counterweight issue
10-12-10, 05:20 PM
#1
counterweight issue
Looking at an aluminum flywheel for a 12a. RB was somewhat helpful but had no definitive answer.
I have a J-Spec 12a turbo. Looking to put aluminum flywheel on but need counterweight for that engine.
Any advice on counterweights for an unknown year 12a that was never sold in
USA?
I have a J-Spec 12a turbo. Looking to put aluminum flywheel on but need counterweight for that engine.
Any advice on counterweights for an unknown year 12a that was never sold in
USA?
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10-17-10, 12:19 PM
#8
Mix matching flywheels and counterweights can be dangerous and destructive. Counterweights are matched to the rotors. Some of the counterweights even have balance indicators in the same year run meaning there were 3 different rotating assemblies.
I work as a firefighter / emt at Road Atlanta. Crank shafts and flywheels fail. A chunk of a flywheel nearly took a man's leg off 3 years ago. Racing Beat says not to use their flywheels over 8500 rpm.
Wrong counterweights may result in vibration up to failures as mentioned above. There were at least 5 different 12a counterweights. Do your research before changing out flywheels.
I work as a firefighter / emt at Road Atlanta. Crank shafts and flywheels fail. A chunk of a flywheel nearly took a man's leg off 3 years ago. Racing Beat says not to use their flywheels over 8500 rpm.
Wrong counterweights may result in vibration up to failures as mentioned above. There were at least 5 different 12a counterweights. Do your research before changing out flywheels.
10-17-10, 01:27 PM
#10
Thanks for the info.
If I got the counterweight for the flywheel would it be alright, or would it still not work.
I know a guy who bought a lightened TII flywheel and put it in his 12AT with a TII tranny and he is making me ask these questions. it wasnt me
If I got the counterweight for the flywheel would it be alright, or would it still not work.
I know a guy who bought a lightened TII flywheel and put it in his 12AT with a TII tranny and he is making me ask these questions. it wasnt me
10-18-10, 01:56 AM
#13
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AFAIK the flywheel has no impact on the balance of the rotating assembly, unless the flywheel itself is out of balance for some reason, in which case it's not safe to install on any engine anyway. A lightweight flywheel will reduce the engine's rotational mass, allowing the engine to spin up and slow down quicker. It's pretty much the same as having lighter wheels.
10-18-10, 03:44 AM
#14
talking head
AFAIK the flywheel has no impact on the balance of the rotating assembly, unless the flywheel itself is out of balance for some reason, in which case it's not safe to install on any engine anyway. A lightweight flywheel will reduce the engine's rotational mass, allowing the engine to spin up and slow down quicker. It's pretty much the same as having lighter wheels.
AUTO vehicles have a separate eccentric mass,, to which mounts the flex plate
this mass is to match the rotor weights
billet light flywheels have no eccentric weight , and so are designed to bolt to the AUTO mass instead
each generation of motor has evolved in rotor weights,, and so must run the correct specific mass
since 12aT didn't actually come as an auto in any production form
you are lucky that mazda maintained the rotor mass for each model to be the same,, irrespective of compression ratios
so,, since 12at is a series 3 rx7 12a,,, it will use the mass from other s3 rx7 engines,, 1983-85
this is the correct way to do it
dodgy shops will look at the total rotor mass,, and realise that some of the 12a rotor weights aren't dissimilar for the 13bt ones
and its then that you see mismatched flywheels on the wrong engine
not a great practice,, as the balance is certainly beyond mazda spec
and that why they dont give you 13b masses for 12a engines,, and have subtle differences that matter,, lots
I was starting to think I was going to be looking for a new flywheel.
10-18-10, 01:02 PM
#16
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FACTORY MANUAL rotary flywheels have the eccentric balance inbuilt
AUTO vehicles have a separate eccentric mass,, to which mounts the flex plate
this mass is to match the rotor weights
billet light flywheels have no eccentric weight , and so are designed to bolt to the AUTO mass instead
each generation of motor has evolved in rotor weights,, and so must run the correct specific mass
since 12aT didn't actually come as an auto in any production form
you are lucky that mazda maintained the rotor mass for each model to be the same,, irrespective of compression ratios
so,, since 12at is a series 3 rx7 12a,,, it will use the mass from other s3 rx7 engines,, 1983-85
this is the correct way to do it
dodgy shops will look at the total rotor mass,, and realise that some of the 12a rotor weights aren't dissimilar for the 13bt ones
and its then that you see mismatched flywheels on the wrong engine
not a great practice,, as the balance is certainly beyond mazda spec
and that why they dont give you 13b masses for 12a engines,, and have subtle differences that matter,, lots
AUTO vehicles have a separate eccentric mass,, to which mounts the flex plate
this mass is to match the rotor weights
billet light flywheels have no eccentric weight , and so are designed to bolt to the AUTO mass instead
each generation of motor has evolved in rotor weights,, and so must run the correct specific mass
since 12aT didn't actually come as an auto in any production form
you are lucky that mazda maintained the rotor mass for each model to be the same,, irrespective of compression ratios
so,, since 12at is a series 3 rx7 12a,,, it will use the mass from other s3 rx7 engines,, 1983-85
this is the correct way to do it
dodgy shops will look at the total rotor mass,, and realise that some of the 12a rotor weights aren't dissimilar for the 13bt ones
and its then that you see mismatched flywheels on the wrong engine
not a great practice,, as the balance is certainly beyond mazda spec
and that why they dont give you 13b masses for 12a engines,, and have subtle differences that matter,, lots
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