Dynamic balance, separate or assembly |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
Dynamic balance, separate or assembly |
930cabman |
Sep 3 2021, 01:16 PM
Post
#1
|
Advanced Member Group: Members Posts: 3,533 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States |
We are building a 2.1 /4 cyl. motor and have sent the rotating parts for balancing. Prior to I had the flywheel resurfaced at NAPA. Unknowing they removed the dowel pins that locate the pressure plate. I got all the parts to an old friend for balancing (he owed me a favor) and he turned the rotating parts around for me. He balanced the crank by itself, then added the fan and flywheel, but NOT the pressure plate.
Question: The factory book states the pressure plate should be aligned with the flywheel with the mating marks. The flywheel was not mounted to the flywheel due to the lack of dowel pins and is the pressure plate balanced by itself or as part of the assembly? |
930cabman |
Sep 5 2021, 04:43 AM
Post
#2
|
Advanced Member Group: Members Posts: 3,533 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States |
I will be calling Kennedy Tuesday, see if they can confirm a 0 balance on their pressure plates.
|
Superhawk996 |
Sep 5 2021, 07:45 AM
Post
#3
|
914 Guru Group: Members Posts: 6,469 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
I will be calling Kennedy Tuesday, see if they can confirm a 0 balance on their pressure plates. Nothing in life is zero balance. Even if someone tells you it's zero balance, there is still a tolerance to the equipment and process used to balance. Go measure same zero balance part on another machine and it's highly unlikely you'll get true zero. Fully agree a fully dynamic balance of all rotating mass is ideal. Mandatory for high RPM race engines. However, are you also having your fan dynamically balanced as part of the assembly? If not why not? Inclusive of fan hub and fasteners? Will all flywheel and pressure plate fasteners be placed back into exactly the same holes they were blanced in? You see where this is going. As stated previously, for a road car, in normal production, components are balanced as individual parts. There is a print tolerance on each part and each part has a six sigma variance of what it could be in actual production. A Monte Carlo simulation can be used to understand what the final balance liklihood is of a given outcome. Most times, some parts will be a little on the plus side, some on the minus side. Same with respect to how they index. In the end, it all works out within an acceptable range due to the statistics and probability working against all parts being all on the plus side or all parts on the minus side simultaneously. Not saying that you shouldn't dynamically balance. However, let's recognize that OEM was not built that way. Full dynamic balance is nice to do for a road car but not a necessity. My first rebuild wasn't dynmaically balanced, I had neither the money to do it nor access to a vendor that could do it back in the day. That engine ran about 100K miles, no issues. |
930cabman |
Sep 5 2021, 01:31 PM
Post
#4
|
Advanced Member Group: Members Posts: 3,533 Joined: 12-November 20 From: Buffalo Member No.: 24,877 Region Association: North East States |
I will be calling Kennedy Tuesday, see if they can confirm a 0 balance on their pressure plates. Nothing in life is zero balance. Even if someone tells you it's zero balance, there is still a tolerance to the equipment and process used to balance. Go measure same zero balance part on another machine and it's highly unlikely you'll get true zero. Fully agree a fully dynamic balance of all rotating mass is ideal. Mandatory for high RPM race engines. However, are you also having your fan dynamically balanced as part of the assembly? If not why not? Inclusive of fan hub and fasteners? Will all flywheel and pressure plate fasteners be placed back into exactly the same holes they were blanced in? You see where this is going. As stated previously, for a road car, in normal production, components are balanced as individual parts. There is a print tolerance on each part and each part has a six sigma variance of what it could be in actual production. A Monte Carlo simulation can be used to understand what the final balance liklihood is of a given outcome. Most times, some parts will be a little on the plus side, some on the minus side. Same with respect to how they index. In the end, it all works out within an acceptable range due to the statistics and probability working against all parts being all on the plus side or all parts on the minus side simultaneously. Not saying that you shouldn't dynamically balance. However, let's recognize that OEM was not built that way. Full dynamic balance is nice to do for a road car but not a necessity. My first rebuild wasn't dynmaically balanced, I had neither the money to do it nor access to a vendor that could do it back in the day. That engine ran about 100K miles, no issues. Back in the 1970's that was my full time job in the family business, and I got pretty good at it. My thought was, while the 2.0/4 is apart, why not. I still have a few friends in the business and dropped the rotating components off, but forgot to include new dowel pins for the PP. My local NAPA had resurfaced the flywheel and removed the dowel pins. |
rgalla9146 |
Sep 6 2021, 10:20 AM
Post
#5
|
Advanced Member Group: Members Posts: 4,621 Joined: 23-November 05 From: Paramus NJ Member No.: 5,176 Region Association: None |
I will be calling Kennedy Tuesday, see if they can confirm a 0 balance on their pressure plates. Nothing in life is zero balance. Even if someone tells you it's zero balance, there is still a tolerance to the equipment and process used to balance. Go measure same zero balance part on another machine and it's highly unlikely you'll get true zero. Fully agree a fully dynamic balance of all rotating mass is ideal. Mandatory for high RPM race engines. However, are you also having your fan dynamically balanced as part of the assembly? If not why not? Inclusive of fan hub and fasteners? Will all flywheel and pressure plate fasteners be placed back into exactly the same holes they were blanced in? You see where this is going. As stated previously, for a road car, in normal production, components are balanced as individual parts. There is a print tolerance on each part and each part has a six sigma variance of what it could be in actual production. A Monte Carlo simulation can be used to understand what the final balance liklihood is of a given outcome. Most times, some parts will be a little on the plus side, some on the minus side. Same with respect to how they index. In the end, it all works out within an acceptable range due to the statistics and probability working against all parts being all on the plus side or all parts on the minus side simultaneously. Not saying that you shouldn't dynamically balance. However, let's recognize that OEM was not built that way. Full dynamic balance is nice to do for a road car but not a necessity. My first rebuild wasn't dynmaically balanced, I had neither the money to do it nor access to a vendor that could do it back in the day. That engine ran about 100K miles, no issues. Back in the 1970's that was my full time job in the family business, and I got pretty good at it. My thought was, while the 2.0/4 is apart, why not. I still have a few friends in the business and dropped the rotating components off, but forgot to include new dowel pins At least they knew enough to machine the mounting surface too. |
Lo-Fi Version | Time is now: 21st September 2024 - 07:11 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |