rusty_wingnut Posted March 30, 2009 Share Posted March 30, 2009 The disco I'm breaking had what appeared to be a needle valve with a hole in the bottom of the body fitted to the wastegate boost pipe is this a dump valve? I've read elsewhere that fitment of a dump valve can help reduce turbo lag and improve spool up How true is this? Quote Link to comment Share on other sites More sharing options...
white90 Posted March 30, 2009 Share Posted March 30, 2009 That is a bleed valve to fool the wastegate into allowing higher boost before opening. and a Dump valve is as good as an astray on a motorbike on a TDI. Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted March 30, 2009 Author Share Posted March 30, 2009 more bits for the bin then! Cheers. Quote Link to comment Share on other sites More sharing options...
white90 Posted March 30, 2009 Share Posted March 30, 2009 ebay! Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted March 30, 2009 Share Posted March 30, 2009 A dump valve throws away your boost to avoid surge when your massflow requirement changes suddenly - eg snapping the throttle shut on a petrol engine. They're not normally useful on a diesel because the massflow doesn't change so quickly - no throttle butterfly. However, I have a surge 'feature' on my VGTdi when coming quickly off the throttle because the vanes can't respond quickly enough to this pressure change and it surges momentarily. However, because I haven't got the calibration sorted yet it surges under load too Your valve sounds like a bleed valve - when the manifold is at 1 bar and the wastegate would normally open, the wastegate only sees 0.5 bar and stays shut to build more boost. If you're throwing it away, I'll have it! Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted March 30, 2009 Author Share Posted March 30, 2009 So if i plum this little device into my turbo, I can tune the boost for 1 bar at the inlet manifold. Quote Link to comment Share on other sites More sharing options...
white90 Posted March 30, 2009 Share Posted March 30, 2009 So you can cause more damage to that poor 300TDI Quote Link to comment Share on other sites More sharing options...
Turbocharger Posted March 30, 2009 Share Posted March 30, 2009 A 300Tdi should already see 1 bar at the turbo - you can ensure this is 1 bar at the manifold by piping the wastegate to the back of the manifold rather than direct from the turbo outlet. If you want more pressure you can also adjust the spring pressure on the turbo diaphragm - just wind out the adjuster nut by 2 turns or so to run more boost but be VERY careful to keep pressures and particularly your EGT at a sensible level, however you do it. Quote Link to comment Share on other sites More sharing options...
rusty_wingnut Posted March 30, 2009 Author Share Posted March 30, 2009 I've plumbed a boost gauge off the back of the inlet manifold and am getting around 0.8- 0.9bar so about right accounting for losses in the intercooler and hoses. To be honest I am loathed to go messing with it, the engine runs so well since i rebuilt it, and it produces no smoke whatsoever. My local garage (AJS who MOT'd it) couldn't believe how well the engine went. Quote Link to comment Share on other sites More sharing options...
TheRecklessEngineer Posted March 30, 2009 Share Posted March 30, 2009 A wastegate can also be used on large (I mean 100,000 hp large) marine diesels to dump boost when slowing down. As the exhaust pressure decreases, the turbo starts to spin down, and there is a moment when the pressure in the inlet manifold is greater than at the turbo - it is entirely possible for gas to exit the turbo backwards - and apparently you don't want to be next to it when it happens... Entirely unconnected to LR diesels of course! But I thought it might interest someone as we are on the topic of wastegates... Quote Link to comment Share on other sites More sharing options...
missingsid Posted March 30, 2009 Share Posted March 30, 2009 I had a look at my BMW Diesel car the other day and it seems to have a valve that puts excess inlet manifold pressure into the exhaust just in front of the Turbo so I assumed that it would keep it spinning when on a trailing throttle?? Marc. Quote Link to comment Share on other sites More sharing options...
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