I'm a little confused about EM injector size settings and I'd like a 2nd opinion..... - Miata Turbo Forum - Boost cars, acquire cats.

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Old 11-26-2009, 10:53 AM   #1
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Default I'm a little confused about EM injector size settings and I'd like a 2nd opinion.....

I posted up some of my saved EM maps earlier because someone said that a lot had gone missing and I found a bunch saved.

Anyway - looking at my current map (the saved version) I'm running 1.8 injectors, and I realised that the before and after injector size setting was at 205, rather than 230(b) and 265(a) (a carry over from some maps I was sent by someone here who was helping me out). This was the case when I had the car dyno'd a while back - something I've been meaning to do again.

Anyway - what has me confused is whether the before and after sizing matters if the correction factor is still 1.0. Now saying I was to change the before back to 230, and the after to 265 (reflecting what's in the car and giving a conversion factor of 0.868), is that going to richen up the fuel map in boost, or lean it out?

The car currently runs great on the current 8-9lbs (bit of boost creep, but tempered by a spinning clutch which limits excessive abuse), but given our tropical heat here, a recent head gasket replacement, slightly bigger cams in the car since it was last dyno'd, and a desire for a safety buffer against things going BOOM, I just want to make sure I'm getting a good AFR in boost (currently running the standard o2 sensor and a narrowband stoichmeter that reads all the way over into rich under boost). I also have a BEGI FPR that I've been meaning to install for ages, which I will probably/possibly/maybe do before the car get's dyno'd again.

Obviously the dyno tuner is going to have the wide band sensor, but this is also about me learning something.

Can I get a second opinion doc????
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Old 11-26-2009, 01:45 PM   #2
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Should richen it a bit? since it wont have to lean it as much for "standard amount" of fuel?

Or wait, you said both before and after was set at 205?

In that case, it will lean it out, since it will try to make the larger injectors flow an equal amount as the smaller. As you said, it will change whatever signal its getting from the ECU to signal*0.868 (+whatever is in your injection map obviously)
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Old 12-04-2009, 09:52 AM   #3
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If you have an a/f gauge try to get an idle of 14.7
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Old 12-05-2009, 05:16 PM   #4
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I believe it would trim less fuel; it would be richer. This is because it would trim more fuel to make the 265s put out like 205s as opposed to 230s.

However, you have to realize that even if this setting was wrong, the ecu is compensating for it during closed loop. If your car was OBD-II, you'd be able to hook up a scanner and see how much it was trimming fuel.

Obviously, during boost, your tune is good enough that you haven't blown the engine. Now, how are you running 8-9lbs of boost without an FPR right now? I was under the impression that a 1.6 with 1.8 injectors could only get away with 6 psi or so before running out of fuel.

Also, I'd recommend getting a wideband o2 sensor and gauge. I consider it another safety feature, and you would be able to do some tuning yourself if you wanted to (I datalog with my EMB to do my tuning). A narrow band sensor hooked up to a wideband gauge will only show three settings, lean, stoich., or rich and won't tell you a whole lot. You could be running a 13:1 AFR at points in boost and you would never know.
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