Several Exige 380 owners have asked me to help them get on track in the UK. With the 3" (76mm) factory exhaust proving to be extremely noisy, it's a challenge! I've had three cars running different exhaust designs at various circuits and I'll have the "Track" system in production end of next week.
Many owners are new to Lotus and I'm using this page to give some information on their present exhaust design. The differences between the early and later systems are: Early downpipes - 51mm diameter. Later downpipes - 60mm. Check out that 2-1 merge collector on the Later design - almost a T-junction! Flattened for clearance too - not great.
Early link pipe (between downpipes and silencer) - 63.5mm. Later link pipe - 76mm.
Early silencer: check out the comparison images. The valve merge pipe on the early cars appears to be more efficient flow-wise. Both pipes are 63.5mm, although the valve "closed" pipework reduces to 54mm internally.
Later silencer: again, looking at the comparison images. The valve merge pipe has a smaller(!) "closed" pipework - 48mm. With a connection to the larger/LOUDER 76mm merge pipe, I guess they had to keep it small/quieter than the early design.
Do you remember the old potato up the exhaust pipe to stop an engine? Check out the clearance dent in the 76mm pipe under the silencer/above the rear anti-roll bar! That's half a potato right there ;-)