ROd bearings with age and knock discussion

[turboglenn]

Something just occured to me, so i want to run it by a few of you and see what you think.

Say you're getting a weird knock that you can pretty much rule out as fuel or spark being poorly tuned as the cause.

Could worn but not spun rod bearings dcreate enough noise under higher loads to be heard and interpreted as knock by the sensor?

Also, i dont' know how much noisier most of your motors that have BSE's got, but mine is poretty noisy when revved up, but leak down and compression show good. I've been thinking about maybe just pulling the pan and putting new bearings in, or first swapping to a 20-50 race oil instead of 0-30 or 5-30.

That's another thought....can too thin an oil ( factory recomended sttuff) be too thin causing this problem with possible noisy rod bearings? this is all speculation, I'm just looking for other peoples thoughts that have built and blown up a lot more of these motors than i have.

 

[spoonman]

My brother's dsm had a knock light that he made and after a day of racing at the track he had found out that two rod bearings were bad, well his knock light started to flash much more frequently after the bearing problem so he replace the bearings and did some head work (bad valves) and the light did not show any irregular knock like before the rebuild.

 

[turboglenn]

I have a J&S knock monitor timing retard unit, and i'm starting to think i'm getting some knock from possibly worn rod bearings. I put in cams and pulled the balance shafts in one night in sub freezing temps and i put a new pan gasket on, so i'm not to eager to tear it apart, but i have been hearing this weird noise when the motor is revving down from a high RPM and not loaded by the tranny (that's the loudest time) it sounds like a big metal pully with a bearing starting to go out and it's vibrating , if that makes sense... i'm wondering if this is BSE , cams or bearings...My motor that was machined wrong sounded similar, but i heard a disting knock on it and knew it was main bearings. Iv'e never heard "worn rod bearings" only spun ones so, i'm kinda poking into things that i'm assuming might happen *shrugs*

And for the noise.. i replaced all timing related pullies and parts , so it's none of that, the head is fresh with under 20Kon it and the short block is the only part with miles on it, this was my "2nd spare" nad it's sitting at probably 75K miles or more now, and when i dynoed i had my knock monitor go bad (old MSD unit) So i could have beat the hell out of the rod bearings that day from detonation on the dyno as i was trying to push timing and boost ( unsucessfully to a point on the boost..damn EBC). And when i put the knock monitor on with the same tune i was showing a good 7-10* being pulled, but when it was too rich...i leaned it out and that went away. so i don't know...stumped on this one and i dont' want to turn teh sensitivity down any further on my motor and do more damage.

I think i'll change to 20w-50 tomorrow and see what happens, if it gets quieter, i guess i'm tearing the pan off anf throwing new mains and rod bearings in there.

Are the stock rod and main bolts on a 6 bolt motor re-usable? THe machinist told me my mains were on my 90 6 bolt because they weren't torque to yield bolts... i wouldn't imagine the rods being torque to yield either, but it is a mitsubishi

Anyone done that before?

 

[KGB Pilot125]

When I was into Syty stuff I had some pretty serious phantom knock. kept showing up, ran race fuel, new sensor, less timing, more race fuel, finally during a pull the front driveshaft exploded into about 3 parts. No more phantom knock. the yoke for the front shaft was so bad that the knock sensor was picking it up but it was non audiable to the ear. something about harmonics I suppose.

 

[GVR4592]

Bad ball joints are probably the number one cause of phantom knock, I would check those first.

 

[turboglenn]

Bad ball joints are probably the number one cause of phantom knock, I would check those first.

All front balljoints are good and most of them were replaced in october of 07... I've tried to find this through chassis noise already and haven't found anything that would be suspect just yet.

I even dropped the timing rediculously low and still got the same amount of knock in the same spot. The alky injection seems to have no effect on it if it's on or off either. So i'm assuming it's either in a moving part in the motor, or something near the engine bay making a bunch of noise.. it only does it around 4500 rpm though somtimes 4k someitimes closer to 5k.. by redline it goes away though, wchich really has me scratching my head. These are the reasons i'm wondering if it could be bearings. being RPM dependant and mainly in 3rd gear ( i can pull through 4th with the same knock but to a far less extent, only 1-2 degrees being pulled)

NOw what i don't understant either, is that i have everything dialed in better than before and i was running a much more agressive timing curve and about 11.5:1 AFR at all areas.

I'm still in the 11.5 range with the meth on, but i can increase the fuel globally to test the problem with out alcohol and be able to keep it at 11.5 since i can see a wideband read out in front of me.

 

[dsm-onster]

Try running a quick 10:1 fuel tune. Pull timing back. If you still have the knock. It is absolutely phantom knock.

I don't think it is the bearings. Bearing noise that is audible gets louder and DOES NOT go away through out the rev range. If you have a rod knocking loud enough to trip the knock sensor, then your crank journal is likely trashed. It will blow up soon with or without new bearings anyway. So try not having the knock retard active under 5K. I HATE tracking phantom knock. My chassis has over 200K miles on it. . . Everything is noisy.

Knock does the most damage at peak torque. . . If you're getting phantom knock at you peak torque rpms, then you'll have to take a chance or suffer through the tracking process.

