Welcome to the SR20 Community Forum - The Dash.
Register
SR20 forum logo

Thread: Got Rod Knock at the convention? Post it here...

+ Reply To Thread
Posts: 181-190 of 190
2009-05-01 17:23:52
#181
This is from wikipedia, so take it with a grain of salt. The core information is there, though.

A harmonic balancer (also called crank pulley damper, crankshaft damper, torsional damper, or vibration damper) is a device connected to the crankshaft of an engine to reduce torsional vibration.

Every time the cylinders fire, torque is imparted to the crankshaft. The crankshaft deflects under this torque, which sets up vibrations when the torque is released. At certain engine speeds the torques imparted by the cylinders are in synch with the vibrations in the crankshaft, which results in a phenomenon called resonance. This resonance causes stress beyond what the crankshaft can withstand, resulting in crankshaft failure.

To prevent this vibration, a harmonic balancer is attached to the front part of the crankshaft. The damper is composed of two elements: a mass and an energy dissipating element. The mass resists the acceleration of the vibration and the energy dissipating (rubber/clutch/fluid) element absorbs the vibrations.

Over time, the energy dissipating (rubber/clutch/fluid) element can deteriorate from age, heat, cold, or exposure to oil or chemicals. Unless rebuilt or replaced, this can cause the crankshaft to develop cracks, resulting in crankshaft failure.

There has been a trend at times by some "performance enthusiasts" to remove the harmonic balancers on their cars, usually when the balancer is attached to the crank pulley. The argument is that they aren't necessary and their mass reduces the performance of the engine. Others[who?] argue that this is not worth it, because the danger of damage to the engine from the vibrations the damper is intended to prevent is too high. Certain cars, however, do not come equipped with an external balancer on the crank pulley, and as such, can have the pulley replaced with a performance oriented product.

While net engine output can be increased without harmonic balancers, in professional race cars harmonic balancers are still commonly equipped, for reasons ranging from safety concerns to regulations. Almost all modern car manufacturers, even "performance" car makers and specialty tuners, include a harmonic balancer on their vehicles, and removal voids vehicle warranty.


While some engines may see crankshaft/bearing failure from harmonic balancer removal, I assure you that it was not the COD of any engine that popped at SR09. Where do you see the largest application of oversize/heavier balancers? High rev, high torque V8 applications (IE: drag cars)

An 8ccw SR is certainly well balanced enough to not have to worry about running a balancer pulley. The 4ccw VE/RR motors MIGHT see a SLIGHT decrease in engine life without one, but I don't see any statistics backing that up.

Point being, we could sit here and argue this all day. Both sides bring up valid points, but without any real statistics to back either one up, we're just pissing in the wind. I think it is safe to say that the use of a lightweight pulley was NOT the cause of any engine deaths at SR09.

As most everyone in this thread has repeated multiple times:

1. LOW OIL
2. VISCOSITY BREAKDOWN (Due to heat or being flooded with gasoline)
3. HIGH OIL TEMPS
2009-05-01 22:35:19
#182
Does anyone see the need to relocate the oil pickup tube from its stock location? I mean, would there be any benefit from placing the pick up point from the left side to a central spot within the oil pan? Or...just throwing this out there...make a secondary pickup point on the right side of the oil pan.
2009-05-01 23:30:44
#183
The pickup isn't on the left side. It's actually past the center of the pan (on the right):

2009-05-02 01:44:04
#184
Originally Posted by bhowle
While some engines may see crankshaft/bearing failure from harmonic balancer removal
I would argue against bearing failure. No way. No how.

Originally Posted by bhowle
An 8ccw SR is certainly well balanced enough to not have to worry about running a balancer pulley.
The harmonic balancer has nothing to due with balancing rotational mass and the need for one depends on crank composition (metallurgy) and rod throw (stroke). I keep looking for a good explanation of it so people can read and understand what's going on with it. Once you do you'll realize very quickly that it couldn't cause rod bearing failure.





Originally Posted by oldman
Or...just throwing this out there...make a secondary pickup point on the right side of the oil pan.
I thought about it too, but if one pick-up out of two or more run dry, then the oil pump will run dry. You're actually making the problem worse with multiple pick-ups.
2009-05-02 02:34:04
#185
Originally Posted by BenFenner
I would argue against bearing failure. No way. No how.

The harmonic balancer has nothing to due with balancing rotational mass and the need for one depends on crank composition (metallurgy) and rod throw (stroke). I keep looking for a good explanation of it so people can read and understand what's going on with it. Once you do you'll realize very quickly that it couldn't cause rod bearing failure.





I thought about it too, but if one pick-up out of two or more run dry, then the oil pump will run dry. You're actually making the problem worse with multiple pick-ups.


