Z32 injector latency setting 740cc

[Gonzo12c]

Hey folks interested to hear what people have their injector latency set to for Nismo 740cc injectors? Wanting to copy for a base map as I’m currently set to 830.

[Matt]

Had my S14 set to 900uS but that wanted a rich idle (13.5ish:1)

Usually I suggest once you have your base mixtures (stoich at cruise with no trims) then set latency so you get a nice idle

[Gonzo12c]

Thanks I had looked at the Tomei 740s and they have a time lag setting of 0.66 so I thought it might be 660 but that seemed low. Will push up to 900 and see how that responds. My cruising AFR is looking good now and I’m idling around 12.4. Have started AFR auto tuning and getting some violent spikes in the fuel map at the moment so will continue with it until I get a happy medium and fine tune the map.

[Matt]

I would normally recommend manually tuning the fuel map. The violent spikes can happen because of rich/lean AFRs on deceleration etc than then adjusts the fuel map accordingly

[Gonzo12c]

Sure I was trying it out to see how well it worked. I did find a target AFR map in the install and used this whether it is correct to be using this though?

[Matt]

Normally the target map should be about 14.7:1 cruise and 11.5:1 on boost. The factory maps seem to show richer with the 'estimated AFRs' so I don't normally recommend using it

With the AFR auto tuner, you may need to adjust speed trigger and TPS decel cut to avoid spikes happening during the adjustments

[PL]

People seem to get hung up on getting latency set exactly as per injector manufacturer's specs. I can understand this when using aftermarket ECU's with fuel models that rely heavily on an accurate latency number. But in reality I've found that for Nissan ECU's it doesn't matter that much - within reason of course. I always start at a latency number close to the manufacturer's spec (if known), get my tune roughly in place, then watch the fuel trims and tweak latency to suit.

Naturally you need to ask questions if you're having to use unrealistic latency figures but don't be afraid to give them a nudge to get your light light/idle AFR's correct.

PL