VADriven.com Forums - the old N1 crank pulley question?

Aren't the OEM CTR pulley and the N1 CTR pulley two different things? I thought I remember that the OEM CTR pulley was almost the same as a regular B16 pulley..

Some random thoughts I had on the N1 debate:

I'm sure the pulley itself would probably be balanced fine from the factory, unless (being a racing oriented part) its meant to be balanced with the rest of the assembly.. Pulleys with dampers built in (on something other than domestic V8s) are often just to quiet noise from the accessories. Balance shafts go a long way toward doing what torsional dampers were used for back in the sloppy V8 days. There is some crankshaft damping going on, but that depends on the balance of the reciprocating assembly obviously. There are a number of import engines that have completely solid pulleys (no rubber inside) that do just fine though, so its really hard to point fingers at the lack of damping with the N1 pulley. I have a hard time believing that the amount of rubber inside one of the OEM pulleys would do much to damp anything but pretty high frequency vibrations too, which is the opposite of what torsional dampers are used for (torsional vibration from the cylinders firing is fairly low freq comparatively)..

The CTR pulley is smaller and lighter than the OEM, and doesn't have any of the accessory stuff on it really, so damping a big heavy pulley with accessories on it isn't really an issue. I still stick with my original statement that if people are blowing oil pumps, there might be something else wrong, like everything isn't balanced as well as it should be. Also, just having extra mass will damp crankshaft vibrations more, with or without a rubber damping coupler in there, so I'm not convinced that the fabled oil pump problems are from getting rid of the damper as much as getting rid of the weight. Change the weight of the rotating assembly and you change the mass damping characteristics and the resonant frequency, etc. It also has to do with crankshaft length, distance between bearings, number of cylinders, type of crank (cast, forged, etc.) and engine RPM.. There are a lot of variables.

I'd be more likely to think that balance problems with the reciprocating assembly would be worse for an oil pump than any small, light pulley...but supposedly some of the pump failure people have had supposedly well balanced rotating assemblies. I'd tend to stay away from the CTR pulley though unless you know that your bottom end is to at least the same level of balance as a CTR bottom end. Even so, unless you have a full CTR engine, you really don't know what the differences between a CTR and your engine are, so a CTR pulley might not be the best thing to use. I'd rather go for caution than risk some bearings or an oil pump, but that's a choice you have to make.

I'm still up in the air over this whole argument though, and as far as I know there hasn't been any actual studies on the oil pump failure stuff, just word of mouth without any good controlled correlation. I don't like to accept things just because some people think that it may be caused by whatever but can't really prove it and don't have anything to really compare to.. In my honest opinion, until someone knows what is actually causing problems like people are having with the lightweight pulleys, I wouldn't take anyone's word over anyone else's. No one can say anything except for what they've seen, NOT what actually caused it. I'm just not really convinced either way; there are known problems with factory Honda oil pumps when engine gets flogged, and they definitely aren't just failing with light pulleys on them. So yeah, if you beat on your engine and something related to a non-OEM pulley makes the crappy OEM fuel pump fail, you have an oil pump failure. Was it because of the pulley or the crap oil pump or the fact that you beat the piss out of the engine? Who knows?? No one has tried to find out why, so we can speculate all we want. If a big race team found a problem like this over the course of a race (or a few races), I'm sure they'd set out to measure the vibrations with the OEM pulley and the non-OEM pulley, put strain gauges on the crank, etc., to see if they could spot a trend. Or they'd just put a better oil pump on and call it a day.

If this pulley was made for the N1 CTR race cars, where bearing life and oil pump failure isn't an issue over the life of a couple races, then that might not be the best thing to put on your street car. Just like a lot of parts, the considerations are different for race cars and street cars. It's all about judgment though, is it worth risking an engine for 2, maybe 3 HP? You can probably find that power somewhere else, without losing sleep over what might happen if you made the wrong decision.. I'd stick with the stock pulley through for safety, and get the accessory drive ribs milled off if you want to reduce weight.

That post really grew fast, I couldn't leave this alone..