RB25 Flywheel on KA24DE-Improperly balanced?

[Hoffman5982]

So I recently blew my ka up, again. The same day it went I was told the rb25 flywheel isn't balanced correctly for a ka and will cause it to destroy bearings. This is the first I've heard of this and it has me a little paranoid. My ka didn't go in a normal manner. Rod bearing number 3 was absolutely destroyed but didn't spin and no visible damage was done to the crank. All tolerances were spot on when it was assembled. I'm throwing my turbo setup on another long block so I want to figure out if I need to get rid of this setup or not.

Thanks!

[EnnEssEnnKAT]

Not sure if it helps or not but I also run the same flywheel on my ka and have for 10k miles and never heard of such a thing. Matched with an ATC clutch, no problems here.

Sent from mTalk

[Hoffman5982]

Not sure if it helps or not but I also run the same flywheel on my ka and have for 10k miles and never heard of such a thing. Matched with an ATC clutch, no problems here.

Sent from mTalk

At the rate I've been going, 10k miles is like 10 years of running for me. I'm good with that!

[ANDY black s13]

if a shop told you the flywheel of death story,don't let them near your engine

[Hoffman5982]

if a shop told you the flywheel of death story,don't let them near your engine

It wasn't a shop, it was just a guy at the event I was attending who said it's what killed his ka.

[ANDY black s13]

imo if it was an imblance issue it would affect no1 and no5 main bearings
as it would pivot ever so slightly round the center main & thrusts
it wouldn't affect one big end bearing only,that is another issue
possibly starved oil feed,con rod out of round (distorted cap?),
bearing layers lifted etc

three bearing mains 4 cyl engines suffer crank flex and take out the center main
the center main will fail first or the crank snaps in two before the BE bearings fail

[PoorMans180SX]

Out of curiosity, what were your main bearing clearances? When did it start knocking and what do you use the car for? Do you have a well-baffled oil pan?

A flywheel has very little to do with crank balance, which is part of the reason why there are so many weight options available.

[mewantkouki]

Flywheel of death is BS. I've put 35k on a white bunny setup collectively on three different cars. I vote oil starvation or pre-ignition...

[Hoffman5982]

Out of curiosity, what were your main bearing clearances? When did it start knocking and what do you use the car for? Do you have a well-baffled oil pan?

A flywheel has very little to do with crank balance, which is part of the reason why there are so many weight options available.

I'd have to find where I wrote down all the bearing clearances and rings gaps etc. But it was right in the middle of the oem allownaces. The car is used for drifting. It was a full rebuild with ross pistons and eagle rods. Oil pan is stock, I just rebuilt the oil pump. In all honesty I got the rods and pistons second hand. The bottom end they came out of was a "perfectly running" motor that had a 4 piece piston and 2 mismatched rod caps when I pulled it apart. I ordered 2 new parts. What I think happened is the rotating assembly was out of balance. I emailed Eagle directly about replacement rods and they never said anything about needing to send the set in to match them all up. I found out once the motor was back in the car. My fault for not doing any research.

Flywheel of death is BS. I've put 35k on a white bunny setup collectively on three different cars. I vote oil starvation or pre-ignition...

I figured. I don't think it was oil starvation because I did about 8 more laps of steady redline after the sound started and there isn't a single mark on that journal of the crank. I haven't taken the head off to see if there was detonation, although the car ran perfectly fine and I never heard any pinging.

[Hoffman5982]

I really didn't think there was any truth to this. I just wanted to be 100% sure because if so I could have sold my current setup. This saves me time and money. Thanks everyone!

[EnnEssEnnKAT]

What clutch are you running on there btw

Sent from mTalk

[PoorMans180SX]

I'd have to find where I wrote down all the bearing clearances and rings gaps etc. But it was right in the middle of the oem allownaces. The car is used for drifting. It was a full rebuild with ross pistons and eagle rods. Oil pan is stock, I just rebuilt the oil pump. In all honesty I got the rods and pistons second hand. The bottom end they came out of was a "perfectly running" motor that had a 4 piece piston and 2 mismatched rod caps when I pulled it apart. I ordered 2 new parts. What I think happened is the rotating assembly was out of balance. I emailed Eagle directly about replacement rods and they never said anything about needing to send the set in to match them all up. I found out once the motor was back in the car. My fault for not doing any research.


Factory tolerance for rod bearings is too tight for an engine that sees abuse. I'd open up the rods to .002" and run a solid 5w40 or 5w50 if I were you. This is the #1 reason that most Nissan engines eat rod bearings at the track.

Also double check the big end dimensions of those eagles, they're notorious for being inconsistent/out of round and needing a resize.

[Hoffman5982]

Factory tolerance for rod bearings is too tight for an engine that sees abuse. I'd open up the rods to .002" and run a solid 5w40 or 5w50 if I were you. This is the #1 reason that most Nissan engines eat rod bearings at the track.

Also double check the big end dimensions of those eagles, they're notorious for being inconsistent/out of round and needing a resize.

That's good to know. I was running 15w-50 Mobil 1, might switch back to 15w-40 Rotella that I've run for the past 5 years. I've switched back to a new/used long block(compression is good and timing kit/oil pump are getting replaced). My tune was done on a stock motor, I just had a garbage cooling system at the time and ended up driving an event on a blow headgasket and when the motor hit 380F it took the rings with it. This old motor is going to sit for a while and when the time comes I will be taking the entire rotating assembly to a machinist to have them completely go over it. I'll definitely open those tolerances up as well.

For reference, I'm only running ~11psi on a 2871 which yielded 290whp and I lowered the rev limiter down to 6850

[Hoffman5982]

What clutch are you running on there btw

Sent from mTalk

I'm running an RB25 XTD 14lb flywheel(I know, but my ka xtd lasted 4 years of abuse with zero issue) and an RB25 Competition stage 3 clutch set

[Kingtal0n]

I do not think of a flywheel as a component of natural frequency damping.


It can be out of balance but that should be obvious (vibrations)
If it wasn't damping natural (resonant) frequencies of the engine in question then that is a whole other story (you would not feel that happen, and it will show as 'perfect balance' with respect to mass)

If you modify the inside of the engine and the natural frequencies change, then something needs to be done about new emerging natural frequencies. Typically people throw a fluidamper and go. I presume that you have a fluidamper and are not trying to utilize a stock damper with aftermarket internals. -.-

also what was said about using tight (factory) clearances with heavy weight oils is correct (=failure)

[PoorMans180SX]

It can be out of balance but that should be obvious (vibrations)

Funny story. I bought a comp clutch for a KA that I bought with a bad clutch. After I installed it I wondered why the car had a shit top end and hated to rev. Later I learned that the pressure plate was drilled off-center. I’d imagine with solid mounts it would have been much more obvious.