Poor braking performance :S

[sailaholic]

Seems we have a winner. Byron!

Starred the car, pedal drops away.
Leave the car for a minute, waited for the clock to change, hard pedal. So I'm assuming vacuum leak either with the check valve, the hose between the check valve, or the diaphragm.

For reference front rotor



Rear rotor


Tonight will be spent on ignition, but should be able to do more testing Sunday.

Thanks to everyone for their help so far.
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[Byron_s13]

ƒü¢k I'm good. Let me know if you want me to explain how to pinpoint the leak!

Ive fixed booster diaframs with bike repair patches before! If need be I can explain how to dismantle.

[sailaholic]

Had a chance to suck/blow on the hose to the booster tonight. Check valve seemed to be working ok.

Also drove Plohls with booster deleted and it felt about the same, maybe a bit worse. His Booster also gave a big pfft! When taking the hose off.

My thoughts on narrowing it down was,
Run a straight house from manifold to booster, test drive. If OK (when engine revs are up, is hose, valve or hose not sealing on valve.

If still bad. Assume booster, remove and refit, do pad rough up and bias valve at the same time.

Happy to hear some more tricks though. Not sure how keen I am on doing doggy repair on the booster, would prefer knowing all a1.

On the ignition side one dead coil, and some unknown electrical problem neat ecu. Wiggling wires seemed to effect it, but locking down which one/s wasn't super effective.


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[Byron_s13]

Cotton braid LOLA (heater hose spec but in 3/8) is good for 300psi so you can use that or silicone hose.

Nope. Heater hose, or similar, will not work.
There's world of difference between a hose that can withstand bursting than a hose that retains wall-integrity under vacuum.

Think of a simple drinking straw. Obviously, block one end and you will never come close to bursting it no matter how hard you blow, but suck it and it's a completely different story.

If the pedal does not sink like normal after being turned off for a minut that valve is stuffed your hose is cracked or your diafram is split

What?!

Cotton braid LOLA the good stuff will work. It's durable and ridged

You can get cheap stuff where the inside braid is thin and rubber is soft! But I don't shop at supercheap

The best way to tell if you have good hose is the wall thickness and the material Braid in the centre, thicker wall more visible braid = better hose.






Your brake booster retains vacume after the car is turned off (stalled) for emergency brakeing. this test checks you booster is getting the vacume it needs to work sufficiently.
If the booster does not retain vacume there is a leak in the system.
If there is a leak in the system you will not get the full leverage supplied by the booster to assist with applying the brake pedal.

Does this help?

[Byron_s13]

Not sure how keen I am on doing doggy repair on the booster, would prefer knowing all a1.

Good man



The pfffft sound was his booster retaining vacume. Swap his valve and hose with yours see how that go's

[sailaholic]

Your brake booster retains vacume after the car is turned off (stalled) for emergency brakeing. this test checks you booster is getting the vacume it needs to work sufficiently.
If the booster does not retain vacume there is a leak in the system.
If there is a leak in the system you will not get the full leverage supplied by the booster to assist with applying the brake pedal.

Does this help?

Yah had a handle on that already, my mistake was assuming the pedal dropping away at engine start/ driving with out it causing a worse result, meant it was working.

Other then what I had planned no nifty tricks?

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[Byron_s13]

Ps. Your slotted rotors are on the wrong sides.

[sailaholic]

Not sure how keen I am on doing doggy repair on the booster, would prefer knowing all a1.

Good man



The pfffft sound was his booster retaining vacume. Swap his valve and hose with yours see how that go's

Wish i could, I run individual throttle bodies so need a much longer hose due to differences in manifold.

Check valve had been cut out of the factory one and put in the middle of a new hose.

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[sailaholic]

Ps. Your slotted rotors are on the wrong sides.

My understanding was that slot design dosent matter in terms of direction of travel, only the cooling fin design inside the rotor matters.

https://www.facebook.com/brakesdirect?ref=stream&directed_target_id=0

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[Byron_s13]

There is a reason behind it try and work it out! It would make a grate topic starter

[MattR]

Or learn to drive the car without a booster......

Gives you better feel at the pedal without one. If you reckon the brakes are firm on a 5 without a booster, try a 1" master cylinder and no booster......

[manga_blue]

Or learn to drive the car without a booster......

Gives you better feel at the pedal without one. If you reckon the brakes are firm on a 5 without a booster, try a 1" master cylinder and no booster......

I'm tempted to try no boost. I've got a stock NA8 setup and I reckon its over-boosted. It has probably cost me a couple of grand in track tyres over the years.

Maybe better still would be to cut boost by about 50%. Has anyone worked out how to do that?

[sailaholic]

Or learn to drive the car without a booster......

Gives you better feel at the pedal without one. If you reckon the brakes are firm on a 5 without a booster, try a 1" master cylinder and no booster......

Having had the car a year now, i don't think it's about "learning", might be ok on a track, but in traffic i don't think it is good enough. if i was really keen on no booster i'd have to think about twin master cylinders. I'm all for better pedal feel, but i think this has gone too far, unless of course i have some other problem (as well).

Drive mine with no booster at this morning, was worse then normal, but not hugely. Will have to wait till Sunday now for anything more.

Manga,
I found this http://forum.miata.net/vb/showthread.php?t=363284 when i was hunting around.
might be able to find what your looking for in there. Running a 929 1" master on a stock booster might get you in the area you looking for.

Or just plug the vac line and go for a drive and see how you like it with no boost.

[Guran]

All this talk of dodgy brakes reminds me of my first car: a 1974 Leyland Mini 1100. No booster and drum brakes all around. Many a time I would almost snap the seat back with all the force I could muster to pull it up quickly. Those brakes were useless!

[manga_blue]

Manga,
I found this http://forum.miata.net/vb/showthread.php?t=363284 when i was hunting around.
might be able to find what your looking for in there. Running a 929 1" master on a stock booster might get you in the area you looking for.

Good find! Thanks for that.

Installed mine today.

2002 non ABS booster came with a 15/16” master which I swapped out for a 929 1” master. I am extremely happy with the results. Pedal is way more solid feeling. Still have plenty of power and don’t feel as if I need to press the pedal excessively hard. Brake pedal doesn’t squish down past the accelerator pedal like it did so Heal toe downshifting and my ability to modulate the brakes just below lockup is drastically improved.

That's exactly what I'm looking for. Changing my stock 7/8" master cylinder to a 1" one would increase pedal pressure by 30% and reduce pedal travel by the same amount. 30% is in the ballpark of the sort of improvement I'd want. My main problem now is really about modulating during heel/toe and it's not easy with a lot of pedal travel.

The only problem is that bbundy notes that the 929 1" master has a bigger snout which won't fit into an NA booster. Anyone know of a 1" master cylinder which does?