"Weight matching" OEM pistons - Page 2 - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


Engine Performance This section is for discussion on all engine building related questions.
Sponsored by:
Sponsored by:

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 03-29-2015, 01:51 PM   #21
Free Moustache Rides
iTrader: (8)
 
matthewdesigns's Avatar
 
Join Date: Jun 2008
Location: Colorado Springs
Posts: 1,656
Total Cats: 49
Default

Balancing the rotating assembly is included with each of our GT-R engine builds, we only send the crank/rods/pistons/pins/bearings/clips, and they turn out exceptionally well. This is all I'm going to do with my BP.
matthewdesigns is offline   Reply With Quote
Old 03-29-2015, 08:24 PM   #22
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,638
Total Cats: 25
Default

Yeah but are your clutches and flywheels already well balanced out of the box?
nitrodann is offline   Reply With Quote
Old 03-29-2015, 09:13 PM   #23
Elite Member
iTrader: (5)
 
Join Date: Oct 2007
Location: Canton, Ga
Posts: 1,707
Total Cats: 19
Default

I don't agree with balancing clutch and flywheel with the rotating assembly. An engine will outlast a clutch and when you replace it, it's no longer balanced. I had my engine balanced and the level of smoothness compared to a stock BP is unbelievable.
Stealth97 is offline   Reply With Quote
Old 03-29-2015, 09:38 PM   #24
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,638
Total Cats: 25
Default

It doesnt need to be balanced as a whole assembly if each component itself is balanced.

Dann
nitrodann is offline   Reply With Quote
Old 03-29-2015, 10:06 PM   #25
Free Moustache Rides
iTrader: (8)
 
matthewdesigns's Avatar
 
Join Date: Jun 2008
Location: Colorado Springs
Posts: 1,656
Total Cats: 49
Default

Quote:
Originally Posted by nitrodann View Post
Yeah but are your clutches and flywheels already well balanced out of the box?
Clutch (multiplate wet) is in the trans at the other end of the prop shaft, and the bellhousing that bolts to the back of the engine has a damper/flywheel combo that is afaik balanced in OEM configuration.
matthewdesigns is offline   Reply With Quote
Old 03-29-2015, 10:15 PM   #26
Elite Member
 
Join Date: Apr 2010
Location: Newcastle, Australia
Posts: 2,638
Total Cats: 25
Default

So they are already balanced. No wonder you dont feel the need to balance them...
nitrodann is offline   Reply With Quote
Old 03-30-2015, 01:12 AM   #27
Junior Member
 
guttedmiata's Avatar
 
Join Date: Sep 2012
Posts: 438
Total Cats: -3
Default

So if you take a gram or two off a piston, but the crank is out of balance on a journal by a half ounce, what do you think you gained. You'll never know if the piston was off by even 10 grams. If you balance the crank by that half ounce, but the pressure plate/flywheel assembly that bolted to the rotating crank is off an ounce, you'll never know if the crank is off or not. In actuality, the pistons would be the last thing I would balance as they make the least difference.

And unless you are going to spin it past 7k, the only thing any of this is going to give you is possibly a smoother idle.
guttedmiata is offline   Reply With Quote
Old 03-30-2015, 09:46 AM   #28
Elite Member
 
DNMakinson's Avatar
 
Join Date: Jan 2013
Location: Seneca, SC
Posts: 2,698
Total Cats: 267
Default

Quote:
Originally Posted by guttedmiata View Post
So if you take a gram or two off a piston, but the crank is out of balance on a journal by a half ounce 15 grams, what do you think you gained. You'll never know if the piston was off by even 10 grams. If you balance the crank by that half ounce 15 grams, but the pressure plate/flywheel assembly that bolted to the rotating crank is off an ounce 30 grams, you'll never know if the crank is off or not. In actuality, the pistons would be the last thing I would balance as they make the least difference.

And unless you are going to spin it past 7k, the only thing any of this is going to give you is possibly a smoother idle.
Fixed the mixed units, with liberal conversion tolerances.

Michael, thank you for putting it into proper perspective.

Research into crank balancing was quite interesting, especially the additon of journal "bob"s during the operation. *EDIT* I'm thinking this has more to do with resonance and flexture during the test, more than acutally affecting the balance? No bob weights needed for in-line 4. That makes more sense to me.

Another thing: Inline 4's are going to have 2X frequency vibration regardless of how perfectly they are balanced (unless there are counter-rotating balance shafts).

Costs to have the system balanced do seem modest.

Last edited by DNMakinson; 03-30-2015 at 10:08 AM. Reason: Updated Bob weight comment
DNMakinson is offline   Reply With Quote
Old 03-30-2015, 12:29 PM   #29
Elite Member
iTrader: (4)
 
Join Date: Sep 2006
Location: Charlotte, NC
Posts: 3,049
Total Cats: 4
Default

This thread sucks.

OP wasn't asking to discuss which parts have the biggest effect on balancing and whether or not it's worth the investment to pay to balance the whole assembly.

I'm pretty sure he was never going to pay to have everything balanced...he's doing a pretty simple "rods only" build and trying to keep costs at a minimum.

The original question was how to and where to remove weight from an OEM piston. Not why.

