So I just bought new injectors- 1050cc primaries and 2000cc secondaries. After thinking about it some I started to wonder about how much idle time is acceptable for an injector. I guess what I'm saying is that since the primaries are so big, the secondaries are just going to sit there doing nothing for far longer than if the primaries were just the stock 550's, especially at my moderate HP goals.

Would they benefit from being exercised more often? Or is there any extra risk of injector failure / lockup / fatigue from having them sit idle except for brief events when the pri/sec transition occurs?

 

If you have moderate HP goals, why did you get a fire hose worth of fuel?

Even the secondaries on the FD stock don't get a lot of exercise.

The transition RPM's and loads are set in the PFC, and I imagine other ECU's would be similar. Even with big injectors the transition RPM will be the same.

Dale

 

Hah, well I wanted a total fuel-redo so bought the FFE full kit. the smallest primaries they offer with the kit seem to be 1050s so that's what I went with. Didn't think much of it at the time, figured it'll just give me more headroom if I want to pump up the boost! I run a Haltech Elite which largely automates the staging for you.

 

I would think that vastly oversized injectors may not give you the spray pattern needed for fine atomization and best power/efficiency.

 

The 1050cc injectors you got are probably from a much newer generation injector (EV14 Bosch) than the stock Denso side feed ones, think mid 2000's tech vs late 80's. So the spray pattern is less of a concern than you would think.

 

My thought on that is a much upgraded fuel supply (fuel-line size, pump capacity, etc.) would be needed to keep the pressure supplied to the larger injectors up where it's needed for good atomization. If that is present, then you are correct.

 

I'm running the ID 1050x and 2200 injector combo on the FFE kit that's modified with a Radium fuel rail and it runs very well with a stock port engine and no diffusers. Idles great at 12.5 just like the stock set up did. New injectors are so much more superior than old side feeds. Mine run around 2ms iirc at idle at about 36psi as well.

 

Thanks for the education - much appreciated.

 

A way I could envision an issue would be to have the maximum stage duty cycle is set so high that the secondaries rarely come on and you drove in a manner that the secondaries never activating, say for over a year. When experimenting with my preference for the driving feel of injector staging I tried a wide rage of maximum stage duty cycles. My car is stock port, stock turbo and at 90% maximum duty cycle the 1050X injectors would only reach this duty cycle as boost reached 10psi. But even if a car was setup and driven in this manner fuel would still be flowing by the injector and the dead fuel zone at the injector itself would be small thus limiting the contributing factors to the injector not opening well once it is finely asked to operate.

 

Your stock idle AFR was 12.5?

 

Yeah, the stock ecu was about 11 with the simplified sequential set up and 12.5 gives enough fuel for idle recovery and seems to work out great for my set up.

 

It's been 10+ years since I had the stock ECU in my car, but I remember it idled surprisingly rich without the O2 sensor connected. I only had one bung in the downpipe so I had to disconnect the stock O2 sensor when I installed a wideband gauge.

It's also been a long time since I had stock primary injectors installed, but I don't think I was able to get them idling much leaner than 13.0 AFR or 13.5 AFR (around 1000 RPM). Years later I picked up tiny little ~350cc/min injectors from an ~2001 BMW and the engine idles at 15.0 AFR, even when cold. I'd like to try modern injectors in the 500-750cc/min range eventually, but the car works pretty well for now and I'm not in a hurry to make changes.

 

I run 1050x primaries on a Haltech and have a pretty solid idle at 1000rpm at 13.8.

 

It's hard to get a good AFR read on a stock ECU at idle. The air pump is running which throws off AFR readings. The stock ECU knows this and fudges the numbers it gets from the O2 sensor to compensate for the extra air pump air in the exhaust stream.

If you do unplug the air pump on a stock ECU, the car will idle rough and have rough on/off throttle transition. Again, this is since the stock ECU is trying to fudge the numbers for the air pump and and it isn't there, so the readings are off.

Dale

 

that is because the Air Pump air is going to the exhaust ports, "Port Air" is what Mazda calls it. some of this air goes into the engine, which makes it run better at low loads, and then also it dilutes the mixture.

the system works really well, if you put the car on an emissions tester, without the airpump and cat its like 4000ppm of HC's and 5% CO, add the airpump, and this drops in half, and add the cat, and its nearly 0