333pg333

I know that there are the Constantine bearings available but came across these. Has anyone seen or used these? Some interesting info on their website regarding Torque Tube failures.

http://www.blackseard.com/site/index...ducts&Itemid=9

s14kev

That website is Constantine.

mikey_audiogeek

I'm guessing the 968 went away from the split TT due to the dual-mass flywheel controlling vibration better.

Patrick, did you make a decision on a new crank damper? I see that Fluidampr make universal parts: http://www.wundercarparts.com/fluida.../i-300585.aspx

The RSBarn one looks like the best option tho.

Cheers,
Mike

333pg333

Ahh...didn't realise. Thanks.

I actually have an RS Barn one heading this way. May use it on this motor (especially if we just rebuild it as an 8v). Will probably be changing the crank over to one that is not knifed as well. Also probably going to remove b/shafts too. Not totally sure which way we're going on this motor just yet.

TonyG

Keep the balance shafts.

TonyG

Dubai944

I need to do my torque tube bearings one of these days. Looks like a PITA job though....will need plenty of beer.

Voith

I still have few delrin tt sleeves if anybody needs them.
https://rennlist.com/forums/924-931-...build-set.html

333pg333

I seem to get a 50/50 opinion on this....and from some pro builders too. What's your take Tony?

TonyG

My take is that it's not worth the HP gain. Things crack, things come loose, and you have to really make sure everything has a lock washer, lock tight, or an aircraft lock nut, safety wire, etc...

I was warned about it from John Millege. Also somewhere subsequent to my turbo 4 days, I read an article from the Porsche engineers that discussed this very same thing on the LeMans 951. They ended up going back with the balance shaft belts tood.

That said... I id it. Wouldn't do it again.

The up side is a few HP but more importantly it makes taking the head off and servicing the cam belt much faster.

TonyG

333pg333

I'd heard that about JME but have also spoken to other top end builders who recommend deleting them for our application. My take is that these motors (i4) were designed and built back in the late 70's through to the early 90's. The 2.5lt turbo was pushing out 250bhp and designed for a nice high speed Autobahn stormer with plenty of mid range tq. Being a large capacity 4 cylinder they suffered from nasty harmonics around the 3000 - 5000rpm mark reputedly and therefore paid Mitsubishi to utilise their balance shaft design to help tune these harmonics out. Fast forward to now and looking at a considerable jump in cubic capacity (3.1lt) with different rods, pistons, crank, clutch, w/ dry sump also. So the ingredients in the recipe have changed considerably. The recip/recirc components are totally different to what originally came with the motor. Further, this is a race car that is stripped out and has no concession for noise reduction at all. So even if we suffer some vibration by not running them it may not be very noticeable anyway. Our plan is to run a dampener on the front of the crank as well. My mistake was purchasing / installing a highly lightened knife crank some years ago on the basis that light = better...but this was before I realised that reducing the integrity of the crank only exacerbates the flex which results in too much vibration at the nose which results in things falling apart. As previously mentioned, the dry sump pulley sheared in half and then once that was replaced with something stronger, the balance shaft pulley on the crank did the same thing. Same day. Same position on the track. This leads us to believe that the cause could easily have been due to the larger vibrations on mid corner backoff from very high piston vacuum drag. It's too coincidental that it happened within 10 yards or less twice in a row! Our objective is to update the TT bearings with some of Constantine's - return to a mildly modified crank - run a dampener at the front of the motor and if we convert to 16v we will also modify the rods to run a smaller, lighter pin and some nice Mahle custom pistons. Then once we get all the components, have them properly balanced down here before assembly. This we feel should give us the best chance of keeping this motor together.

Note the 2nd pic showing the crank b/shaft pulley. It certainly looks like this was suffering stress previously rather than the one clean break on the day. 3rd pics shows b/shaft pulley with witness marks showing movement. Might have skipped a tooth but we'll never know due to the main pulley shearing in half.

m42racer

Patrick,

I was told years ago when I was having a race version built, that these engine require extra balancing either internal or external as there was not enough room to add more counterweight to the crankshaft due to the Oil pan design. If you were to run a Crankshaft dampener designed for your engine then I am sure the removal of the balance shafts would not be an issue. I would think a crankshaft dampener would be more efficient than a pair of balance shafts driven via toothed rubber belt.

