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Uncivilized Street Car

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Car history:

Back in 2003ish, I wanted to build a stroked turbo engine. Unfortunately, there was little to no resource/information on anything related to it. So being a dumb kid with ambition, I jumped in headfirst into a cheap N/T 2g 4g64 Spyder. The interior trim pieces apparently was where the last owner stored his corroded razor blades covered in salt. Guy must have seen some awfully tough winters scraping road salt off that icy windshield, bless his heart. Still, it was incredibly cheap at the time.

The day it arrived at the shop is when the engine was pulled. Back then, the DSM-o'sphere wanted nothing to do with the '64, claiming the shortblock would explode if revved anywhere near/over factory limits boosted. Most ran 16g's on the original SAFC, and you were considered the big dick on the block switching over to Garrett t3 equipment. Ha :D , views have quite drastically changed since then--not particularly about this engine, but everything concerning the DSM platform altogether. I've much love for the 4g64; all cars I've ever owned have had their 4g63's replaced with one.

Anyway, I kinda just did my thing for 15 years. This ride is a GSX, bought in 2007. It's an amalgamation of upgrades and changes done mostly on a whim, for little reason, and chiefly just for the hell of it. Currently, I find myself interested in the clever and unusual things others do around here (keep it up! :applause: ), so may as well show some reciprocity in return.
 
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Revisiting the step height specification. I'm not contesting the established tolerances advocated by the community and tuner shops, however, I'd like to revisit these numbers as I am actively making measurements and observations on an aftermarket clutch and flywheel system. Depending on the conclusions, I may deviate and use a new set of parameters. I've seen a number of other users questioning these under various circumstances, and I'm curious to see if status quo is upheld or overruled given a different pretext. The FSM has a blank box with bold text where the flywheel specifications are to be listed. It's also interesting to note that when listing any procedure or operation involving the flywheel, the manual just...mentions it in passing or pretends it doesn't exist? I even went though the hard copies of the 2g FSM only to find the same. Wonder what happened there.

Clutch systems are designed with a useful service life in mind. As the friction surface wears, the clamping force of the pressure plate actually becomes greater due to the decreased clearance between the flywheel and the pressure plate. Though as the wear process continues, the diaphragm fingers begin to relax, causing a stark drop in clamping force, thereby propagating a condition where engine torque can overpower the impaired capacity of the clutch. This parabolic curve is specifically designed to extract the most usable life from the clutch friction surface as possible, all while retaining optimal torque capacity and smooth engaging characteristics. It's quite an effective system: simple, requiring little to no technical precision.

Though a bit complicated of a process, holding capacity and engagement characteristics may be tuned to bolster some driveline needs, sometimes at the expense of comfort and drivability. There are many points to reference available for clutch system changes, many of which are interconnected in one way or another. The clutch cover is installed over the friction disc and flywheel observing a predetermined load. The vast majority of the time, variables like the directional thickness ratio or clamp load of the plate diaphragm are preset and not expected to be trifled with.

We're all aware that the clamping load can be adjusted through flywheel clearance: friction surface and deck height changes in relation to the friction disc and pressure plate clearance. Once assembled it forms a static clamp load upon friction surface. Wear of diaphragm / sprung parts is regulated of uniform variance and specifically designed into the clutch set, establishing how the system wear status is monitored. The liner riveted to the clutch disc is referred to for calculating remaining acceptable service life of the entire clutch assembly. The clamping load of pressure plate can still be calculated and enumerated at any point in its lifespan; in a stock system it typically is only the disc liner that wears. If either side individually fails to meet the minimum depth requirements, then the clutch unit is no longer considered fit for service.


At any rate, I was curious to see the diaphragm trajectory on the dogshit clutch as I suspect there is great room for improvement while using a nonferrous metallic clutch disc. Just not this one. I've a couple of these--the absolute beaming pinnacle of engineering failure manifested in the form of a 4g63 clutch. I remember when they came in to my life, borne through the corn-specked stench that is the colon .... ok distracted for a second. ACT is garbage.

I've a few ideas to increase clamp load while still maintaining a complete disengagement ability. Just not on this yellow turd grenade--on an actual, decent clutch. That actually works. And doesn't fail. Three times over. In a matter of days. From faulty materials

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In the meantime....


Checking clearances with new disc on Clutchzilla, my beastly homemade 2-ton clutch (3700? 3500?). It's the 1-gallon soda jug of clutches: completely and totally unnecessary, but went ahead and scooped one up anyway. Cleaned and brushed up nicely, most of that paint had faded off.


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It features doubled up stock diaphragm fingers, doubled up torsion straps, and enlarged pivot surfaces all stiched together behind that chunky retainer. There is a lot of consideration that goes to how these are affixed to each respective fulcrum, along with the angle and distance each finger has relative to the friction surface An old friend turned me on to this modified OE unit idea while running one in a 9 second Honda. Sadly, I couldn't be of much help in the technical aspects of building it--blindly went along with the machinist's direction. I do regret not building another one of these with that guy; given the tools and ability, they cost peanuts to make.

Hands down this is the best value of any DSM part, costing something like a measly $250 total (disc, plate and machine work put together). Now on its 13th birthday after seeing several engines, flywheels and discs (beat up two AL units), it survived enough awd launches to bang my t-case coupler teeth into fangs, and show no signs of fatigue other than an easily repaired surface distortion. Disclaimer: I conscientiously avoid overheating the clutch, avoid riding it partially engaged.

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These hardly wear, and a readjustment to the base clamp angle of the diaphragm could be very beneficial in light of this...

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These splines don't like to be beat on. This is the older style of disc that uses a shorter hub. Good idea to revise the design eventually, however, this new style that has been going around completely screwed me. The hub is too tall and interferes with my diaphragm. I'm bottomed out at just .230" :( Either custom disc or solid hub up next to work around :?

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