[ever_green]

Originally Posted by superchow

Now if we could have BSFC curves for partial loads... I know, I know, never satisfied!

See article below:

Technical Overview of Honda's new R18 i-VTEC Implementation

for most modern engines the BSFC sweetspot (RPM) is the same in partial load as in WOT. Here is a WOT BSFC chart for a 2.2L DOHC vtec engine:



here is the partial load BSFC (2.2L DOHC vtec):



Unlike i-VTEC engines, VTEC engines are easier to understand because high lift cams are engaged at a specific rpm (In this case it's 5800 rpm). On an i-VTEC engine it can happen anywhere above 1000rpm. Note the effect VTEC has on BSFC in the chart above. So we must avoid high speed valve lift in order to save fuel. This means that with our typical 1.8L i-VTEC honda engines we should get into 4th gear as soon as possible with moderate loads. The theory of high loads low RPM does not apply to i-VTEC or any other variable valve lift system as it might engage the high lift valve mechanism. I have noticed that some people here pursue lugging methods to achieve good MPGs. On older engines this might be fine aside from the damage it does to their engines, but on a modern variable valve lift equipped powertrain it is counter productive. it's really easy to engage high lift cams below 2000rpm as honda engines have serious lack of torque below that speed.