Author Topic: Harmonic balancer? Good till 7200? (Read 3361 times)

fumstoo · « **on:** July 13, 2012, 12:56:41 PM »

Whats this i hear about the harmonic balancer only being good till 7200 rpm? Ive searched and i cant find any real sources. Just people posting on forums. Is there any real proof of this? Whos tested it? I know there som erev happy people out there.

bmwman91 · « **Reply #1 on:** July 13, 2012, 03:30:30 PM »

I am also interested to know about this as I have heard the same rumors over the years. Considering that I have a MM motor coming that will easily rev to 7700RPM, this seems important!

fumstoo · « **Reply #2 on:** July 13, 2012, 04:16:22 PM »

Theres a video somewhere of an mm motor revving to 8k. Found this

Quote

The crank damper thing WAS widely accepted as truth for a long time. A few quite knowledgeable and experienced people on here debunked it though...maybe one or 2 people had it come apart, but it was probably damaged or totally crapped out from road salt or something. A damper in good condition should be fine beyond what the motor can do.

The REAL worry is the hydraulic lifters. Above 7200RPM the can cause valve float from the immense oil pressure. You need solid lifters if you are planning on going beyond 7200RPM.

http://www.m42club.com/forums/archive/index.php/t-1456.html

But again its just someone talking.

bmwman91 · « **Reply #3 on:** July 13, 2012, 04:43:30 PM »

I would assume that it is a good part, unless abused or damaged. Metric Mechanic goes to immense lengths to make their motors reliable and dependable. If the damper was an issue, I would assume that they would either tell customers to get a new one, include a new one, or put a software limiter on the motors to prevent revving over 7200RPM.

wazzu70 · « **Reply #4 on:** July 13, 2012, 05:18:16 PM »

Its total crap

harmonic balancers wear out by design anyway so who is to say the damper did not fail due to age and not RPM?

Secondly, dampers on 4 cyl motors fail far less frequently than an I6 motor. At higher revs the 6cyl has a lot of torsion due to the looong crank. The I4s actually are pretty nicely balanced in the high end. Most 4 cyl race motors have no damper at all, just a solid pulley.

In GrandAm teams usually replaced the damper on S54 motors every other race, S14 race engines and S42 race engines dont have a damper at all.

In short, you are fine and the valvetrain is what limits rpm as previously stated.

fumstoo · « **Reply #5 on:** July 13, 2012, 06:54:17 PM »

FINALLY! Thank you for a legitimate answer and not just "no, its a lie." Wazzu's the man

bmwconnect · « **Reply #6 on:** July 13, 2012, 08:26:17 PM »

Autocross guys are always having me change the rev limit to 7500 rpm and they are hitting it all day long without issues to the balancer.

all the best

romkasponka · « **Reply #7 on:** July 13, 2012, 09:00:10 PM »

How often do you hear about broken crankshafts on m42, probably never, so do not put components on your engine if you cannot trust them. If system is more simple it is more reliable!