Thanks, Charlie. I knew it was used as a modifier for the REQ_FUEL measure - and knew it wasn't an exact measurement of the engine's true VE, but I thought it was closer to reality than what you're saying. Thanks for the insight.

On that thought, I would imagine the VE number also has a great deal to do with fuel pressure - particularly if REQD_FUEL is calculated incorrectly - or if it's calculated initially, then later changed - which would cause the VE tables to change on follow-up use of megatune. I suppose you could massage the REQD_FUEL number to obtain a VE table closer to reality.

Here's what the manual says should be theoretically achievable:

Quote
pulse width = Req_Fuel Î VE(rpm,kpa) Î MAP Î E + Injector_open_time
In essence, the mass of the air entering a cylinder is computed using the ideal gas law (PV=NRT), where the pressure p is a function of VE and MAP, the volume v = cylinder displacement, the air temperature t is a function of E, r is the gas constant. We are looking for n, the mass of inducted air) and then that result is combined with a characteristic number for a given injector.

If you get the injector opening time correct, and the REQ_FUEL accurately represents the flow rate of your injectors, then the VE entries will be close to the VE noted above. However, if your opening time is not right, or your REQ_FUEL is not, then the numbers will be skewed by the amount the values are in error. In general, except for when you are first trying to get your engine started, use the calculated value for REQ_FUEL and do not change it.

In theory, at stoichiometric mixtures, the VE values at 100kPa would reflect the torque curve of the engine at WOT (ignoring friction effects), assuming a constant AFR level.


How true in practice that might be is not something I can say with any authority, but it would seem to me that if I was seeing 200 numbers, I'd probably look for an incorrect REQD_FUEL value calculation. I'll take a closer look at the table values when the tune is better.

Now, let's see some pictures of that turbo bike. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Frank