lighten the flywheel?
 

I am in the middle of my 4-speed conversion ('85 300CD). While I have it out, has anybody tried shaving a few pounds off the flywheel? Any input?

Why not just use a 616 flywheel? They are lighter than the 617 flywheel by a few pounds. The 617 flywheels are relatively rare so you could probably sell it for more than a 616 flywheel would cost.

Most of the people who have done the manual conversion have used the lighter 240D flywheel with no ill effects.

I think he means.. a lot lighter

The 616 flywheel works fine, but I would not go any lighter.

The 616 flywheel is already some 10-odd lbs lighter than the 617 FW. Supposedly, I haven't seen anyone weigh the two yet.

The idle is fine with the 616FW so I bet you could shave more off without problems. There is one video of an engine idling with just the auto flex plate (About 1/4 the normal mass without the torque converter and fluid).

You want some weight or you'll get the engine returning to idle too quickly between shifts and you'll wear out the clutch quicker.

Does this give anyone the same idea that it gives me?

the 616 was for the 240d right? I have that one...and was planning on using it.

I might feel stupid for asking this...but what idea did you have?

616=240D engine

I think MTU is thinking that a really light flywheel could counter the problem of the engine not returning to idle properly when the injection pump's torque control is over-adjusted or when larger elements are used, but I'm not sure if it is the answer.

Part of that problem is fuel delivery (injection), lowering the rotating mass may help but I have this feeling it could make it worse instead...

I wouldn't rush to modify the flywheel on a six cylinder diesel - mainly because the inertia of the whole system is tuned in conjunction with the vibration damper on the nose of the crank to prevent the buildup of damaging torsional vibration. If you change the rotary inertia of the system, you change the resonant frequency of the vibration, and you may move it to a frequency where the vibration damper no longer works to reduce the amplitude of vibration. As the vibration is torsional, and high frequency, you won't feel it, but it causes damage nevertheless. The stress resulting from this torsional vibration is responsible for snapping crankshafts, and this is a big problem in diesel engine development - meddle at your peril.

Would be nice to see if Fluidamper would make a piece for MB Diesels... May be dreaming though...

I'm sure they would, but as the old saying goes: "Speed is just a question of money -- how fast do you want to go?"

The market for such an item would be, what, three or four people? :P

Yep- but I think I'd better put the linkage spring back on first...:o it's not installed right now. I'll be doing that right after the FLFL comes out. Right now my alda is set so that it returns just fine- while I am looking for ways to increase fuel and still return to idle, there are a few things I should do first before making the flywheel lighter.

Ya, keep dreaming. I wouldn't run one on my 7000 rpm big block. They like to come apart. Sicne I dont race anymore, I use oem.

I dont think you want to lighten the flywheel much, if any at all, at a low rpm app like a diesel. Unless its WAY modifed and you need to get rpms coming out of the corners!

I think we are on to something with RPMs, seeing as we can't get longer pump stroke or bigger elements very easily or cheaply...

I read somewhere (I think VW Vortex?... maybe the link was posted on this board?) about people revving VW 1.6L IDI motors to somewhere north of 6000rpm. This was possible due to the fact that its IDI (bingo! so is the 617) and it has a very square bore to stroke ratio (so does the 617). More RPMs = more horsepower. Seemingly, the old wives tale about the flame front not propogating fast enough to warrant high rpm operation was not true.. I wish I had the link to the discussion, because it was very informative.

We know the 617 has a VERY strong bottom end. What we don't know is whether we need better valve springs to prevent float, and whether the engine is balanced well enough to spin 7000rpm. Also possibly need to set valve lash differently and set timing differently. I'm sure there are other design parameters I am completely overlooking as well, someone please chime in... Oh, btw. the bosch MW pump is only rated for 2500rpm, so this could be a stretch for it....

I don't intend to hijack here, just seemed like maybe a good place to insert this idea fragment because the topic of conversation is relevant to RPMs.