A long boring story for you insomniacs
With the recent addition of an intercooler, my bike makes mad power now and I'm worried about proper fueling particularly at high boost where you're more likely to perforate a piston.
Power commanders come from the factory with bike-specific plugs. Yeah, I chopped those right off.
It's a pretty simple device really: 4 injector signals in, 4 injector signals out, tps, and dc power. The 750 turbo has one injector wire out of its ecu that splits into four somewhere in the loom. After chopping the plugs off the pc5, I cut my bike's injector wire, grouped the eight pc wires into two groups of four, then attached each group to the appropriate single wire on the bike.
PC-5's have a 0-5v analog input that you can use for just about whatever you want so I thought it'd be the perfect device to tune a turbo bike because I could attach a boost sensor to this input and add fuel based on boost pressure.
The problem was with my old tps. All the new ones show 0v with the throttle closed and 5v wide open. Mine shows 5v closed. Dammit.
So I attached the PC5's tps wire to my boost sensor the way Turbo guys in the UK do with their pc3's. This makes the tuning confusing at first until your brain gets used to it. The 0% throttle column is all my off boost adjustment while 100% equates to 20psi of boost.
I installed new injectors for this project as dynojet requires high impedence ones. My pc5 was originally for a zx14 but as soon as I got it I loaded a zero map. With the new fat injectors, the zero map was so rich it wouldn't even run. I entered negative numbers ten at a time into my 0% column until it idled happily which turned out to be -30. With the bike on the lift, I revved to a few different rpms, listened, and slowly created my own base map.
Now I'm ready to activate the Autotune module.
With this and the 5-wire Bosch o2 sensor in place, you bring up a Target afr table and tell it where you want to be at what rpm/throttle. But also, with the bike running and the laptop connected it displays current afr onscreen which gives you some more data to rough tune with.
After filling out the table and going for a ride, it creates a list of suggestions and you choose to apply them or not. While watching the laptop, I noticed some latency of the o2 sensor sniffing the exhaust and displaying the data. I kept this in mind while riding, trying my best to maintain certain boost levels at certain rpms for several seconds at a time so the sensor had time to adjust.
For safety, it will only change the current map 20% at a time so if you're base is way off it will take a few rides to get where you want to be. Mine was pretty close.
My fabricator friend thinks we can install a 2nd tps solely for the pc5 so this is really just the beginning but in the meantime, the bike is running great and I'm reasonably confident I won't go too lean when trying to break the sound barrier.