The factory race system has no muffler. It is a turbo car that does a decent job at killing dBs. Since it has catalytic converters, it is not as loud as you might think. It sounds great at idle and when you are really going for it. It is loud and won't pass noise limits at Laguna Seca - as Eric@SuspensionPerformance found out. But the real issue for me is the the drone that the car creates when cruising on the freeway. When you are in 6th gear, anywhere from 2250-3500 rpm, the car creates a resonance that hums so loudly in the cabin that you need ear plugs. Forget listening to the stereo. I dreaded having to take the car anywhere that required freeway travel. Luckily we have a great exhaust partner who knew how to fix our issue.
We lent them our 4C for about a week so they could measure the frequencies inside our car. They use sophisticated equipment to map out the frequencies and identify the offending range. They then employed Helmholtz principles to kill the range that was causing the drone. This Helmholtz Chamber is a canister that sits outside of the main flow of exhaust and does not interfere with the straight through design. This allows this system to keep power as stock and not create any additional back pressure or power reduction. Sophisticated exhaust suppliers are now employing these Helmholtz principles to great effect. Learn more about this: HERE
I brought another fellow 4C LE owner, Martin, along with me to pick up my 4C. See his car above compared to our 4C - note the exhaust tip difference. We took the car with the prototype system installed and were shocked at the difference! The car has no drone when cruising. The only thing you hear is wind and tire noise. The difference is amazing. Watch the video we made of the car:
We are now putting the system into production as we know there are many other 4C LE owners who share our opinion. We believe that once standard 4Cs (with actual mufflers) start getting delivered, our system will become a great choice over the factory race exhaust option. Now we have to decide on the size of the exhaust tips. Unfortunately we have to send the prototype system back so they can measure it for production. The stock system is getting reinstalled until our first production part arrives. Where are my ear plugs...
Finding unsprung weight savings has always been one of our goals with all of our cars. The 4C is heavier overall than the Elise/Exige so we would like to find any savings that we can. We have had great success with our ULTRAdiscs on the Lotus. Our partner, Girodisc, has been a key ally in our attempts to find weights savings while delivering excellent performance. The factory rotors are a one piece rotor but are made in a innovative manner that frankly is fairly light. We had Martin make us some ULTRAdiscs to fit the 4C and found a 1.25lb savings on the rear and .5lb savings at the front. This is per rotor. We installed them onto our 4C and ran them on track. We still had the stock pads and they performed well. Unfortunately we discovered that the front stock pads were already at about 30% life after 3 track days. One of our brake pad suppliers worked to get us pads but they did not arrive in time for this test.
The pad shape on the 4C are not made by anyone other than the OE supplier so we had to get them specially made. The pads arrived a day late so we did not track test them. We received a compound that is not a strict race pad so it should work for aggressive street use. Stay tuned as we will report back soon. Looks like we have to go back to the track for more testing...what a rough life! ;^)