dandan Posted January 4, 2004 Share Posted January 4, 2004 Hi all, I was wondering about using a lightened stock flywheel instead of something like the Fedanza (sp?), anyone ever done so? I know it's a two piece damped flywheel but that in itself surely does not rule out lightening, although I haven't looked at one in detail. Physically mounting the thing on a lathe may be impossible owing to its construction. Also if the stock assembly is approaching the safe limit for material in critical areas then further material removal may be 7000rpm timebomb territory! Just considering how a "slightly" lighter stocker may be more appreciated than a rattling fully lightweight. Dan Quote Link to comment Share on other sites More sharing options...
Gaz Walker Posted January 4, 2004 Share Posted January 4, 2004 Hi Dan, The RPS item is much superior to the the Fidanza. A ratting aftermarket flywheel is only due to the owner not increasing the idle to 1000rpm Gaz. Quote Link to comment Share on other sites More sharing options...
dandan Posted January 4, 2004 Author Share Posted January 4, 2004 OK cheers Gaz, Only using the Fidanza as an example really as I'm not sure what the choices are and how they compare. Anyone have a lightened flywheel fitted...any opinions? I have heard the RPS and their Stage 2 clutch is a good combo. I'm running BPU with possible hike to hybrids or small single in the distant future. Opinions? ....... Prices? And back to the original thread...lightened stocker? Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 4, 2004 Share Posted January 4, 2004 I did some blathering on about lightened flywheels here. Quote Link to comment Share on other sites More sharing options...
dandan Posted January 4, 2004 Author Share Posted January 4, 2004 Cheers Darren I was reading that post earlier on today. The stock flywheel is a dual mass damped assembly isn't it. As far as I'm aware there are no lightened flywheels which maintain this damping (may well be pointless as decrease in inertia would probably not stack up well against the cost) only lightened solid flywheels. I'm not keen on blindly replacing the stock flywheel as it obviously serves a purpose with regard to crankshaft vibration. Weight reduction resulting in a change of damped natural frequency is one thing, but removing it altogether (in my view) is something totally different. Perhaps if a full rebuild was on the cards and dynamic balancing of the whole rotating assembly could be carried out, I'd think differently. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 4, 2004 Share Posted January 4, 2004 Yeah, since writing that I learned that the flywheel is dual mass. AFAIK, as you say, all the bolt-on replacement units are just plate flywheels with no dual mass action, as are all the lightweight front crank pulleys. My bugbear about crank torsional vibration is that since the whole cranktrain is a tuned assembly, as soon as you change one part of it you may as well bin the lot or accept the possible consequences, which can vary from worse NVH to a snapped crankshaft. There's no real way of telling in advance what will happen. The thin about the Supra, however, is that the cranktrain not only has a dual mass flyweheel, but a front crank pulley with both a torsional AND a bending damper, which suggests to me that the crank may get into trouble if the tuning is significantly altered. In isolation, as far as the question of lightening the stock unit is concerned, bear in mind that flywheel burst tests are done in small armoured concrete cells, just in case they break. Its doing 7000 RPM and its next to your legs, and the bell housing aint gonna stop the bits if it lets go. If you really want a lightened flywheel, I'd go for an off the shelf one. Quote Link to comment Share on other sites More sharing options...
Scooter Posted January 4, 2004 Share Posted January 4, 2004 I'm curious whether the flywheel / clutch in my 6 speed Non turbo is different to a TT? Not sure if it would have been worthwhile for toyota to look into lightening these parts, but they may have? I know for a fact that the clutch pedal pressure if very much lighter than on my old UK manual but i guess this could be attributed to other factors. From an availability point of view, I'd be quite interested to find out if mine is the same, if someone knows the standard flywheel and clutch part no.'s i could compare to the part numbers toyota say for my chassis / model number. Do the 5 speed NA's have a dual mass flywheel? if not may be the NA 6 speed doesn't either? Quote Link to comment Share on other sites More sharing options...
