I just moved to TX, where the air is much heavier than in Reno so I decided to do a little street tuning. I've got a B18C1 with Blox A cams and some basic breather mods tuned on NeptuneRTP.

The car is performing well, with a street start 5-60 in about 6.7 seconds, suggesting to me that it's making the power it should (Car and Driver records about a 7 sec. 5-60 for an ITR, RSX-S is about the same). And yet, here is the max duty cycle on a 8400 rpm run: 67%. I would've expected more in the 90% range. Here is an example line from my datalog:

RPM: 8333
MAP: 987 (down from 1016 at lower revs)
ECT: 188
Table Ign: 30
Actual Ign: 40.25
Direct Serial: 11.61 (it's at 12.6 at most of the pull).

Obviously I have some more tuning to do, but what should I think about these duty cycle numbers?

In Neptune...

Stock Injector Size: 240
New Injector Size: 240
Overall Fuel Trim: 0

All the other injector settings are left untouched.

 

Unless you have an aftermarket intake manifold, >65mm throttle body and a good header, the GSR chokes out over 8k. So yeah it takes less fuel to reach the same AFR. More importantly you're rapidly dropping power up there, so you should be shifting sooner.

Don't worry about duty cycle. Not only is it incorrect most of the time, but as long as you're getting fuel without hiccups it's irrelevant.

Lastly, that's way too rich for a naturally aspirated GSR with stock pistons. Any richer than 12.8:1 AFR is just rolling coal, unless you're using crap fuel.

 

I need a professional tune for sure. But that'll have to wait until all the airflow mods are done. I was surprised at how rich the datalog indicated. I've been street tuning in 3rd and this was the first run in 2nd I've done in a while. 1st and 2nd have their own fuel trims above 700 mBar. I guess I need to tinker with those. I have been shooting for 12.7 to 13.3. Does that sound like a "safe" target for street-tuning?

I also don't want you to think I go around revving to 8300 all the time -- it's just to get datalogged to my rev limit. I'm not one of these Honda racer bros lol.

OK, I won't worry about duty cycle. I feel the car is where it should be with how it is running in general. I was just weirded out by the low duty cycle numbers. But if it's not accurate I won't worry about it. I doubt I'll be reaching the limits of the injectors any time soon.

You could see from the datalogs that the MAP starts drooping a bit around 7.5k or thereabouts. Is that a sign that the intake side is the bigger bottleneck?

 

Injector duty doesn't lie. If stock 240cc injectors support 200~210whp @ 100% then you're making about 134~140whp @ 67%. But this is at redline, not peak hp.

 

I would be shocked if this engine was only making 140 whp. It just feels stronger to me. But who knows? I haven't had it dyno'd yet so if the injectors are telling the truth I guess that is where I am at.