I'll sit back and have a beer (my day off) and not worry about my PK. I disabled the knock sensor until 4500 rpms. If it's a rod knocking, I'll whine at the wife enough to get a rebuild.

 

[turboglenn]

I know it's not a rod knocking, i've heard that plenty of times, i was thinking a rod with bearings that are just barely out of spec and if they could cause noise. There's just a weird noise like i said that sounds like a big pully vibrating just slightly at a high RPM , most noticable when you push teh clutch in and let the revs fall after a high RPM pull.

But i have richened the tune, need to pull some more logs now. But the thing is i can't disable knock detection by RPM (other than it has to be over 1250rpm to "arm" or a TPS volt of 1.75 or more)

and yea, it's right around peak torque, i make peak at ~4750rpm and it hits right around 4500 give or take a few thousand RPM's, but it's always gone by redline, and the higher gear i'm in the less it knocks. first and second go by so quick i see knockbut not for long....weird thing is, i had all knock gone before the tranny replacement and the added meth count in teh water/meth mix and i haven't changed much

 

[dsm-onster]

I know it's not a rod knocking, i've heard that plenty of times, i was thinking a rod with bearings that are just barely out of spec and if they could cause noise. There's just a weird noise like i said that sounds like a big pully vibrating just slightly at a high RPM , most noticable when you push teh clutch in and let the revs fall after a high RPM pull.

But i have richened the tune, need to pull some more logs now. But the thing is i can't disable knock detection by RPM (other than it has to be over 1250rpm to "arm" or a TPS volt of 1.75 or more)

and yea, it's right around peak torque, i make peak at ~4750rpm and it hits right around 4500 give or take a few thousand RPM's, but it's always gone by redline, and the higher gear i'm in the less it knocks. first and second go by so quick i see knockbut not for long....weird thing is, i had all knock gone before the tranny replacement and the added meth count in teh water/meth mix and i haven't changed much

Color coded rsponses :


If it were a rod, then ANY noise would mean contact with the cank journal. ANY contact with the crank journal will get worse exponetially. It will blow in a matter of days. I'm not saying that a knock sensor cannot detect rod knock. I AM saying that your engine noise should be getting much louder now or locking up soon.

You have phantom knock. If it were real kockin a4g63, from my experience, you would see knock to red line once it begins. Our cylinder heads don't shed heat really good. Once detonation begins knock stays "alive". With water injection and a FAT nozzle I saw this. After a certain tune, nothing stops knock.

The higher the gear the more load on the engine. More knock earlier should be seen at higher gears. This is not happening to you. Your recent tranny install is suspect. Something is vibrating.

If youre shiftig fine.. . No cocked tranny intall. . . I would screw it and change my knock detection perameters. You have the stock hg. IIFF you do get any significant knock before your system detects it, your hg will blow before you damage anything. And a hg swap is easy. I can coach you through it over the phone without a camera. I know your good. You know that pushing any system means assuming certain risks.

 

[turboglenn]

WEll, guess what... I just went on several errands in my car to keep breaking in the tranny... all the same timing and everything, and i pulled 3rd through 4th all the way to 7500 RPM with no knock. WTF????????

I'm glad, but what's gonna make it come back and when? Who knows, could be next year, could be right now!

The only knock parameters i can change are

Sensitivity
Switch between 10 and 20* max allowable amount to be pulled
And the last thing i can adjust is if it pulls all cylinders together or pulls only the ones knocking individually.

I have it set on "individual retard" and "max 10* retard allowed" What's weird is for phanton knock I noticed that it was only pulling timing in one cylinder at about 7-8 degrees tops. I could not tell what cylinder with out an oscilliscope because each cylinder has it's own frequency value for identification of what cylinder's being pulled.

I am on a felpro HG ( or whatever is in the NAPA gasket kit )But i'm running ARP studs in the head. When i put this motor in it was because i had just found out my fresh 3k dollar motor with only 1500 miles on it was machined wrong and eating main bearings( i was changing them every 500 miles untill i got this block. This was suppoosed to be a temp unit but financial situations made it a longer term lease

 

[tkelly27]

'90 rod bolts are not torque to yield. At least according to the FSM. You'll also note there's a single torque value for it, not a multiple step plus 1/4 turn. If you're planning on putting HP to it, you may or may not want to replace it. Good idea, but with all the 250k mile guys running 400hp out there, who knows.

 

[Black_Bullet]

Try running a quick 10:1 fuel tune. Pull timing back. If you still have the knock. It is absolutely phantom knock.

I don't think it is the bearings. Bearing noise that is audible gets louder and DOES NOT go away through out the rev range. If you have a rod knocking loud enough to trip the knock sensor, then your crank journal is likely trashed. It will blow up soon with or without new bearings anyway. So try not having the knock retard active under 5K. I HATE tracking phantom knock. My chassis has over 200K miles on it. . . Everything is noisy.

Knock does the most damage at peak torque. . . If you're getting phantom knock at you peak torque rpms, then you'll have to take a chance or suffer through the tracking process.

I'll sit back and have a beer (my day off) and not worry about my PK. I disabled the knock sensor until 4500 rpms. If it's a rod knocking, I'll whine at the wife enough to get a rebuild.

I agree with this post.
Also my knock sensor is disactivated until 3500 + for a phantom knock reason as well...