This is the info that appears on the link:

http://cgi.ebay.com/ebaymotors/Mazda...QQcmdZViewItem

"...This Spark plugs are the same dimensions and specs as the $39 a piece NGK R6725- that Racing Beat recomends for turbo engines with higher than stock HP levels. The only difference is that this outperform the NGK R6725 series due to the fact that this are Iridium and can withstand more heat.

In fact , a few of our Salt Flats top speed challenge rotary customers have reported no pre-ignition even at 1950F+ exhaust gas temperatures levels, ussually seen in long periods of high boost/high rpm racing aplications.

During our many Dyno hours of testing , we have found that in some aplications there has been an up to 73 horsepower increase after 5500RPM over the factory spark plugs when tuned at safe rich A/F ratios that rotaries must be tuned to..."

Is possible to get a rise of 73hp by just changing the stock spark plugs with Denso Iridium? Who are using this spark plugs?

 

I am going to highly doubt 73 hp unless you have every other supporting mod EXCEPT plugs and wires. And even then...

Besides...it's ebay so you have to take almost everything with a 1000 grains of salt.

I think this was on a FD, but its a good run down of plugs.

http://silverbulletrx7.com/plugs/index.html

 

Sure...
Use the wrong heat range plugs, and you'd either get preigniton or fouling.
Either would plummet power...
This just means these guys are a bunch of morons when it comes to tuning.

Either that or they are tuning 700hp+ engines and gaining 10% from the spark plug change...


-Ted

 

bwaaaaaaahahahahaha, yeah