My neighbor and I both have RV-7A's.  He has a carborated Lycoming 360 with "E" Mags and claims about 185+ hp with a fixed pitch metal prop.   He told me the "E" mags really improved fuel efficiency and added noticeable horsepower.  I have a 4 port Renesis with Tracy's RD-1C and Catto 76/88 composite prop.  We have similar performance on take-off and climb - we will be doing some high altitude speed runs in the future. 

Saturday we flew in  formation from Austin (40XS) to south west of Dallas (0TX1) and returned.  Total flight mileage was about 140 miles each way.  We filled both tanks on each aircraft to the filler neck before and after the flight.  He uses 100 LL avgas and I use regular car gas.  At 0TX1 I had to execute a go-around because 3 aircraft were taxing on the runway and did not clear it for landing aircraft!.  My neighbor was able to land without going around.  I estimate I used about 0.7 gal for the go-around.  I leaned the Renesis some but did not try to run as lean as possible. 

When we got home we checked the fuel meters on the mogas and 100 LL fuel storage systems using a 5 gallon fuel container and made sure both fuel delivery meters measured the same.

After the flight I required 18.7 gal. -0 .7 for the go-around = 18.0 gal. of  mogas.    My neighbor's aircraft took 19.0 gallons of 100 LL.
My fuel costs $2.00/gal or $36.00  His fuel costs $3.50/gal or $65.00.

The Mazda Technical Papers on the Renesis indicate a significant improvement in fuel efficiency over earlier RX-7 versions..  I believe this flight proves it - the Renesis beat a Lycoming with fuel efficient "E" mags.

Dennis Haverlah