VEMS looks to be just the thing I was looking for to go beyond carburettors.
My project
- Guzzi V75/4 motorcycle
- 90 degrees V-twin, firing interval 270/450 degrees
- 750 cc, Normally aspirated. carburettors: 2x Dell'Orto 30 mm
- 65 Hp approx, 7000 rpm max.
- I already have a NB O2 sensor in one of the two exhausts (helped in jetting the carburettors. )
I will use the bike for street use only. Basically, I want to learn hands-on about EFI. I am not looking for a performance increase. Lower fuel consumption might be nice, though.
Me and my Guzzi on a cold morning last winter:
Bought lots of second hand EFI bits from a Moto Guzzi Quota to make a start.. :)
- Two intake manifolds with Weber-Marelli IW 042 injectors (16.2 Ohm, 190 cc/min @ 3 bar)
- Throttle body with two 42 mm throttles and TPS
- Fuel pump (Weber PI021), filter, regulator (2.5 Bar)
- Various sensors and the original Marelli P7 ECU which I will not be using.
Plan
- Modify intake manifold to fit engine; fit throttle body, air filter, fit other EFI bits.
- Generate more timing info; either by multi-toothed wheel for the camshaft VRS or add VRS on the crankshaft.
- Buy VEMS!
Eventually
- Have the VEMS do ignition as well as injection. Load-dependent ignition advance would be nice, I only have an RPM-based advance now.
- One, maybe two WB02 sensors?
Current issues
I would welcome any thoughts from others on these issues:
1. At present I only have this (VRS) trigger for the ignition on the camshaft. There is no cranksensor.
I want to make a new rotor for this with more pulses. At present I am thinking of 12-1 teeth. Since I have two pickup coils (135 degrees apart), I can then do 'static' position detection: Normal operation means the two pickups generate alternate pulses and the missing tooth gives two consecutive pulses from the same sensor. Is 12-1 on the camshaft a sensible idea or are there good reasons to make something else?
2. I have a pressure sensor rated at 100 kpa. I would like to be able to use this as a MAP sensor. I think this should work in an NA engine. Or is there a good reason to go with the 250 kpa sensor from the webshop?
3. I am rather short on electrical power. I have a generator that puts out 280W at most, and after 80W for lights and 25W for heated handgrips, that doesn't leave a lot for EFI. I was thinking of doing PWM for the pump to save power. I can see two possibilities.
a) Measure fuel pressure, no return line, and PWM the pump to keep the pressure constant.
b) Keep the pressure regulator and the return line, but PWM the pump (feed-forward, based on injection pulsewidth, RPM and battery voltage, all of which the ECU knows), to keep the return-flow as low as possible to save power.