I dyno tuned a IX over the weekend which had Deatschwerks 740cc injectors. My usual scaling procedure yielded a strange behavior in fuel trims, specifically LTFT-Lo. I'm wondering if anyone has seen this before or knows the cause.

The vehicle had Cosworth cams, TBE, EBC, and a stock intake w/drop-in.

- Start car. Fuel pump is on high for about 10 seconds (normal)
- Get to 4,000rpm in 3rd gear to check cruise trims (they're in good shape)
- Let it come back down to idle at a stop (trims were perfect)
- Wait about 45 seconds without touching anything while idling, and the STFT drops to about 65, pulls down the LTFT-Lo to about 88 and then the STFT pops back up to 100 and stays there

I've never seen this happen before. Latency adjustments didn't seem to impact this behavior at all. I'm wondering if it's something unique with these injectors...but not sure. Thoughts?

 

Maybe they are the wrong type of injector (e.g. high Z instead of low Z)?

 

I'm not sure, but would be surprised if they were wrong and this was the only circumstance in which the Z made itself evident. No?

 

You sure they are the 740cc's? Those are a subaru application and probably wouldn't even fit.

The 750cc's for Mitsu look like RC/Denso.

 

I honestly don't know exactly what size they were, but they did scale out to be in that 740/750cc range. The customer told me they were 740cc, but who knows.

I dimly recall looking and the tops of the injectors and seeing that they were black in color.