Knocking / tapping sound over 3k RPM

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Knocking / tapping sound over 3k RPM

Postby binary » Fri Sep 28, 2018 2:12 pm

I've now got an ultrex dump pipe installed, and have had the car tuned to suit. Very different car now to standard and is great fun to drive.

I have just noticed a knocking / tapping sound over 3k RPM, most noticeable from 4k onwards. Quite noticeable when raising revs slowly with window down while moving, can't hear it with windows up. Sound is there when revving in neutral but much less. Seems to only be present under throttle, during deceleration the sound disappears.

The sound reminds me of when I spun the big end bearing in an old N/A car I had years ago... but much less noticeable / severe. I'd say it's mild sounding right now. 'll try to get a video of it. The sound follows the RPMs from 3k onwards but can't hear it once revs get say past 5.5k RPM (probably because so much noise). No difference in power at all (from seat of pants feel anyway).

I am thinking it could be rod or big end bearings. Any way to identify this via RomRaider logs? They're all clear so it's not pinging (no FKC / FBKC showing up, IAM still at 1). I'll drop the oil out this weekend and see if there's metal shavings present.

Hoping it's not time for a new motor :(

Update: further research leads me to think it could potentially be the timing belt tensioner. I’ll have a look into that and report back!
MY05 Liberty GT auto wagon | Ultrex dump pipe, tuned by Torqued Performance http://www.torquedperformance.com/
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Re: Knocking / tapping sound over 3k RPM

Postby bigBADbenny » Mon Oct 22, 2018 3:51 am

Keep the oil up and send it :)
Any update?
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Re: Knocking / tapping sound over 3k RPM

Postby binary » Thu Nov 08, 2018 10:00 pm

bigBADbenny wrote:Keep the oil up and send it :)
Any update?


LOL yep decided to do just that! I haven’t been driving it but just started running it again this week, and I’m thinking the sound could be some of my dodgy hack work on the turbo heat shield. I still need to drop the oil and check that, but she’s still running sweet, pulls hard, and doesn’t make any unusual noises from idle to about 4K which is where the tap / knock starts.

Worst case scenario, EJ207 from GRB STI wouldn’t be so bad?! :twisted:
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Re: Knocking / tapping sound over 3k RPM

Postby bigBADbenny » Thu Nov 08, 2018 10:47 pm

There’s mic kits for this purpose on eBay, or you can tap all the shields manually to see which rattle or ring :)
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Re: Knocking / tapping sound over 3k RPM

Postby binary » Sun Nov 18, 2018 6:53 pm

I bought a mechanics stethoscope off eBay, waiting for it to arrive. Meanwhile... dropped the oil today...

1) as the oil was finishing draining I shone a torch on the trickle that was still coming out and could definitely see tiny metallic glints in the oil

2) chopped the end off the oil filter and pulled the filter apart... yep, visible copper flakes. Arrrggghhh!!!! Biggest piece would have been maybe 5mm long.

Image
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Given the knock is happening over 3k rpm but only under load (completely disappears when decelerating), and I’m seeing copper, I believe one or more of my big end bearings are shot.
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Re: Knocking / tapping sound over 3k RPM

Postby bigBADbenny » Sun Nov 18, 2018 8:11 pm

Hopefully this can be an opportunity for you.
Jdm ej207 short?
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Re: Knocking / tapping sound over 3k RPM

Postby binary » Sun Nov 18, 2018 8:31 pm

Yep thinking either that or GRB swap, as both would run a similar cost... although shortblock plus machined heads may be wiser given it would effectively be a new motor, plus a whole lot easier as no need to replace loom. Will be a while though as don’t have the cash to throw at it right now unfortunately :?

One positive though, at least I know my sense that there was a serious issue was right, and that it is what I thought it was...! I mean I guess it’s speculation as to which bearings have gone but from the symptoms I think it’s one or more of the big end bearings shot.

Question is, what caused it? I’m thinking most likely the dreaded detonation
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Re: Knocking / tapping sound over 3k RPM

Postby bigBADbenny » Mon Nov 19, 2018 1:11 am

What were the tune specifics?
Upgarage have a ver10 spec C mostly dressed long for around 6k atm :)
https://yahoo.importmonster.com.au/yaho ... 2084199182
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Re: Knocking / tapping sound over 3k RPM

Postby binary » Thu Dec 13, 2018 7:02 pm

We were most of the way through tuning when the bottom end knock appeared, running 18psi (spiking to 19-20 at certain points). I saw some random high knock events in 3-4K rpm range (talking -8 FKC). IAM wasn’t dropping so figured must have been ok but the knocking sound didn’t lie. Spewing...

Oh man those GRB Spec C motors are wicked... I’m torn between just grabbing a replacement EJ20X off importmonster vs EJ207 short block vs Spec C full motor plus turbo.

Cost is somewhat of a factor so definitely leaning toward a low km EJ20X from importmonster. Seeing some decent examples even with turbo and 80-100k on the motor for $2k landed. I’ll still need to proceed with tuning whatever I get but I think getting a wideband will be essential to avoid the issue I faced this time around.

For now the old girl is in the garage not being driven. Still runs fine and pulls hard but it’s a matter of time before the bearings fully go and she throws a rod lol... so figure better to not drive till I get the new motor in.
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