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So what exactly is surging?Comment
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Wise guys will answer (like always in complex wayOriginally posted by DJones
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Thread muppets like myself
say like this: surging happens when engine is not able to consume amount of air that turbo is trying to pump. Say turbo is trying to push 1 cubic feet of air per second, and engine due to low rpm needs only half of that. This is bad for turbo and for whole pumping process. I've heard some tales, that big Garret turbos have something called anti-surge housing on cold side, but have no idea what is that 
Sau200 20vt 88' 3b, human carrier
CQ typ85 with AAN inside, see project blog at http://kwlw.blogspot.comComment
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My engine-specialist did it for me, so I can't say what he did other than that an adjustable chain gear was used on other cam and woodruff key was removed from the belt gear.Last edited by kalsket; 22 March 2006, 07:40.4F 2006 avant 3.0tdi quattro
4B 2002 S6 avant quattro
typ85 sedan quattro with "minor" changesComment
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here are some intresting reading about turbo spoolup:
K24 vs RS2 vs RS2 comp vs KKK/GT2871 vs KKK/GT3071
RS2 chip by mihnea,PKM short IM, forge dump valve, 3" custom stainless exhaust, 18"X8" Porsche 996 rims, conti contact 245/35 Front 225/40 Rear, QR sport top mount, Powerflex bushes, aloy sub frame bushes, neuspeed 19mm RARB,Hard tranny mount, V8 torsen on RS2Comment
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Do you have any dyno graph from your engine after cam adjustments?
J
Originally posted by kalsketComment
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Originally posted by maRS2
cheers for that
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Tried to find some things on Google regarding surge and everywhere they are telling that a to big turbo can cause surge. In that way it is a bit surprising to read that in this case the smaller turbo's GT28RS and GT2871 suffer most from surge. Is that due to the case they spool up so quickly and then have so much potential in the lower midrange they actually need to be eased a few tenths of boost when mapped? And because the GT3071 is slightly bigger and therefore is later on song it doesn't suffer from this kind of surge?
Apart from the surge problem (which I hope is mappable) I do believe the GT2871 would be my choise as I intend to keep the bottom end (and 3B cams and single coil) stock as long as it can...
I understand that this GT2871 can give a massive spike in the lower midrange, but if you would lower that boost could this turbo give a smooth 500 Nm from onboost till ??? and a matching 375-400 bhp all hand in hand with a good engine / turbo respons?
I am already start saving then... (just recovering from AP's and big maintenance)Comment
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