Brake delay when hitting at top revs

[N3me-350z]

So I'm having an issue and wondered if someone can help, I've recently gone supercharged and I've now noticed that if I'm pushing hard and slam the brakes on It takes a split second or so for the brakes to engage, can be quite worrying because it feels as if the cars not going to stop, then suddenly it brakes as normal.

 

So only thing I can think of is I changed to a cosworth intake a while before and had to change the brake hose for a longer one and maybe this new hose is collapsing now when it the intake pressure goes from boost to vacuum.

 

Only happens when I'm really pushing the car. Does anyone have an idea what it might be?

 

I'm guessing first thing I should do is get a better vacuum hose and try that but just wondered if anyone else has experienced this?

[GMballistic]

Did you put a non return valve in between your brake servo & plenum?

 

I've had this done on my supercharged Zed as the garage that fitted it recommended doing it to prevent boost pressure affecting the brake servo.

Non return valve I bought is this one: http://www.carbuildersolutions.com/uk/nylon-non-return-valve-10mm

 

I would say check out my build thread but don't think I have a picture. I'll try to take one now for you.

[N3me-350z]

Awesome thanks, no I don't have a non return valve fitted between servo an plenum, I'll buy one and give it a try

[GMballistic]

Ok so it's a terrible picture but in my defence I live in Wales & it is pi**ing down outside.

 

 

 

You can see the non return valve in the pipe leading to the servo.

 

Hope that helps & let us know how you get on.

[N3me-350z]

Ok cool cheers for help, infact I've just found one in my box of goodies, hopefully this will be good enough, what do you think?

[N3me-350z]

Opps here's the pic

[GMballistic]

Ok cool cheers for help, infact I've just found one in my box of goodies, hopefully this will be good enough, what do you think?

Do you have a picture then?

 

If it's a non return valve & fit's the pipe then it should work.

[N3me-350z]

Looks a bit cheep lol but seems to work when I blow through it and it's 10mm

[GMballistic]

Opps here's the pic

Just check it works first by blowing through it. Hard to tell from the picture but can't hurt to give it a try.

 

The nylon one I linked though from Car Builder Solutions is a very solid little piece so should the other one not be up to the task then it's not exactly an expensive part to try.

[GMballistic]

Beat me to my response.

[N3me-350z]

Yeah exactly I'll probably just get one you posted anyway as it's a proven item. Will try this out tomorrow and let you know if it's worked, thanks

[N3me-350z]

I'm good at doing that, I also tend to start talking at the exact same time someone else does lol

[GMballistic]

Yeah exactly I'll probably just get one you posted anyway as it's a proven item. Will try this out tomorrow and let you know if it's worked, thanks

No problem ~ Fingers crossed it fixes the problem and that's all it was.

[Keyser]

I had that problem - standard pipe has one in - I think I blew mine up - I just replaced the pipe and that solved the problem.

 

Double tap the brakes also gets round the problem - I first discovered the exact same brake fail coming into quarries at CC at around 125mph Hit the brakes nothing - release and press - Phew :

 

I assume it is because when you come off high boost the pressure in the plenum goes positive before the blow off valve releases it, servo uses vacuum and you don't get any at that point.

 

Hope the new valve gets you sorted

[Tricky-Ricky]

There will be a one way valve fitted to the servo, but its not intended for FI so I would suspect that its being overwhelmed while on + boost and thats whats causing your problem.

[N3me-350z]

Cheers guys hopefully the one way vavle will sort it otherwise I'll get a better hose and try again

[N3me-350z]

Fitted the non return vavle and all seems fixed, I've tried a good couple of full speed brakes and it feels nice and responsive now cheers for the help guys

[Keyser]

 

Useful for other FI builders to note this as well

Edited November 13, 2014 by Keyser

[jumping350]

noted and bought two today

[GMballistic]

Fitted the non return vavle and all seems fixed, I've tried a good couple of full speed brakes and it feels nice and responsive now cheers for the help guys

Great stuff ~ glad it's fixed & we helped.

[Sam Mcgoo]

Good info. Not a problem I have come across as yet but I have the OEM hose fitted still.

If it happens in the future, I'll know where to go.

[RobPhoboS]

Just spotted this thread.

IF my oem one requires replacing, does it matter which material (nylon or aluminium) ?

[GMballistic]

Just spotted this thread.

IF my oem one requires replacing, does it matter which material (nylon or aluminium) ?

No it won't matter imo.