out.
I can send you the spread sheet I developed but it is pretty confusing, my spread sheet isn't well labelled.
From a first principles POV you work out the braking g, which in combo with your CoG height and static weight distribution gives the longitudinal weight transfer.
Now you know the weight distribution you can work out the reactive torque your brakes need to produce based on your tyre diameter.
This will lead you to the circuit pressure required to produce that torque based on piston size, rotor diameter and pad friction.
That's where piston size comes in.
From that you can work out the M/C bore size based on foot pressure you want (Requires the motion ratio of your pedal box). This of course can be modified based on the bias you have set.

Or you can skip all this and use general rules......The more piston area you have the less circuit pressure you need to run.
The larger the disc diameter the less circuit pressure you need to run.
5/8" M/C for front circuit and 3/4" for the rears works for just about anything :)

Bryan

yep.
For your reference not all CAs have them