Miata Mailing List: May 1998, Message #83

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Bryan T. Jones wrote:
> 
> A few days ago this thread started when someone ask about the weight and
> performance of a lightened flywheel.  Some great info was given on the
> different weights but I never read how those of you who have one feel
> about the performance advantages the new flywheel provides.
> 
> Would those of you (forced induction and normally aspirated) care to
> share how the lightened flywheel effected performance and drivability..
> 
> --
> Bryan T. Jones
> mailto:btjones@feist.com
> Miata-If you can't go topless, why go?
Tango does not have a lightened flywheel...yet.   Not allowed in stock 
autox category... so what follows is a simplified historical opinion.

The lightened flywheel allows the engine to rev much more freely.  The 
lighter the flywheel the more freely it revs.  In fact, it revved so 
freely it was clearly unwise to use the light flywheel with out a rev 
limiting rotor in the distributer (not a problem for the Miata).  The 
importance of the free revving seems to be that more of the engines 
power actually gets to the wheels.  IIRC correctly dyno runs on my 
race prepped Bug motors were substantially higher with a 9 lb flywheel 
over the stock 30 lb unit.  Old age and a good dose of CRAFT disease 
prevent me from giving actual numbers here.  The engine didn't create 
more horsepower, but it did use less turning itself over thus making 
more available at the crank and off to the wheels. 

Caveat... while the engine revs up quicker it also spins down quicker.  
Not sure what this means for the Miata... didn't bother the Bug or 
it's Webers but made it a little more necessary to do the double 
declutching trick when downshifting.

The difference was measureable on a dyno, you could feel it, and even 
hear it  (vroom, vroom... becomes whappa! whappa!).  

FWIW, I also had the flywheel lightened in a stock 79 Honda Civic 
(what was I thinking... what the heck, I had to do the clutch and the 
flywheel was out).  No big performance gain but an overall brighter 
feel to driving it.
-- 
Bob Schnider & Tango - 90A Red
MCA #68117, Sea to Sky Chapter
Team There and Back Again
Team CRI
Team Voodoo

"Never start a vast project with a half-vast idea"