NoPistons -Mazda Rx7 & Rx8 Rotary Forum - Black Thunder Down Under

There's nothing like watching a Rotary launch at 9,000rpm off the line…. https://www.nopistons.com/forums/pub...1047683894.gif

Chris Anderson's Series 4 RX7 is taking challengers in the U.S rounds of the Pro Import series. Late last year Chris ran 9.20 at 150mph at the Moroso IDRC Nationals. Making the time even more impressive is the fact that the car is still un-tubbed (26x10 inch Mickey Thompson ET slicks) and still weighs 2600lbs.

Under the bonnet, the 13B Rotary engine has received some serious modifications. Unlike in Australia where most people opt for a large turbo type extend port, Chris' RX7 utilizes a secondary 'Bridge Port'. For those that aren't quite familiar with Rotary porting, this is where a second hole or port is cut into the plate above the standard one which is also enlarged. The common myth is that by running such a large port, there will be too much overlap and your boost will go straight out the exhaust. Well Chris says that when done correctly, the bridge port works well. Actually just about all the top runners there are either using a BP or PP! The secret is in the amount of overlap to make it work effectively. The rest of the engine is fairly standard. Now running a 13BRE intake manifold from the Cosmo, 9.0:1 rotors' and Mazda 3mm Apex seals. For extra strength, the housings have had extra dowelling performed.

Rotary's love boost and Chris has amended this by installing a large Garrett T-72 turbocharger with a P-trim wheel and a HKS waste-gate. Fuel delivery is taken care of by a Haltech ECU, .Weldon 2035 fuel pump, 2 x 680cc primary injectors and 2 x 1600cc secondary injectors, while an MSD controls the ignition. On 32psi the car has made 608rwhp. A direct port Nitros system has also been trialed and on 35psi, the car turned the rollers to a tune of 689rwhp. The 9.20 pass was also only on 32psi. You don't produce numbers like that on unleaded fuel, with VP-C16 fuel being the chosen juice.

Obviously with so much power and a sticky track, drive-line breakage's can occur on a frequent basis. To overcome this the RX7 is fitted with a Richmond 5-speed Transmission which is a pro-shifted version. It basically means he still has to use the clutch to shift. This is taken care of by a Tilton twin plate unit and further down the line is an Mopar differential with mega strong 35 spline Moser axels. Chirs is still using standard front brakes to pull up from such insane speeds. Chris says "The parachute is not mounted on the car as yet because I'm building a wing for the rear. Trust me I've been warned numerous times about the chute from the track officials".

Having to compete against 1500lb Honda's can become quite frustrating so Chris is currently in the process of removing as much weight as possible by adding some fiberglass body parts, doors, rear hatch etc. The aim is for 2000lb's, and to be competitive in this weight class really does call for some chassis modifications with either mini tubs or just go all the way and run a half chassis! Future engine modifications are mainly centered around converting to an Alcohol/Methanol fuel.

In just the last month Ari Yallon of Rotary Performance in his un-tubbed S6 RX7 has run 9.116 at 149.52mph, while in Puerto Rico, Toledo Racing's un-tubbed Series 5 RX7 ran 8.90 at 152mph, so as you can see, the competition is certainly fierce! Chris is keen however to give just one more try at the World Import Challenge in March to break into the 8 second time zone with a uni-body un-tubbed car before making the changes listed above.

By Muzza & Mates