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4" Dump - Will It Help Take The Load Off Valve Springs?


FAST-XR

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  • EVIL T
  • Member
  • Member For: 15y 11m 3d
  • Gender: Male
  • Location: Liverpool NSW

Currently mods as per signiture.

While being tuned the car started valve floating at 14-15psi at top end, so the tune was backed off a couple of pounds to be safe.

Currently running stock dump into 5" 100 cell cat, stock cat back...

If I was to upgrade the full exhuast, would it relieve the valve springs enough to push the tune a little further? or at least be making more power at the same boost level?

currently around the 300rwkw mark, was hoping to push 320-330 without having to do valve springs.

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  • Donating Members
  • Member For: 14y 9m 25d
  • Gender: Male
  • Location: Christchurch, New Zealand

even if you did something else in time your going to need springs as they will soften more. So it was quite a useful post to be honest, just spend the money and do the springs.

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  • EVIL T
  • Member
  • Member For: 15y 11m 3d
  • Gender: Male
  • Location: Liverpool NSW

How many KM on it? The valve spring in a BF II should be good for close to 400... When do you feel it valve floating under load or when it goes back to idle?

89k on the clock, I also thought they would be good for more than 300kw, but I suppose you win some you lose some!

I am going to have to do the dump pipe, with or without upgrading the valve springs. Just wanted to know if it will give me an extra few pounds to play with, or if id be wasting my time...

thanks ralph, I like it! haha, it is a bandaid solution, but if its a 3psi solution ill be happy!

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  • Member
  • Member For: 13y 9m 25d
  • Gender: Male
  • Location: Auckland, New Zealand

I've been running ~17psi with the same springs and about 180k on the clock and no noticeable float. Just wondering what the PSI limit is with the BFll springs and is there much risk of valve damage etc?

We had 420kw out of it on the dyno with the same springs.

Never really thought much more about it until reading this.

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