rx7will

iTrader: (6)

I have a lighten flywheel in my car, its the RB version. And i have poly mounts, the group buy ones. I get a little vibration but it goes away at about 2k. This is normal and i understand this. In install the same poly mounts on another fd that had the stock flywheel and that car has almost no vibrations.

I use to have nylon dif mounts from Rotary performance and they made a little noise and could feel more of the road. In a bad way. I later install the same diff mount on the above fd and his rear end does not make nearly as much noise as my Rx-7 did. You could barely tell that it had solid diff mounts.

We both have tein suspension. New toe links, trailing arms, and pillow *****.

The only major difference is that i have a lighten flywheel. We both have stock like clutches. The vibration is not huge but very noticeable between the two cars. Does anyone ever notice this about the lighten flywheel. I dont have any high rpm vibration but just when i take off from a stop and it goest away about 2k.

Since the lighter flywheel have less mass, does it actually mean it has less mass to absorb vibration? I guess this would make sense but I have never read anything about lighter flyweels having more vibrations. Everything on my car works, i dont have anything worn or broken, my wheels and tires are balanced and properly inflated. I just aligned my car.

Anyone have any input on this topic?

adam c

iTrader: (2)

A light flywheel will not cause vibrations unless it is out of balance, which is unlikely. If it were out of balance, the vibrations would get worse as RPMs increase. Poly engine mounts will always cause more engine vibrations to be transmitted to the chassis.

BigJim

since the 2 cars,. even with the same parts, are 2 completely different cars it could be anything. Normal wear and tear will eventually cause vibrations, drive an old beater around the block and you will understand. The onyl thing to do is to slowly narrow it down like you have been doing by replacing and fixing stuff until it stops.

Howard Coleman

iTrader: (6)

you really shouldn't have a vibration from your motor at a given rpm. i used to roadrace piston engine cars w solid motor mounts and i was forever using loctite and checking bolts that had vibrated loose.

when i raced rotaries w solid mounts i never had a bolt loosen in 75 races. no vibration as the motor just goes round and round.

OTOH, should your flywheel be out of balance you would have such a problem. it is unlikely but possible.

another possibility is your driveshaft. generally they are indexed. i always put mine back at the same index point.

this is something that could be important to fix. if it is the flywheel, it will wreck your E shaft bearings and rotors... i suggest you find someone to figure it out.

good luck,

howard coleman

rx7will

iTrader: (6)

My car actually has lower miles than the other fd. I had the same lighten flywheel in another car and it did not make any vibrations with the stock mounts. The vibration is normal from what i read with solid mounts. The vibration is from a dead stop. When i take off and it goes away at around 2k.

So i dont have vibrations at a certain rpm. I guess it goes away as the load decreases. Before i put in the solid mounts i did not have any vibrations at all. But after the mounts i get it. Only if i could drive anyther fd with a lighten flyweel and solid mounts.

I recently put in solid metal mounts on a TII with the stock flywheel and it has less vibrations than my car. I guess the only way to rule out the lighten flywheel is to actually take it out and replace it with a stock one.

dontlift

Are you sure it's not just a low RPM misfire?

bryant

sound like howards maybe on to something.

i also have the same flywheel and no noticable vibrations, **** my car drives better than my wifes car and its 10 years newer than mine.

rx7will

iTrader: (6)

Bryant, are you running the stock mounts, i'm running the poly mounts.

And i'm positive its not a misfire.

Speed of light

iTrader: (8)

Sounds like a small out of balance condition exists. Don't forget that the clutch is part of this part of this balance equation.

Vibrations from balance problems can be complex and are often harmonically related to RPM. It only takes a small amount--we're talking inch-ounces here--a few percent of an out of balance to produce a noticable vibration at some (usually lower) speed. Note that it doesn't necessarily get worse, and will often become indicernible as the rpm's increase.

bryant

stock mounts