Dull knock in the motor

[Kaldek]

It will still spin pretty quick, if you could stop it spinning then you could confirm if it was the turbo. And i just saw your other question, yes you can remove the turbo without dropping the motor, still a pita though.

There's not much on this car that isn't a PITA to work on. I'm almost battle hardened now.

 

[6A13TT TYPE S]

as said on facebook you can leave the turbine housing on the engine and just swap the core and compressor takes about and hour. to an hour and a half.

but yes if you try take the turbine housing off the manifold or the manifold off the head its almost easier to take the engine out as steve said.

 

[Kaldek]

Well today I bought a mechanic's stethoscope. I went all round the motor listening to it as I snap the throttle. As expected, the knock can be heard pretty much everywhere but it is MOST noticeable on the intake side housing of the rear turbo.

Had a wiggle on the turbo shaft and it seems like it has too much play in it.

Made a short crappy video of the play. Let me know what you all think.

 

[Kaldek]

Hi everyone, just checking back in on this thread after another couple of months. The car runs like a champ still, noise aside.

I've got the parts here to drop out the rear turbo and replace but I also have a complete spare motor I'm planning to rebuild to take E85 and more boost. I'm really not the kind of guy who likes living with problems, but I am trying to force myself to let it be and spend my money on the rebuild.

 

[Kaldek]

Well today I connected my home made det cans (aka engine microphone) to the rear turbo housing and went for a drive. Wow, talk about a lot of knockin'.

I *really* need to get off my ass and swap that rear turbo out so I can either fix it or eradicate it as the source.

 

[Dice]

Can you compare to front turbo? Could that sound be normal?

 

[Kaldek]

Can you compare to front turbo? Could that sound be normal?

No way is it normal. It will either be the turbo or it will be bearing knock from somewhere else which is just being most audible in the turbo housing. Will go do front turbo noise check.

 

[Kaldek]

Just went for a drive with the mike hooked up to the front turbo manifold.

• The noise is barely audible at this location, but it can be heard
• When hooked up the rear turbo manifold the noise is very pronounced

When listening at the front turbo, if I put my foot to the floor in fifth gear, the noise becomes more evident at around 2,500rpm.

I'm deducing a couple of things from the tests today.

1. It's not main bearing noise as this would surely be audible to the same levels anywhere on the block or connected to the block
2. The noise builds as the turbo spools; but
3. The timing of the knocks is odd. They are consistent in getting noisier as boost comes on but seem timed more with engine rpm.
4. The knocks can also be heard on a snap throttle test at idle.

Note that I've had this noise now for probably 5,000km and it has not gotten worse.

 

[Kaldek]

And FINALLY, a recording of the sound as taken using the Det Cans feeding into my microphone socket on a Windows PC.

This sound was recorded with the det cans clipped to one of the bolts that hold the rear turbo housing to the dump pipe. The noise will be *obvious* when you hear it. If I accelerate slowly there is no knock/thud, but if I snap the throttle it knocks repeatedly.

Download the attached file and play using any WAV capable player.

@TME_Steve I'm particularly interested in your thoughts on this.

 

[Kaldek]

Well after a massive delay I finally swapped out the rear turbo. The turbo that came out looked mint and span freely, but for the hell of it I put my spare turbo in.
It did not cure the knocking sound. Sure I'm disappointed but it was constructive in that I now know my turbo is probably OK.

I'm getting another motor rebuilt but I'm still bloody curious as to what's going on. The car has had this knocking sound for nigh on 7,000km and it has not gotten worse or gone away. There's been no visible metal in the oil the last two times I've changed it too.

Next step is to take a close look at my harmonic balancer, even though the sound is loudest at the rear turbo housing.

 

[Boblobsta]

Hi Kaldek,

Sorry I haven't gotten a video reply in your other thread, but I just had to chime in and say that your thread here is describing almost exactly the knock sound I'm hearing and when I'm hearing it.
Just last weekend I bought a car stethoscope to do further diagnosis but I got crook so I haven't checked further yet but it's scary how accurate your description is.

Steve - the sound my car made when I was leaving your place is what this guy is describing. I'm 99% sure it's not an exhaust component or heat shield, I suspect it's either an engine knock or wonky turbo.
I really want to get this sorted before your trip up to QLD so that I can get a decent tune done with the replacement MAF

 

[Kaldek]

Hi Kaldek,

Sorry I haven't gotten a video reply in your other thread, but I just had to chime in and say that your thread here is describing almost exactly the knock sound I'm hearing and when I'm hearing it.
Just last weekend I bought a car stethoscope to do further diagnosis but I got crook so I haven't checked further yet but it's scary how accurate your description is.

