Flywheel?

[Dave Stark]

Does anyone know the weight of the engine flywheel for 4.0 AX15 '91 model?

 

I'm doing an engine swap & will need to use the Jeep's wheel. I'm concerned it may not be heavy enough for the engine i want to go with...

 

Mercedes OM617 five cylinder turbo diesel. I believe the MB wheel is somewhere in the neighborhood of fifty pounds.

[1987Comanche]

I have a spare Renix flywheel in the basement (I think from a BA 10/5). I can weigh it if that would help.

[carnuck]

Are you going to use the flywheel to use a Jeep starter? There is a std flywheel already available for the Mercedes 5 cyl which has a different balance than the Jeep 4.0 and just use the Jeep disc.

[Dave Stark]

Are you going to use the flywheel to use a Jeep starter? There is a std flywheel already available for the Mercedes 5 cyl which has a different balance than the Jeep 4.0 and just use the Jeep disc.

 

Where would that be available through? Here is a link to the thread of the guy who's building the adapter:

 

http://www.dieselbombers.com/diesel-engine-conversions/58670-mercedes-om617-5-cyl-turbo-diesel-engine-swap-jeep-wrangler-yj-conversion.html

 

He's using the stock Jeep wheel, but I think it will be too light & cause vibes. If i can get a different flywheel & still use this adapter that would be great! :banana:

 

~Dave

[Eagle]

He's using the stock Jeep wheel, but I think it will be too light & cause vibes.

Does not compute.

 

Light weight does not cause vibrations, imbalance causes vibrations. A light flywheel means there is less rotating mass to keep the engine spinning when you try to engage the clutch from a stand-still, so you have to know how to drive a clutch -- well.

 

That said, a light flywheel is normally used for racing applications, when quick throttle response is more important than smooth operation. They are not recommended for street driving, but that doesn't mean you can use a light flywheel if that's all you can get.

[Dave Stark]

I suppose i wasn't being as clear as i could be on this one. All engines vibrate all the time, it's inherent in the design, anytime there is a rotating mass it is impossible to have no vibrations, even on turbine engines that turn 50+ thousand RPM's. Piston engines typically have two peak vibration zones, the first one is usually in a lower RPM generally 1K to 2K RMP & it only lasts about 100RPM (this is the one I'm concerned with) it is generally considered a transitional vibe, the second one is your red line & is far more drastic. When you start changing the weight of the rotating mass at the end of the crank you change the vibration characteristics of the engine, a lighter flywheel means faster response & a higher RPM limit, but it changes the characteristic of the lower peak as well, possibly making it wider. My concern is that with a diesel engine that has a fifty pound flywheel going down to a thirty? pound Jeep wheel may move the lower vibe peak into a normal operation RPM & cause damage to my engine.

 

I'm an aircraft engine mechanic by trade & after reading what i just typed i may be going a little extra rain-man on this one, but it's there like an itch i can't scratch... All of that being said, if there is an issue, the engine would exhibit signs of wear long before it had catastrophic failure, so I may as well go for it. :dunno:

[Eagle]

Part of your problem is too much theory and not enough practice. An in-line 6-cylinder engine is inherently balanced, and any imbalance that is introduced is a result of manufacturing tolerances that allow a degree of mismatched parts being used in the rotating assembly. I have NEVER heard of an I-6 engine having two vibration zones, and I'm quite certain that there isn't one between 1k and 2k RPM. The natural vibration zone for the I-6 is, IIRC, at 6,000 RPM ... which happens to be above the redline on Jeep engines so, unless we're drag racers running modified engines, we just don't worry about it.

 

However, you're worrying about a 5-cylinder engine, and there is essentially no way for a 5-cylinder engine to be inherently balanced. Rather than gross flywheel weight, I would start off by asking if the Merc 5-cylinder engine is internally balanced (i.e. the flywheel is completely symmetrical) or if the engine is externally balanced (the flywheel has an eccentric weight on one point of the periphery).

[carnuck]

5,850 RPM is the vibe point My old motor went past that

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

once!

[Eagle]

5,850 RPM is the vibe point My old motor went past that

 

once!

They'll usually go past it any number of times. The problem (as the original poster has alluded to) is when you try to RUN at the vibration point for a prolonged period.

[carnuck]

I DID AND THE MOTOR VIBED APART! Oops! Sorry for yelling. I passed this link to the Mercedes diesel guys. There was one with a 4 speed in the local junkyard about 6 months ago, but no time to go play there anymore.