Compressor Surge/Flutter (standalone engine)
 

Hey Guys
I haven't driven the car yet (will be soon) and I noticed that there is a compressor surge, flutter sound when I let off the throttle. I have the trans in 5th gear (no axles installed) and if I jab on the throttle I can get some boost and when I lift off the throttle I get that noise which I am calling surge (not sure if that is the correct term).

If you know about this circuit I shouldn't have to explain much more, so to save some time, I wont. :) Hopefully the video will help explain.

1) I read about the vacuum canister bypass so I did that right away to get that out of the equation. Did not change anything, and I left if off permanently.

2) Checked the rubber bypass valve seal on the compressor and it looks brand new, and it holds vacuum.

3) I checked all the vacuum hoses and there are no leaks or obstructions.

4) The boost bypass solenoid is getting 12V and appears to be working, it is brand new.

5) Teed in a vacuum/pressure gauge to the hose that connects solenoid to the bypass valve on compressor to see what is going on. At idle the gauge reads zero pressure (atmospheric pressure) and when I jab on and let off the throttle the needle just jumps around 0-5 psi positive pressure (no vacuum), and that is when I get the compressor surge noise.

6) I disconnected this hose that I teed into and with a brake bleeder applied 10psi vacuum, so I was opening the bypass valve to confirm that with the valve help open, there is no compressor surge noise.

7) reconnecting everything now and if I unplug the solenoid switch, the hose (going to the bypass valve) is now drawing vacuum from the intake manifold at idle and now when I jab on the throttle, no compressor surge. Which makes sense. This is what the video shows.

8) Then I plug the solenoid back in and the gauge goes to zero psi and you can hear the surge noise and needle fluttering at a positive pressure. This is also in the video.

8) With the solenoid switch back in and I reversed the two hoses on the solenoid valve (the hose from the intake manifold and the hose from the cold side of the intercooler and I get the same results as step 7 and all sounds good.

So Im not exactly sure how this solenoid valve is suppose to work.

I am wondering if the control wire for the solenoid valve, which I assume is ground switched is maybe connected to the wrong pin on the ecu that just grounds it continuously, when in fact maybe it is not suppose to be? I'll have to check that later.

What does the ECU look for to determine when to open or close the bypass solenoid valve? MAP sensors? I checked the MAP sensors (which are new) and they are all wired correctly and all wires in tack. (I tried to read boost pressure on the Torque App on my phone and it is not reading it correctly, so I am not sure if that is because the map sensor circuit is not working of if the app is not configured correctly.

link to video (when it finished uploading) :

y don't u just plug the bpv directly into the manifold to eliminate that from the equation, if it works, its probably ur bpv solenoid or vac canister. just cause the bpv solenoid is getting voltage doesn't mean it is working properly. and just get ride of the vacuum canister altogether. it really doesn't do anything but change the sound of the blowoff.

video doesn't work

This is how the lines should be with no vacuum canister. If the lines are reversed (coldside and BPV) you will get flutter after letting off the throttle. It sounds like you had it hooked up right in #8.

Attachment 24085

Video is still uploading, sorry.

I have the vacuum canister removed, so it was mimicking the image that is posted in #4 response (just like it is on a Solstice). (thanks for the image). And the hoses were correctly hooked up, 100% certain of that.

It appears that my solenoid valve is just stuck "on" or "energized" all the time, meaning that when its all hooked up correctly, the solenoid valve never shuttles or turn off to allow vacuum to get to the BPV. So then my next question is: what does the ECU use to determine when to turn on/off the solenoid...and maybe that is where I need to look next.

Now the video is working:

Is that a dune buggy

It's hard to diagnose over the internet. The solenoid is not just opened or closed though. It can be anywhere between 0-100%. I don't believe that solenoid can be logged with HP Tuners, but maybe Trifecta can see it, whom I assume is doing your tuning. A tech2 and the more expensive OBDII scanners can read and control the solenoid, so that may be another option.

It is a replica Ariel Atom that I designed and am building.

So its obvious that the ECU is not controlling the solenoid at all. So what sensors does the ecu gather information from to determine how to pulse the solenoid? throttle, map?

I sent the question on to Vince at Trifecta, yes that is where I got the tune from. I'd rather not bother him, I'm sure he'd rather focus on other things.

Can that external bov shit and youll be much happier

Ive actually messed with the values in the table for when the bpv opens and closes in hp tuners. Very small adjustments are veeeerrryyyy touchy in those tables, I gave up after many attempts to adjust. Just left it stock ended up being the best results. Sounds like the solenoid may be bad.

And just FYI hooking the stock bpv up to a vacuum source like the intake will cause the valve to hang open. I put a value too much on one table and the valve had constant vac going to it through the solenoid being open at idle, opening the valve at idle and ran like crap lol.

Any Ideas??
 

I am working on the same issue, with the exact same behavior. If I restart the car it will boost temporarily then back to 5psi with the fluttering noise. This is a transplant motor in a 53 Nash Healey, I have checked all the clamps hoses, and intercooler. There are no leaks, and have replaced the TMAP and MAP sensors with same behavior. Also contacted WOT trifecta, with the response that hose is loose or blown\cracked intercooler. This is not the case and not sure what other sensor could be causing the issue.