Steve - the sound my car made when I was leaving your place is what this guy is describing. I'm 99% sure it's not an exhaust component or heat shield, I suspect it's either an engine knock or wonky turbo.
I really want to get this sorted before your trip up to QLD so that I can get a decent tune done with the replacement MAF

Bolobsta somehow we need to get together and listen. Shame you're so far North as I'll be in Canberra on the week of the 29th of Feb and then going up to Sydney to drop my spare motor off with Steve for its rebuild.

FYI some of my audible knocks were removed when I replaced the exhaust (from front pipes back). You could hear this noise when pulling away from a standstill.

 

[Boblobsta]

I'm trying pretty hard to organise another work trip to Sydney in the near future
If I can get anything sorted it would be awesome if we could align our visits to Steve for the same date... Except for Steve, probably not as awesome for him

I'll keep you posted, unfortunately Cupid has reserved a chunk of this weekend but I'll do what I can to get some gopro of the engine bay sounds.

Cheers, Bob

 

[Kaldek]

Well today I visited Steve's workshop to drop off my spare motor for a rebuild. I also took along with me the original rear turbo from my car that I thought was making the knocking noise. I showed this turbo to Steve, he took one look at how much lateral play there was in the shaft and he said this turbo is stuffed.

He proceeded to show me an example of another turbo from a different car that had 170000 kilometres on it. There was no lateral play in the shaft on that turbo. The turbo that is now in the rear of my engine came from a car that had a similar number of kilometres on it to mine. That turbo also has lateral shaft play. And even more interesting, whilst my car still makes that knocking sound it has changed somewhat with this different turbo.

It may well be that this is the cause of the noise. Unfortunately it does mean I'm going to need reconditioned center housing and rotating assemblies probably for both my turbos. If I don't do this then all the money I'm spending on my engine rebuild could be useless because I may be stuck with turbos that can't make the required boost reliably.

 

[jungle]

Well today I visited Steve's workshop to drop off my spare motor for a rebuild. I also took along with me the original rear turbo from my car that I thought was making the knocking noise. I showed this turbo to Steve, he took one look at how much lateral play there was in the shaft and he said this turbo is stuffed.

He proceeded to show me an example of another turbo from a different car that had 170000 kilometres on it. There was no lateral play in the shaft on that turbo. The turbo that is now in the rear of my engine came from a car that had a similar number of kilometres on it to mine. That turbo also has lateral shaft play. And even more interesting, whilst my car still makes that knocking sound it has changed somewhat with this different turbo.

It may well be that this is the cause of the noise. Unfortunately it does mean I'm going to need reconditioned center housing and rotating assemblies probably for both my turbos. If I don't do this then all the money I'm spending on my engine rebuild could be useless because I may be stuck with turbos that can't make the required boost reliably.

So you're putting standard turbos back on? If you're now going to the effort to rebuild the turbos, then it's not much extra to get them hi flowed.
I'd get the compressor wheel from Kinagawa, should be under $100 each for the 12t any turbo place can machine the housings. See my thread for details.
How will they go? No idea but I'd expect better mid range and top end. with standard cams expect power to drop off at the same rpm. If you're getting cams and cam gears then Steve will be able to adjust the power curve. I think it would be a pretty decent combo. Sad mine is still sitting in the garage waiting to go in

 

[Kaldek]

Thanks @jungle. Right now I want a strong motor that can take E85 and higher boost reliably forever. Being strong though, I can choose later to upgrade the turbos without having to pull the engine down again.

Right now I'm just shooting for 230kw at the wheels on E85 and a smooth reliable engine.

 

[jungle]

I think you might struggle to get 230 with oem turbo's. Steve's car maxxed at 220 on E85.
Its really not that much more to get hi flows, maybe an additional $550. While you've got it apart. You'd have them before me!!
But, if funds don't permit they don't permit.

 

[trotty]

Ahem, I made 229 and had more in it. I lifted heads. With a solid motor I think 230 will be upper limits, but doable.

 

[TME_Steve]

I got 227 thank you very much lol (cos those 7kw were so noticeable, not), Rob also got 227 the other day with pretty old tubs. Trotty got 229 just before he broke something else in his drivetrain @Kaldek will have cleaned up ports and valve cuts though, none of us did....

 

[Boblobsta]

So just for closure, in case anyone else is visiting this thread in the future.
My ticking sound was my wastegate actuator being loose, allowing the wastegate to flap on down rev - and also solving the noticable lag I was experiencing.
Thanks to Steve @ TME for finding it, I have noticed that I'm starting to hear the sound again, approx 12 months on, so I will go and tighten it up again soon.