Feel said:
Looks the right way round to me too (not that I really need to confirm what the m0rker said).
Glenn's description seems wrong to me
- boost comes in at the side, on the Leon anyway.
Interestingly, I have heard the same chatter/flutter that you describe. Low revs, boost builds, lift off and "tchtchtchtchtch". Can remember now whether that's with the DV relocated or not, I've changed it that much.
For reference, I call the top of the DV the bit with the small nipple.
If you stick boost in to the side of the DV, then you can't push the DV open with boost pressure because the body of the piston can't move laterally. In that case, why would you need a stiffer spring? All it would do is slow the response of the DV down by, as Bill says, resisting the suction from the vacuum at the top of the DV. Think of the DV spring as a damper, like those on your suspension, it's purpose is to smooth the transition as the DV opens, so that it's not slamming wide open at the slightest pressure differential across the DV. It also prevents the DV opening at the onset of boost where the manifold pressure may lag the pressure at the base of the DV - this doesn't apply if your piston DV is reversed.
Take a look at a stock Bosch DV, if you run it reversed (boost in the side), you can see that you are applying pressure to a soft neoprene diaphragm that has give in it. Any wonder that they tear? That makes no sense to me, what does make sense is to apply pressure to the metal plate at the base of the diaphragm? It also makes no sense to have a device that operates via pressure differential only to hook the opposing pressure sources up at 90 degrees to each other.
In theory, I absolutely agree with Bill that overly-stiff springs are a bad idea because they make it harder for the DV to operate and why have a DV at all if we're going to hinder it? In practice though, I find my car is much nicer to drive with a stiffer spring but it's still not OEM perfect. I've experienced this "chuff-chuff" effect and my theory is that the DV isn't opening wide enough or for long enough (due to the stiffer spring) to satisfy the ECU (MAP isn't dropping off fast enough with respect to TPS rate of change?) so the ECU is pulsing the N249 to open the DV and there's a 'tug-of-war' going on for control of the DV piston between the spring & N249.
This would occur whatever the DV orientation, but with the DV in what I believe is the correct position (boost from the bottom), the boost pressure will "assist" the vacuum at the top in opening the DV against the spring preload. I'm going to try bypassing the N249 to test this theory.
