Perrin Light Crank Pulley - Page 2

GreenMarine · #16 05-12-2003, 09:28 AM

Dude, I'm just jackin' with ya....

mbtoloczko · #17 05-12-2003, 10:14 AM

Nothing snide or patronizing, but I do have many counterpoints to your points. :-)

I forgot to mention that the link I posted (http://www.dalemfg.com/dale_026.htm) shows harmonic twisting of a crankshaft for a Covair motor which is a 6 cylinder boxer. This shows that boxer motors, in general, are not immune to harmonic twisting. It also shows that 3rd and 6th order harmonics can be present and important to damp in at least one boxer motor. The plots on that page are very interesting. They show a harmonic at low rpm and at about 4600 rpm. Perhaps its just coincidence, but peak HP in the Covair motor is around 4400 rpm. I would speculate that if the crankshaft were made stiffer so as to have a higher natural torsional frequency, the harmonic peak at 4600 rpm could have been avoided. Maybe SVX crankshafts are stiff enough that their natural frequency is beyond any torsional vibrations that are induced in normal operating rpm ranges? Anyone have the answer? What about the WRX motors? I think there is evidence to suggest that there is a harmonic that can occur within the operating powerband of the motor. As best as I can tell from searching threads at NASIOC, at least a few people have seen odd problems when using a lightweight pulley where the motor begins cutting out at ~6500 rpm (normal cutout begins at 7000 rpm). Cobb Tuning has even stated that they've observed 2.0L motors cutting out at ~6500 rpm, and this was directly attributable to a lightweight pulley. (In response, they are developing a lightweight damped pulley. I don't know if they will be successful in developing a lightweight damped pulley that actually damps the torsional harmonics because the weight may be a neccessary part of the design to effectively damp the harmonics.) If the longer SVX crankshaft has the same basic diameter as the WRX crankshaft, it seems reasonable to expect that there could be a harmonic within the operating powerband of the SVX motor.

I'm not surprised that the aircraft people have not seen a problem as the harmonic vibrations, if present in our motors, occur at specific frequencies, and as long as they don't run their motors at those frequencies for extended periods of time, there would be no problem.

I did all this research on harmonic dampers because I would like to get a lightweight pulley if I could prove to myself that they are safe to use, but all the evidence I've seen tells me that there is a strong chance that harmonics are present. The degree to which the harmonics may be damaging the motor is inclusive though because no one has run a motor long enough. Running a car for 50k miles with a lightweight pulley with no apparent adverse affects is not good enough for me when Subaru motors are capable of lasting more than 200k miles. So, I think I'd rather take the cautious approach and not put one on until someone can prove to me definitively that they allow no damaging harmonics.

That's all I have to say. :-)

svxfiles · #18 05-12-2003, 10:28 AM

ive got 73000 miles on my 92 svx, and installed a revline underdrive pulley at about 40000 miles with no ill effects. just my 2 cents. ps it does rev quicker

Chicane · #19 05-12-2003, 01:15 PM

the SVX has a forged crank, remember. :P

- Rob

mbtoloczko · #20 05-12-2003, 01:52 PM

Quote:

Originally posted by Chicane
the SVX has a forged crank, remember. :P

- Rob

The WRX crank is forged too. Forging can make the crank more resistant to plastic deformation, and it may increase the fatigue life. However, forging has no effect on the spring constant of the metal, and its the spring constant of the metal that strongly affects the natural harmonic frequency of a crank.

#21 05-12-2003, 02:57 PM

Quote:

Originally posted by mbtoloczko
The WRX crank is forged too. Forging can make the crank more resistant to plastic deformation, and it may increase the fatigue life. However, forging has no effect on the spring constant of the metal, and its the spring constant of the metal that strongly affects the natural harmonic frequency of a crank.

Actually, I don't believe the WRX crank is forged. I believe it's nodular iron, just like the EJ25 and EJ22 motors. I could be wrong on that, I know the pistons aren't forged and I may be mixing my memory, but I think the crank is non-forged.

The SVX has the strongest engine internals of any Subaru motor other than the STi.

jsvxstyle · #22 05-13-2003, 09:28 PM

porter you think so huh

well let me put my .25 cent in.

svx has the weakest piston rods
svx has the weakest crankshaft due to bearing surface which the rod bearing mates on, is way too soft.
but everything else is fine

#23 05-14-2003, 06:32 AM

Ok, what is it that makes the rods and crank so weak in your opinion?

jsvxstyle · #24 05-14-2003, 10:16 PM

The crank is very soft,the hard surface is very thin. Never polish without re-nitrating. The rods will bend if the engine is run in LITTLE detonation.

alltrac · #25 05-14-2003, 10:37 PM

yon is the only member i know that is running cams also upgraded ignition I trust what he says about the svx motor. Victor

mbtoloczko · #26 05-15-2003, 03:01 AM

Quote:

Originally posted by jsvxstyle
The crank is very soft,the hard surface is very thin. Never polish without re-nitrating. The rods will bend if the engine is run in LITTLE detonation.

Did you score the crank and bend the rods on your SVX? If so, how?

jsvxstyle · #27 05-15-2003, 01:31 PM

done that to my own car, torn down the engine and found out the hard way, thats why i say this.

just for the turbo guyz to know plus the nitrous users as well

mbtoloczko · #28 05-15-2003, 02:24 PM

I'm kinda surprised that you bend the rods because they are forged steel. Forged steel has a very high yield strength. Maybe there wasn't enough material in the rods for adequate strength?

Chicane · #29 05-15-2003, 03:48 PM

No offense, but I'm not really believing you here. The H6 is an INCREDIBLE engine, and aside from its leakiness, it's EXTREMELY durable. Mine has a 146k, and it doesn't burn a drop of oil. As with most of ours. I would think if there was a weakness in the internals of the H6 it would show up in a lot of the higher mileage SVXs, but it doesn't.

- Rob

Beav · #30 05-15-2003, 04:51 PM

Not to change the subject or create upset for/by those that have or intend to convert to a manual transmission but does the EG33 have a sufficient crankshaft thrust bearing to handle the pressure of a clutch, let alone a heavy duty pressure plate? As the engine was never really intended for a manual tranny did the engineers allow for the axial thrust loads generated by a clutch? If they didn't, they wouldn't be the first or only to do so.