I will do my best to clarify...
Stage 1 - two tips that protrude strait out the back. Very big - almost like stock in appearance and sound to standard NA exhaust.
part # LOTAC05334
This is only for NA cars and has a mild sound enhancement
Here is where things get complicated...
Stage 2 - has 2 tips that sit level with the diffuser. Smallest and lightest exhaust Lotus offers at this time. Also the loudest.
part # LOTAC05335
This exhaust was originally developed for the normally aspirated engine but was also used on supercharged Exige Cup cars up till 2009 - even the Cup 255 offered this very exhaust as a no cost option (without cat though). Original stage 2 exhausts suffered from weld issues that caused cracks at certain points but Lotus changed manufacturers and current versions are now built by Janspeed. The Janspeed versions do not suffer from the same weld problems and are generally trouble free.
Stage 3 - has 1 tip that sit level with the diffuser. Also built by Janspeed and slightly larger muffler than stage 2 and slightly quieter.
part # LOTAC05450
Lotus designed this specifically for the supercharged cars - primarily to tone down the resonance and loud sound db's of the NA Stage 2. When this exhaust came out in early 2007 - the Exige S was already for sale in the US for a few months before - and this exhaust was called the Supercharged stage 2. The diameter of the pipe connecting to the cat is the same as the NA stage 2 (and stage 1 for that matter - it really has to be to be able to fit). What is different (other than the size of the muffler and sound baffling) is the diameter of the pipe exiting the muffler to the tip is the same (2.5 in) diameter as the inlet. Some argue this is important for a supercharged car to breathe. Some argue there is no difference at this point in the exhaust system - especially with the bend needed to get through the diffuser anyway.
Ever since 2005 there had been rumors of a stage 3 kit in the planning stages that also included some kind of intake and filter enhancement - even pictures were circulated at one point of this system - but it never was distributed by Lotus. So to add another layer to all this confusion - some people who were involved with Lotus then think of this when they hear stage 3. It really hasn't been until recently that this single tipped exhaust was called stage 3. The first reference to it as a stage 3 was in the Lotus Sport accessory catalog. It seems now that a new one just came out and they are continuing with calling it a stage 3 that it is sticking. So no matter what, at this point if you have a single tip, non standard, Lotus exhaust - you have the stage 3.
Albert, to answer your question about --
They made it to tone down the resonance and sound for a supercharged car rather than what the NA stage 2 produced. Lotus took the opportunity to ensure the larger diameter pipe exited the muffler as well.
And yes, fitting a stage 3 to a NA car will cause it to produce a slightly different sound but it shouldn't be radically different. The normally aspirated engine's 2nd cam (when standard) kicks in differently than a supercharged car (who's 2nd cam variably kicks in throughout the RPM's instead of all at once). The FI in the intake and breathability differences between a NA and supercharged car also affect the sound.
Bottom line -
- Fitting a NA stage 2 (with dual tips) to a supercharged car can be done (as I said it was fitted to the CUP cars up till 2008) but it is going to be LOUD and produce a great deal of in cabin resonance. So Lotusforsale, if you want the loudest Lotus exhaust you want the stage 2 # LOTAC05335
- Fitting a stage 1, 2, or 3 exhaust (or any exhaust for that matter) will not enhance HP. Even if it did help - the ECU would compensate for that enhancement and adjust out the improvement.
- Stage 3 has a single tip - if you have a single tip exhaust by Lotus that isn't the stock exhaust then you have a stage 3. When it was released this was also known as the stage 2 exhaust but now Lotus Sport seems to be continuing with calling it a stage 3.
- Having a custom ECU tune, LSD, intake, filter and snorkle modifications will change the loudness of the exhaust. You can't easily compare cars that have differences in these areas.
Sorry it is so long but I hope this helps clear up some confusion
