thebrander

What is it about the Grand Am GT rules that favors the RX8's so much?

bosco022

They only weigh about 2300 #, get a six speed gear box, the rotary
makes a lot of power.

The light weight makes them especially strong on long runs and late in
the race.

For comparison the Camaro with transaxle has to weigh about 2900#
and the body isn't particularly slick.

The Corvette's have potential as they are nearly 200# lighter than
the Camaro.

The Porsche's mostly stayed home.

Grand Am may need to make another adjustment. That said, they do a pretty good job of balancing
the tube vs tub chassis to go with the various powerplants.

I think about every marque had at least one car that ran in the 1:28's at Barber today.

FOXMO

And what's up with the #19 Vette taking out the #07 Vette...AGAIN?

sspeed30043

Yea I noticed that too, at least LG was the top finisher out of the vettes, supposidly there are a couple more vette teams coming soon.

Doc V.

The RX8s are fully tube-framed racers and run with a lighter minimum weight.

FOXMO

I was at the 24 hour race in Daytona and spoke with a Sahlen mechanic. They were in Vettes last year, RX8s this year. He said they were easier to work on and seemingly bulletproof.

TLGunman

It's a superior design

vette6aut0x

In what way?

Falcon

I would bet Mazda's financial support to the teams has a lot to do with it.

vette6aut0x

From what I was told a prep 1 Corvette is at 2550 and a prep 2 Corvette ( tube frame) is 200 lbs more weight.

thebrander

Pretty cool summary of each car's spec limits: http://admin.grand-am.com/assets/GTrulesforweb3.pdf

2-5 Chevrolet Camaro
2-5.1 Stock LS6.
Stock LS2 engine # PAX0662 with spec cam and installation
Contact: Jeff Kettman at jeff.kettman@gm.com
2-5.2 Minimum weight 2750 or 2860 lb with DP transaxle
2-5.3 Five-speed transmission
2-5.4 Allowed #2301-E2-0900R&L front spindle
2-5.5 Allowed #26E1-0201W upper control arm assembly
2-5.6 Tire sizes are 305/660-18 front and 305/675-18 rear.

2-6 Chevrolet Corvette C6 ( Prep1 and Prep 2 )
2-6.1 Stock LS6 engine. Prep 2 may use OEM engine location.
Stock LS2 engine # PAX0662 with spec cam and installation
Contact: Jeff Kettman at jeff.kettman@gm.com
2-6.2 Prep 1 six-speed transmission, prep 2 five-speed transmission. Prep 1 cars permitted to use CG46 EMCO replacement transmission.
2-6.3 Must use original brakes or as allowed in brake section.
2-6.4 Minimum weight Prep 1 is 2550 lbs, Prep 2 is 2575 with solid axle, 2600 with IRS or 2756 with DP transaxle.
2-6.5 C6 bodywork allowed with 105.7 inch wheel base.
2-6.6 Complete rear wing height w/ end plates cannot exceed roof height.
2-6.7 Allowed to use non-OE brake pedals and cylinders.
2-6.8 Prep 1 Corvettes may use OEM ABS system.
2-6.9 Prep 1 Corvettes may use 1” drop spindle.
2-6.10 Tire sizes are 305/660-18 front and 305/675-18 rear.
2-6.11 May use side of rear back window for NACA duct mounts.

2-15 Mazda RX8 (Prep 2)
2-15.1 20B Cosmo three rotor (Mazda Spec parts). 2.0 liter, 9.7 compression ratio, 3-52mm throttle bodies, maximum of 6 injectors, maximum fuel pressure 4.2 bar, intake manifold is free. Maximum RPM 8600. Call GRAND-AM for parts list at 386-681-6681.
2-15.2 Minimum weight 2220 lbs or 2310 lbs with DP transaxle.
2-15.3 Six-speed transmission.
2-15.4 Maximum body width is 73.5 inches.
2-15.5 Engine set-back 5.125 inches from spindle centerline to 1st spark plug.
2-15.6 Complete rear wing height w/ end plates cannot exceed roof height. 2-15.7 Fuel capacity 24 gallons May use oil in fuel. May machine the blue fuel rig restrictor
to an inside dimension of 1.200 inch with square edges.
2-15.8 Allowed larger/higher exhaust position.
2-15.9 Tire sizes are 285/645-18 front and305/660R18 rear.
2-15.10 2009 Mazda RX-8 "R3" bodywork permitted with 3" maximum front splitter dimension.

Sidney004

The 20B Cosmo three rotor engine is a very well developed,light racing engine that makes big power.

thebrander

Wow, so the RX8 power is on par with the Vettes and Camaros, yet they are allowed to be up to several hundred pounds lighter? Is this based on "chassis safety" I wonder?

F4Gary

Actually, it was the other way around. 07 hit the 19.

AU N EGL

What Falcon says.

Plus the Mazdas are built by Riley Engineering IIRC

http://www.rileytech.com/PDF/GT.pdf

Grand American GT Chassis Mazda / BMW

Price
$103,000 Rolling chassis, from the 20” line down (Contact Riley Technologies for kit breakdown)
$305,000 Complete Car, Less Engine, Fuel Management and Data System…
Price Subject to Change, contact Bill Riley for latest pricing.

Everett Ogilvie

A Mazda rebalance is due, and IMO will happen very soon - that is WAY too much Mazda domination.

redvetracr

who is the series sponsor? Mazda maybe?

TLGunman

Just kidding, since I worked on the Mazda design, while at Riley. They built and designed the chassis and suspension, and SpeedSource finishes the cars.

Sidney004

The factory naturally aspirated 20B racing engines produced 450 Hp in 1997, so I assume there has been a little development.

Coc5

I figured it would have to be the 3 rotor. I driven enough Rexes to know they won't pull a Vette on the straits. When you see that, something is up.