> 1. At what point in your modifications did you opt for larger injectors
and
> at what point would you realize any performance gain? (i.e. stock
engine?)
If your stock injectors are not running over 80% duty cycles, then there is
really no reason to go to larger injectors, unless the larger injectors have
a better atomization pattern or something. So, you need to know what the
duty cyles are at WOT, or calculate a value based on how much HP you're
producing.
I use a duty cycle monitor from EFI Systems http://www.efisystems.com to get
injector loads as well as air/fuel mixtures. After installing the monitor,
I noticed that my 19lb injectors were running well over 90%, so I upgraded
to 24lb. Now I max right about 80%. Here's some pics:
http://www.geocities.com/MotorCity/Track/9668/dGauges.html#dGaugesStart
To calculate how much injector you need based on HP, multiply the number of
injectors by the fuel injectors lbs/hr rating , divided by the brake
specific fuel consumption (BSFC). For naturally aspirated engines the BSFC
range is 0.45-0.55 and for turbo or superchargerd engines from 0.55-0.65.
For a naturally aspirated 8 cyl engine with 19 lb injectors, this formula
would give (8*19)/0.45=337 horsepower. Therefore, 19lb injectors can handle
up to 337 horsepower (as measured at the engine, not the rear wheels), and
24lb injectors can handle up to 426 HP. Keep in mind that these figures are
reduced significantly for supercharged/turbocharged engines. Also, remember
that the stock computer can only handle 24lb injectors. If you try to go to
30lb, you will almost definitely run too rich at lower RPMs and create
performance loss.
Bob C.
'98 Durango 5.9
http://www.geocities.com/MotorCity/Track/9668/index.html#dHomeStart
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:51:11 EDT