Noise from waste gate? (1 Viewer)

[Lumpskie]

Hey guys,

I recently installed a PDI intercooler, and I am loving it. I am running 22psi out of my Gturbo as well. Today, on my drive to work, there was an accident so I had to take a new route that involved back roads. I had to deal with a lot of high throttle acceleration and hard braking. During the course of my drive, I noticed that, when transitioning from 15psi+ to hard braking, I could hear what sounded like my waste gate whoosing air. Previous to today, I have never heard this before.

Now, I am wondering... is this normal? Am I only hearing this because the unusual route to work required me to drive in a different way? (combination of relatively low RPM combined with highish boost?) Do I have some sort of boost leak (even though my max boost remains the same) that I can hear... maybe due to my intercooler install?

Any ideas or feedback?

Thanks guys,

 

[IanB]

If it's only when you let off the gas, the wastegate should be snapped shut right away...you should only be hearing the wastegate when you're on the gas at high boost levels when it opens.

Is this maybe just some new noises from the air passing through the intercooler and piping? Are you hearing this with the windows up or down, or both?

 

[Lumpskie]

If it's only when you let off the gas, the wastegate should be snapped shut right away...you should only be hearing the wastegate when you're on the gas at high boost levels when it opens.

Is this maybe just some new noises from the air passing through the intercooler and piping? Are you hearing this with the windows up or down, or both?

Thanks for the reply. I'm hearing this with windows up. The sound is a lot like a blow-off valve on my gas car. When I lift, having high boost, I can hear the sound. It sounds like it has a little flutter to it as well.

 

[IanB]

Does it sound like fluttering at all? Abrupt off-throttle situations is where compressor surge happens, I don't know a lot about it, and we don't have throttle plates in our intakes that block things off, but it could be that?

 

[Lumpskie]

Does it sound like fluttering at all? Abrupt off-throttle situations is where compressor surge happens, I don't know a lot about it, and we don't have throttle plates in our intakes that block things off, but it could be that?

Yeah, it does have a little flutter to it. And, it does only happen when I release throttle very abruptly... Any ideas on why the compressor would be surging this morning versus the last few weeks? Surging happens when there is low airflow, right? Do you think a high flow intake would help the situation?

 

[gerg]

This makes me think of surge. It can sound like a chugging whoosh sound. If the turbo is spooled hard at a high engine rpm.....then the engine rpm drops rapidly the turbo rpm stays high so your turbos putting out a high volume of air at a high pressure ratio but the engine can accept only a small volume of it. I venture to say the higher the boost the more easily this will occur without having a compressor map in front of me. The sudden drop in rpms very quickly forces the plot over to the surge line (left). If youve mapped the compressor close to the surge line already then its easy to do. This is why mapping is so important and why sourcing "surge resistant" compressors is so helpful. It's not just about max pressure ratio or best effeciency. Blow off valves can prevent surge by alowing the excess air to leave the intake track but they require a throttle plate to create a pressure differential on either side of the plate so it tells the BOV when to open. In the diesel (except B, 3B and 2H) engine there is no throttle plate so the whole intake tract sees the same pressure. You would need a sophisticated system to detect surge and activate a BOV to prevent this. Another way would be to get a more surge resistant compressor, lower your boost or don't allow your rpms to drop so quickly when under heavy load as in drive like an old man. I think your seeing your systems limitations.
g

 

[Lumpskie]

Thanks for the teply @gerg . It's a wierd situation... I couldn't get it to surge at all on the long ride home. I tried snapping from 9n throttle to off and got nothing. Maybe the unique combination of low speed hills with emergency braking forced the situation?

I'll turn the boost down a bit, just in case. Maybe I'll shoot for 20 or 21psi rather than 23.

 

[gerg]

I think if you adjust your off throttle manners you can compensate for it. Try giving it a burp of fuel in between shifts to maintain engine rpms a bit longer to allow the turbo to spool down. I had to drive this way with one of my turbos when boost was high. Mine had a throttle plate though.

 

[Lumpskie]

I think if you adjust your off throttle manners you can compensate for it. Try giving it a burp of fuel in between shifts to maintain engine rpms a bit longer to allow the turbo to spool down. I had to drive this way with one of my turbos when boost was high. Mine had a throttle plate though.

That's a good thought. I'll drive it tomorrow and see how it does. It has been awesome at 23psi for the last 3 weeks and I like having a max EGT if 1050 when flooring it up long hills. I'll report back after tomorrow's commute.

Thanks for the feedback

 

[gerg]

No problem. If possible dropping it a gear going into a corner might help by keeping the rpms up but also let you slow down fast. Might be a win win.

 

[Lumpskie]

The Cruiser drove to work perfectly this morning. I couldn't recreate the noise. If it comes back, I'll update this thread. But, for now, it seems almost like yesterday's commute in was a fluke. Thanks for the help, guys.