Comparison - Bandit 400 across the years (restricted/non-restricted, VC vs reg)

[T2098]

So my Japanese service manual for the Bandit 400 series finally arrived in the mail today, and I'm going to be scanning a bunch of stuff from it and uploading it online to help out the community - I've learned a ton from this forum so far, but even after reading every page back to 2006 or so, there didn't seem to be a lot of concrete information on the JDM and early VC models.

As a teaser, here's the official horsepower, torque, and BSFC specs for each model, straight from Suzuki for all 4 flavours of the engine they sold in Japan - fun to see exactly how the VC system varies the torque and BSFC curves.

Interesting things of note:

- The later (restricted, 53HP) versions have a much more linear torque curve and are largely devoid of the 'black hole' dip in torque between 4000 and 7000rpm that the earlier ones had.

- The huge dip in torque happens in slightly different spots for the earlier unrestricted ones - looks like ~4k-7krpm for the non-VVT version, and ~4k-6krpm for the VVT version.  Notice how the VVT 'fills in' the torque curve on the earlier models.

- The reduction in valve lift/profile for the VC cam in the low RPMs pays some significant dividends in BSFC (brake specific fuel consumption) with a very pronounced minima around 6000rpm.   One would assume the added valvetrain mass (and presumably slightly stiffer valve springs to deal with said mass) would increase BSFC due to valvetrain friction in the VC engine, and sure enough, it does.  The VC engine hits 260 g/PS*h up at 12.5krpm versus 240 for the regular engine.

- Given that the later restricted engine only had variable timing on one camshaft, one would expect the differences to be a lot less pronounced, and that's exactly what we see.   The VC on the later models actually fills in the high end up near redline rather than fililng in in the bottom end of the torque curve like on the earlier dual-VC engines.  Below 10krpm the differences are very minor for the later engines.  I'd expect the later VC engine to respond very well to opening up the intake and exhaust though, given how its power is only gently dropping off up toward redline.

[Squishy]

Very nice 

However my experience is the very noticeable dip on the 59 HP, non-VC version, is 100% fixable by simply giving it more fuel.
I'm now on 110 mains and +1 rich on the needle, and it pulls like never before.

Before, on stock, the dip would noticeably go away at a~6000rpm, and then at 8000rpm the "powerband" would start.
Now, it starts pulling from 4000rpm all the way to 10000rpm, and then at 10000rpm the (now much stronger) powerband starts all the way up to 14000rpm. Normally my experience was that after 10000-11000rpm torque would fade, and I can now see why 12000rpm was my max rpm in 6th gear.

I think this engine can perform a lot better but was detuned for emissions or fuel consumption (like most engines).
If I now ride in 1st gear 4000rpm, close the throttle and fully open, it will go on the back wheel.