Callumgw - 84 EXA

[Callumgw]

Darren
Your all right except one small point. The Exa has different front and rear pistons in the master cylinder and diagonal brakes. The piston diameters are different but magically the areas are the same.......
because the rear (larger diameter piston) has a reduced area because of the arm which goes forward to act on the front piston. This means it has a toroidal area, not a pure circle, giving the same area as the smaller front piston.
I think the ET maybe the same and the prop is done in the cylinder that is parallel to the piston bores. Like in the sylvia and some other Nissans.
The Prado, AFAIK, has two equal piston diameters.

If your converting to the exa layout the guy who did my braided lines will also do solid lines. So he may be able to bring your lines to a single point for the prop valve.

C

oh, and none of this is off topic, not that off topic bothers me too much.

[tassuperkart]

If you pull the ET master cylinder apart you will see it has 2 different piston sizes on the one mainshaft with diagonally opposed outputs to the wheels. (so 4 outputs from the master cylinder) These 2 different piston sizes setup the bias in standard form. With the 4 diagonally opposed outputs - my understanding is this is a safety feature so that if you lose a cylinder/split a line you don't lose that 'end' of braking EG: the front left and rear right are one circuit and the front right and rear left are another circuit. This keeps the car a little more balanced than if you lost say all front braking.

Errrmm U certain of this?????
Ive never seen a system that diagonally splits the system. I can just imagine the fun and games if I slam the brakes on with a failure and get one front wheel....... Sheesh TURN LEFT (or right) major time! Like tear the wheel out of the hand......
And how would differing piston sizes work? Well..it wont really since under this scenario, youd have one front and one rear connected to a small piston and the other two cylinder connected to a larger piston....nup I doubt that would work.
Clarify?

Every setup i have had my grubby little kent scratchers on has always fail-safe'd either front, or rear in case of a line failure.
2 seperate cylinders, one feeding fronts and one rears.
Ill go out shortly and have a closer look at a MS laying around but Im not convinced this (diagonal circuits) is the case.

As C points out, the ET M-S determines brake bias by piston/cylinder sizes, not some funky inline valve.

The EVO brake setup should work well enough straight up. C points out that the combined piston sizes are significantly smaller in the EVO setup than the ET. however, the EVO setup had bigger disks by a mile and larger area pads.

This means a harder pedal to begin with no? This is good for me anyway as i cannot stand soggy brake feel.
I like to "squeeze a brick"! (old fashionede)
However, brake bias may still go towards the front due to the larger disk diameter and pad area. Remains to be seen I spose.
Not such a bnad thing when the N12 is so light on the arse end.
All will be revealed in time.
L8r
E

[Callumgw]

E,
I think you've misread what I wrote (I wasn't very clear actually!) When I said the "front" piston, I meant within the master cylinder, not front piston for front brakes. same for rear.
Many systems are diagonally split, the idea is that when you loose one you get a balanced pull up, not all left or all right. The Exa and NA are diagonally split at the prop valve.
I think older systems were split front to back.
I'm not sure about modern systems, but they feed twin lines into a single ABS block, and maybe be diagonally split.



C

[tassuperkart]

Nah didnt mean all same side. Diagonally as in LF and RR.
Ive just never seen a split where in the even of a failure, it pipes to just one or the other front (ignoring the diagonally opposite rear) of course.

Seems to me a brake application with jjust one front working would rip the wheel out of the hands despite the opposite rear trying to balance.

Not saying its not done this way, if it is then it is, but Ive never seen it and dont really like the idea is all..

L8r
E

[Callumgw]

yeah, I know what you mean, Many would agree with you too. I'm undecided.

C

[tassuperkart]

Just went out and had a close look at the ET. Its a twin piston, side by side and one side feeds front and other rear.
Oh well.
E

[Callumgw]

I thought yours was an NA (or astra) conversion? or did you buy a new one?

C

[tassuperkart]

Nah its a GX (Langley 4 door) atmo so comes with the same braking system as the ET.
E

[Callumgw]

Heading to Sandown on Sunday or John Mott Super Sprint (event runs Sat and Sun). The weather for sunday is forecast wet, so might not be too much fun.

Got the wheel alignment done, the rear has TONNES of alignment now. I've dialed in 1mm toe out per side and -0.7 deg camber. Hopefully the toe will aid turn in and the camber add grip mid and exit. I decided on these as a start from some on line reading. See how we go.

The other thing that I'd like to adjust is front caster. At the moment mine is 0 on one side and 1 on the other, which obviously aint good. I'd like to get both to 2-3 degrees I reckon.

Figure crossed it comes back un-broken, I'm more worried about a failure than a crash, but you never know!

C

[Timmzy]

Good luck,

Unfortunately I cannot come down on sunday due to family events in Gtown, but have fun!

Watch out for turn4 in the wet! No room for mercy there

I shall be extremely interested in how the rear end goes with those settings. I think I might go and get a digital print out of my setting now so that I have a reference to go back to. Did you do that?

Darren.

[Callumgw]

I normally do a before and after, but not worth it with the last change, because of the mod I did to the rear. But I do have previous read outs to compare with, but don't have them here...found ones for my old mr2 though.

C

[japcrap]

how often do you go to sandown? I live like 5 min away from it. I thought about doing circuit run with my peugeot but i dont have a cams licence

[Callumgw]

not very often, would like to do more. Timmzy's had a much better run than me there. .... i'm mainly held up with time to get the work done on the car, then it breaks and takes more time then....

[Callumgw]

Went for the John Mott today. Rain forecast, but day started dry.
Started the first run, warm up seemed OK, brakes felt good, first lap ok, brakes still good surprisingly good braking WAAAAAYYYY to early. that should improve through the day though....

last timed lap of the first run car looses power.....mmmm could be plug wiggler....no poor boost too.....better bring it in.

In the pits find oil coming from the just behind the AFM (mine is only 12 inches from turbo inlet).....smokey, doesn't like to rev....

bugger. That the second John Mott where the car has bust on the first session of the day. two from two aint good.

limp home (I drive to the track)

at home check plugs, This is plugs 1 to 4:




somethings not quite right with number two...can't quite figure it out though.....



ohh well guess its time for the rebuild and Haltech.

C

[Panda_ET]

Going for a nice fine plug gap there callum? lol