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When using a single plate clutch (upgraded with a high clamping load= increased stiffness in clutch pedal)..
The increase of clamping for has to be decreased to change gears (pushing clutch pedal in).. This puts force on the rear of the crank, "pushing" it forward, which in turn, could (on other cars it happends for sure) put alot of stress on the thrust bearing/washer. Since the car is not started, there is no oil pressure and no lubrication on that bearing/washer, So its basically "metal to metal" which causes premature wear and if it happens enough (once you have the signs, its pretty much too late and either have an un-usuable crank (somtimes block, main girdle etc) It was cause play in the crank and allow it to "walk" (shift around when obviously its never supposed to move (forward and backward) because it causes an misalignment of the rods (slight), which in turn will cause more stress on the main bearings, rod bearings, wrist pins, pistons, crank etc.. you get the point.If the VG's thrust washer/bearing is not designed well enough to where this could be an issue, By-passing the clutch switch to complete the electrical circuit to allow voltage to the starter WITHOUT having to depress the clutch pedal= no high stress on thrust bearing/washer when no oil pressure is present. Since its so easy to just by-pass the pedal switch, Its really a no brainer. However; Don't get me wrong, IF crankwalk is potential on our VG's, Just doing the clutch by-pass does not "cure" a future potential problem. It will just prevent much wear that happens when no oil pressure is present, along with the clamping force of a high pressure, single disc racing clutch "pushing" agianst the thrust apparatus. Just imagine pushing two metal objects, at over a thousand pounds of force (ex. ACT 2600) (one of which is a softer metal than the other) without the proper lubrication versus the same two metal objects WITH proper lubrication (I believe the VG has an oil jet that squirts oil at this location as well). The life theoretically, would be dramitically reduced of the scenario without proper lubrication. Although, the clutch by-pass in theory should help. There are also other situations that this same damage could occur even WITH proper lubrication. Ex. High RPM shifts, especially with a warm motor/hotter than normal from racing etc) There would be more force applied since the heat will make the metal get damaged easier, even with "cooler" oil is being jetted on the surface of the thrust bearing/washer. One of the main problems is because a single disc high peformance (high clamping load) Uses the pressure plate and single disc with its friction materials) to overcome and maintain the amount of friction/pressure than what the engine's power is requiring. This is what YOU WANT since it simply means that the clutch is NOT slipping But with high RPM shifting (with oil pressurized being squirted on desired location or depressing clutch pedal and turning over motor (without oil on surfaces) with over a thousand pounds of pressure against a spinning crankshaft against a somewhat small ( not sure of technical size of VG's thrust bearing) A way to help (tremendously) by putting much less pounds of force against the crank is simply getting a lighter pressure plate and especially by using a multi-disc clutch setup (I recommend Billet RPS carbon/carbon since the materials used in the clutch discs actually hold better when it reaches very high temperatures (drag racing, on street tires, drag slicks, or even track racing when down shifting, up shifting, rev matching etc). From what I have learned, is that carbon gets better the hotter it gets (to an extent of course, but this is opposite of most single disc, heavy/high, pedal/clamping loads. Most materials used in single disc clutches and some multi-disc are ceramic, organic, feramic etc.. which most actually will lose peformance (holding power/reliability) the hotter they get. Not to mention, you can completely ruin a non-puck and puck style if it gets so hot that it "glazes" the friction surfaces. Using a multi-disc clutch uses a light pedal pressure= much less clamping force is required (either very close to stock or somtimes even less!) You should always get away with the lowest pressure plate clamping load/pedal effort as possible that still maintains no clutch slippage. Multi-disc don't require a high clamping load because it utilizes the actual friction area amoungst the setup of discs (ex. on a twin disc, there will be a front/back of each disc, multiplied by 2. The stock Z32 was build with a clutch that had a clutch that wouldn't put excessive amounts of stress on thrust bearing/washer. And almost 80% (guess) probably have over twice of the power in stock form. Which requires an upgraded clutch. IMO, If you have the money, just get a multi-disc clutch. There are quite a few of different options out there, some make lots of noise, some don't. The RPS twin disc (especially the new billet series) is very streetable and doesn't sound as bad as some of the others (OS Giken etc). There is another option in terms of oil pressure pre-startup, and its a pre-oiler system that will pressize oil thoughout the whole system before starting the vehicle..
 Here is the website that I found some pre-oiler kits and dry sump setups. [ http://www.syntheticwarehouse.com/amsoil_amsoiler_precharger.htm ] I believe the prices for the pre-oiler system is sub $500.00.. The pre-oiler system would help against the wear on the thrust bearing, but it can only do so much if you are "pushing" the crank with as much force using a heavy clamping force, single clutch disc. This pre-oiler has many ofther benefits that probably wouldn't be so bad as an investment on a highly modded Z motor, I believe I also saw there were some dry sump oiling systems as well.. Just some ideas to toy around with. In closing; I am not still 100% on the failure rate on thrust bearing/washers on VG's. But atleast the clutch pedal switch by-pass is a very easy and quick way to have the "most potentially damaging" part of using a very high pressure single disc clutch (Staring or turning over the motor that fast without any lubrication on parts that need it). However, the clutch pedal switch by-pass will not do anyting in terms of
alleviating any potential wear in very high RPM shifts with very high pressure against the crank via single very high clamping load rated clutch. Food for though... enjoy!
NO, This picture is not photoshopped. It took many times to take this picture. Setting up the timer, shutter speed etc, then jumping on my bike and getting the tire to spin.
AIM:Shawn300zxTT "-Any closeups on the nuts? - zboost(tx) 19:17:53 08/08/05
-Not really something you want to ask another man about... (n/m) - LordZ 19:24:00 08/08/05" "I just took 45 min and scrubbed the heck out of my rear"
teambushido(San Diego, CA) 19:24:51 12/11/04 -1991 Stage _ TT 5spd (Upgraded to hell and back)
-1990 Super White 2+2 Na Stage 3 Auto (Daily Driver, contemplating selling.. )
-1990 Cherry Red Pearl ,Auto Coupe (Parts car)
-1990 11 Sec Eagle Talon Tsi AWD, (SOLD!)
-1996 Hyundai Sonata (Given to me for FREE , due to broken timing belt,bent valves.. fixed it myself and its my new DD that gets over 25 mpg!
-2004 Honda CBR 600RR (Candy blue, FOR SALE) |
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07:25:42 04/18/10
