Printable Version | Subscribe | Add to Favourites
New Topic New Poll New Reply
Author: Subject: Balancing rotating bits

posted on 18/5/19 at 08:51 AM Reply With Quote
Balancing rotating bits

Building a toyota 3sgte with forged pistons and rods an not sure how seriously I should take balancing. RPM limit will not be increased. It's a side project so I can take my sweet time about it.

I can think of 3 areas to affect balancing:

1. Balancing crank statically (on a grinding stone balancer) - won't tell me if the front and back are unevenly balanced.
2. Balancing crank dynamically - to counter the above point.
3. Getting pistons and rods to the same weights on digital scales.
4. Dynamic balance of the crank with weights simulating pistons and rods. Seen a few videos about this and it looks to be mostly on vee engines where the adjacent cylinders don't balance each other out like they do on an IL4. That said if the rods and pistons are significantly heavier than stock units, I guess the crank counterweights don't do their job on the individual cylinders.
5. Flywheel, clutch cover - can probably be done static or dynamically as the crank is being balanced.
6. I'm probably over thinking this!

I'm guessing when you pay 150-250 for a full balance you get 2, 3, 5. Done at home you get 1, 3, 5 (or you pay for 2 and do 3, 5 yourself). And guessing 4 is solely for big ticket race engines and would probably involve adding quite a bit of weight and I should stop worrying about it.

I'm tempted to just check static crank balance at home (and toyotas are said to be quite good from factory) and get dynamically done if it isn't right. Partly because local machinist can do my engine work but I'd have to go further afield for balance. Would be a waste to not do it while its apart if its a big deal though.

View User's Profile View All Posts By User U2U Member

posted on 18/5/19 at 12:35 PM Reply With Quote
Hi Luke. I have just built a 3SGE. During the planning phase I discussed the matter of balancing, dynamic or otherwise, with a knowledgeable chum. He said" It's a Toyota. Don't waste your money".
He was right.
The crank came back with one tiny, tiny correction. Similarly, the flywheel had one tiny mark not much more than a dot punch would make. Waste of money.
It might be the case that using forged pistons could make a difference but apparently some people add a notional figure for the weight of oil clinging to the crank whereas others don't so what accuracy are we aiming for?

[Edited on 18/5/19 by SPYDER]

View User's Profile Visit User's Homepage View All Posts By User U2U Member

New Topic New Poll New Reply

go to top

Website design and SEO by Studio Montage

All content 2001-16 LocostBuilders. Reproduction prohibited
Opinions expressed in public posts are those of the author and do not necessarily represent
the views of other users or any member of the LocostBuilders team.
Running XMB 1.8 Partagium [ 2002 XMB Group] on Apache under CentOS Linux
Founded, built and operated by ChrisW.