If your engine doesn't require premium, you really don't gain any performance by using it. The higher octane fuel equates to the mixture having a higher resistance to ignition. It can handle the high compression and/ or advanced timing of performance engines without detonation...

Having said that, I have some friends who swear by 108 octane race fuel, running it in air cooled v-dubs, claiming they can tell a difference. I dunno, I'm guilty of using it from time to time in my dub too. ($7-$8/ gal) It sure smells good!! If nothing else, the premium gas usually has better additives in it which equals a cleaner engine.

Mick, I bought my Miata new in 1991 and have always loved it.  Even though it has plenty of zip I felt it was a bit underpowered for a real sports car.  When I looked into adding more power I read that a turbo or supercharged Miata would go through a stock clutch in about a week so I forgot about it for a while.  But when I had to replace the clutch at about 88k I used an ACT Stage I which would handle the extra power.  So I bought the Jackson Racing Supercharger kit and had my local garage install it.  It makes about 6 lbs of boost for a hp increase of about 40%.  So it went from 113hp to somewhere around 158hp.  Yeah, I thought it was worth it!  The stock 0-60 time is advertised as 9.3.  I timed it at 7.02 on my first try.
Of course anyone on here can tell you that once you start modding it's a slippery slope.  Soon I added the boost upgrade which gets you about 12lbs of boost.  Then a high flow exhaust. Then a header. Then I blew my rear end and got a limited slip out of a '95.  Added the bigger '95 brakes while I was at it.  And on and on.  0-60 now is about 6 seconds.
The supercharger is bypassed until you step on the gas so there's no difference in drivability, just a lot more power when you want it.
That said, after a few years it failed it's emissions test and no one could figure out why.  I was saved by Mass laws changing to exempt cars before a certain year.  Right now it runs very strong but doesn't idle well and again no one can figure out why.  There's a guy out in Marlboro who specializes in modified Miatas who could probably fix it but that's about an hour from here.  Right now it's still in winter storage while I get my bikes going then I've gotta figure out what to do with it.  Lots of info at http://www.miatamania.com/
But if you want to go REALLY fast I think turbo is the way to go, look here http://www.flyinmiata.com/
And lots of good info at http://miata.net/

jef.savage wrote on 05/23/10 at 07:45:32:

thanks Jef ,really helpful