Gen 3 fuel system

[PoCoBob]

This is really just a curiosity question, but does anyone know how the dual fuel systems work on the gen 3 engine? Does it use only the direct injection most of the time, or does it switch back and forth between that and the multiport, and does it sometimes use both systems at once? I have my theories of how it works but I can't find anything online that states for sure what the engines doing.

Sponsored

 

[KeyLime]

https://www.enginelabs.com/engine-tech/efi/how-does-dual-fuel-work-on-a-gen-3-coyote/

 

[engineermike]

I’m not one to brag but I’ve probably spent more time tuning the Gen3 coyote fuel system than anyone outside of the oem. I could write a dissertation on the subject.

The port injectors never turn off. The lowest they supply is 10% if the total fuel flow. The gdi injectors do shut off totally at times. In general, the gdi “blend” increases with load because the intent is to suppress knock, which happens at higher loads.

I’ve tuned everything from the lift pump pressure control, hpfp pressure control, gdi injection timing (including soi, duration, and eoi on the dyno). The system measures both actual fuel pressures and adjusts the duty cycles or durations if needed. It calculates how much gdi duration is desired vs what is possible, picks the lower number, then sends the rest in through the port injectors. I believe it will also cut the throttle if it can’t meet target lambda at max gdi duration plus pfi duty cycle but I haven’t tested this.

The general goal of the tuner *should be* to maximize gdi blend (minus the 10% mentioned earlier) to get maximum knock suppression, while staying inside the injection window available. Too early in the intake stroke and it wets the piston, so you lose the benefit. Too late and there is insufficient evaporation time and you lose power. I’ve seen nearly 100 hp loss if you try to inject too late into the compression stroke.

There’s so much to this subject…

 

[markmurfie]

https://www.enginelabs.com/engine-tech/efi/how-does-dual-fuel-work-on-a-gen-3-coyote/

Its got some of the tables... but the information in the article seems contradictory and hard to follow IMO.

The article has you believe immediately after startup it uses the cold or warm blend table... it doesn't. Then they state " Once start-up is initiated, the clock is then activated and with coolant temperature rising, the direct injection begins to take over." What they are referring too is cold start emissions reduction mode- CSER. This has been around for a while. Basically what its job is, is to get the catalytic converters up to functional temperature ASAP. Theres another blend table for CSER mode that it uses. CSER can last 1-2.5 minutes after starting the car. It will then go to, most likely,the warm blend table. if your car has been running for that long and your coolant is still below 32*f, you probably choose to take the wrong vehicle. Durring CSER,yes a high percentage of DI(80%) is used. Once the car has been running for a short while it goes into stability mode and immediately switches to 100% PI.

" The DI setup gets the win for better fuel control at wide-open throttle and part throttle loads, which results in better fuel economy and a smoother, longer life of pistons and cylinder walls, as the control of the fuel mixture is more precise. "

I would daily drive my car and see up to 28-29MPG, never even using the DI outside of that initial catalyst warmup. How they concluded DI has better control and is where the fuel economy comes from IDK. My guess is this was their inital guess as the article is a few years old, but they are wrong. The DI is there to shorten CSER time, and help with detonation at higher loads. Not utilized for Fuel mileage increase as far as I can tell, if that can even be a benefit Ford could implement. Theres very little more you can do that PI doesnt achieve, to keep the engine running a stoich AFR and doing its redox cycles to take care of the criteria polutants.


Also for CSER I think it uses a split shot injection method, part in the intake stroke part in the compression. Once its out of that, it switches to just a single shot, and trys to get it all in the intake stroke. Control over the direct injector durring the compression stroke is impercise and difficult with the rapidly changing cylinder pressure.

I am not a fan of DI. I would have perffered an external catalyst heater/cooler and a cylinder pressure sensor.

Sponsored