- Sat Oct 07, 2023 2:02 am
#65162
Hey all
Ive almost finished my Bultaco road race replica built from my old 1978 370 Pursang motocrosser.
The old air-cooled engine has had a reed valve added and some good porting in the past and was a very capable motocrosser in its day. Being an old school Euro dirt bike, the engine is relatively low revving with a long midrange which makes should make it good for a lightweight road bike and I have zero plans to develop it further.
I managed to get its dry weight fully faired from 110Kg down to 95Kg with a very savage weight loss programme!!!
Now fitted with Speeduino EFI and is triggered with a 60-2 wheel and VRS.
42mm throttle body/240cc injector with built in TPS and stepper IAC. Fixed 45psi fuel pressure.
Delco D585 ignition coil.
I fitted a 240w flywheel/alternator setup off a China scooter to power the whole show.
Nothing groundbreaking there and to begin with load sensing via TPS only but Im looking at incorporating a MAF at some point in the future by inserting a hotwire MAF into the inlet in front of the TB. Fuel reversion impacting on the sensor may or may not be an issue as the engine is reed valved but.......
I do have some space to increase the length of the inlet pipe between the air filter and the TB mouth and I believe there are some MAF's that shield the hotwire sensor from anything splashing from downstream but only future datalogging and testing will reveal that.
2 strokes with expansion chambers have some, ahhh....... rather "interesting" load sensing/fuellingignition demands and TPS only is barely adequate and at best, the ECU just guesses the engines fuel demands.
However, for a bigger cube, relatively lower revving motor I can happily get away with it to begin with. Its been done before plenty of times.
The entire electrical and electronics system has been built and tested on the bike by spinning the trigger wheel in the lathe and mounting the VRS onto the toolpost!
Datalogging showed a dead clean VRS waveform and no EMI/RFI interference even with the sparkplug zapping away resting on the head.
Other than a few pesky small jobs left it only awaits a full engine rebuild before being ready to light up.
I have done several custom EFI setups on bikes and cars over the years on various engines, turbocharged and NA so this is not really my first efi rodeo but injected air cooled 2 stroke............ We shall see!
I have written a specific ignition map for a 2 stroke but the fuelling demands are kinda partially educated guesses at this point!
Just looking about for any other injected 2 stroke tragics who might like to chime in with their experiences.
Ive almost finished my Bultaco road race replica built from my old 1978 370 Pursang motocrosser.
The old air-cooled engine has had a reed valve added and some good porting in the past and was a very capable motocrosser in its day. Being an old school Euro dirt bike, the engine is relatively low revving with a long midrange which makes should make it good for a lightweight road bike and I have zero plans to develop it further.
I managed to get its dry weight fully faired from 110Kg down to 95Kg with a very savage weight loss programme!!!
Now fitted with Speeduino EFI and is triggered with a 60-2 wheel and VRS.
42mm throttle body/240cc injector with built in TPS and stepper IAC. Fixed 45psi fuel pressure.
Delco D585 ignition coil.
I fitted a 240w flywheel/alternator setup off a China scooter to power the whole show.
Nothing groundbreaking there and to begin with load sensing via TPS only but Im looking at incorporating a MAF at some point in the future by inserting a hotwire MAF into the inlet in front of the TB. Fuel reversion impacting on the sensor may or may not be an issue as the engine is reed valved but.......
I do have some space to increase the length of the inlet pipe between the air filter and the TB mouth and I believe there are some MAF's that shield the hotwire sensor from anything splashing from downstream but only future datalogging and testing will reveal that.
2 strokes with expansion chambers have some, ahhh....... rather "interesting" load sensing/fuellingignition demands and TPS only is barely adequate and at best, the ECU just guesses the engines fuel demands.
However, for a bigger cube, relatively lower revving motor I can happily get away with it to begin with. Its been done before plenty of times.
The entire electrical and electronics system has been built and tested on the bike by spinning the trigger wheel in the lathe and mounting the VRS onto the toolpost!
Datalogging showed a dead clean VRS waveform and no EMI/RFI interference even with the sparkplug zapping away resting on the head.
Other than a few pesky small jobs left it only awaits a full engine rebuild before being ready to light up.
I have done several custom EFI setups on bikes and cars over the years on various engines, turbocharged and NA so this is not really my first efi rodeo but injected air cooled 2 stroke............ We shall see!
I have written a specific ignition map for a 2 stroke but the fuelling demands are kinda partially educated guesses at this point!
Just looking about for any other injected 2 stroke tragics who might like to chime in with their experiences.
- By stum
- By PSIG