Mike W - hmm, how long is a piece of string? I'm not sure I can explain it in basic terms, I could do it with our lab-techs because they'd ask questions along the way. The ECU, injector and mapping is a Keihin system but I'm none too sure I'd describe the whole bike system as computer designed. If one changes say the exhaust silencer one alters its resistance and that alters the air-fuel ratio (AFR) in the exhaust seen by the Lambda O2 sensor. That will attempt to maintain the AFR at 14.7:1. The stock system will attempt to do this from below sea level to over 18,000-ft up the Himalayas. That's a huge range and I cannot think of any other bike that does this. The problem with that is it has to have a rather bland power map to cope with that range and run on very low quality fuel. The problem with the narrow-band O2 sensor is it cannot make fine alterations to the AFR in real time. The stock map can cope with a simple silencer swap but not full system and K&N
Hitchcocks do sell after-market exhaust systems and K&N air filters, they also sell the PCV dyno mapped by them. This PCV ostensibly corrects the ECU map when gross changes have been made to the bike; you can go further with big-bore, piston, head and cams; they have different maps for all occasions. The basic problem with the map is it covers the main power band, which is fine because that covers most normal riding but there are lots of noughts in it which means control is handed back to the stock ECU map, that's where we close the throttle from high revs and experience banging and popping. The 0% and 2% throttle positions are all zero from 0rpm to 7500rpm and when one fits the PCV the O2 sensor is removed and bypassed; the ECU hasn't really got a clue what to do then.
By profession I'm a physicist-engineer so things that go bang in the bike and analysing reams of exotic data, yes on a computer, computer design or as I prefer modelling, is right up my alley. This is interesting light reading
http://www.velocetteowners.com/techinfo ... efull1.pdf
So I decide to go the whole hog and fit the Dynojet Autotune AT-200, this uses a Bosch wide-band O2 sensor that does finely adjust the AFR in real time. This means I have to buy another exhaust down pipe so we don't choke the welder chap to death with fumes when he fits the 18mm bung, another £100 on top of the AT-200. Not everyone will want to do this. The AT-200 produces a Trim table which shows how far the AFR is from the set value and it can use this to update the Fuel Map. By using a bunch of simultaneous equations between the Fuel Map, AFR Table and Trim Table, I can calculate the the intended AFR of the Fuel Map and the intended AFR of the stock ECU map (which is pretty much 14.7:1 across the board). I like what Hitchcocks Fuel Map does so I do not want to lose that, so I want to use the data I've acquired to fill in the gaps and cure the popping and make the response smoother. If one reads online about the AT-200, it can be used to cure popping because on the over-run on most bikes the sensor sees air in the exhaust and squirts more petrol in (which besides banging, is not economical), it can be used to cut off fuel at high revs and zero throttle (many cars do this). I have already done this but corrected-out Hitchcocks dyno Fuel Map (oops), however the bike became very smooth to ride with much less vibration (for a big single). So this is very much a work in progress.
To re-cap, if you have only swapped the silencer you probably don't need the PCV.
If you also swap the down pipe and go for the K&N you most probably do.
If you do mechanical mods to the motor (cams etc), you do. (I have not done engine mods)
Fitting the PCV is easy, it's just a bunch of wires and plugs to connect up and H's unit is pre-mapped but you do need to hook it up to the laptop to enable it, it is not quite fit and forget but that's it, you do not have to modify the mapping.
