I recently bought an 85 gsl with 13b, bolt on perf mods and a lightened flywheel.
The car is jerky at lower on/off throttle applications. Is this inherent with the reduced flywheel mass? It revs like a sportbike...

 

Read here:
Mazdatrix - Flywheel and Clutch Explanations

Also, note that the industry dumbs-down terms for non-engineers. "Light" in this case means low inertia, which may or may not mean less mass. If this is confusing, then ignore what I just wrote.

 

Yes, jerkiness is a side effect of a lightweight flywheel. It's quite a controversial modification choice in the rotary world.

 

You'll just have to get use to it, its more touchy just like a high performance clutch.

Rotary >Pistons

 

Thanks to all for the info. This is what I susspected.

 

these small diplacement engines suffer from under achieving torque. the lightweight flywheel will greatly lessen your torque output, adding the jerkyness and harder stand still take offs. just requires getting used to. like every aftermarket upgrade

 

Stock flywheel for na is 24 lbs and stock Turbo is 27 , needless to say a lightweight one is roughly half the weight of stock.

I'm not sure of the weight of the entire rotating assembly (rotors/e-shaft, etc), but I'd venture to say taking 12 lbs off it is a huge reduction and will help the car rev more freely as well as accelerating faster into gears.

Reduced torque is meh, if you can get use to it you'll be fine, these cars were never known for torque but are known for their top end power, which a lightweight flywheel will help you get faster as well as putting more HP to the wheels from reduced weight of drivetrain.

Rotary >Pistons

 

My experience with light flywheels is that they only exacerbate existing issues. If something in the car or the driver's technique is jerky, it will come through more with less rotational mass to mask the issue. Have you looked at the motor's state of tune? It may be running poorly at light throttle. You also might look at the drivetrain lash and bushings.

The Fidanza aluminum flywheels are about 9lbs. The ACT Prolight flywheel I'm using now is around 9.5lbs. The automatic counterweight is another 2.5. A lightened rotating assembly may not add HP, but it can strongly affect acceleration, especially at lower speeds/lower gears.

I know people are down on light flywheels for street use, but I find they're pretty easy to live with. They also make the car feel a lot more lively. When I drive a car with a stock flywheel I have to remind myself that it's not broken. I know engineers need to cater to the lowest common denominator, but 24-27lbs for a flywheel on a small-displacement sports car is ridiculous.

 

I have owned several small displacement performance cars.
I had a 77 rabbit with a biult 1870cc screamer. When building it I had considered having the flywheel lightened, but was told not to because of a loss of drivability.
Now several cars later this is my first experience with a lightened flywheel.
I like it, much more lively, just takes some attention in order to drive smoothly.
When I bought the car it idled@ 1500 rpm, I set the idle at 900rpm and adjusted the carb as best I could(48 dhla) runs a little lumpy at idle but great otherwise...

 

Which flywheel did it come with Robbins?

 

Racing beat