Turbo Shuffle

[donkeypunch]

so was talking to my mechanic today about the ol' turbo shuffle, he spoke to his turbo rebuilder and was mentioning to him about that the new turbos coming out (not garrett yet though) have some back-cut on them to reduce the shuffle?

he said he can do it to my -5's (i know R31nismoid put on standard BOV and piping to fix problem ) at around NZ$1.5k

im over trying to tell him to put the original GTR BOV on (he insists not to) balance pipes, standard piping etc im just gonne leave it as is and crank the boost up from 18 - 20lbs and be done with it.

anyone heard about this back cut(ing) of turbos? sorry cant explain this in more detail/better

[Equinox]

.... Anti-Surge housings?

Edited March 26, 2009 by Equinox

[wolverine]

let me get this straight you want to spend NZD$1500 vs re-using the standard BOV's and piping?

umm, we can do some funny things in australia but this must be a trick question.

[R31Nismoid]

Rob - dont back cut the wheels on the turbos.

It'll hurt response, thats the point, slows the compressor down to avoid the shuffle (too much air etc)

For my sanity's sake - take the car elsewhere if your mechanic is arguing nonsense.

It honestly sounds like he's had very little experience with twin turbos and GTR's

[bloodzkull]

Rob - dont back cut the wheels on the turbos.

It'll hurt response, thats the point, slows the compressor down to avoid the shuffle (too much air etc)

For my sanity's sake - take the car elsewhere if your mechanic is arguing nonsense.

It honestly sounds like he's had very little experience with twin turbos and GTR's

i'll agree with you there.

as per the pm you sent me ive got -5's mostly stock pipeing and stock blow off valves. 346kw at the wheels and NO shuffle at all

[The Dan]

Rob - dont back cut the wheels on the turbos.

It'll hurt response, thats the point, slows the compressor down to avoid the shuffle (too much air etc)

For my sanity's sake - take the car elsewhere if your mechanic is arguing nonsense.

It honestly sounds like he's had very little experience with twin turbos and GTR's

Does the compressor turn seperately to the turbine now?

Back cutting the turbos compressor allows some air to pass on to the secondary blades which actually cools the charge air and allows you to run more boost and timing without the shuffle.

If anything, it has improved response on the 4 cars I have done it on.

[R33GTRKid]

can someone please give me an accurate description of shuffling?

If I boost hard and then go back to light throttle without closing altogether i can get a 'choo choo choo' noise that can last a second or two but I thought that was just the wastegate doing its job or even the stock BOV's making noise through my pods??

[The Dan]

can someone please give me an accurate description of shuffling?

If I boost hard and then go back to light throttle without closing altogether i can get a 'choo choo choo' noise that can last a second or two but I thought that was just the wastegate doing its job or even the stock BOV's making noise through my pods??

That's reversion, not shuffling.

The air chops back through the compressor and 'bounces' back and forth.

[R31Nismoid]

Does the compressor turn seperately to the turbine now?

Back cutting the turbos compressor allows some air to pass on to the secondary blades which actually cools the charge air and allows you to run more boost and timing without the shuffle.

If anything, it has improved response on the 4 cars I have done it on.

Tell me where he said back cutting the compressor?

Normally when someone talks 'back cutting', its the exhaust wheel. It was a what you saw people in the 90's doing because of poor wheel combinations.

Allows more exhaust to pass, turning the comp wheel less earlier, and surprise - no surge. But this hurts response in a logical sense.

Its only going to improve response in a situation where the compressor is surging, and your bringing it out of the surge area and letting is spool freely. Surge generally hurts response.

But, when there is a perfect and much better solution (ie correct fitment of parts), it shouldn't be required for -5s (the topic at hand)

Simon - that's just the BOV's letting go most likely. GTR BOV's 'bounce' off each other under certain conditions

[The Dan]

Tell me where he said back cutting the compressor?

Normally when someone talks 'back cutting', its the exhaust wheel. It was a what you saw people in the 90's doing because of poor wheel combinations.

Allows more exhaust to pass, turning the comp wheel less earlier, and surprise - no surge. But this hurts response in a logical sense.

Sorry, misunderstood his statement. And yours. You mentioned it slowing down the compressor so I naturally assumed we were talking about the compressor.

I have the compressor cover back cut for the reason mentioned above.

Back cutting the turbine blades does slow the compressor, but it's probably better to refer to it as allowing the turbine to flow more freely, which in turn slows the compressor down.