You're right. I do understand the reason for one, but didn't quite have it right. The name explains the purpose. It cancels out harmonic vibrations (which would be a much higher frequency than normal engine running vibrations) in the crankshaft caused by resonance at a certain RPM range due to the effects on the crankshaft caused by combustion.

Lack of a balancer could possibly lead to crankshaft failure (ie: crack/full break) However, I do see this possibly leading to main bearing failure. But that is pushing it a bit.

Again, I'll stress to everyone here that, as far as I know, there are no reported crankshaft failures related to the removal of a balancer in an SR engine.

In regard to multiple pickups: it certainly isn't feasible without the use of multiple pumps. Just for the record- Porsche's newer flat six uses a pump/pickup at each corner of the engine to assure complete oiling during cornering.

The real solution for that would be a dry sump system.

EDIT: I found this tidbit as well:
Harmonic balancers are designed to prolong the engine life by reducing wear on the main bearings and main journals and preventing crankshaft failure. The harmonic balancer or the vibration damper is a piece of equipment connected to the crankshaft which job is to lessen the harmonic vibration. Each time a cylinder fires, the connecting rod pounds the crankshaft journal as the force turns the crankshaft, causing energy to be dispersed through the engine. The front of the crankshaft takes the brunt of this power, so it often moves before the back of the crankshaft. This results to a twisting motion and after that, when the power is removed from the front, the halfway twisted shaft unwinds and snaps back in the opposite direction. Even if this “unwinding process” is somewhat diminutive, it causes harmonic vibration.


You'll notice I didn't reference rod bearing failure in my posts, just bearing failure in general. I was referring to the mains, and should have been more specific. I will agree that replacing a balancer with a regular pulley WILL NOT lead to rod bearing failure.

When I said that the 8ccw was less likely to have problems with balancer removal- my thought is because it has more rotational mass to absorb the impact of each cylinder firing, keeping the harmonic vibrations down.
2009-05-02 03:01:53
#186
I remember reading an archived post recently that with the 8ccw crank, the harmonic balancer was for NVH, not premature failure (in the SR20). It was either from Mike K, or another one of the old wise men.
2009-05-02 04:23:09
#187
i have personally seen deaths from lightweight pulleys mostly gfb's and the benefits from ross units so hence my bias. Lightweight pulleys can lead to bearing failure, especially when not balanced. However we wont argue this any more as i have had no first hand experience with the gspec units, which most of you run.

the other big issue for bearings that i didn't write, but is very obvious is oil starvation. baffles and winged sumps can help fix this. I read back through the thread and it seems that only 2 cars out of 40 or something got rod knock? if this is the case then i would put the faults down to oil starvation, high oil temps, oil brak down and crappy oil.

The reason i mentioned the pullys in the first place is because going by the pages flicked through it seemed like an epidemic of rod knock. I thought heeps of car got it with comments like this track is the sr20 killer etc. Therefore i thought damn this is a common prob for these guys. Noticing that most on this site run light weight pulleys i suppose i saw a bit of a link. But if its only 2 freaking cars big deal.
2009-05-02 04:44:45
#188
double post
2009-05-22 04:15:46
#189
I posted this in another section, but I will post it here as well. I really think we need an answer to why the bearings failed.

"Well, this is what I know from the different pumps. The GTiR and Ve pumps are higher flow pumps, with larger pickup tubes. They both have vastly improved flow designs to prevent pump cavitation at higher rpms. The VE is the best design.

There is an oil starvation issues with the SR? I'm not sure I believe this is the #1 cause of failure. These cars have been heavily tracked for 15 years, this weak point would have been sorted out by now?

Has anyone asked questions about which oil was being used at the time of the failures at the convention? Seems like this year there were a lot more failures.

A little bit of this may be attributed to the stock oil pump and higher rpms, but I doubt it was oil starvation from cornering G forces. I could be wrong, but I have taken corners at Gs higher than .95 and have not had an issue with oil pressure dipping AT ALL. Both with a stock DET pump, and on my VE-T with a GTiR pump. Perhaps this is a real issue that needs to be solved, or maybe I am rambling. I just don't get all the failures."

I don't believe this is an oil pan starvation issue, or an oil pump issue. Call me crazy, but I honestly believe it is an oil issue. Maybe not in every case, but likely the culprit in some.
2009-05-22 14:42:50
#190
BTW I did not get rod knock, and I have a full lightweight pulley set on a motor that has 180k on it. YMMV

So maybe my memory's bad, but based on everyone's feedback in this thread, aren't the incidents of actual bearing failure low? It seems I remember everyone having different problems...
+ Reply To Thread
  • [Type to search users.]
  • Quick Reply
    Thread Information
    There are currently ? users browsing this thread. (? members & ? guests)
    StubUserName

    Back to top