Flywheel balancing

[Scott Cee AKA 2drx4]

I've got this stupid project with a Mercedes OM617 and a Jeep. Current hurdle is the flywheel balancing.

Allegedly the Merc has a neutral flywheel that is then assembly balanced with the rest of the rotating mass before final assembly. I can confirm the Merc flywheel definitely has a heavy spot. That said, I don't think it's that heavy, maybe 10 grams at 10" diameter according to my knife edge. This would make sense given the story that they did a final balance with the other components.

Jeep flywheels are neutral balanced. I don't really know what tolerance is deemed to be neutral. But they're "neutral." Of the two I have they spin to different points, but my balancer is not that good.

So my questions for people who have had flywheels balanced in the past, how close do they actually get it? How close is an OEM flywheel? Or a replacement from Luk, Sachs, etc? This thing is a 5000rpm motor if you're pushing it, that's it. Does a guy really gain anything by trying to get it closer than about 10 grams in this case?

I haven't called anywhere to see how much they will want to try to match the balances yet, or how soon it could be done. I just figured out tonight that my knife edge balancer isn't as good as I hoped, and now I'm torn between ordering some precision ground stock and trying again, farming this out, or just saying screw it and bolting it together.

[Scott Cee AKA 2drx4]

I took it to an engine shop today.

They were not impressed. They don't want to do it. The guy said if it's within 20 grams he'd be inclined to leave it alone. I'm somewhat concerned about what I'm going to get back from this.

[Haywire Fab]

Currently my plan is to just put the flywheel on and see how the vibration is from there. Yota flywheels are neutral balanced as well, AFAIK. I dont have a flexplate on mine and as far as i know never marked either.

My buddy never had an issue with his when he swapped it into his tacoma. Runs and drives great, needed an intercooler with the 7.5 mm pump tho as egts are definitely a thing.

[HillBilt]

I took it to an engine shop today.

They were not impressed. They don't want to do it. The guy said if it's within 20 grams he'd be inclined to leave it alone. I'm somewhat concerned about what I'm going to get back from this.

Id be more inclined to bring it to a machine shop and see if they can balance it. Brunett or KJM in PG might be able to. Engine shops don't seem to give you the time of day unless its performance based, from my experiences anyways.

[Scott Cee AKA 2drx4]

I took it to an engine shop today.

They were not impressed. They don't want to do it. The guy said if it's within 20 grams he'd be inclined to leave it alone. I'm somewhat concerned about what I'm going to get back from this.

Id be more inclined to bring it to a machine shop and see if they can balance it. Brunett or KJM in PG might be able to. Engine shops don't seem to give you the time of day unless its performance based, from my experiences anyways.

It was Jim's Engines and I think he gave his guy hell after I left. When I went back to get it he said it was out 10 grams, which was what I had measured it as, and I was only a little off on the angle. I'm surprised I was that close with the knife edge, given the issues it has.

So there's a hole in the other flywheel now, so it should be heavy in the same manner as the stock one was. Jim said it will be within a gram of what the other one was.

Interestingly I don't think 10 grams would have made that big of a difference at that low of a max RPM.

Next time I will fix the knife edge though. I might anyways just to prove it would work. There was no reason to pay what I did based on the fact I was that close with bodge equipment.

[Scott Cee AKA 2drx4]

Currently my plan is to just put the flywheel on and see how the vibration is from there. Yota flywheels are neutral balanced as well, AFAIK. I dont have a flexplate on mine and as far as i know never marked either.

My buddy never had an issue with his when he swapped it into his tacoma. Runs and drives great, needed an intercooler with the 7.5 mm pump tho as egts are definitely a thing.

There seems to be a lot of variation in how far out they are. Some guys removed a LOT of material from their flywheels to get it the same. Some guys who just bolted it up and went have reported excessive vibration, although I'm not sure how they would know given it is an archaic diesel. And other guys have just bolted it up and ran it without issue.

[Helidump]

I was going to suggest we throw the old Chadwick 177 on when its running but we wouldnt have a baseline to know what a normal ips reading is...or a clock angle...or a way to adjust it....but it would be a neat experiment


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[Scott Cee AKA 2drx4]

I was going to suggest we throw the old Chadwick 177 on when its running but we wouldnt have a baseline to know what a normal ips reading is...or a clock angle...or a way to adjust it....but it would be a neat experiment


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Thought about it. Could spin it on the lathe and match the reading and angle, then remove material until it was the same. If I had a Vibrex on hand I would have probably tried it. I guess you have a 177 that can run a photocell there? I always forget they made ones that are capable of it. Would be easy to just put some reflective tape on the lathe chuck and hold the photocell pointing at it so it would read correctly.

It actually would be interesting to see how close you could get it. I think my lathe's limited speed (or my willingness to run it faster with a flywheel that big on it) might not make it super accurate.


Oh yeah, I tried modding my knife edge and still couldn't quite replicate the results that Jim's produced. But it was close. I think with a precision ground rod a guy could do it easily enough. As it was I had determined the MB flywheel would be right about 10 grams out, it was just the clock angle was a little hard to verify for sure. Then on the much heavier Jeep flywheel it just got a little hopeless as it seemed the weight of it was bending the rod, which already had some runout, so you just couldn't get it to do anything but show it had about 12 grams of imbalance, but it would always correspond with the runout of the rod.

[pointsnorth]

Umm potato ?


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[Scott Cee AKA 2drx4]

Umm potato ?


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Crap for balancing spinny things that fly.