Best to listen to your builder on this one.

TonyG

The first issue is using anything but steel for drive pulleys. That will always fail due to the vibration.

Bolting on that long snout on the end of the crank is what caused that pulley to fail.

The second thing is that the vibrations that the counter shafts counter... occurs at 3000rpms and again at 6000rpms, so the argument that it's a race engine, which operates above 3000rpms and thus is not subject to the vibration in question is not valid.

This because ... the 1st order vibration (the crank vibration) without balance shafts can clearly be felt at approximately 3000rpms. The next set of vibrations, which are the 2nd order vibration (non-sinusoidal motion of the piston and connecting rod) occurs at exactly double the rpm of the first order vibration (approximately 3000rpms)... which results in the 2nd order vibration at approximately 6000rpms.

The 2nd order vibration is more harmful than first order vibration. This is what cracks and breaks ****.

Third... the crank being lightened isn't the issue. It's the firing order of a 4 cylinder engine which is exacerbated by the large displacement.

If you cut down the crank counter weights (ala knife edging...), it's still balanced against the weight of your specific pistons and rods combination. And assuming it's done correctly, the crank is perfectly balanced. Thus cutting it down (or knife edging) has zero effect on the vibration produced.

Lastly if your piston and rod combo is heavier than the stock 2.5L or 3.0L combo (which it might be due to it being stronger and physically larger) the vibration will become greater (or smaller if the weight is less) in amplitude depending on the weight difference.

Again... the vibration is a result of the fact that it's an inline 4 which inherently produces specific types of vibrations. The heavier the piston/rod combo, the higher these vibrations are in amplitude.

I wonder if the counter weights in a 3.0L are the same weight of those in a 2.5L? (probably not but it would be interesting to know).

TonyG

333pg333

Yes, Simon. Pretty much what I'd decided. Just need to see what we've got when the motor comes down.

TonyG

That info is incorrect. 100%

The vibration is the same in all inline 4 cylinder engines.

You cannot balance it out, to eliminate the inherit vibrations produced by the engine design, no matter how much counter weight you use.

The reason is simple.

In an inline 4, the outer 2 cylinders are opposite the inner cylinders. When they are at TDC and TBC, everything is balanced perfectly (2 pistons at the top, 2 pistons at the bottom). But when the crank is turned 90 degrees from that position, the inner and outer pistons are not at the same position (not even with each other).

That's the simple version. Specifically, it's because the acceleration of the piston is greater at TDC than BDC.

F=MA (force=mass * acceleration). Therefore, the forces of the pistons at the top and bottom of the stroke (and specifically at mid stroke) do not completely cancel each other out.

This is what causes the 2nd order vibration.

This is the exact reason that the larger the inline 4 engine... the larger the vibrations (amplitude).

This cannot be balanced out no matter the size or location of the counter weights.

Anybody telling you this is either blowing smoke up your *** or just doesn't know that they are talking about.


TonyG

333pg333

The problem is that this current motor was sort of thrown together in a manner of speaking. The knife crank was done by whoever does LR's. The rods were bought from another vendor and the motor was assembled with another set of pistons. I don't know if the components were ever actually balanced as this was motor was kind of initially designed as more a street rod thing. I had another 16v project with the builder going on simultaneously. The motor was shipped down here and we didn't pull it down to do our own balancing, plus we added a custom puk clutch. Hanging the extra dry sump pulley off the nose would have just made things worse I suspect. Retaining the balance shafts may have made things worse or not. The system wouldn't have been very integrated, more like a 'suck it and see' outcome. Running all these unmatched and unbalanced parts was probably a recipe for disaster.
Also can't think of other i4 race motors that run balance shafts?