wigenOut-S30 Posted October 22, 2007 Share Posted October 22, 2007 I have a HKS 9.4lb billet steel flywheel. I have ran it on a stock na.Throttle response is amazing espacially with a 60mm throttle body. no issues of negative that I experianced When I built the motor that I have now I had a stock flywheel machined down. 15lbs was the end result. seems to work fine but not as responsive as the 9.4lb. I would have used it instead but it was in my car when the new motor went together so. If anyone is interested in the 9.4lb let me know. I will sell it to someone here for $150. it has about 500 miles on it. I have a pic of it on a digital scale. if not I will flea bay it someday How much did it cost to get your stock Flywheel cut down to 15lbs? Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted October 22, 2007 Share Posted October 22, 2007 I have a 11lb flywheel on my RB25DET. Made a great difference in throttle response. Its not "easy" to drive but thats in combo with an act sprung 6 puck and a heavy duty PP. I am used to it, just have to bring the revs up to get off the line. Evan Quote Link to comment Share on other sites More sharing options...
Slow_Old_Car Posted October 22, 2007 Share Posted October 22, 2007 Had a fidanza unit on my car, had the holes strip out where the clutch pressure plate mates to the flywheel... Originally i'd ordered and intended on starting with a 13lb billet steel unit from AZ car, but when my 240mm order came, it turned out to be a 225mm unit and he was out of stock of 240's... hence why i ended up w/ the aluminum fidanza. The throttle response was damn impressive while it was in there, though i did have a hard time coming off the line in drag situations since i lost alot of that inertia mass that previously helped with clutch slip. Just took some getting use too. I'm not totally out on the fidanza unit either, one of these days i'll take it down to a machine shop to have the pressure plates bored out and steel thread sleeves installed. Then she'll go back in... For now i'm using a stock 240mm turbo flywheel... big difference in rev up and you can feel the mass of it too. Quote Link to comment Share on other sites More sharing options...
Zmanco Posted October 22, 2007 Share Posted October 22, 2007 How much did it cost to get your stock Flywheel cut down to 15lbs? I went this route but had the shop stop at 16 lbs as that is all they felt they could safely take off using a lathe. After that, they would need to use a mill and the $$$ would go up a lot faster. I think I paid about $125 plus another $30 or so to balance it. This was a few years ago when the cheapest aluminum units were over $400. Today they're a lot less and I think I'd just spend the extra and buy one of those. As for driving it, like others, I have no issue with starting up, even at my altitude where I loose ~20% torque/hp. 82 5 speed + 4.11 rear end helps. Taken all together (L28 w/flat top pistons, N42 head, Megasquirt, headers, tranny + diff), it's just a lot of fun to drive. Not the fastest, but very satisfying! Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 22, 2007 Share Posted October 22, 2007 will adding one of those afi race dampers help to make an even bigger difference over the current setup? i figured maybe just to go the extra mile with lightening the rotating mass. any of you have am aftermarket damper/harmonic balincer? Don't make the mistake thinking that lightening the harmonic dampner will do anything to accelerate your engine faster! All you will do is induce a torsional imbalance into the crankshaft. The way they function is that a HEAVY ring dampens the power pulses. You get a lighter wheel, and the accelerative forces are not as well dampened. The reason it's so heavy is because it's so close to the centerline of the rotating mass, if you increase the diameter of the harmonic dampener, you can get by with a lighter ring for dampening. Same as the flywheel, nothing is free. Like on the flywheel you want your weight behind the clutch frictional area (ideally the 225mm, but I won't open that can of worms), and you want the inertia ring gone. As long as the weight of the flywheel at the frictional surface equals the weight of the dampener at it's outer diameter, you will have perfectly balanced torsionals on each end of the crankshaft. Gene Berg started selling a 7# damper for VW's. Nobody thought it could be used without affecting the acceleration of the engine, considering they usually ran a 9# Flywheel. Yet cranks fitted with the Berg "Equalizer" lived longer without breaking, and accelerated just as fast as those without. Underdrive your pulleys, but don't cut down your damper weight. Quote Link to comment Share on other sites More sharing options...
TONY C Posted October 23, 2007 Share Posted October 23, 2007 well i live in the land of cheap machine work. got mine whittled down for $60 Quote Link to comment Share on other sites More sharing options...
Tony D Posted October 23, 2007 Share Posted October 23, 2007 well i live in the land of cheap machine work. got mine whittled down for $60 Mine was $40 at Griffith's Machine in Paramount. It was 5000 yen in Okinawa, they cut it to 7Kg, and would cut the smaller 4 cylinder flywheels down to 5Kg for the same price. My 5000 yen flywheel revs considerably better than the one cut down in the USA. The Japanese Machine shop cut more out on the inertia ring, and did a nice overall finishing on the whole rear of the flywheel. And on a manual machine at that! Someone could NC my flywheel and turn them off on a CNC Machining center like nothing! I just bought one of those 4.2Kg Kamaeri Chrome-Moly Flywheels. I'm incorrigable... Quote Link to comment Share on other sites More sharing options...
Dane Posted October 23, 2007 Share Posted October 23, 2007 Don't make the mistake thinking that lightening the harmonic dampner will do anything to accelerate your engine faster! All you will do is induce a torsional imbalance into the crankshaft. The way they function is that a HEAVY ring dampens the power pulses. You get a lighter wheel, and the accelerative forces are not as well dampened. The reason it's so heavy is because it's so close to the centerline of the rotating mass, if you increase the diameter of the harmonic dampener, you can get by with a lighter ring for dampening. Same as the flywheel, nothing is free. Like on the flywheel you want your weight behind the clutch frictional area (ideally the 225mm, but I won't open that can of worms), and you want the inertia ring gone. As long as the weight of the flywheel at the frictional surface equals the weight of the dampener at it's outer diameter, you will have perfectly balanced torsionals on each end of the crankshaft. Gene Berg started selling a 7# damper for VW's. Nobody thought it could be used without affecting the acceleration of the engine, considering they usually ran a 9# Flywheel. Yet cranks fitted with the Berg "Equalizer" lived longer without breaking, and accelerated just as fast as those without. Underdrive your pulleys, but don't cut down your damper weight. Hmm...this made me think. Does this mean that bringing the rotational inertias of the flywheel and damper closer together (by using a lightweight flywheel, closer to damper inertia), you will reduce torsional vibrations in the L6 crank? And since there will be less torsional vibration in the crank, less vibrations need to be dissipated through the damper? So a lightweight flywheel by itself could improve crankshaft durability? Is this the way it works? Quote Link to comment Share on other sites More sharing options...
jerryb Posted October 23, 2007 Share Posted October 23, 2007 I ran a AZC light flywheel on the 3.1L for years. It was completely streetable with a centerforce 2 clutch. Completely! and it rev'd up real quick as well. Over the winter Im putting a light flywheel on my RB20DET as the stock unit is an anchor and the RB revs a bit sluggish. I guess the rb20 lacks the torque to turn that mass quickly...I miss that instant RPM........... Quote Link to comment Share on other sites More sharing options...
datsun40146 Posted October 23, 2007 Share Posted October 23, 2007 I had mine lightened down to about 14-15 pounds at griffen's machine shop (thanks TonyD) shipping wasn't too bad either I think I got a light flywheel for like 65 bucks shipped and it works great. Let me give you a tip if you want to go this route, don't ship YOUR flywheel buy one in cal for 5 bucks and ship to griffen's that will save you money on shipping. Then you can can any other flywheels you have cut down and sell them to make money. Quote Link to comment Share on other sites More sharing options...
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