[Cjmartz2k]

Your talking about anti surge slots/holes and they do exactly what 3ltrR32 says. Holsets, Borg-Warners, some GT series Garretts, and some HKS turbo's run them to name a few. Has nothing to do with the noise when you let off the gas.

People on this board really love to worry about "turbo shuffle", don't they?

[R31Nismoid]

Sorry, misunderstood his statement. And yours. You mentioned it slowing down the compressor so I naturally assumed we were talking about the compressor.

I have the compressor cover back cut for the reason mentioned above.

Back cutting the turbine blades does slow the compressor, but it's probably better to refer to it as allowing the turbine to flow more freely, which in turn slows the compressor down.

Back cutting (allowing more exhaust gas to pass) must slow the compressor... basic logic dictates this.

More too it (like all things), however the basic principle says a back-cut exhaust wheel would slow down the compressor

People on this board really love to worry about "turbo shuffle", don't they?

Well yes, people worry about compressor surge, and with good reason being it hurts turbo response.

If you were not worried - then there would be problems

[The Dan]

Back cutting (allowing more exhaust gas to pass) must slow the compressor... basic logic dictates this.

More too it (like all things), however the basic principle says a back-cut exhaust wheel would slow down the compressor

Well yes, people worry about compressor surge, and with good reason being it hurts turbo response.

If you were not worried - then there would be problems

I'm not saying I disagree but you don't back cut a turbine to slow the compressor, even though it has that effect. You do it to relieve pressure build up in the exhaust manifold.

[donkeypunch]

hey sorry about confussion, in all honesty i wasnt quite sure what he meant, i pretty sure it wasnt to do with back cutting compressor, because it was to do with the actual turbo housing, and how he mentioned it was on new turbos?

r33gtrkid 'reversion' is more like the sound/noise i have, and as he explained it, but my noise goes on light throttle, hills, cruising motorway, as soon as i put my foot down, or boost, it goes away, sorry if i misslead anyone with the my 'shuffle' theory

[Cjmartz2k]

That's what I thought you were talking about the whole time. That is what people are usually posting up here about, not actual compressor surge, or even full throttle lifting/shifting.

I was saying it seems like a lot of people are worried about the noise that happens when you lift during light throttle acceleration. It sounds like to me you or you mechanic are confused about what a ported shroud does/would do in your case. Bottom line, if your worried about "shuffle" or "flutter", don't. Ported shrouds don't help with that anyways.

[donkeypunch]

That's what I thought you were talking about the whole time. That is what people are usually posting up here about, not actual compressor surge, or even full throttle lifting/shifting.

I was saying it seems like a lot of people are worried about the noise that happens when you lift during light throttle acceleration. It sounds like to me you or you mechanic are confused about what a ported shroud does/would do in your case. Bottom line, if your worried about "shuffle" or "flutter", don't. Ported shrouds don't help with that anyways.

hey thanks for the that, i guess that what these forums a for aye, people like me who dont know that much learning from a wide range of people with good knowledge

[R31Nismoid]

Bottom line, if your worried about "shuffle" or "flutter", don't. Ported shrouds don't help with that anyways.

Umm not really.

Compressor surge/shuffle on light throttle (acceleration, usually up a hill is a good example) CAN be helped by a ported shroud.

Have a 10min google and you'll find a dozen pictures and explanations about it

[The Dan]

Umm not really.

Compressor surge/shuffle on light throttle (acceleration, usually up a hill is a good example) CAN be helped by a ported shroud.

Have a 10min google and you'll find a dozen pictures and explanations about it

+1 and it's called surge porting for a reason

[Cjmartz2k]

I was under the impression the surge port is the same thing as what holset calls their "map width enhancement" groove which fights off REAL compressor surge i.e. compressor "chopping" at WOT because you are running it outside what would normally be it's efficiency range or something like a mis-matched hot side. The slots/holes have the effect of making the efficiency islands on the compressor map wider. If they also cut down on light throttle lift noise, cool, but that's not their intended design function.

[Beer Baron]

yes back cutting your turbine wheels will cure the surge. no it's not the best way to go about it. compressor surge is a conditon that happens when the turbo is producing more air than the engine can ingest at a given rpm. an easy way out is make the turbo less effecient at low rpm. back cut exhaust wheel will do that as it wont spin up the compressor as early. downside is loss of response. upside is surge cured and it can flow more exhaust gas up top so possibly an increase in peak power.

anti surge compressor covers are another way to do it. they have holes or slots around the compressor inlet and this can reduce/eliminate surge.

if nismoid reckons that returning to the stock GTR piping and BOVs then I'd try that first. it's cheap and has no downside (apart from looks maybe).