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Author Topic: TFSI Gear change sound  (Read 14644 times)
hackish
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« Reply #15 on: October 27, 2015, 08:26:24 AM »

Could it be the ecu monitors also the turbocharger intake pressure, instead of blindly cut spark or whatever?
I've no clue about A2l/maps, but when my wastegate got blocked in open position, i had a lot of farts from dsg. Even farting in N when fulltrottle reving up then releasing, engine was making small delay untill "accepting" my gaspedal release, then reving down with "machine gun" farts, like if ecu wanted the intake pressure to not go below xx value.

I think you're describing active antilag which is frequently used in motorsports. It is highly unlikely that you'll see any OEM using this sort of thing because it puts a _LOT_ of stress on the exhaust system and turbo. In rally we'd send the turbo(s) out for a rebuild after every race. Forget about warranty.
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Geremia
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« Reply #16 on: October 27, 2015, 09:26:45 AM »

Yes, sort of "light" bang-bang effect, but my 1.4 tsi is a crap CAXXA model and not tuned at all, not sure if they were late ingitions (so less power to pistons but high exhaust flow, if i'm correct), i've no knowledge at all about this stuff, i just observed the engine didn't do a quiet revdown, instead it seemed to want more pressure in intake but faulty wastegate was blocked in open position, so the machinegun farting timedout after 1 second. I was just wondering if the dsg fart (which i've observed to be similar if not same) could be increased by lowering up the map value related to such "min intake pressure", if such variable exists.
About stress on exhaust and turbochargers, i think vw engineers have found a solution: "tell customers the turbocharger got broken for no cause, never occurred before, this is first time we see such problem" Grin
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adam-
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« Reply #17 on: October 27, 2015, 03:15:33 PM »

Are you sure this just isn't a delay between lifting off and the on-set of the over-run fuel cut taking place?

The stuck open wastegate would bypass the turbine blades and you'd have a more "naturally aspirated" engine as such.  Turbo's kill a lot of noise.

I'm thinking that the stuck open wastegate is allowing the exhaust to be more vocal, and you're hearing a small over-run fuel cut for one second.
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