dandan Posted January 4, 2004 Author Share Posted January 4, 2004 For the moment at least I think It's something I'll stay away from. Tuning wise I still have a whole heap of things I'd like to do before the flywheel needs attention. I just wondered if anyone had any experience of lightened stockers. I have seen the effects of a lightened cast flywheel explode in an A Series engine at 8000rpm from a missed gear. It may as well have been a hand grenade going off and I think people would do well to think of it as such! My Mini engine had an ultralight steel flywheel fitted as i wanted the response without the risk of a cast one letting go, now it's safe to 8,000 with no worries. Edit: Owing to a huge list of other components also, and the quality of the engine build itself. Resulting in a healthy 204bhp/ton. Not to be sniffed at especially in a car that will out corner a Lotus Elise all day long. Quote Link to comment Share on other sites More sharing options...
Scooter Posted January 4, 2004 Share Posted January 4, 2004 Originally posted by Scooter From an availability point of view, I'd be quite interested to find out if mine is the same, if someone knows the standard flywheel and clutch part no.'s i could compare to the part numbers toyota say for my chassis / model number. searched some and it appears the flywheel is the same flywheel part no.'s for TT and NA here Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 5, 2004 Share Posted January 5, 2004 I am looking at a dual mass TT flywheel now, and there's no way you could safely lighten it. It's also VERY bad practice to lighten cast iron flywheels, as Darren says, they can burst, with shocking results. If you do want a lighter flywheel the JUN ones seem the best. I would not recommend an alloy flywheel with bolted on steel friction face on a road car, they easily warp, or the friction face comes loose, blah blah. A well designed steel one in decent material (EN40 or something) can be made as light as a safe alloy one, IMO. 6 speed N/A engine uses same flywheel as TT, not sure about 5 speed N/A lumps. Quote Link to comment Share on other sites More sharing options...
TRD3000GT Posted January 5, 2004 Share Posted January 5, 2004 Lightend flywheel I had = crap. had to change withing 3 months again. Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 5, 2004 Share Posted January 5, 2004 light flywheel i have = superb wouldnt dream of going back Quote Link to comment Share on other sites More sharing options...
Wez Posted January 5, 2004 Share Posted January 5, 2004 What one do you have eyefi? Quote Link to comment Share on other sites More sharing options...
eyefi Posted January 5, 2004 Share Posted January 5, 2004 i had the hks to start with, now i have the fidanza (as recommended by south bend, who supplied my kevlar clutch). no problems so far, though i havent had it for years. i loved the response of the hks triple, just hated the switch feel. this setup i have now is great. i agree there r certain risks with lightened flys but from my research failure rates where low, i never heard of anyone with crank damage. i did speak with jun regarding their molly fly and they clearly stated that it was not for use with the GTE. they offered no explanation for this, but confirmed when i questioned them (i didnt like to say to jun. "are you sure you are right about that info you just gave me on yr equipment") some people love 'em some hate 'em. Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted January 5, 2004 Share Posted January 5, 2004 I've got a lightened flywheel too. The only thing I don't like about it, is the way it makes the car sound like the bottom end is hanging out, but the throttle response is great! Quote Link to comment Share on other sites More sharing options...
Wez Posted January 5, 2004 Share Posted January 5, 2004 What one do you have matt? Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted January 5, 2004 Share Posted January 5, 2004 Unorthodox Racing Lightened Aluminum Flywheel And here's the sales talk... "This flywheel weighs only 13 pounds and is constructed of billet aluminum. The stock flywheel weight 34 pounds, thats a difference of 21 pounds of rotating mass you can save with this flywheel!! Compared to a stock flywheel, the Unorthodox flywheel gives you: More usable horsepower and torque throughout the RPM range; Quicker rev's; Less turbo lag; Lowers stress on drivetrain, extended service life; and Higher RPM's." Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 5, 2004 Share Posted January 5, 2004 Jeez, more HP and torque, and less tress on the drivetrain. *ollocks.... They should be politicians, they have a natural bent.... Quote Link to comment Share on other sites More sharing options...
Matt Harwood Posted January 5, 2004 Share Posted January 5, 2004 I thought that might provoke a reaction! Quote Link to comment Share on other sites More sharing options...
