hi

Does it make sense to turn/switch off four pistons by removing injectors electric signal in order to save fuel if you dont wanna run fast?

thanks

 

Maybe if you can modify the firing order

 

^^^^what Liquid said. The TPI injectors are "Batch Fired" meaning the the left bank is a batch, and the right is another batch

 

ecm sure the hell wont like it, the tattle tell Check Engine will tell you that, Good thought. my ram has it and when you turn the O/D off it by-passes the MDS

 

it would have to be computer controlled. Another option would be to rotate thru which pistons received ignition, while turning off fuel injection to the ones that did not. First place I'd go would be to study how the Cadillac Northstar system did it.

 

interesting topic, just did a quick search. Looks like to be efficient you also need to shut down valve opening, which makes sense. http://www.jdpower.com/cars/articles...ion-saves-fuel

 

you can freely choose what injector to switch off, since it's a manual wires hacking

from the article:
" Rather than cut off fuel to the unused cylinders, the engine's injectors continued to keep them supplied, causing gasoline to accumulate. "

OMG
It's simpler and cleaner and more efficient to just switch off some injectors. I dont see the need of shutting down the valves, and they say they do.

Concerns are:
1- what injectors to switch off
2- is it going to be a problem for the ECU

 

You cant just unplug them, The ECU will read a lean condition and try to adjust fueling to compensate. You must alter the tune or create a new subroutine that alters target afr while doing this.

I created a hack that does exactly this on a newer ECU. It was easy when I could monitor gear, load, rpm, throttle position and turn off injectors through the oem torque management fuel cut flags.

 

You have to be able to deactivate the lifters on the shut-down cylinders, otherwise you will have massive pumping losses that will actually hurt your fuel mileage. I would suggest a DOD 5.3 swap if you want to do something like this.

 

How did Cadillac do the cylinder deactivation on their ~1981 368 engines?-these got a bad reputation for slow mode switching response and rough running in v6 mode,but the idea was ahead of it's time

 

By deactivating the rocker arms on the cylinders they were shutting off. I actually helped convert a 500 to 8-4 configuration for a 1978 GMC Motorhome. Worked quite well too. Ditched the original electronics that ran the switching setup and the TBI unit and used some custom code in a 7730 with a relay to deactivate 4 cylinders rockers and injectors at the same time. Used a 500 seville EFI intake manifold with some machine work to hold modern injectors and used a 454 TBI minus the injectors for an air valve, IAC mounting, and TPS. It was amazing how well the resulting PFI 255 CID 4 cylinder was able to keep 12,000 lbs rolling down the highway too. I also used the TCC output to control the switch pitch torque converter he added the the TH400 based TH425 FWD transmission. It was possible to switch to high pitch/higher stall speed while in 4 cylinder mode to climb small grades and keep the load off the engine. With the right settings for V4 to V8 and V8 to V4 the transitions are barely noticeable even without drive by wire. The coding I wrote basically gave the engine all 8 cylinders at idle. Above 30 mph and 1,500 rpm it was able to enter into 4 cylinder mode, provided the MAP was between 40 and 75 KPA. It also had a maximum RPM to enable/stay in 4 cylinder, I chose 3,500. Once in 4 cylinder mode, I had a MAP threshold, MPH, threshold RPM threshold, and TPS threshold to EXIT into V8 mode. You are able to still run on the same VE and Spark tables on 4 and 8 cylinder mode. When the 4 cylinders switch off, the throttle plate is still open a certain amount, the same flow is still taking place, it pushes the MAP reading much higher anoud the 4 remaining cylinders take a denser intake charge. The cylinder charge is really no different in 4 or 8 cylinder in relation to intake manifold pressure aka MAP. As long as you switch back to V8 mode before you reach zero vacuum there is no harsh transition to and from 4 cylinder mode. The only difference is you notice a little loss of torque in response to the pedal but you are only running on 4 while cruising down the highway or low load cruising around town anyway.

 

Fast355: Gen V engine deactivates valves via oil flow to lifters. How did you electronically disable rockers?

 

Cadillac 8-6-4 engine deactivated the rocker arms and had electrical solenoids under the valve cover. On the Cadillac all that had to be done was convert the 368 rocker system to the 500 head.

 

wouldn't it be just easier to find a JY 05,06,07 engine and harness that offered that option