Desleration sensative valve
 

Hi ALL
Anybody know what should be the angle of the above as the book states it should be the same angle as the donner car. I am afraid my donner car is well gone now. Secondly should this be in rear brake circuit.

Yes to rear break circuit.

I will have a trawl through my pictures to see if I have a picture of the item in situ, when I get in from work.:cool:

Cheers Ginge

didnt bother with it on mine. from memory i think it slopes up towards the front of the car

Phew
:o :D
I,m glad you said that Ash, cos I ain,t got the foggiest clue of what ya talkin about :eek: :D

cheers
andy

I think its "Deceleration Sensitive Valve" Andy. Hope it makes sense now, must say though it took me a while.

Same as Ash mine didn't need it and yes it does slope forward.

AndyH

I thought we were talking about the "pinto engine" :D

sorry Ash.....couldn,t resist :p :D

Cheers Spud....glad i now know I don,t need the gizmo ,:cool:

cheers
andy

I didn`t fit mine either, but I did fit smaller rear wheel cylinders from an Escort, around 18mm bores instead of 20 ish ones from the Sierra.

Dennis.

I fitted one to my car, you can see it on page 4 of my build diary - www.deepfolly.co.uk. You should build it so it can be adjusted slightly, about 45 degrees pointing up towards the front should do it. The steeper the angle the more deceleration is required to activate it. It just makes sure that the rears don't lock first.

Cheers that looks brilliant, just one more question, is that in the rear brake circuit?

Hi Axle, hows your car coming along? Not seen you on here for ages. It is in the rear circuit, it limits the pressure to the rears under heavy breaking.
One really important point, the valve must go in the brake circuit after the pressure switch for the brake lights. If it is before the brake lights could turn off if you go really hard on the brakes as the valve will cut in and drop the pressure.

Can it drop the pressure? Doesn't it just stop the pressure in the rear from increasing further? I think the rear is pressurised when the deceleration valve is closed, definitely enough for the switch. What do you think?

I don't know but good engineering practice says don't take the chance.
Enoch

Hi
Thanks for asking and your help. The car is comming along not badly work pressure is a bit too much but the car gets a little attention and does unwynd from work.

here is how it works

its fitted angled with the input to the top/front angled to the front of the car

when you step on the brakes hard there is a little spool valve that travels uphill by enertia preventing the rear brake lines form increaseing fluid pressure
stoping the rear wheels from locking as the back goes light

so the harder you push the pedel the rear gets no pressure rise
the steeper you set the angle the harder it is for the valve to work

when your stoped and level the back should get full pressure

hope that helps

This might be a really stupid question - but on the rollers for the IVA test will these deceleration valves work as the car is not actually physically decelerating :confused:

Same for any car thats on test, weather new or old.

So it would seem then that for our purpose of IVA there is no benefit in fitting one.

But! it will give you better braking benifits, I think :o

I would have thought that when braking all the weight transfer will be forwards so the majority of the braking will be done by the front brakes and you will then become traction limited. At the back of the car, the weight will reduce and you will also become traction limited because of the reduction in load on the tyre - i.e. the rears will lock because they are lifting off the road and have a neglibile braking effort.

I've heard off this before David and once the inspector has seen that the deceleration valve has been fitted he is confident that the rear wheels are not going to lock and will be okay with it.

Regards....AndyH

When I took my 2B in for test it failed the auto brake test as it was over braked on the back. The tester saw the valve in circuit, drove it round the car park and braked hard to make sure the backs did not lock up. He then manually marked it as a pass. Having been through that once, fitting the valve seemed the obvious thing to do. The valve will not come in to effect on the test rollers.

cheers guys you all have been brilliant.

Hi all

I know it has been ages, since we last talk about this thread but the input should be to the back of the car as it was with the donner car?

Cheers Axle

On the sierra it's fitted on the passenger side front inner wing

Hi James
I agree with you how this is fitted on sierra, but can you agree the outlet from the brake master cylinder goes to the botton of the anti brake lock?

Thanks Axle