Lotus Elan and Lotus Elan Plus 2 Forums

I hope this helps,

Looking at some maths, and my dyno graph, where peak torque is approx 5000,and rounding cid per cylinder to 97/4, gives a 33.5mm ID requirement for the primary pipes,.
I have no idea what standard lotus tubular version is to compare.
If you go smaller then you increase torque below the 5k peak and off course larger will increase above the 5k peak.
This is simple and doesn't take into account cam timing etc which some equations do, also doesn't give a length. Theres plenty of info available to do this tho.

Certified Lotus wrote:I installed a complete TTR 2? system from headers to muffler (I won?t call it a silencer because it certainly isn?t). Now I have a ?built? engine with 147HP at the crank so the better free flowing exhaust is needed. It?s a bit loud when you push the pedal hard but it goes like stink so all part of the sensory experience.

Here is a short video:

https://youtu.be/dgrl1NBuaWc

that sounds ( and looks) great