E-fighting isn't BNZ. It's different, in that you are working to force your opponents to deplete his energy state relative to your own, such that in the end, you have energy to position for the killing shot, and he has none left to evade.
Actually BNZ is an E-fight, just as Ghastly mentions the point is to get your opponent to lose NRG relative to your own. That's basically the definition of E-fighting but he's also right, there are different forms of the NRG fight just as their are different forms of racing. The BNZ sort of equates to a drag race (a series of short, high-speed dashes) while getting into a turn fight with the same objective (deplete his NRG while maintaining or building your NRG advantage) can be more like a stock car race.
The NRG fight is generally harder to master than the angles fight for two main reasons. First, people have the tendency to see just about any potential shot opportunity (i.e., snapshots or HO's) as worth taking regardless of the Pk. They'll crank on a bunch of G, chop throttle, or pay no attention to what their position will be after the attempt. These actions cost the alleged NRG fighter both E and position advantages while turning the desired NRG fight into an angles fight prematurely. The NRG fighter needs to be disciplined and patient, he can't just put the lift vector on the target and pull. Second is failing to keep the pressure on the adversary allowing him to separate and regain his E. This is the problem with typical BnZ tactics.
You notice that previously I mentioned only the loss of only E and position, not angles? The reason is that in an E fight you want your adversary to generate angles because that's an indication he's burning E. If you're flying your E fight effectively who cares if he's got 90 degrees on you if he can't get his nose on you for a shot? Effectively, BTW, means staying at or near your corner velocity and, generally speaking, keeping your nose higher than he does so you gradually work in some altitude (stored E) advantage, using the vertical and, most importantly keeping the pressure on.
A good tip is to use the angles he generates against you to help you judge how much E he's burned. Say you're in an engagement and the adversary does an early turn on you and has about 20 degrees on you at the first pass. The next pass he has 50 and the next he has 90. Well, those angles had to come from somewhere (assuming you didn't goober things up and give them to him or give him too much time to recover). That somewhere is E so you now know he's got less E than he started with and that tells you some things. For instance, if he's slow you've taken away his vertical fight so if you transition to a vertical fight he can't compete very well. Using the vertical you gain position advantage and, at the right time, convert that to angles for the kill.
As for keeping pressure on your adversary, you do this by NOT extending too far. Many think they're NRG fighting when they extend as far as 3k, 4k or even 5 or 6K. This is very poor flying as the adversary has plenty of time to climb and rebuild his NRG state and he only has to deal with what amounts to a series of individual BNZ attacks. Instead, you want to have enough separation to deny the adversary an early turn on your reversal, generally that's about 1k to 1.5k. Also use a nose-high reversal to bring your nose around quickly and get it down to accelerate back to your target speed. If your adversary is chasing you that's good, go ahead out to 1-1.5 but if he turns away or dives then immediately reverse, that keeps you close and the pressure on.
A simple NRG fight can look something like a Lazy 8 where the NRG fighter's only high-G turns are the reversals at the ends of the 8 while the adversary is turning high-G circles at the center trying to get snapshots or defend. After your reversal you threaten your adversary with nose position but you don't want to blow your E so limit your turns to low-G and perhaps 20 or 30 degrees of heading change. You have to threaten the adversary here, you can't just do high-speed fly-bys. He has to either react to you with a high-G defense or attempt to gain a snapshot. In both cases he burns E. Do this a few times, look at the angles and judge your adversary's NRG state. When it looks like he's beat down the NRG fighter turns in nose low with WEP, aims for a point below his adversary but rather than continuing in the Lazy 8 the fighter instead goes up vertical through the adversary to gain a postion above. Properly done the adversary doesn't have the E to follow and the NRG fighter simply rolls to place his lift vector behind the adversary and converts the position advantage to angles for the kill. This is just one example but a fairly easy one for an aspiring NRG fighter to master. (It also used to be a favorite of mine in an F14 vs an A4...sort of the equivalent of a P38 vs Zeke)
That said, the significance of NRG is key in every engagement so we should always be aware of our NRG state vs his even if we're in a pure angles fight. There is no definitive line differentiating NRG and angles fights, most fights are a combination of both. The NRG fight becomes an angles fight when you achieve a positional advantage (using NRG techniques) where your stored NRG can then be converted to angles for a kill shot.
