Ok I am probly being dull here but why the need for different spring rates for the higher boost , as if the dv is fitted like the std one is the boost is against the side of the piston and there should be equal boost on top (due to the small pipe from mani) and a suction beneath the piston from the intake to the turbo..

Like I can under stand maybe if the boost was against the bottom of the piston it would need a stronger spring, but a stronger soring will slow down the dv response time too surley..

anyway i'm sure someone will be along to maybe explain or something :wonder:

Ok I am probly being dull here but why the need for different spring rates for the higher boost , as if the dv is fitted like the std one is the boost is against the side of the piston and there should be equal boost on top (due to the small pipe from mani) and a suction beneath the piston from the intake to the turbo..

Like I can under stand maybe if the boost was against the bottom of the piston it would need a stronger spring, but a stronger soring will slow down the dv response time too surley..

anyway i'm sure someone will be along to maybe explain or something :wonder:

Your correct, under load the DV does have equal boost pressure at both sides of the piston, but the reason the DV closes and remains closed under boost is because the surface area of the top of the piston is greater than the bottom, therefor the piston is pushed down and in doing so, seals off the exhaust port.

The spring serves two purposes.

It creates a closed default position, and it effects the DV's opening and closing pressures.

Prob one of the most common reason for fitting a stronger spring to a modified 1.8t, could be to overcome the effects of boost spikes.

My car peaks at 1.5 bar and I have run it with the std 007P spring for about 4 years, and it works fine

HTH

Bill.