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***HDi fun*** · 14-03-2008, 11:22 PM

I'm with O.G on this. I can't see the need to vent excess exhaust gas volume given my understanding. The wastegate does that as standard.

Or, is it that the screamer vents compressed air from the induction side that is not required because the throttle valve is shut (diesels don't have a throttle valve so it won't apply to those / again, I'll ignore diesels here).

O.G - is it because the throttle has been snapped shut suddenly, the turbo(s) is (are) still spinning and there's a build up of air mass (therefore pressure, assuming that the intake manifold geometric volume remains constant!). THis could stall the turbo's or perhaps even send it/them into reverse?

But, given the extremely low mass of a turbocharger's rotating turbine assembly, therefore it's low moment of angular inertia surely it would not take very much to bring it to a halt pretty swiftly. Or, have I missed the point - that being that anything spinning at 200,000rpm plus is going to take quite a lot of stopping.

Therefore maybe that's why there's a need to discharge excess intake (engine side) pressure.

But I'm still not sure, why not just fit a damping mechanism to the throttle in the first place? Thus avoiding all the complication and associated noise.

Anybody out there that can advise?

Kind regards,

Paul.

14-03-2008, 11:22 PM	#9 (permalink)
*HDi fun* Moderator Torque Junkie Car: Peugeot 406 Join Date: Apr 2006 Location: SOUTH EAST Posts: 2,586	Re: Screamer pipe I'm with O.G on this. I can't see the need to vent excess exhaust gas volume given my understanding. The wastegate does that as standard. Or, is it that the screamer vents compressed air from the induction side that is not required because the throttle valve is shut (diesels don't have a throttle valve so it won't apply to those / again, I'll ignore diesels here). O.G - is it because the throttle has been snapped shut suddenly, the turbo(s) is (are) still spinning and there's a build up of air mass (therefore pressure, assuming that the intake manifold geometric volume remains constant!). THis could stall the turbo's or perhaps even send it/them into reverse? But, given the extremely low mass of a turbocharger's rotating turbine assembly, therefore it's low moment of angular inertia surely it would not take very much to bring it to a halt pretty swiftly. Or, have I missed the point - that being that anything spinning at 200,000rpm plus is going to take quite a lot of stopping. Therefore maybe that's why there's a need to discharge excess intake (engine side) pressure. But I'm still not sure, why not just fit a damping mechanism to the throttle in the first place? Thus avoiding all the complication and associated noise. Anybody out there that can advise? Kind regards, Paul.