The team did it with a combination of concealed intake tubes, resonator components and special exhaust components, squirreled away on the car's existing architecture. The trick wasn't to simply make the engine louder. The group had to identify resonator points within the car, silence some parts of the sound, and then blend other sounds to find precisely what they considered to be the right tone for a sporty compact street vehicle.
Aftermarket shops can pull off this sort of after-the-fact enhancement because they don't have to answer to anybody. Pafumi's team had a world of people to whom to answer.
To say Honda Motor Co. had its hands full with the Civic's redesign and launch is putting it mildly. The change in engine sound was just one small part of the new Si. And the model is just a minor piece of the overall 2006 Civic program, which went into production in East Liberty, Ohio, in August.
East Liberty is one of 13 Civic plants around the world. Honda engineers from Ohio to Vietnam to Turkey have been carefully choreographing this year's launch.
The fact that they were able to pull off the change so close to the launch is a testament to what Honda calls manufacturing flexibility.
Pafumi's team includes one other engineer from the U.S. r&d group, Bruce Fouts; two participants inside Honda's local supplier of intake modules, Tigerpoly Manufacturing Inc. of Grove City, Ohio; and two designers in Japan who accommodated the project -- sometimes against their better judgment.
Pafumi, principal engineer for noise, vibration and harshness, says changing the Civic's sound was a two-front effort. The first challenge was to identify the correct sound. The second was to insert the components that would deliver it -- without interfering with existing parts.
On the first front, Pafumi's team used computer modeling to zero in on what he calls "five different whole and half orders of sound." Basically, the target was a blend of mechanical sounds as if coming from a quintet of musical instruments made out of steel and aluminum.
"We know our engines and the sounds we want to create," he says.
To capture it, the group ran a 70 mm intake pipe off of the front fender and connected it to a 3-liter resonator that would be planted on a spot inside the bumper. Various side branches were fit into unclaimed real estate inside the engine compartment cavity. The entire system was considered an engine part and fell under the direction of the engine-design team at Honda's engine plant in Tochigi, Japan.
But the design hit a snag. Engineers discovered that one of its side branches would have interfered with headlight bulb maintenance. If left alone, it would have required owners to use a tool to replace the light -- something that Civic project leaders had prohibited.
In August 2004 -- 12 months from the start of Civic production -- the team realized they would not meet their deadline. Tsutomu Tsukii, the Civic's lead engine designer in Tochigi, informed them that there was no more time.
"He said, 'I have a schedule to maintain,'" Pafumi, 34, recounts. "These guys in Japan are pretty intense about keeping the project on track."
Pafumi asked Tsukii and his colleague, Sugaki Komiyama, to come to Ohio and hear the sound system they were trying to perfect. They agreed and made the trip. At the company's Raymond, Ohio, r&d center, Pafumi put them into a prototype Si with the system installed, and the Japanese designers drove it.
When Tsukii got out of the car, Pafumi says, he nodded and said he understood.
"He was quite excited," Pafumi says. "He owns a Civic Type R in Japan with an aftermarket intake system."