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Pud237 · 06-02-2008

Dump valve won't work on a JTD, cause there is no throttle to close. On a turbo petrol, coming off the accelerator closes the throttle butterfly, allowing a build up of pressure outside the inlet manifold for the valve to then 'dump' in a big hiss.

On a JTD (or any TDi) there is no throttle butterfly, so any boost the turbo creates when you come off the acclerator just goes straight through the engine, only no fuel is injected.

I think this might have been one of the first things I asked when I bought my JTD

06-02-2008	#5 (Post Link)
Pud237 AO Platinum Member Join Date: Apr 2006 Location: North Yorkshire Posts: 14,649 Member car: Alfa 156	Re: dump valve on a 2.4jtd Dump valve won't work on a JTD, cause there is no throttle to close. On a turbo petrol, coming off the accelerator closes the throttle butterfly, allowing a build up of pressure outside the inlet manifold for the valve to then 'dump' in a big hiss. On a JTD (or any TDi) there is no throttle butterfly, so any boost the turbo creates when you come off the acclerator just goes straight through the engine, only no fuel is injected. I think this might have been one of the first things I asked when I bought my JTD Weekend toy: Alfa 156 3.0 24v V6, Silver with red leather, Q2 diff, GTA Teledials, headlights & inlet manifold, AutoDelta carbon intake, BMC CDA, decat pipe and SuperSprint rear box, FK coilovers, Dastek Unichip - my 245bhp beast! Gone but not forgotten: Alfa 156 2.4 JTD Veloce, Vela Blu, Angel 'mad map' & BMC CDA, Ferodo DS2500s - the fastest tractor in town! AO 'Bratpacker' No 5.