The asymmetrical firing order of a V2 causes not only an uneven rotation of the crankshaft, but also offers a huge period ,when the cylinders fire at close to the other., wherein substantial valve overlap occurs.This "overlap time window" makes this type of engine prone to harmful wave superpositions and "inter cylinder charge robbery". The stock KTM airbox now is a powerful candidate to amplify such superpositions.
For this reason the first thing to bring culture into the KTM V2, is to "re-tune" the acoustics of the stock airbox by modifications like this:
1. Remove the snorkel:
2. Remove the inspection covers located at lower part of the airbox. Grind the ridge at the inside away to achieve a plain surface here. Then apply M8-nuts to the screws to realise a 5mm - gap, when the covers are reinstalled:
I know it has been discussed here at another place that removing the snorkel reduces performance. When removing the snorkel alone, this happens actually. Removing the covers alone makes torque in the middle but costs peak power at the top. This sounds curious,but it demonstrates how delicate this subject of wave action, superposition and "intake ram" is essentially.
The suggested two modifications are able to re-tune the acoustics of the stock airbox But they work only together, side by side.
The following power graphs show you the effect in the case of a new SD-R, the model with heads and throttle bodies of the RC8:
Here nothing is done with the fueling, no Acra, just the stock map working. The Remus installed at the other end of the engine just makes 2-3 HP . An Acra , Leo or what ever offers no larger gains. The SD-R engine suffers no huge restricted by the stock KTM muffler. So you must not aspect to much by a simple swap of the can.
This means the larger portion of the improvement is caused by airbox mod described. This explain furthermore why the mod works preferably at lower engine speed up to mid range, because here the "interference suppression" by "acoustic-tuning" makes the impact. At high rpm the vibrations inside of the airbox are at such a high amplitude, that the velocity stacks, and hereby the engine, are ruling the harmonic system as a whole. This is the speed, where the engine starts roaring "OMMMM" into the world.