I've installed several including one on my 04 or the same vehicle that we are watching here. It nor any of the others have this issue.
(Engine experts needed) Chirp, Vibe, Pop (What is Wrong?)
- Thread starter toximus
- Start date
Going back and listening to the video on my computer speakers and watching your AFRs drop below 10.0 we really have no idea how rich you're running. I didn't even see your AFRs when I watched on my cell. Still, your belt issue is priority followed by a good AFR/tune.
I have found where Rick Rimmer supposedly moved to after BoostedTech but the business went under shortly after and all of the phone numbers have been disconnected.
Edit: I called.
Edit: I called.
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I don't remember lifting immediately after the pop because I was focusing on keeping a steady throttle. But even if my foot did flinch:
The human auditory reaction time is said to be "170ms for an audio stimulus". I played the video back 10 times with my eyes closed and paused each time after the pop and my best reaction time was 150ms on the 9th try, highest was 200ms, my average was around 170ms.
The video is 60 frames per second or 1 frame every 16ms.
The suspension drops 94-99ms after the pop. And the belt settles 200ms after the pop. The automatic tensioner moves again 320ms after the pop I think it's around here that I lifted.
Before the pop:
94ms after the pop:
The human auditory reaction time is said to be "170ms for an audio stimulus". I played the video back 10 times with my eyes closed and paused each time after the pop and my best reaction time was 150ms on the 9th try, highest was 200ms, my average was around 170ms.
The video is 60 frames per second or 1 frame every 16ms.
The suspension drops 94-99ms after the pop. And the belt settles 200ms after the pop. The automatic tensioner moves again 320ms after the pop I think it's around here that I lifted.
Before the pop:
94ms after the pop:
What other inputs can I get that will help narrow down what's going on?
It's sounding like either:
1) The SC unit is the issue (good luck getting BT to warranty it and I'm not buying another)
2) The tune is the issue (I can get it tuned by somebody else but that cost $200 the last time)
3) Or the transmission is the issue (I can pay to have it looked at and repaired but I don't want to invest in a new transmission).
I don't have access to another GoPro but I can use my cell phone or buy a second GoPro. I'm thinking a maximum budget of $250 to diagnose and another $200 to repair (I'd go as high as $500 to repair if I've properly diagnosed the issue and know the fix will work). Anything more feels like throwing money at something that isn't up for my long term goals and takes away from the engine swap budget.
It doesn't for me. The pop maybe, but
Thinking of how to pare this down a bit within the 3 systems you named above. (excuse me if you have done some of these).
1. Series of tests changing driving style to rolling on throttle and more slowly building boost to see if it eliminates chirp, eliminates vibration, and eliminates belt slap.
2. Series of test locking tranny in 2nd and then again with OD off and driving per the original video to see if trans gear selection nets different result than the test in normal automatic mode.
3. Open bypass valve and run it. Tune is the same just wont build boost. just trying to rule out excess fuel backfire cause of pop. Because there is no S/C load its not a valid test for tranny or belt tension though. limited help at best.
4. Video of the dash view for each so that we can try and draw a correlation between rpm, noise/vibration, and boost/afr levels.
I've watch the video a few times,(work productivity has dropped to near zero), and noticed that at the 1.17 mark you appear to be running 14.3 AFR with 5# boost. If my observation is correct the tune definitely needs work in the long run. Watch the video it seems this happens twice - .35 and again at 1.17.
We're on page 8. You're forgiven.
If I hold the accelerator coming up to a hill (meaning I don't move my foot). The chirp happens as soon as the engine goes into boost when the Jeep reaches the hill. I don't have to adjust my foot on the throttle as the boost takes care of maintaining the speed. In fact if I rev it while still in OD and accelerate a little bit I can get the chirps to stop.
The original video was shot at a location 2-1/2 hours away and I don't have any comparable hills around here. Would small hills where it normally chirps but doesn't vibe or pop be okay?
With the BPV zip tied open I do not have any issues.
I'll go for a couple of drives and see what I can do.
Thankfully it's for a good cause.
Is that too lean? 14.3 seems to be the most common value I see and what it idles at.
Could it directly or indirectly cause the chirp, vibe and pop? I'm convinced that they're all related since there is a repeatable progression between them.
14.3 is too lean for a boost condition. That's close to what the O2s try and hold the naturally aspirated engine at for a target AFR. Your AFR does eventually transition to the 10's but its taking waaaaay too long and during that time I'd say its severely lean.
Thinking further about the possibility of a back fire I came up with a theory:
Too much fuel is washing the cylinder walls causing a chirp (heat builds changing the sound and frequency of the chirp), the engine vibrates as the cylinders aren't lubricated, the unburned gas ends up in the exhaust until it hits the lower cat (no upper cats) and ignites with a pop. The metalic sound could be ceramic cat bits tumbling down the muffler and tailpipe.
