Rattle from wastegate flapper
Tensioning the actuator is not likely to solve the problem. In the case I experienced it made the problem worse because the extra tension just forced the flapper to sit at an angle on the seat, leaving the wastegate ports partially open. This made spool up even worse. It could only make 10 psi at 5000 rpm (stock turbo).
Given the OP's new MAP turbo, and assuming the flapper puck's face and its seat at the outlet of the turbine housing's bypass port are parralel and true, then increasing spring pressure is going to cure his problem. This is most assuredly true.
It is worth emphasizing, at the risk of being repetitive,, that when discussing an internally gated turbocharger, the actuator's spring pressure is the ONLY pressure that keeps the flapper closed down onto its seat(leaving aside for the sake of simplicity the diversionary role of ancilliary boost control devices and the BCS, and WGDC, etc.).
The other 3 types of pressure involved in an integrally gated turbo's boost control via turbine inlet exhaust diversion circuit[ i.e., 1)manifold boost pressure, 2) turbine inlet pressure, &, 3) atmospheric pressure] all combine in contrary concert to open the flapper valve.
What I am saying, is that your specific example is atypical and therefore, any conclusions derived therefrom should not be applied in a general sense and as a result are not relevant in the OP's scenario which involves a flapper valve assembly in good working order.
As a practical matter he should first adjust(shorten) the overall length of the actuator rod thereby increasing seat pressure. I would guess that 3 complete 360* clockwise rotations of the turnbuckle tip would be a good starting point.
EDIT: wreckleford: I vaguely recall your case since a few days have passed. But, correct me if I am wrong didn't it involve a stock VIII turbo with a stock MHI WGA? So, tell me what was the solution in your case? What was the cause of the problem and how did you remedy the issue?
Last edited by sparky; Jan 2, 2014 at 05:59 AM.
I had this problem on a car. The rivet type of thing that holds the flappers onto the arm got loose, causing the noise. It also caused lazy spool as any amount of exhaust pressure would push the flapper to one side and allow exhaust to escape....You may be able to get away with welding the flappers to the arm. If not replace the housing.
The term "flapper valve" is derived from the flapper valves that control hydraulic flow in your toilet tank. The flapper valve's arm which rotates on a shaft draws an arc of radial motion. This is contrary to a poppet style valve whose movement is axially inline with a valve stem centerline as in the valves in your motor's cylinder head.
The puck on a flapper valve setup cannot have a rigid point of attachment to the rotating shaft/arm assembly. The puck requires that slight bit of slop or take-up, because one edge of the circumference of the puck touches the seat surface slightly before the edge that is diametrically opposed to it.
Last edited by sparky; Jan 2, 2014 at 11:38 AM.
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Yep, all is well with my flapper. MAP confirmed that it's perfectly fine. I've got the wastegate arm preloaded properly and on the flapper. The valve seats perfectly and is snug with no rattles. I'm just waiting on the manifold and o2 housing to return from ceramic coating and get my turbo blanket in the mail before reassembly
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Here is the preload. I confirmed with my tuner that this would be okay for the tune currently on the car, but I will still need to do a log to check boost levels with him. Problem is I don't have a working laptop battery so maybe a friend will let me borrow a computer to do some logs
Assuming that your particular case involved a faulty flapper valve assembly, for example a warped puck resulting in non parralel puck face/seat interface, that to my mind still doesn't rule out insufficient spring pressure as a possible cause of the OP's problem.
Given the OP's new MAP turbo, and assuming the flapper puck's face and its seat at the outlet of the turbine housing's bypass port are parralel and true, then increasing spring pressure is going to cure his problem. This is most assuredly true.
It is worth emphasizing, at the risk of being repetitive,, that when discussing an internally gated turbocharger, the actuator's spring pressure is the ONLY pressure that keeps the flapper closed down onto its seat(leaving aside for the sake of simplicity the diversionary role of ancilliary boost control devices and the BCS, and WGDC, etc.).
The other 3 types of pressure involved in an integrally gated turbo's boost control via turbine inlet exhaust diversion circuit[ i.e., 1)manifold boost pressure, 2) turbine inlet pressure, &, 3) atmospheric pressure] all combine in contrary concert to open the flapper valve.
What I am saying, is that your specific example is atypical and therefore, any conclusions derived therefrom should not be applied in a general sense and as a result are not relevant in the OP's scenario which involves a flapper valve assembly in good working order.
As a practical matter he should first adjust(shorten) the overall length of the actuator rod thereby increasing seat pressure. I would guess that 3 complete 360* clockwise rotations of the turnbuckle tip would be a good starting point.
EDIT: wreckleford: I vaguely recall your case since a few days have passed. But, correct me if I am wrong didn't it involve a stock VIII turbo with a stock MHI WGA? So, tell me what was the solution in your case? What was the cause of the problem and how did you remedy the issue?
Given the OP's new MAP turbo, and assuming the flapper puck's face and its seat at the outlet of the turbine housing's bypass port are parralel and true, then increasing spring pressure is going to cure his problem. This is most assuredly true.
It is worth emphasizing, at the risk of being repetitive,, that when discussing an internally gated turbocharger, the actuator's spring pressure is the ONLY pressure that keeps the flapper closed down onto its seat(leaving aside for the sake of simplicity the diversionary role of ancilliary boost control devices and the BCS, and WGDC, etc.).
The other 3 types of pressure involved in an integrally gated turbo's boost control via turbine inlet exhaust diversion circuit[ i.e., 1)manifold boost pressure, 2) turbine inlet pressure, &, 3) atmospheric pressure] all combine in contrary concert to open the flapper valve.
What I am saying, is that your specific example is atypical and therefore, any conclusions derived therefrom should not be applied in a general sense and as a result are not relevant in the OP's scenario which involves a flapper valve assembly in good working order.
As a practical matter he should first adjust(shorten) the overall length of the actuator rod thereby increasing seat pressure. I would guess that 3 complete 360* clockwise rotations of the turnbuckle tip would be a good starting point.
EDIT: wreckleford: I vaguely recall your case since a few days have passed. But, correct me if I am wrong didn't it involve a stock VIII turbo with a stock MHI WGA? So, tell me what was the solution in your case? What was the cause of the problem and how did you remedy the issue?
We had to replace the housing. I will see if I can find the old housing and take some pics or video to explain the issue better.
Last edited by wreckleford; Jan 2, 2014 at 07:30 AM.
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