So i now have headers, intake and exhaust on an h23 prelude and i read when you increase the air flow like that the engine can tend to run lean especially in higher rpm resulting in a slight loss of power. I picked up a fuel pressure regulator and gauge and realized that i have no idea what exactly to jack the pressure up to. Will the stock injectors be able to handle this? any help would be bawlin.

 

here's a dyno chart from my bolt-on H23 with an air/fuel ratio plot as well.
AEM cai Megan header test pipe 2.5" mandrel bent catback (other mods include clutch and flywheel, but hold little to no value to your question)
You can see its running SUPER lean. I bought a B&M fpr and a run-of-the-mill gauge. Installed the gauge first to check its acuracy. Stock @ idle is ~35psi. I bumped it to 42/43 and it was running too rich. Alot more backfiring than should've been.
Lowered it to about 38-39 and it seems to be good. Keep in mind though, this "blind" tuning and highly innacurate (leave me alone Blake!! lol). A trip back to the dyno in a couple months will show me where its really at, but its still not as efficient as a full tune.
One final note: each car is different but a slight bump will be ok (around 2-3psi)

 

leave it alone. You have no need to adjust it anywhere different than stock.

 

What about me? You see how lean it is. That can't be good?

 

i dont see how your so lean... h motors run rich as hell with stock ecu

 

tell me about it. Since I richened it up, I've bumped the base timing (via the distributor, obviously. lol) about another 1.5* to ~17.5* BTDC on 93 octane and seems to a bit better.

 

Yep. If you do want to play around with FPR on a dyno or with a wideband go wild, but otherwise don't mess with it.


Re the sheet:
As someone said on another forum, and I agree, I can see it leaning out when you drive around with your FPR unplugged like the guy with the dyno chart (which is both stupid and would make it run much richer during cruise...and cause the ECU to pull fuel, and those trims are applied to high load iirc).
So definitely don't pay attention to that chart.

 

lol you remembered my whole thread on PP. lol I'm h23bb2 on there.
I'm not ENTIRELY convinced of that, but I have been thinking about it since either you or motoxxxman mentioned it.
It will be back on a dyno (with A/F) before spring so we'll see. I will say this though: even after hooking up the vacuum and resetting the ECU the motor with about 1000 miles of it being driven like that followed by 6000 (a total of 7000 miles o the engine before the oilpump failed and I had to rebuild it again) with the vacuum hooked up the exhaust valves were white as paper. Is't that idicative of a lean A/F ratio?

 

Skip the Dyno runs and go buy a wideband.

Simple bolt-ons will not require any adjustment to fuel pressure.

 

yup acidcrakker is right