What doesn't work with that theory is that you'd think I'd hear those bits stuck in the muffer bouncing around at idle.
Edit: Looking at the cats or an oil analysis would show this I think?
Too much fuel is washing the cylinder walls causing a chirp (heat builds changing the sound and frequency of the chirp), the engine vibrates as the cylinders aren't lubricated, the unburned gas ends up in the exhaust until it hits the lower cat (no upper cats) and ignites with a pop. The metalic sound could be ceramic cat bits tumbling down the muffler and tailpipe.
What doesn't work with that theory is that you'd think I'd hear those bits stuck in the muffer bouncing around at idle.
Edit: Looking at the cats or an oil analysis would show this I think?
Thats where I was headed in my last post. Id focus on the belt slip, unless the engine vibration is causing that issue, from you AFRs being so far off. You really want in the low 12 range for AFRs under boost, yours are dropping so low, your gauge doesn't even read them. Get someone to datalog/tune it properly and see what happens.
Maybe I'm just finding what I want to see, but I found this from KenneBell (similarish SC design) (bolding is mine):
"As previously mentioned, worn or defective gears will be noisy at ANY rpm and becomes noisier as rpm increases. And bad gears do not “rattle” – they “whine” at all rpm. The clicking or rattling noise is caused by an uneven engine idle or surge which creates torsional vibrations that are transmitted to the crankshaft pulley. Some engines use a rubber or viscous dampener in the crank pulley to help absorb these pulse vibrations. Many of the new engine designs eliminate these dampeners and are therefore more sensitive. In any event, a slight lope, whether it be audible as with a cam or an inaudible tune up problem, will result in the crankshaft pulley “jerking” the serpentine belt back and forth. This uneven undampened belt oscillation jerks on the supercharger pulley and shaft which is connected to the supercharger gears with a coupler. The lash/clearance in the coupler is responsible for any noise – not the gears. There is no lash in the supercharger gears. However, there is some normal wear or lash (clearance) in the coupler. This can be felt by turning the supercharger pulley fore and aft. Again, “lash” does not mean there should be any noise. Note: This lash is very slight 0-.060″. A½” lash indicates the plastic dampener in the coupler is completely gone – melted. The only way to melt the coupler is to overfill the superchargertherebyboilingtheoil. This is a rarity, but it hasbeendone.
...
One may have difficulty in believing their engine is responsible for the noise, but it is the obvious culprit as the supercharger cannot mystically decide to begin “jerking” on the belt. It is being DRIVEN by the engine’s crankshaft. It performs no DRIVING function and doesn’t get out of tune and jerk on the belt."
http://kennebell.net/tech/supercharger-tech/supercharger-gear-noise/
"As previously mentioned, worn or defective gears will be noisy at ANY rpm and becomes noisier as rpm increases. And bad gears do not “rattle” – they “whine” at all rpm. The clicking or rattling noise is caused by an uneven engine idle or surge which creates torsional vibrations that are transmitted to the crankshaft pulley. Some engines use a rubber or viscous dampener in the crank pulley to help absorb these pulse vibrations. Many of the new engine designs eliminate these dampeners and are therefore more sensitive. In any event, a slight lope, whether it be audible as with a cam or an inaudible tune up problem, will result in the crankshaft pulley “jerking” the serpentine belt back and forth. This uneven undampened belt oscillation jerks on the supercharger pulley and shaft which is connected to the supercharger gears with a coupler. The lash/clearance in the coupler is responsible for any noise – not the gears. There is no lash in the supercharger gears. However, there is some normal wear or lash (clearance) in the coupler. This can be felt by turning the supercharger pulley fore and aft. Again, “lash” does not mean there should be any noise. Note: This lash is very slight 0-.060″. A½” lash indicates the plastic dampener in the coupler is completely gone – melted. The only way to melt the coupler is to overfill the superchargertherebyboilingtheoil. This is a rarity, but it hasbeendone.
...
One may have difficulty in believing their engine is responsible for the noise, but it is the obvious culprit as the supercharger cannot mystically decide to begin “jerking” on the belt. It is being DRIVEN by the engine’s crankshaft. It performs no DRIVING function and doesn’t get out of tune and jerk on the belt."
http://kennebell.net/tech/supercharger-tech/supercharger-gear-noise/
Checking the cats would be fairly quick. Fuel will destroy them.
IIRC you pulled a couple plugs, you may want to check them all.
I tapped the exhaust down the entire length with a hammer and I can't hear anything broken up inside. I'll remove the tailpipe later so we can know for certain that it's not breaking up.
Unless the issue is a leaking stock injector (which I don't think we're seeing while not in boost?) the 7th injector sprays into the intake so it'd be mixed with the air into all of the cylinders equally?
The 7th injector in your situation is concerning, if it’s an extra fuel issue. I’d check the plugs just to make sure they all look to be running the same.
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