I'm going to be using an obd1 jdm h22 swap which comes with 345cc peak and hold injectors, and would like to run the stock ecu (P13). Once a year though, the obd2 ecu needs to be used for emissions (obd port scan) and the obd2 engine uses saturated 290cc injectors. Normally, I wouldn't mind swapping injectors once a year, but the obd2 harness will be modified for the low impedence injectors. So..

Will the obd2 ecu (meant for 290cc injectors) with 345cc's, run rich enough for a 'too rich' code, or can the ecu modify a/f enough to compensate in closed loop?

tia.

 

The ecu will not modify enough for the larger injectors.
Easiest solution would be to run the obd2 290cc injectors for your situation.

 

The reason I'd like to stick with the setup stock to the motor is the .6 bump in compression compared to usdm. I know it's not a lot, but I don't want to leave any power on the table by using the usdm ecu. I'm assuming I don't need to worry about pinging type issues with a bump this size.

What'd be the easiest/safest way to artificially to lean the a/f (if possible)? We're talking about a situation that arises once a year that lasts an hour.

 

If you all you drive is part throttle on the OBD2 ECU, the closed loop functionality should trim the fuel properly. Just remember that when you have the OBD2 ECU in, drive like a grandma. If you had a much more crazy setup, I would say don't try.

 

The ~16% increase is really close to the max swing that the stock ECU can pull with closed loop. I have a feeling it will set a CEL unless you do something else to compensate.

I'd suggest lowering the fuel pressure till a wideband tells you that it's right.
Personally I'd run the wideband in the car until you drop back to the ECU you'll run all the time. Just to keep an eye on it to make sure bad things don't happen.
That will work fine for your once a year event. (should be every two years once you pass twice in a row)
Also keep in mind once you know the fuel pressure so the ECU works, you shouldn't need the wideband again...

ALSO your OBD2 ECU will require more than an hour to clear the readiness flags so you can pass emissions. More like a couple of days to get through the required drive cycles.

Also, you can use the adjustable FPR to pull a little fuel from the normal ECU, (wideband monitored of course) Honda OEM ECUs tend to run rich... pulling the right amount of fuel will give you better mpg, smoother throttle response and more power.
But pulling too much will kill the engine quickly so the wideband is required.

 

I agree, the stock ECU should be able to trim enough (16-18%) through the O2 sensor enough to pass emissions. If it throws a CEL...then you will know it cant pull enough

But keeping a set of 290cc on the side for emissions time would be the best thing to do...