Ringing sound on SC car
06-05-2014, 01:30 PM
#1
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Ringing sound on SC car
Hi guys
I finally got my fuel management unit working, and car is running strong. AFR on full boost is 11, at idle it is 13.5. I have developed a mid-tone ringing sound at idle that seems to come from the center rear of the engine compartment. It seems to go away with increased revs, or gets covered up. Manifold vacuum at idle is 17".
Thanks for ideas
Dave
I finally got my fuel management unit working, and car is running strong. AFR on full boost is 11, at idle it is 13.5. I have developed a mid-tone ringing sound at idle that seems to come from the center rear of the engine compartment. It seems to go away with increased revs, or gets covered up. Manifold vacuum at idle is 17".
Thanks for ideas
Dave
06-05-2014, 04:55 PM
#5
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How far 'off' would you have to be to have detonation at idle?
06-05-2014, 05:06 PM
#6
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It's probably just a vacuum leak. When sitting at idle your at pretty much the strongest vacuum... -17 If you blip the throttle does it go away? If it does then I'd guess you either have a vacuum leak or its the idle control valve.
06-05-2014, 05:16 PM
#7
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Thread Starter
Thanks guys. Airpump is gone. I suspect a vacuum leak too, Victor. I will look more closely soon. I think a rubber hose stethoscope will help me.
Will report back.
Dave
Will report back.
Dave
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06-05-2014, 07:12 PM
#9
Rennlist Member
Check all your intake clamps on 3in hoses. also at the AFM where the adaptor is. The blind inserts that keep the AFM from blowing back out, are a pita to get tight. The s/c still pushes a significant amount of air at idle. enough to cause a small whistle type noise at a leak. check any vacuum plugs you may have installed onto throttle body during conversion. also the vac hose that goes to the fuel regulator.
06-05-2014, 08:18 PM
#10
Rennlist Member
Thread Starter
Thanks guys,
I have a little more data. The noise happens only when the car is warm. I was listening around and I decided to clamp the crankcase breather hose to the intake plenum. The sound stopped completely, and came back when I reclamped it. Carl's breather system exhausts his oil separator and cam tower vent into the plenum through a one way PCV valve. Clamping the final line stopped the sound tonite.
I am still not 100% convinced that there is not another cause, but for now I am thinking this way. I will check again tomorrow and look all over for vacuum leaks.
Breather system noise sounds benign, but annoying. I could look at changing the final hose diameter. We will see.
Thanks again,
Dave
I have a little more data. The noise happens only when the car is warm. I was listening around and I decided to clamp the crankcase breather hose to the intake plenum. The sound stopped completely, and came back when I reclamped it. Carl's breather system exhausts his oil separator and cam tower vent into the plenum through a one way PCV valve. Clamping the final line stopped the sound tonite.
I am still not 100% convinced that there is not another cause, but for now I am thinking this way. I will check again tomorrow and look all over for vacuum leaks.
Breather system noise sounds benign, but annoying. I could look at changing the final hose diameter. We will see.
Thanks again,
Dave
06-05-2014, 09:23 PM
#11
Administrator - "Tyson"
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Your breather system is plugged, the sound is the pressure building and finding a way out.
The pressure will find a way out and the next weakest link in the chain is usually the crank seal.
The pressure will find a way out and the next weakest link in the chain is usually the crank seal.
06-05-2014, 10:14 PM
#12
Former Sponsor
Hi guys
I finally got my fuel management unit working, and car is running strong. AFR on full boost is 11, at idle it is 13.5. I have developed a mid-tone ringing sound at idle that seems to come from the center rear of the engine compartment. It seems to go away with increased revs, or gets covered up. Manifold vacuum at idle is 17".
Thanks for ideas
Dave
I finally got my fuel management unit working, and car is running strong. AFR on full boost is 11, at idle it is 13.5. I have developed a mid-tone ringing sound at idle that seems to come from the center rear of the engine compartment. It seems to go away with increased revs, or gets covered up. Manifold vacuum at idle is 17".
Thanks for ideas
Dave
06-05-2014, 10:23 PM
#13
Rennlist Member
Thread Starter
Thanks Hacker, you may be right.
Let me please ask how the noise goes away when I clamp the suction line to the plenum from the PCV valve? It seems I have too much vacuum, not too much pressure?
Also the PCV valve rattles nicely, and I can blow through it fairly easily. I understood that PCV valves are controlled one way valve that only allow a couple of inches of vacuum.
I will try asking Carl if I have done something wrong in my installation.
I really appreciate your thoughts on this.
Dave
Dave
Let me please ask how the noise goes away when I clamp the suction line to the plenum from the PCV valve? It seems I have too much vacuum, not too much pressure?
Also the PCV valve rattles nicely, and I can blow through it fairly easily. I understood that PCV valves are controlled one way valve that only allow a couple of inches of vacuum.
I will try asking Carl if I have done something wrong in my installation.
I really appreciate your thoughts on this.
Dave
Dave
06-05-2014, 10:25 PM
#14
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Thread Starter
06-06-2014, 11:02 AM
#15
Developer
What I said to John today:
Of course, I have not heard the noise personally, and am only speculating based upon his description.
I wonder if your PCV valve is "humming" (cycling so many times it makes noise).
At idle, if your engine is nice and tight, you should be drawing a vacuum on that crankcase. That is a good thing. Off idle, there will be less vacuum, and I bet the noise you report stops.
You may remove the PCV valve if you wish for the noise to stop. It is a one-way valve. You noted you can blow through it in one direction but try to blow through it in the OTHER direction - it will not allow that.
The design is to allow the intake manifold to draw in crankcase fumes when the intake is under vacuum. However, when the intake is under boost pressure, we do not want the gases to flow in the opposite direction and pressurize the crankcase.
Carl
At idle, if your engine is nice and tight, you should be drawing a vacuum on that crankcase. That is a good thing. Off idle, there will be less vacuum, and I bet the noise you report stops.
You may remove the PCV valve if you wish for the noise to stop. It is a one-way valve. You noted you can blow through it in one direction but try to blow through it in the OTHER direction - it will not allow that.
The design is to allow the intake manifold to draw in crankcase fumes when the intake is under vacuum. However, when the intake is under boost pressure, we do not want the gases to flow in the opposite direction and pressurize the crankcase.
Carl