I-NRD - Grand AM Mazda RX-8

SpeedSource Grand AM GT RX-8

SpeedSource Grand AM GT Mazda RX-8

The Rolex Grand Am Mazda RX-8 Race Car I-NRD Experiment

Again, several hundred additional thermal-acoustical prototype concepts were evaluated for the I-NRD in other applications including race cars during this period.

In 2007, we were fortunate to have been given the opportunity by the management of Mazdaspeed (now Mazda Motorsports) of the Mazda North American Operations (MNAO) Corporation (Steve Sanders, John Doonan and Robert Davis) and Sylvain Tremblay, principal of SpeedSource, to develop an I-NRD for the Mazda SpeedSource RX-8 race cars using a 20B, 3-rotor engine competing in the Grand Am series which is now the IMSA series.

All of the Grand Am race cars had to meet a noise limit requirement of 105 db-A.  This noise limit was measured with the sound meter in a 45 degree diagonal from the exit of the car exhaust tail pipe, at distance of one (1) meter (~3.3 ft) while the car was placed in a specific space and the engine was running at 5,000 RPM with no load.  This noise requirement was similar to the one used at the time by the Fédération Internationale de l'Automobile (FIA), for its endurance racing series.

SpeedSource had been using a muffler that they built in-house. This unit caused a lot of issues and had become a major distraction in their efforts to develop the race car and improve their program. These issues included not meeting the Grand Am noise level limit at most tracks plus spending a substantial amount of time constantly repairing and re-packing this unit, sometimes during the race weekend, and most definitely after every race weekend. Additionally, their unit made the car very hot inside the cockpit.

The dimensions of the I-NRD were to be the same as the unit built by SpeedSource.  These dimensions were dictated by the space allocated for this unit by the Mazda SpeedSource RX-8 Race Car.

The first version of the I-NRD was tested by SpeedSource during a Grand Am scheduled test session at the Daytona International Speedway in October 2007.  This I-NRD achieved such an advantage in overall performance that from that point forward, all of the cars under the SpeedSouce program never used another product once they had made the switch to the I-NRD.

These Grand Am clients included the SpeedSource Team, the Patrick Dempsey Racing Team, the Nonnamaker Racing Team, and Yellow Dragon Motorsports Race Team.  A total of 11 race cars used the I-NRD.

Only one car (Car No. 30) decided not to use the I-NRD and continued with the original SpeedSource developed muffler. This car suffered a major fire during the Homestead-Miami Speedway Florida, USA race event in 2010 which was caused by the failure of this muffler. The fire destroyed most of the right side of the car.


I-NRD Before the 24 Hours of Daytona

 An I-NRD before the 24 hours of Daytona


I-NRD after the 24 Hours of Daytona
An I-NRD after the 24 hours of Daytona weekend
with several dozen hours of continuous use


The I-NRD achieved the following accomplishments during this period:

  1. In every instance, all of the Mazda RX-8s using the I-NRD easily met the Grand Am established noise limit. Additionally, the I-NRD was on average 3-5 db-A quieter than the previously used alternative muffler which made it a lot more comfortable for the driver inside the race car.
  1. The I-NRD was 25% lower in weight than the SpeedSource muffler unit it replaced. This weight advantage could be placed anywhere in the sophisticated race car, thus improving the handling performance of this vehicle.
  1. The outer skin temperature of the I-NRD was ~250-300F (121-149C) versus 1,300-1600+F (704-871C) for the unit it replaced. This feature of the I-NRD provided the following advantages:

3A. The mechanics could start to work immediately under the car once it came into the pits or the garage for maintenance or set-up changes.  Rotary engine race cars employing other sound attenuation solutions generally require a cooling off period of up to 1 hour to allow for the temperature of the outer skin of these mufflers to drop to a safe limit.

3B.  None of the delicate components surrounding the I-NRD, including the electronic hardware, were ever affected by exposure to extreme temperature.

3C. The driver cockpit remained at a reasonable temperature of between 105 and 110F (41 and 43C) throughout a race as opposed to a temperature of 145F to 150F (63 and 66C), which was typical when using the alternative system.  This was extremely important for the driver since he was able to remain thermally comfortable for a stint that could last 3.0 hours or longer.

  1. The reliability of the I-NRD used in the Mazda RX-8 Grand Am cars was remarkable. There was never a failure of an I-NRD as a result of a design flaw or a craftsmanship issue even after thousands of hours of use accumulated between all of the race cars in the Grand Am Series from 2007-2012.
  1. The durability of the I-NRD used in the RX-8 Grand Am cars was also extraordinary. All of the I-NRD were designed to last an entire season of over 100-130 hours of very demanding professional racing type use, without refurbishing.  Furthermore, the last I-NRD done for SpeedSource, car No. 70 ran for almost 2 full seasons without refurbishing and, per our estimates, could have easily completed an additional 3 extra seasons or over 500+ hours of use without any maintenance.
  1. An unexpected benefit of the I-NRD was that it consistently provided ~2% improvement in rear wheel engine power over a straight pipe muffler with a similar internal diameter.

Major Achievements of the Grand Am Series Mazda SpeedSource RX-8 race cars I-NRD

Some of the major accomplishments of this I-NRD included:

  1. The first use of the I-NRD in competition was with the Mazda SpeedSource RX-8 car No. 70 during the 24 hours of Daytona race event in January 2008. According to Sylvain Tremblay and David Haskell of SpeedSource, the I-NRD provided the advantage which allowed them to achieve the pole over other high profile factory supported race cars like Porsche, as well as win their first 24 hours of Daytona race.
  1. Winning a second 24 hours of Daytona race in 2010, again with the Mazda SpeedSource car No. 70.
  1. Winning the Grand Am Series Championship in 2010 with the Mazda SpeedSource car No. 69. And;
  1. Several Grand Am series race wins and podium finishes.

It should also be mentioned that these accomplishments were also achieved with the use I-Rotary Flywheel (Mazda P/N 0000-02-9207) and the ceramic Iannetti Apex Seal (Mazda P/N 0000-01-9113).


We want to thank the people in the following organizations for allowing us the opportunity to assist them with this project:

John Doonan, Robert Davis and Steve Sanders of Mazda North American Operation,

Sylvain Tremblay and David Haskell and the rest of the SpeedSource Staff

The Nonnamaker family and Mr. Saleen of Nonnamaker Racing and their staff,

Patrick Dempsey and Joe Foster of Patrick Dempsey Racing and their Staff and

Jack Smith of Yellow Dragon Motorsports

We want to thank HLS Precision Welding of Durham, North Carolina for their assistance with this project


Continue the I-NRD Story Here:

I-NRD Home

I-Noise Reduction Device History Introduction

Team Highball IMSA RX-7 GTU 1985

WSC IMSA Prototype Race Car 1994

The LMP-2 Mazda Courage 2005