Scooter Posted January 5, 2004 Share Posted January 5, 2004 Originally posted by Chris Wilson Jeez, more HP and torque, and less tress on the drivetrain. *ollocks excuse my ignorance but does this mean a lightened flywheel basically equates to reducing the transmission losses ie more of the engine power makes it to the wheels? I have a TT gearbox flywheel combo reputedly good for 550bhp which only ever sees 240 tops, so does this make it a more worthwhile, sensible and less risky mod for me? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 5, 2004 Share Posted January 5, 2004 Originally posted by Scooter excuse my ignorance but does this mean a lightened flywheel basically equates to reducing the transmission losses ie more of the engine power makes it to the wheels? I have a TT gearbox flywheel combo reputedly good for 550bhp which only ever sees 240 tops, so does this make it a more worthwhile, sensible and less risky mod for me? Changing to a lighter or heavier flywheel merely changes the inertia of the engines rotating assemblies, and that of the whole drivetrain when the clutch is engaged, in a gear. It is totally impossible for it to change the engines running torque or horsepower. If you managed to start the engine and "magically" unbolt the flywheel, clutch and propshaft, but still drive the back wheels the inertia would be radically reduced, but you's still get EXACTLY 240 tops... Assuming launching from a standing start was mastered by judicious clutch slip, the lighter flywheel would allow faster acceleration, just as would lighter wheels and tyres, a carbon propshaft, lighter C/V joints and driveshafts, blah blah. The flywheel has more effect as it isn't "seeing" any gear reductions though. Quote Link to comment Share on other sites More sharing options...
Digsy Posted January 5, 2004 Share Posted January 5, 2004 And further to that, it'll only reduce inertia if the majority of the mass is removed from the outer edges of the flywheel. The closer you get to the hub the less effect mass reduction has. And the reduced drivetrain stress bit is potentially rubbish, because as I have said in earlier posts, it is quite possible to increase drivetrain stresses by changing the natural torsional frequency of the drivetrain, which a lightened flywheel would certainly do. Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 5, 2004 Share Posted January 5, 2004 Originally posted by Darren Blake And further to that, it'll only reduce inertia if the majority of the mass is removed from the outer edges of the flywheel. The closer you get to the hub the less effect mass reduction has. And the reduced drivetrain stress bit is potentially rubbish, because as I have said in earlier posts, it is quite possible to increase drivetrain stresses by changing the natural torsional frequency of the drivetrain, which a lightened flywheel would certainly do. I well recall a Vovo 240 I built years ago (don't laugh people, she was an awesome beast ), that had a none damped clutch driven plate and a VERY light flywheel. the gearbox and propshaft harmonics were staggeringly bad. I had a sprung centre clutch driven plate made by AP at great expense, and the car drove like a stock one, drivetrain noise and vibration wise. Instead of spitting out second gears every few weeks they lasted about 5000 miles, too! Stock box, but with a genuine 350 BHP it was asking a lot of it. Quote Link to comment Share on other sites More sharing options...
Scooter Posted January 5, 2004 Share Posted January 5, 2004 thanks........so power the same but increased max acceleration. out of idle curiousity the often talked of 'transmission' losses re Dyno prints etc, is this purely due to friction within the gearbox diff etc or is this too simplistic a view? Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted January 5, 2004 Share Posted January 5, 2004 Originally posted by Scooter thanks........so power the same but increased max acceleration. out of idle curiousity the often talked of 'transmission' losses re Dyno prints etc, is this purely due to friction within the gearbox diff etc or is this too simplistic a view? basically "drive train loses" usually encompass gearbox, propshaft joints and centre bearing if used, differential, rear drive shaft joints on an IRS car, and hub bearings. They include tyre friction and deflection losses too, if the dyno uses rollers, but on something like the Thor one, obviously not, as the load cell absorbeers bolt straight to the hubs. So a power figure from pete betts dyno wouldn't be directly comparable to a rolling road where the tyres drive rollers. Not sure how the figures are adjusted as a comparison, but for sure the direct drive rolling roads are more accurate and repeatable. There should be adjustments for air pressure / density / temp and altitude too. Quote Link to comment Share on other sites More sharing options...
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