985cc Turbocharged Nova Sprint Car

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Originally Posted by Stuart

tbh just adding a layer of grease might reduce things enough

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I did consider that......

But fortunately it looks like the problem is now solved.

I ran it on the brake rollers at my friendly local MoT station, and the back brakes were locking up with almost no pressure on the pedal.

And it didn't seem to make a blind bit of difference on where the pressure valve was adjusted to either. Also, rather worryingly there was no physical 'stop' on the valve, so you could actually unwind the knob completely out of the valve (and then spray fluid over the whole interior!).

So I pinched the AP Racing pressure valve off my Fiesta circuit race car, and installed that in the Nova.

With the brakes bled and back on the rollers, there was an immediate improvement, as I needed to properly stand on the pedal to lock the backs up.

On the (private, naturally) road it pulls up nice and square, and all seems well, steering nice and straight and pulling right up to the rev limiter in 5th (about 115mph, although I really must work it out properly).

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Originally Posted by Stuart

Removing pad material wont 'lose' much braking imho... The pads are small and assuming the contact is in the middle of the pad he will wind up taking the top 75% off the pad, it will sit wonky and really go wrong when braking, so the upper 25% would need leaving on too, which will result in more force on the outer edge.

tbh just adding a layer of grease might reduce things enough

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the grease idea will make a mess of the pad.

i'm serious about cutting the area down, it was a method used lots when everyone had drum brakes & there weren't off the shelf bias valves.., i'm not on about simply hacking it, more like a spot of cnc machining..

simply reducing the pad area wont necessarily change the actual braking effort... just increases pad wear. Like I said, if you only had the smallest diameter part exposed then yeah reduced braking effect (marginally as its not going to be far from the pressure centre), but you may get a wonky pad when trying to stop.

Seems like using a proper inline limiter has worked, what was the one you had before? a tilton etc?

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Originally Posted by Stuart

Seems like using a proper inline limiter has worked, what was the one you had before? a tilton etc?

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I have no idea who made the previous one, it was absolutely tiny, with no markings on it to indicate a manufacturer. I will post up a few photos shortly, I would be curious to find out.

We carried out some rudimentary testing of the 2 valves by blowing through them, and the one which was on the car originally offered no restriction to the amount of air flowing through it.

The AP one which is now on the car is much more substantial, and heavier, but it works!

This was the valve which came off the car (the one that was faulty). Anyone recognise what make/origin it has?;

http://i285.photobucket.com/albums/l...ort/016-22.jpg

http://i285.photobucket.com/albums/l...ort/017-25.jpg

And this is what's been fitted now (being bigger the brake pipe is now too long so it isn't fitting quite straight);

http://i285.photobucket.com/albums/l...ort/018-24.jpg

Looks like a tilton style one.

The blow test also implies its the type that has a 'free flow' rating then the adjust simple changes how much it limits after a given pressure.

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Originally Posted by Stuart

Looks like a tilton style one.

The blow test also implies its the type that has a 'free flow' rating then the adjust simple changes how much it limits after a given pressure.

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The design certainly looks similar to Tilton (here's a photo of the latest version);

http://i285.photobucket.com/albums/l...imagethumb.jpg

It seems brake pressure valves are very much prone to faults/failures, I spoke to 2 of my racing friends this morning, and both of them have knackered valves sat in drawers......

old valve looks identical to pneumatic restricters we use at work.

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Originally Posted by gary_808

old valve looks identical to pneumatic restricters we use at work.

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thats all they are.

Hi Colin how did you get on at Gurston Down ?