Direct injection pump question

[Joshinator99]

DI cars often lower desired rail pressure at idle and light load because otherwise the injector on time would be too little and would make for wonky spray pattern.

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[Cory S]

What are your fuel trims and lambda showing when it starts to act up and stall???

 

[scoobaru88]

What are your fuel trims and lambda showing when it starts to act up and stall???

I’d have to recheck but I believe stft start going positive until it stalls, ltft don’t fluctuate at all.

 

[bankyf]

Ay chance your tuner could send you a new calibration using only PI at idle for diagnostic purposes to see if it fixed your stalling issue?

 

[engineermike]

@bankf the stock tune uses 100% pi at idle. Sometimes I’ll run 100% di as a test, which may be in order in this case.

 

[Cory S]

@bankf the stock tune uses 100% pi at idle. Sometimes I’ll run 100% di as a test, which may be in order in this case.

So odd. One would think the DI would be much more suited for idle/cruise efficiency/control, and then port fueling coming in with a supplement for increased demand.

 

[Joshinator99]

So odd. One would think the DI would be much more suited for idle/cruise efficiency/control, and then port fueling coming in with a supplement for increased demand.

Your assumption is spot on and that’s why the 2019 LT5 Corvette ZR1 does fueling that way. But DI makes for a “diesel-like” idle so many manufacturers don’t use DI at idle due to customer noise complaints. Lexus has been using port at idle and light throttle for years, and the PI comes in under enrichment. Plus using PI at idle helps make sure there is less build up on the back of the intake valves too.

 

[engineermike]

Di is for knock suppression but is worse in most other ways such as idle stability, valve cleanliness, and particulate emissions. As such, ford only uses DI at heavier loads when knock is most likely.

 

[bankyf]

@bankf the stock tune uses 100% pi at idle. Sometimes I’ll run 100% di as a test, which may be in order in this case.

That's right. I always get that backwards because it actually doesn't seem logical the way Ford does it. Perhaps his tune is running DI at idle, otherwise it seems pretty unrealistic that just resistance from pump alone would be enough to stall the engine.

 

[bankyf]

Di is for knock suppression but is worse in most other ways such as idle stability, valve cleanliness, and particulate emissions. As such, ford only uses DI at heavier loads when knock is most likely.

Interesting. I thought I had read that DI was much better for emissions.

 

[engineermike]

Interesting. I thought I had read that DI was much better for emissions.

I believe the way they twist that these days is that di allows more compression which improves fuel economy which lowers co2 emissions…but it works in our favor so there’s that.

 

[SilverUri]

I’m leaning towards my direct injection pump is bad, desired pressure is 400psi, and it shows actual pressure is over 2000psi and creeps up to 2700/2800psi until car stalls out. No engine codes. Car just runs horribly and stalls out after idling for 5-10minutes.

Assuming new direct injection pump will fix the issue, but anything else that would cause this issue? Tuner says that the tune is fine. Ran on tune for 3k miles with no issues.

Hi
Have you ever figure it out what was wrong?

 

[scoobaru88]

Hi
Have you ever figure it out what was wrong?

I put gt500 injectors and all problems went away.

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