Gt2860r-5's = Surging & Flutter

[700HP-GTR33]

I have the same turbo's.....I though the same as you.

The turbo's sounded like they were fluttering......but all is normal.

Get a tune and wait a little while.

I don't notice this anymore on mine..either the surges have gotten softer

or I have got use to them.

[bradsm87]

I'm curious how tuning can fix it too. I assume that the surge you guys are talking about is when you very slightly back off the throttle, it flutters and the car sort of shudders. my S14 does that too and i wanna get rid of it.

[700HP-GTR33]

I'm curious how tuning can fix it too. I assume that the surge you guys are talking about is when you very slightly back off the throttle, it flutters and the car sort of shudders. my S14 does that too and i wanna get rid of it.

I believe the intake wheel of the Turbo slows down when you back your pedal off or change gears.

The excess amount of air is pushed back onto the incoming air it has tried to create.

Thus causing fluttering, the longer you drive around the softer this sound becomes.

the harder you push the car...the better the sound becomes

[paulr33]

from my knowlege it occurs when the engine is on load and throttle is half backed off

so to me it sounds like the bov's are half opening so pressure is vented back into the front of the compressors

and some how causes it to either surge or vary excessively which gives the compressor flutter / chop chop noise

confused how tuning would fix it, even though it does

[700HP-GTR33]

from my knowlege it occurs when the engine is on load and throttle is half backed off

so to me it sounds like the bov's are half opening so pressure is vented back into the front of the compressors

and some how causes it to either surge or vary excessively which gives the compressor flutter / chop chop noise

confused how tuning would fix it, even though it does

I don't think the tune actually fixed mine,it was their after the turbo's where fitted and tuned......and went away slowly.

Does the AVCR boost controller learn from excessive flutter and driver behaviour?

I have an AVCR boost controller...and seeing that it creates/controls boost it can also slow the spikes...maybe.

I wonder if the boost controller is controlling my flutter?

Just my 2c

[paulr33]

i doubt it would tekin

i would be surprised if it would

most controllers are purely interested in build a good ramp for boost build and keeping it stable

im not even sure it would see the bouncing pressure

go for a drive and replicate it, let us know

does boost pressure bounce? i bet it doesnt

[700HP-GTR33]

I am just trying to figure out why it has gone away on mine....

Are new turbo's tighter in the wheel construction?

Do you need to break in a Turbo....get it to loosen a little maybe.

Has anyone had this thing on anew turbo that has slowly gotten quieter?

Or is it as I had stated....you just get use to the noises...

[paulr33]

actually it makes a bit of sense if it is seeing the pressure vary

cos then it would close and open its solenoid based on pressure

so the turbine would speed up quickly as the gate would close

then it would open again, like rapid chatter

try it and let us know if the boost varies rapidly (as in the controller display)

plot BOOST on analog chart display and see what it looks like

[wolverine]

getting more air into the cylinder rather than having it revert should be the key.

changes to cam gears could/should help.

exactly why tuning beats me. i spoke to a few tuners that feel it can be difficult to get around but others seem to think it is no problem. so i imagine the degree of mismatch of the turbine/compressor wheels might make this easy or near impossible.

and these turbos are not mismatched.

Edited March 19, 2007 by wolverine

[enzan]

there is no such thing as wastegate flutter

remove the phrase, it does NOT exist, there is no such thing

im curious how the tuning can correct this

Ok so what do you call it when the wastegates go chu,chu,chu,chu and the car surges and carries on? please elighten me. I've already ruled out the BOV's as I said earlier.... I'm confused

[700HP-GTR33]

Hey everyone, I just finished fitting the GT2860-5's to my R32 gtr and must say they've made a huge difference, the car feels more responsive and comes on boost earlier too. On full throttle it's fine but on really light acceleration and at cruise I now get bad waste gate flutter and surging. I never had this problem with the original turbo's and haven't changed anything other than the turbo's and a bit of metal off the exhaust manifolds.

