When tuning the canbus fuel percentages at each PSI - does anyone have any data recorded on what percentages can reach a maximum fuel command (4095) at full throttle?

 

Example: If the 30+ psi setting is set to 100%, there should be stock fuel. Full fuel command would not be achieved, even at full throttle. What about 110% or 120%? I'm thinking around 128% with some fuzzy math I did. But I'm curious to hear about the findings of others. 

112% should do it to just touch max fuel.  125-130% for steady max fuel

Pretty soon I'll have to create a winter tune. Getting way to easy to break the tires loose. 

22 hours ago, Me78569 said:

112% should do it to just touch max fuel.  125-130% for steady max fuel

 

Thank you. Bonus question. Does increasing the canbus fuel command increase pressure, duration, or both? Wiretap in my mind is duration only. I'm curious because I am thinking about how it affects injection timing.

 

16 minutes ago, kzimmer said:

Does increasing the canbus fuel command increase pressure, duration, or both? Wiretap in my mind is duration only.

 

Both. Pressure is created to make a longer duration because of the nozzle size. Smaller the nozzle the longer the duration and more pressure. Larger nozzles flow more quickly so the lines pressure is reduced and the duration much shorter. Pump can only squeeze Y amount fuel past a small nozzle it X amount of time.

Understood. However increasing pressure should increase flow on any given orifice size, which should lesson the need for more duration. Kind of like raising rail pressure in a common rail. 

Does it actuallt increase pressure?  I don't believe so, it might keep pressure at peak longer, but overall pressure not so sure. 

 

 

The way I understand it the pump is always pumping peak amount, but the solenoid is what control how much to release to the nozzles.  

Understood. Thanks fellas.

As long as Engine Load is reaching 100% then you made max fuel on your tune. 

 

Engine load is the same as CANBus Fuel. Engine load is a 0% to 100% number. The CANBus fuel is 0 to 4095 number. 

Yep I know, I am well versed in that. It's the behaviour of stock programming that I sometimes have a hard time wrapping my head around. It's not always consistent, and sometimes it makes you wonder wtf they were thinking. Example: once in a while my truck decides to use OD unlocked instead of 3rd locked during steady state cruise around 75 km/h, especially if I started out a little faster and backed off. Why? Who knows. Step on it or Lock out OD and it's back to 3rd locked. That's PCM instead of ECM but you catch my drift. It's like they threw darts to connect an action to a reaction. Keep it simple!

PCM software more so. My 96 does this same thing. What is part of the problem is how much fuel you add or don't. This will cause deeper throttle or shallow throttle which changes the TPS value and TV pressure in the transmission.

Yeah definitely. I wish someone would develop a tool to custom tune the PCM. I'm sure the technology exists that if I wanted to get into the PCM and make adjustments I could, but I don't have the time to dedicate to a project like that. And I don't want to destroy a PCM. It'd be easier to manipulate signals like APPS to the PCM at key times to adjust how things react.

 

Side note while my brain is in tinkering mode... Any idea if torque management is a function of the ECM only, or does the PCM play a role? I'm thinking ECM only. But then the ECM would have to get a speed signal from the PCM. I'll have to check out the schematics. The reason I'm curious is because maybe momentarily interrupting or reducing the APPS signal to the PCM would disable torque management. Or... Cause some sort of completely unexpected result. Either way. Sounds fun. 

Pcm tells the ecm to defuel as tm looks at trans gear and speed.

 

Thats why the tm rad box taps into the ccd bus.

Do you think APPS feedback has anything to do with the level of fuel being pulled, or purely based on speed/gear?

Dont think its app i think its gear mph and boost

Even my truck has a low power band right up to about 20-25 MPH then huge change in power. It's not the APPS for sure its the speed and tach signal for me. Since the PCM had no tie to the transmission. Usually that power jump is what breaks the tires loose being in 4th gear matting down the throttle at 25 to 30 MPH and it off to the races at that point.