I need advice on choosing injectors for my XE 224/230. It seemed to run fine on the dyno, but when I do the math it seems like I'm running into trouble...

All equations from this site.

366rwhp / ~18% drivetrain loss = 366/.82 = 446 at the flywheel

Using a couple more equations on the site and assuming a brake specific fuel consumption (BSFC) of about .45 and a duty cycle of no more than 85%, the stock 24 lb/hr injectors should be good to...

24 lbs/hr * 8 injectors * 85% cycle / .45 BSFC = 362.6 fwhp. (notice, at the FLYWHEEL)

Well, that's all fine n' dandy... about 60 horsepower short.

If we calculate for 100% duty cycle...

24 lbs/hr * 8 injectors * 100% cycle / .45 BSFC = 426.6 fwhp.

The A/F graph on the dyno sheet didn't look too bad (it crept leaner than 13:1 after 5200 RPM but didn't get too far into it). Interestingly enough, that's right about where the car makes 350 at the wheels... or 426 at the flywheel.

Now of course this is all on paper and doesn't count until I actually go out and do some data logging, but from the looks of it the stock injectors are running into trouble.

Any ideas / comments on my math?

 

If you plan on keeping that cam in, go with the SVO 30# injectors. With the LT1 fuel pressure, they are more like 32# so that should be plenty for your current setup. But if you plan on going bigger (cam and heads-wise), I would go with 36#, maybe even 42# injectors. When tuned right, even the 42# injectors will run with no problems. Good luck.