Any ideas?? Help please!!!

Do you have a boost controller?

What make and model?

[enzan]

Nah, no boost controler. Do you think it would help?

[paulr33]

i dont understand how it can be a case of stuffing too much air into the cylinders

from what we know it happens when the engine is on some load (not max) and its up a hill

a hill usually brings on good engine load, which is great for boost building

but it happens when the user is on half throttle, not what i would call max throttle

at least, what i have read it occurs when its half throttle, and not max, is that correct?

[enzan]

I didn't touch the wastegate preload before fitting the turbo's... Was I supposed to perhaps

[wolverine]

paul this is exactly what i have experienced with an ordinary hi-flow of unknown origin.

light to medium throttle openings caused surge, WOT all good.

changes to tension of the BOV spring eased the symptoms, changes to tuning and cam gears cleared the issue.

[paulr33]

its not the wastegate's fault, there is no such thing as wastegate flutter

its do with the bov's, i suspect they are half opening

and its causing a conflict with either the compressors or the actuators opening and closing rapidly

as pressure in the manifold varies rapidly

as simple as adjusting the duty cycle on the boost controller so its slow and progrssive would possibly cure it out

i suspect thats what most tuners do to correct it, make the solenoid open slow and in small increments instead of fast and hard

that way it doesnt induce open/close/open/close type behaviour, which dictates massive changes rapidly in manifold pressure

as the compressor is sped up and slowed down repeated really quickly

[paulr33]

i also think there are two issues here (well maybe)

compressor surge of "fluttering" occurs when pressure past the compressor is beyond what the compessor can supply

ie:

workshop A hiflow and do whatever and you go and run the turbo

you dial in 15psi but forwhatever reason (mismatched combo, bad wheel, etc) then manifold pressure ramps to 22psi

the compressor wheel surge's as the pressure past the outlet is greater than what it can supply so it flutters/surge's

i would expect this problem to only occur at full throttle, wide open throttle and aggressive boost building / full load

the other scenario is the common after market twin turbo flutter / chuffing

which i think is a combo of the bov's half opening and venting back and then actuators opening/closing

in a harsh and on/off type fashion instead of soft and progressive.

this only occurs during light / medium load and usually up a hill is a good example of when it occurs

[enzan]

its not the wastegate's fault, there is no such thing as wastegate flutter

its do with the bov's, i suspect they are half opening

and its causing a conflict with either the compressors or the actuators opening and closing rapidly

as pressure in the manifold varies rapidly

as simple as adjusting the duty cycle on the boost controller so its slow and progrssive would possibly cure it out

i suspect thats what most tuners do to correct it, make the solenoid open slow and in small increments instead of fast and hard

that way it doesnt induce open/close/open/close type behaviour, which dictates massive changes rapidly in manifold pressure

as the compressor is sped up and slowed down repeated really quickly

Hmmm, but I blocked the vacuum line to the BOV's off and tried it, and made no difference at all. And it's only on very light throttle right on the transition from manifold vacuum to boost that it occurs

[R31Nismoid]

Ok so what do you call it when the wastegates go chu,chu,chu,chu and the car surges and carries on? please elighten me. I've already ruled out the BOV's as I said earlier.... I'm confused

The wastegate is located on the Turbine/Rear of the turbo

The surging is from the comressor wheel, which is on the Intake/front side of the turbo

Comp surge (the type we are talking about here) occurs when the turbos are flowing more air than then motor can handle

The air is coming from the compressor side, and has nothing to do with wastegate operation on the rear end of the turbo.

How it is tuned out, i am not sure. I'm yet to go across that in my travels

[paulr33]

hmm well then im not sure

i cant see a reason why a new pair of turbo's would surge when going from vacuum to positive pressure

knowing what the tuners do to fix it could help give it away

maybe they just retard the timing a touch during boost build

that could help, but a bit of a poor mans fix maybe?

id love to know the cause