Rob Humphris - Cambridge, UK.
VEMS Wideband Guage Question
I have been asked about the effective operating range of our Wideband system: What level of accuracy does it provide for ethanol fueled engines?
No real idea on the accuracies, but very interested in the results! I intend to power the TVR on ethanol eventually.
- I read through that and didnt really see an answer, but now reading this the answer clear as the sensor is effected by oxygen, so what ever the fuel's stochiometric AFR the oxygen balance will be the same around 1.0 lambda.
Reading through the above link, I'd guess that the sensor has more-or-less the same accuracy whatever the fuel. The sensor measures free oxygen in the exhaust gas, so is measuring actual lambda not the AFR. But AFR is proportional, if the fuel is known. If the fuel is not exactly known, AFR is problematic, while lambda is clear even than. Therefore calculating with AFR just causes a lot of confusion. It's best to think (get used to) and display in lambda.
The difference is a lambda of 1 no longer represents an AFR of 14.7:1 - ethanol is approximately 7:1 if my memory is OK.
VEMS doesn't know AFR, it only knows lambda. Maybe at some points 14.7 * lambda is displayed as AFR for the convenience of users who hasn't yet got used to the proper lambda unit.
Actually, VEMS doesn't even know how big the cylinders or injectors are. it just knows the basic fuel pulsewidth, and the rules to change that based on MAP, coolant, MAT, .... and in case of the ego-correcion: target lambda and measured lambda.
Incidentally you can get some kind of specific gravity sensor for fuel tanks now. This can be used to decide what fuel is in the tank (or indeed what mixture of fuels is in the tank).
More alcohol might allow higher ignition advance or higher boost (or less water if water injection also applied).
Lamda-target could also be changed depending on fuel in the tank, but that's not as important as changing boost-target.
Hope this is sane and that it helps
dnb
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The closing times are also needed (it is the function of injector current and flyback voltage). The flyback voltage actually makes a huge difference.
The opening times are not (by far) enough to calculate GenBoard/Manual/Config/InjectorOpening parameters. You can start from other's values, make sure
- injopen=00 (or very very short for low-voltage flyback, max 100 usec)
- battfac=10 (256..700 usec is usually OK)
- injocfuel=2C (500..1200 usec usually)
- injrampup_battfac=FF (IIRC 4082 ... in MegaTune, it does not have a simple physical unit like "usec" or similar)
http://www.pgmfi.org/twiki/bin/view/Library/EcuSensors
v3.2 Assembly documentation:
v3.2 How-to power-up a new board.
http://vems.hu/www.vems.co.uk/VEMS/
In an attempt to document my installation:
For UsabiLity to be more useable studies like this are of interest.