If he wants to take the time to try to balance out the weight of pistons, I say more power to him. Even if it has basically zero impact on the final product.
Efini~FC3S is offline   Reply With Quote
Old 03-30-2015, 01:49 PM   #30
Elite Member
 
Join Date: Jul 2005
Posts: 6,454
Total Cats: 80
Default

I question the usefulness of balancing pistons in the presence of combustion pulses.
JasonC SBB is offline   Reply With Quote
Old 04-12-2015, 03:25 PM   #31
Elite Member
Thread Starter
iTrader: (13)
 
Join Date: Dec 2006
Location: Taos, New mexico
Posts: 5,702
Total Cats: 237
Default

Quote:
Originally Posted by Efini~FC3S View Post
This thread sucks.

OP wasn't asking to discuss which parts have the biggest effect on balancing and whether or not it's worth the investment to pay to balance the whole assembly.

I'm pretty sure he was never going to pay to have everything balanced...he's doing a pretty simple "rods only" build and trying to keep costs at a minimum.

The original question was how to and where to remove weight from an OEM piston. Not why.

If he wants to take the time to try to balance out the weight of pistons, I say more power to him. Even if it has basically zero impact on the final product.
Thank you. This, exactly.

Anyways, it's already been done. I'll be putting this motor together shortly and will see what happens. I will also update this thread. If it does nothing it all, it was only a few hours wasted, so whatever.
Fireindc is offline   Reply With Quote
Old 04-12-2015, 08:07 PM   #32
Elite Member
iTrader: (15)
 
patsmx5's Avatar
 
Join Date: Aug 2007
Location: Houston, TX
Posts: 8,796
Total Cats: 247
Default

Quote:
Originally Posted by Fireindc View Post
Thank you. This, exactly.

Anyways, it's already been done. I'll be putting this motor together shortly and will see what happens. I will also update this thread. If it does nothing it all, it was only a few hours wasted, so whatever.
Yeap, this happens here unfortunately. I would start removing weight by cleaning up casting marks, then probably around the base of the piston where the casing for the wrist pin meets the top of the piston.

IMO it should help. If it's every apart again, you can balance the entire rod/piston/rings/wrist pin/clips/bearings assembly using basically just the scale you're already using and a couple simple fixtures. You can at least make them all match, last step would be to have the crank balanced to them, but to do that you'll have to take it somewhere but if you had all the parts already balanced it would be cheaper to have just the crank done by a machine vs paying them to do everything.

You got pics of what you did? I never balanced my engines when I built them, always wanted to. I'll probably do the next one I build myself. My spare engine I have now was balanced/assembled by a machine shop.
patsmx5 is online now   Reply With Quote
Old 04-12-2015, 10:07 PM   #33
Ben
Supporting Vendor
iTrader: (33)
 
Ben's Avatar
 
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,689
Total Cats: 99
Default

Quote:
Originally Posted by Fireindc View Post
Hey guys, I did a bunch of searching before creating this thread but could not find anything definitive, so bear with me.

I have a set of OEM pistons that are going back into this motor, for a "mild" build, aka Vlad style. Anyways, the heaviest piston is some 5-6 grams heavier than the lightest, and I'd like to do some balancing.

All of the rods are almost exactly the same weight (ebay forged), so I can't really match the heaviest rod with lightest piston, etc.

So now I'd like to get these pistons closely matched, but I cannot figure out WHERE I should be taking weight from them. I've read a few different opinions on the matter, and from what i gather there are a few options.

1) take the weight from underneath the top of the piston. IE dril/dremel from underneath and remove material.

2) Remove "casting" marks from the inside of the piston.

3) "shave" the weight from the bottom of the piston skirts with a belt grinder.

4) don't take any material from the pistons themselves, but rather remove material from the inside of the wrist pins.

Whatcha guys think? Want to get rolling on some miata related stuff, and this would be the next step.

Thanks <3
1,2,and 3 are all pretty commonly done. I think 4 would be a last resort. The right area to remove mass from depends entirely on the piston and the application. Here's a great article:
Eaton Balancing Engine Balancing, Part 3
Eaton Balancing Engine Balancing, Part 4

You should also balance the rods, both big and little ends. You can buy (what I feel is an overly expensive) scale system, or you can make your own pretty easily. Ours consists of a rod with a chain hanging off it. We suspend one end of the rod with the chain and weigh the opposite end on the scale. We had pictures on facebook a while back ago, but it's a pretty simple setup.

You won't spend more than a couple hours balancing both the pistons and rods, and it's pretty fun.

Not everyone has the budget or need for a full spin balancing, though it's great in an ideal world.
Ben is offline   Reply With Quote
Old 04-12-2015, 10:11 PM   #34
Ben
Supporting Vendor
iTrader: (33)
 
Ben's Avatar
 
Join Date: Jul 2006
Location: atlanta-ish
Posts: 12,689
Total Cats: 99
Default

FYI, I have David Vizard booked to give a presentation at MegaMeet this year. Google him if you don't know who that is, but he literally wrote the book on engine building--actually he wrote A LOT of books on engine building.

MegaSquirt Mega Meet 2015
Ben is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Garrett Turbo, 1.8 Oil Pan, & Misc. Stuff nbdooey Miata parts for sale/trade 9 08-30-2017 10:50 PM
Project Gemini - Turbo Civic on the Cheap Full_Tilt_Boogie Build Threads 57 07-19-2017 05:11 PM
OTS Bilstein to motorsports ASN conversion stoves Suspension, Brakes, Drivetrain 5 04-21-2016 04:00 PM
WTB MP62 (Hotside) (NB2) Rick02R WTB 3 01-03-2016 08:18 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 10:56 PM.