Turbo flutter

[wrighar]

I have what I think is a small problem...

Earlier this year it was noted (at Wilsher's garage) that SCAero turbo boost would 'flutter' or waver between about 2500 and 3250 rpm.

By flutter I mean hunt up and down between 15-18psi about once a second, with a definate pulseing to the pull of the car.

I swapped down to a temporary ecu last month (2.3T CSE one) and the flutter was still there, but at about 14-16 psi with the same change in pull when accelerating. I was also runnig a MBC set to 1bar as this ecu was faulty in the APC department.

I've now refitted my original ECU and reconnected the APC (removed the MBC), and the flutter is still there (now between 15-20psi with a definate surging in the acceration. Below this flutter point boost is about 17-18psi, above the fluuer point (3250rpm), boost rises to about 19-20psi and holds to at least 4500rpm.

Does anyone have any ideas? I know Pete Tandino suggested that my wastegate actuator might be weak and allowing the WG to flutter open.

I'm guessing my car has something wrong somewhere...

I assume other's Aero's don't have this flutter.

Andrew.
Looking for solid boost, and maybe a bit more

[mark e]

Hmm, not off the top of my head. You could try shortening the wastegate actuator rod (also raises base boost) to see if that helps.

[wrighar]

Originally posted by Mark E:
[qb]Hmm, not off the top of my head. You could try shortening the wastegate actuator rod (also raises base boost) to see if that helps. [/qb][/b]

And thereby lies a tale.

The wastegate rod is siezed and very nearly rusted through, I dare not try to free it (the wastegate works fine, even if the R pin and hole have vanished...).

To adjust the base boost a few weeks ago I had to pack the WG actuator bracket with 3 washer per bolt to raise it to standard (about 4mm).

With the JT pipe, base boost has dropped to 7psi (from the previous 8.5psi)

Andrew

[wrighar]

I've been out trying to fix this tonight (and it was another excuse just to drive it).

Checked all the vacuum/pressure lines. OK
Checked all the wastgate lines. OK
Checked all the connectors on the intake pipe. OK
Checked the thropttle body (a little gummy/oily in the bottom)
Changed the plugs (are these old ones ok, look a little brown??)

)

Other than that I'm a little stumped for now.
Peak bosts seems to be 22psi, settled boost about 18-19psi (about 17 at 5000rpm), surging boost 16-21 ish psi.

Andrew

[wrighar]

Continuing the challenge.

I tried removing all the 'adjusting' packing washer from the Wastegate actuator, dropping the base boost down to 5.5psi and went for a drive.

The surging is still there, but pickup is slower and peak boost about 2psi lower, so that's not it.

Next I may try upping the base boost to about 10psi and try again.

As this does it with No APC connected, I'm wondering if it could be anything to do with resonances, tube lengths and tuube diameters, either that or a problem with the wastegate / wastegate actuator (as it would do i with just the C/W pipes connected via a MBC set to 15psi.

Andrew

[Julian]

Sounds to me like the wastegate actuator is playing up. The fact that you required 4mm of adjustment to get to some semblance of base boost makes me think it is past its best. Perhaps the flutter is the wastegate blowing open under boost?

[zeke]

I could be wrong but it sounds as if the base boost is set too high. Is Scaero a trionic? The Aero's base should be set at 6-7 psi, IIRC.
If set too high, negative adaptation will result and peak boost will actually drop. I've also seen bad BPC solenoids give vascillating boost - just a thought.

[Firefighter]

I might be going off in the wrong direction, Does the car have an Air Mass Meter that you could clean, I had a 9-3 diesel that felt like the throttle was being put on,off,on,off, between 2800 & 3500 rpm during acceleration, almost like water in the fuel, had the meter cleaned and it got better for a week or two then the dealer finally changed it, big jump in pulling power and 5 MPG more on the fuel, hope it's as easy to fix as my prob.

[wrighar]

Originally posted by robert lavergne:
[qb]I could be wrong but it sounds as if the base boost is set too high. *Is Scaero a trionic? *The Aero's base should be set at 6-7 psi, IIRC.
If set too high, negative adaptation will result and peak boost will actually drop. *I've also seen bad BPC solenoids give vascillating boost - just a thought. [/qb][/b]

Yes it's a trionic 5.
I've had the base boost set at 5.5, 6.5 and 7.5 psi (no washers, 3 washers, 5 washers...) and the surging is still there with all 3 settings.

I've now reset to 3 washers (6.5 psi).

Also tonight I've changed the APC valve, checked the 3 larger vacuum pipes, checked the main intake pipe is clear and changed the airfilter.

Flutter still there, but not quite so pronounced (but it was raining and fuel is now low).

Nect I may remove the airbox and check the snorkel is clear (or even remove it and drill the airbox...)

I'm still thinking it's the Wastegate actuator and or the TCS throttle body. as you still get the surging completely bypassing the apc with a MBC from the compressor to the wastegate.

Andrew

[wrighar]

Originally posted by Firefighter:
[qb]I might be going off in the wrong direction, Does the car have an Air Mass Meter that you could clean [/qb][/b]

Firefighter,

No it's got a MAP sensor instead up at the far end of the intake plenum.

Andrew