So I've been through a couple of aluminum flywheel experiences on different cars. Some with problems, some not. Now I'm looking to do a steel FW for my 3.4DOHC/F40 swap. I haven't gotten any prices yet, but of course the first is always expensive, so I'd probably do a small run to defray costs.
What would be your input if you were interested?
Weight? I was thinking 9 pounds (but probably more like 12 pounds)
Clutch? I was planning the stock pattern, but I'd be open to suggestions.
Also, does someone have the definitive dimension from the crank face to the flywheel friction surface? I thought I read 1.75" - 1.80".
------------------ 1988 GT, 5-speed, white, beechwood leather, 3.4 DOHC crate motor with Getrag 5-speed. C.A.R.B. legal, Corvette power steering, Boxster wheels and 12" brakes. On to the F40 installation.
[This message has been edited by sspeedstreet (edited 03-13-2015).]
There's no way a solid steel flywheel for the F40 is going to weigh 9 lbs.
The aluminum flywheel for the LS4/F40 from fieroguru weighs 12 lbs. The 60 degree V6 flywheel is going to be about the same size, so you're looking at closer to 18lbs for the flywheel.
On the N*, I think the thickness of the flywheel (flange to friction surface) is about 1.6". The input shaft of the trans is deeper into the bell housing than a normal Fiero trans, so you need a pretty thick flywheel to be able to get the splines engaged properly, which is why the aluminum flywheel from fieroguru weighs 12 lbs for the LS4/F40.
If you have a neutrally balanced 60 degree V6 though, is there any reason you can't use the OEM F40 flywheel? The 3.9 flywheel should be able to bolt up to a 3.4, no?
[This message has been edited by dobey (edited 03-12-2015).]
Well, they claim a 10.50 inch billet steel FW @ 9.0 pounds. True, by the time the friction surface is raised to the needed height it may be in the 12.0 pound range.
Given fieroguru's billet aluminum flywheel is 12 lbs, I think you're probably looking closer to the 15-20 lbs end of the spectrum listed for that diameter flywheel on that page.
The modulus of elasticity for aluminum is ≈100,000, for steel ≈300,000. Steel weighs about 3X as much as aluminum. As long as you're not at the extremes of design, weight vs modulus of elasticity of the two metals is ≈ 1:1. A 12 pound aluminum flywheel can be replaced by a 12 pound steel flywheel. Why are aftermarket "light" flywheels traditionally made in AL? The machining is much easier.
Originally posted by sspeedstreet: The modulus of elasticity for aluminum is ≈100,000, for steel ≈300,000. Steel weighs about 3X as much as aluminum. As long as you're not at the extremes of design, weight vs modulus of elasticity of the two metals is ≈ 1:1. A 12 pound aluminum flywheel can be replaced by a 12 pound steel flywheel. Why are aftermarket "light" flywheels traditionally made in AL? The machining is much easier.
The steel flywheel will only be lighter or equally as light as the aluminum flywheel, if it occupies less volume. I'm not sure it will be possible to make a steel flywheel for the F40, which would occupy less volume than the already existing aluminum designs. At least not enough where the weight would be equal to the aluminum one. The steel billet flywheel for the LSx from RAM Clutches is about 7lbs heaver than their aluminum billet flywheel, for the exact same application. You might be able to get a 12 lbs flywheel, but don't get your hopes too high on that.
I don't think the "machining is easier" argument really matters for turning a flywheel down on a lathe. They're almost all done by CNC, especially the mass market ones. The aluminum can be turned faster but not significantly enough that I'd expect that to be the reason it's chosen by Fidanza and others. On the other hand, huge rods/discs of aluminum are probably much cheaper than forgings that billet steel parts are made from.
The billet steel flywheel from Ram claims to be approx. 11 lbs.
Ram has them available for the 88V6.
Part number is 798-1570
Hope this helps.
That's for the 88 V6, but that flywheel isn't thick enough for the F40 transmission, which has a deeper bell housing, and the input shaft splines are deeper into the bell housing. It would work when using the stock Fiero transmissions, but not when using the new transmissions which have a deep bell housing on engines that use dual mass flywheels.
A round chuck of steel 11.5" in diameter and 1.8" thick (your suggested dimension, not mine) would be 52 lbs. To get it down to 9 lbs (excluding the weight of the ring gear) you would have to remove 83% of the material. Assuming it is a flat flywheel (which it can't be with the 1.8" thickness) the average thickness would have to be slightly less than 3/16" to get it that light.
An aluminum chunk the same size would be 18.7 lbs. Assuming 3 lbs for the friction plate, you need to machine it to be 6 lbs, so you need to remove 68% of the material and since aluminum is softer, you can turn it at much larger cuts and feed rates... Again, assuming it would be flat, the average thickness would be about .57" thick.
[This message has been edited by fieroguru (edited 03-14-2015).]
Originally posted by dobey: I don't think the "machining is easier" argument really matters for turning a flywheel down on a lathe. They're almost all done by CNC, especially the mass market ones. The aluminum can be turned faster but not significantly enough that I'd expect that to be the reason it's chosen by Fidanza and others.
If they turn them on a lathe, they have to flip it half way through the process to turn both sides, then they have to do a second setup on a different machine to drill the crankshaft bolt pattern and drill/tap the pressure plate hole. The steel ones have an advantage here as all these holes can be drilled/tapped from the same side. Aluminum has the disadvantage of needing the wear strip and all of its holes (most of which are also counter bored), so it normally has to be machined from both sides (wear strip holes counter bored on the backside, pressure plate holes counter bored on the front side). Given this, most of the aluminum flywheels are CNC machined in a milling center, not on a lathe. Do one side, flip, do the other, done.
If you look at the sample steel flywheel from the site above, it was also done on a CNC milling center as they needed to leave more thickness around the pressure plate bolt holes, but have to maximize removal of any material they could to keep the weight down. If both are milled vs. turned, the aluminum flywheel will be much quicker to machine due to the less volume needed for removal, as well as the larger cuts and faster feed rates you can run with aluminum.
[This message has been edited by fieroguru (edited 03-14-2015).]
