brettxw

So I've been reading, trying to learn things about how everything works.. The hotter the outside air is the faster the turbo needs to spin to create the boost... Got me thinking.. Since it's 120 degrees out here in Vegas, that turbo is spinning a lot faster now then it has been.. Wouldn't that create that random flutter sound since it's spinning a lot faster than usual? I'm still replacing the BPV but was wondering if maybe that could be a cause for the flutter? It has only started since this hot weather has hit.

I could be completely wrong but like I Said, I'm trying to learn things on my own so I thought I would ask.

CudaJoe

iTrader: (1)

it wouldnt spin that much faster. it would be directly proportional to the change in air density. A faster spinning turbo wont create the flutter. Its the bpv not opening or the spring is too strong. have you tried taking it apart and inspecting it?

What psi is your tune set too?

brettxw

Ah, well.. I'm still learning haha. I have not inspected it, I'm just going to replace it with the forged one just to play it safe. Then I'll know that can't be the issue in the future.. I just hope that IS the issue and I don't need to buy a new turbo.. I really don't know what Kevin tuned the psi too? I haven't seen it go over 23 when I would do pulls to log.

tomj77

iTrader: (2)

The real problem is when ur turbo makes the flutter while in boost. That's bad, means ur engine can't use all the air the turbo pushes so it goes back into the compressor wheel slowing it down, which is very hard on the turbo

CudaJoe

iTrader: (1)

yea 23 psi should be fine. I was wondering if you were one of the few that had like a 30 psi tune and your turbo's over spooling like crazy in the heat.

so mathmatically.

Density of water at 70*F is about 0.99802 g/mL. But at 120*F its roughly 0.98870 g/mL. The density change in water is 0.9% decrease. If a water pump was set to flow 20L/min when the water temp is 70*C, then the pump would have to adjust for 120*F by 0.9%. The flow would adjust to 20.2L/min to flow the same volume of water. Barely an increase in pumps efficiency.

Air is going to behave in a similar way with a compressor. I believe density in air changes a little more drastically than water.

Since I googled it, I might as well show a more valid example lol. 70*F dry air density is 0.075 lb/ft^3. 20 psi 70*F air density is 0.177 lb/ft^3.

At 120*F its 0.069 lb/ft^3. 20 psi 120*F its 0.162 lb/ft^3.

The change is about 9% decrease in density. A turbo pushing 23 psi at 70*F would push about 25 psi to move the same volume of air at 120*F programmed by the ECU for stoich ratio.

A possibility is your wastegate. Im not a tuner so I dont know what can be adjusted by Hptuners and what cant but maybe its the wastegate duty cycle set incorrectly. I know the wastegate can be physically adjusted but I can see if the wastegate opens too early to allow exhaust gasses to bypass the turbine then the backpressure of 23 psi in the charge piping could cause the flutter? Just really stretching for ideas lol. No matter what, when the throttle closes, the back pressure should push out the bpv.

CudaJoe

iTrader: (1)

^that is really the only need to concern for flutter. And THAT flutter sounds much different than the bpv flutter your experiencing. Ive had that flutter a few times when the psi is right at 0 or just into vacuum. Mainly not enough pressure to open the BPV but there is some pressure.

Im still thinking its your BPV or spring stiffeness. (maybe broke?).

brettxw

Wow!!! Thank you for taking the time to explain that. My theory on the faster spinning turbo has failed. Haha. I don't hear the flutter when I am in boost, only when I take my foot off the accelerator and doesn't happen every time. I'll be replacing the BPV next week when it comes in and let you guys know.

I may even try that mod to bypass the vac to see if that helps.

tomj77

iTrader: (2)

Ur gonna have flutter no matter what on k04 and even zfr, k04 with stock spring works best for that turbo. Minor flutter. Of u don't have a vac tank then it is worse. The vac tank I think was out in there to get the bpv open fast enough to not have flutter. The zfr on the other hand is usless trying to solve the issue, my theory is that the bpv port just isn't big enough to get all the air out on time so some hits the compressor wheel anyway.

63 Nova SS

iTrader: (3)

Don't think the forge will never wear out and do the same as I had issues with mine. I went back to running the stock one and never looked back. Mine flutters more when the motor is cold and as other have said, at part throttle. If it's not doing it at wot then I wouldn't really worry a lot about it.

brettxw

Okay, I had to push this issue off to the side as I had the fuel pump pressure issue again and just replaced the in tank pump today.. Hopefully that resolves that issue and then I can get back to this flutter issue.. I did find out that the previous owner replaced the turbo in it last year so its a new turbo!

tomj77

iTrader: (2)

Fuel pump pressure issues are usually the high pressure pump on the head not the in tank pump. What symptoms or codes did u have?

brettxw

There's already a thread I started about this. I had already replaced the hpfp two weeks ago. Everything was fine till the other day. We shall see how long this one lasts.. Next I'll be putting the stock fuel rail and injectors back in.