Hey guys,
well, i'm trying to figure out the new fuel injector constant for my bigger injecotrs. I have 32lb (336cc) bosch injectors. But what fuel presure stock fuel pressure is used to for the sc310cc injectors? Make sure the fuel pressure is read with the key on and engine off. If the engine's running the pressure reading will be too low.
Thanks
Nate
Evolution of Cavyboy-->C22t--> C24na--->c24s/c
1995 Cavalier W/2k1 Engine
GM S/C 13.940@99.78pmh w/2.068 60ft
better question. Gm rates their injectors at what psi? (for 2001 ld9)
What psi does ford rate their bocsh injectoers?
Nate
Evolution of Cavyboy-->C22t--> C24na--->c24s/c
1995 Cavalier W/2k1 Engine
GM S/C 13.940@99.78pmh w/2.068 60ft
shifted, have a look if you don't mind.
so ..
310cc @52psi = 5.9615384psi/cc
336cc(32lb)@43.5psi= 7.7241379psi/cc
so the 32lbs (336cc) at 52psi= 7.7241379psi/ccx52psi = 401.65517cc
is that correct??
which would mean... (old constant taken from hpt with gm s/c reflash)
New constant = Old Constant x (old injector size/new injector size)
nc = 0.32359 x (310ccx401.65517cc)
nc= 0.32359 x (0.7548912)
nc =0 .2442752
but if i just plug in it in as 310cc/336cc without adjusting for which base pressure they are measured at i get:
New constant = Old Constant x (old injector size/new injector size)
nc = 0.32359 x (310cc/336cc)
nc = 0.32359 x (.922619)
nc = 0.2985502
Which do i use? 0.244 seems really low since dcstang67 with 440cc injectors has a constant of 0.27xx. To me the 0.29 constant sounds right. But then whats the point of knowing the base pressure the different injectors are flowed at?
Nate
Evolution of Cavyboy-->C22t--> C24na--->c24s/c
1995 Cavalier W/2k1 Engine
GM S/C 13.940@99.78pmh w/2.068 60ft
Well... let me help out a bit...
The injector constant is wierd, very wierd. Some people have luck with raising the number, some have luck with lowering it (when installing larger injectors). Pick a number, start with the .29 number, and plug it in and try it. If its too rich, lower the number a bit, if it gets worse, try raising the number. Unfortunately its the only way to get to a number that works correctly.
Otherwise, your math looks good, I'd use the second number first.
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k. thats what i was thinking too. 0.29 sounds right. Just a little lower, so stay open a little less to compensate for the more cc flow of injectors.
However, i don't want them to only allow the same amount of fuel the 310cc injectors let in b/c that wasn't enough on the top end.
But how do you explain the point of know in the flow (cc) at the base psi. Cause obviously, when i try to corrent that..the numbers are way off.
Anyhow, cant drive just yet..just had surgery on my knee on tuesday. They fixed the cartilage, so a week and i should be able to start testing the tunes. Trying to take this 'couch' time to learn as much as possible. Printed off the whole hpt help file...lots of reading. Pretty dry and boring.
If you have any other pointers or tips send me links
Cause you seem to know ur stuff shifted.
Nate
Evolution of Cavyboy-->C22t--> C24na--->c24s/c
1995 Cavalier W/2k1 Engine
GM S/C 13.940@99.78pmh w/2.068 60ft
Shifted wrote:52psi for GM, 43.5psi for Ford
You sure? thats the first time I've ever heard GM rating their injectors at 52psi..........
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