Dual Valve Springs

[pittersuk]

Hello all

Just curious seen a few race engines now and ive noticed that alot of them have dual valve springs.

I dont want to sound thick or anything but never really noticed this before. Just wondering what the advantages are of using dual valves? How does this effect the spring rate or does it?

AJ

[Pigeon]

Not dual valves, dual valve springs... one inside the other, and usually wound in the opposite sense.

Partly it's just to get more spring force so the valves can close quickly enough in a high-revving engine. Partly it's because the inner and outer springs have resonant frequencies which are both different from each other and higher than what a big single spring would have, so you don't get the same valve spring resonance problems you could have with a big single spring.

[fixedwheelnut]

what Pidgeon said The differing resonance frequency helps prevent valve bounce at high rpm

[steve_D]

I have double springs on my engine. When selecting the springs I could also have had triple springs.
The third spring was there to damp the resonant frequencies of the other two.

Steve

[pittersuk]

Thanks Guys

What about the spring rates of the two springs inside each other? how would you calculated that?

[deltafox]

Squash em both at the same time and measure the force required to compress em by whatever amount i guess....

[steve_D]

pittersuk said:

Thanks Guys What about the spring rates of the two springs inside each other? how would you calculated that?

You don't need to. The springs come as a set against the manufacturers data sheet.
You do not want to go trying to select your own pairing of springs.

Steve

[zcacogp]

pittersuk said:

Just curious seen a few race engines now and ive noticed that alot of them have dual valve springs.

I've never seen an engine that didn't have dual valve springs ... but then I have only taken Golf GTi engines apart. However, I don't have them up there as being particularly sporty (after all, they were only Audi estate engines in the first instance.)

Actually, I lie. I once dismantled and rebuilt a lawnmower, and that had single valve springs ...



Oli.