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Old 04-12-2009, 01:37 AM   #1
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injector size.... help!!!

i need help trying to find the correct injector size. here's my setup......

308ci
69cc ported iron heads "heart shaped combustion chamber"
headers..off road x pipe..mac mufflers
bbk ssi intake..70ml throttle body
e-cam w/1.7rr.... ".529 lift"
26lbs injectors
11psi of boost
msd 6a and coil
pro-m 70ml. mass air meter
93 octane pump gas w/2gallons of 110octane race fuel

here's what it's doing....
i have to crank the f.p. to 80psi. to get it to start.
it pings at idle with 65psi. (sounds like someone is thumping an aluminum can)
it is still not getting enough fuel @80psi. , not to mention it's not safe to run an injector at that pressure.
anything less than 10degrees advance on the timing makes the pinging worse.


80psi should have a 26lbs injector running at the the capacity of a 31.5-32lbs injector. so my question is.... should i go with a 36lbs injector or should i go with a 42lbs. injector? if i run a 36 will it have me operating @50-60psi? i prefer to run 38-45psi. i would like to get some feedback from you guys. i think 42lbs is where i need to be at for 11pounds of boost, but im not really sure.
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Old 04-12-2009, 11:03 AM   #2
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Re: injector size.... help!!!

I would go with 42. It's better to go high and let your tuner tweak the EEC to get the right A/F ratio.
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Old 04-12-2009, 11:06 AM   #3
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Re: injector size.... help!!!

plus you want a little room to grow
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Old 04-13-2009, 10:57 PM   #4
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Re: injector size.... help!!!

agreed, a good tuner can tame the big injectors back down (within reason)

remember, i've always heard that you'll have to run 51lbs of FP with a blower (yours at 11lbs) in order for the injector to meter as if it were running at 40 NA... i've seen FPR's that adjust things according to boost levels. though your tuner can probably adjust around needing one with load and loadx scaling.
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Old 04-15-2009, 11:42 PM   #5
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Re: injector size.... help!!!

i just picked up a set of 42's...i will put them on in a week or so and let u guys know how it went. i was looking through 5.0 mag and seen a few guys with my similar set-up. most were running 60cc edelbrock heads with 9lbs of boost, but still using 42 pound injectors. i figure with 69cc heads and 11pounds of boost i gotta be real close.
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Old 04-18-2009, 07:07 PM   #6
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Re: injector size.... help!!!

so i put the 42's on.... i gotta drop it down to like 20lbs to keep it from boggn down. we all know injectors dont work worth a fuk below 35lbs. so i guesse this means i will strick on a set of 30's
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